Technical guides for successful air conditioning audits: volume 10 case studies

Technical guides for owner/manager of an air conditioning
system: volume 10

Successful Case Studies in
AuditAC

1

Team

France (Project coordinator)
Armines - Mines de Paris

Austria
Slovenia
Austrian Energy Agency
University of Ljubljana

Belgium UK
Université de Liège Association of Building
Engineers
Italy BRE
Politecnico di Torino (Building Research
Establishment Ltd)
Portugal
University of Porto Welsh School of
Architecture

Eurovent-Certification

Authors of this volume
José Luís ALEXANDRE (University of Porto, Portugal)
André POÇAS (INEGI, Portugal)
Emanuel SÁ (INEGI, Portugal)

The sole responsibility for the content of this publication lies with the authors. It does
not represent the opinion of the European Communities. The European Commission is
not responsible for any use that may be made of the information contained therein.

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CONTENTS

SCOPE OF THE PROJECT ...................................................................................4

INTRODUCTION OF CASE STUDIES ..................................................................4

HIGHLIGHTS FROM CASE STUDIES..................................................................7
Office Buildings ............................................................................................................................................ 7

Hospital Buildings .......................................................................................................................................11

Commercial Building ..................................................................................................................................12

Other Service Buildings ..............................................................................................................................12

WELL DOCUMENTED CASE STUDIES..............................................................15

RESULTS AND ENERGY POTENCIAL IMPROVES............................................27
General energy Improves............................................................................................................................27

Equipment Replacement.............................................................................................................................28

DETAILED INFORMATION FOR AC CASE STUDIES .......................................29

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SCOPE OF THE PROJECT
The Propose of the AuditAC

The aim is to demonstrate how much advantage can be taken from the implementation
of the inspection of air conditioning systems. More than the inspection itself, the project
promotes audit procedures as the real and effective method to reach such energy
savings.
The inspection characteristics are analyzed and an effort is made, in collaboration with
the European standardization body CEN, to modify and adapt the standard inspection
for detecting actual system’s problems.

A number of tools are developed to help auditors; inspectors and energy managers
identify the most important energy conservation opportunities in existing AC systems
and to avoid the most common errors that lead to a waste of energy.

Moreover, AuditAC attempts to reach all actors of the air-conditioning market
(manufacturers, installers, maintenance staff, etc.), in order to involve them in the
procedure of equipment auditing, make the audit procedure easier and, furthermore,
improve the acceptance of the audit itself.

Throughout all project a database called AUDIBAC was developed for the building
owners and respective systems. This data base will inform the users about the best
solution to increase the efficiency in what concerns to energy of the buildings system. It
is a tool of great importance for the effective accomplishment of the auditing procedures
in AC systems. This tool will be responsible for the creation of results in line with the
EPBD requirements, from the viewpoint of both the customer and the auditor.

INTRODUCTION OF CASE STUDIES
To develop this data base, it became extremely necessary to know well different cases
of application of air conditioned systems at a European level. In fact that Europe present
different climatic areas and consequently different types of building envelope turns the
knowledge of the system operation for each case very important. The case studies for
the database were developed by the several partners in the AuditAC project, Austria,
Belgium, France (project coordinator), Italy, Portugal e Slovenia and UK.

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Research Center

Cultural Dpt.
Commercial
Auditorium
Informatics

Laboratory
Hospital

Archive
Library
Office
No Name and Location
1 ACS-1 Salzburg, Austria ●
2 ACS-2 Linz, Austria ●
3 BCS-1 Namur, Belgium ●
4 BCS-2 Brussels, Belgium ●
5 BCS-3 Liège, Belgium ●
6 FCS-1 Orleans, France ●
7 FCS-2 Paris, France ●
8 ICS-1 Turin, Italy ●
9 ICS-2 Vercelli, Italy ●
10 ICS-3 Oderzo, Italy ●
11 ICS-4 Bologna, Italy ●
12 PCS-1 Porto, Portugal ●
17 SCS-1 Maribor, Slovenia ●
18 UKCS-1 Leicester, UK ●
19 UKCS-2 Westminster, UK ●
20 UKCS-3 Cardiff, UK ●
23 UKCS-6 Oxford, UK ●
24 UKCS-7 London, UK ●

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Case studies will concern different sizes and types of buildings, which are classified by
building type (functionality) and by type of HVAC system. This classification makes
possible the comparison between the different case studies and allow for the first time to
estimate on a statistical basis the magnitude of the gains possible on European A/C
installations as well as to give a list of possible malfunctions of the equipment, which the
auditor can probably find during the audit phase.

Building type Classification:

Office buildings (O)
Hospitals (H)
Commercial (C)
Other Service Buildings (S)

HVAC system Classification:

Centralized
Primary system (PS)
- Chiller
- Boiler
- Heat Pump
- Thermal Storage
Secondary system (SS)
- Air base system
- Water based system
Non Centralized
DX system
- Split
- Multi Split

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- VRF
- Heat Pump

UKCS-2 - Westminster

UKCS-7 - London
UKCS-8 - London
UKCS-9 - London
UKCS 1 Leicester

UKCS-3 - Cardiff

UKCS-4 - Cardiff
UKCS-5 - Cardiff
UKCS-6 - Oxford
ACS-1 - Salzburg

BCS-2 - Brussels
FCS – 1 Orleans

SCS – 1 Maribor

ICS-2 - Vercelli
ICS-3 - Oderzo
PCS-1 - Porto

BCS-3 - Liege
BCS 1 Namur

PCS-2 - Porto
PCS-3 - Porto
PCS-4 - Porto
PCS 5 - Porto

ACS-2 - Linz

ICS-1 - Turin

FCS-2 - Paris
O O O O O H H H S S S S S S O S S O C O O O O O O
- Chiller • • • • • • • • • • • •
- Boiler • • • • • •
PS
- Heat pump •
HVAC System Type

Centralized
- Thermal storage • •
- Air based system • • • • • • • • • • • • • •
SS
- Water based system • • • • • • • • • •
Not Centralized
- Split • • •
- Multi Split •
DX system
- VRF • • • • •
- Heat pump •

HIGHLIGHTS FROM CASE STUDIES
Office Buildings

BCS 1 – Namur
Case: This case aimed at assessing and managing the HVAC system
installed in an office building located in the center of the town of Namur.
Installed HVAC system: Heating – three gas boilers with variable flow to
feed radiators and AHU’s. Cooling – two chillers with reciprocating
compressors and air condensers with variable flow to feed AHU’s and fan-
coils.
HVAC system modifications: During the audit phase the cooling and
ventilation performances were not as expected. Alteration of the control
strategy, the implementation of new parameters and administration rules, the
regulation of the set points and of the VAV boxes thermostats were some of
the modifications for this case.
Lessons learned: After commissioning, most of the errors were eliminated
but some of the problems continue to exist. Modeling some retrofit
opportunities can increase further more the heating and cooling
performances of the installed system.

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BCS 2 – Brussels
Case: This case is about a 13 story office building.
Installed HVAC system: The installed HVAC system is composed by 4-
pipe terminal units, AHU’s, Chiller, boiler, cooling towers and circulation
pumps.
HVAC system modifications: There are some suggestions made in order
to improve the system performance. The AHU’s were partially renovated
and all induction units and thermostatic valves were replacement. The
replacement of existing induction units by more efficient devices (other
induction units or fan coils), should make possible to run the system with
higher chilled water temperature and therefore better COP.
Lessons learned: Other options can always be considered to improve the
systems efficiency; even small ones can produce a big effect when you
have a big building with a large system.

FCS 1 – Orleans
Case: This case is about a refrigeration plant of a commercial company.
They started having problems with the high energy bills, so the target to start
reducing the energy consumption was the cooling production unit.
Installed HVAC system: The system installed was composed by centrifugal
compressors groups functioning in stages. This system was oversized and
NO PHOTO AVAILABLE used forbidden refrigerant according with the actual regulations.
HVAC system modifications: The modifications consisted on the
substitution of the cold production unit by one other, adapted to the cold
demand and modulated in stages.
Lessons learned: The real saving reached 56 % of the electricity from the
cold production groups.

FCS 2 – Paris
Case: audit preformed to an office building located in the Paris suburbs. The
building has one floor and a basement. Its overall clear surface is 1140 m ².
The building can be divided into three types of spaces: circulation zones,
conference offices and rooms.
Installed HVAC system: The five conference rooms are climatized by an
AHU and a group of cold water production. About thirty offices have AC
based on 2-pipe fancoils and natural ventilation. The cold water that feeds the
loop of the AHU and the fancoil is produced in a non-reversible alternative
Chiller. The system operates 24 h /24 and 7 days/7.
HVAC system modifications: Two main improvement scenarios were
foreseen: the first scenario consist in keeping air conditioning in summer and
the heating with Joule effect in winter; the second scenario would be the
replacement of the refrigeration unit by a reversible heat pump with an
average seasonal COP of 2,5. Associated with these two scenarios other
measures were proposed in order to reduce the energy consumption:
Change the water loop set points, change the functioning schedules, reduce
the internal gains etc.
Lessons learned: This study shows that the improvement scenarios
combined with other measures can result in a decrease from 30% to 77% of
the HVAC system energy consumption.

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SCS 1 – Maribor
Case: This case relates a high efficient system for an office building. At
minimal energy consumption, thermal comfort and good work conditions are
achieved. The investment costs are similar with the traditional buildings.
Installed HVAC system: The building is heated with a combined heat-pump
(water-water) which provides heating and cooling energy. As a support for
heating there is also a low temperature condensing gas boiler. Whole space
is ventilated with high energy efficient ventilation / air conditioning units with
energy recovery more than 90%. There is also a possibility of direct cooling
with ground water. In summer period, it has a temperature of 15 – 16ºC.
HVAC system modifications: This study only intents to present a case of
good performance, so there are no modifications.
Lessons learned: It is possible to have a high efficient HVAC and obtain
good levels of comfort without much more than an usual building.

UKCS 1 – Leicester
Case: This case illustrates an exceptionally energy efficient/low energy air
conditioning system. This is a 4 storey office building.
Installed HVAC system: The HVAC cooling system consists on chilled
beams. The cold water production unit is a package air cooled chilled using
NO PHOTO AVAILABLE R407c as refrigerant.
HVAC system modifications: There are no modifications suggested
Lessons learned: This building seems to be very energy efficient according
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to is overall annual energy consumption/m when compared to national
benchmarks.

UKCS 2 – Westminster
Case: This case study aimed at assessing the energy performance and its
potential for improvement, of a comfort cooling system installed in a UK office
building. The building comprises six-storeys (Ground plus 5) of mainly small
cellular offices and a lower ground containing support and storage areas.
Installed HVAC system: The basic system configuration features passive
chilled ceilings and perimeter passive beams with night-time ice storage and
NO PHOTO AVAILABLE some DX systems serving computer rooms and conference suites. Ventilation
is provided mechanically via centralised AHU’s and heating is provided by
perimeter radiators.
HVAC system modifications: This case study focus on the actual system
analysis, thus no modifications were implemented.
Lessons learned: Detail thermal simulation tool can be very helpful to
predict HVAC system consumption and consequently avoid some errors in
the project or correcting them during an Audit.

UKCS 3 – Cardiff
Case: This case study compares the energy consumption values obtained
using thermal simulation tools such as EnergyPlus with real energy
measurements.
Installed HVAC system: The HVAC system installed is a 2-pipe Multi-Split
DX system. This system has the possibility to free cool the spaces.
HVAC system modifications: This study focus on the actual system
analysis, thus no modifications were tested.
Lessons learned: Detailed thermal simulation tool can be very helpful to
the project.

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UKCS 5 – Cardiff
potential for improvement, of a comfort cooling system installed in a small
administrative office, located in a historic building of Cardiff University.
Installed HVAC system: The office has a DX split comfort cooling system
NO PHOTO AVAILABLE with a roof mounted condenser and a 4-way ceiling mounted cassette.

UKCS 6 – Oxford
potential for improvement, of a comfort cooling system installed in a light
industrial building on a small rural estate near Oxford. The conditioned area
consists of a large open plan office, 3 cellular spaces of executive offices, a
conference room and a production area room.
Installed HVAC system: This area is serviced by VRF indoor units, ceiling
mounted, from external condensers on a 2-pipe heating and cooling “change
NO PHOTO AVAILABLE over” only basis. The supply AHU consist of an in-duct axial fan, filter pack
and electric heater battery. The system has plenum return ventilation with
ducted supply and partial recirculation in the fan-coil units.

UKCS 7 – London
potential for improvement, of a comfort cooling system installed in the ground
floor of a 2 storey office block. The conditioned area consists of open plans
and cellular office rooms, meeting rooms, training rooms and a reception.
Installed HVAC system: The conditioned area has a 2-pipe fan-coil system
with the electrical reheat, supplied by two reverse cycle air-cooled chillers.
NO PHOTO AVAILABLE The indoor units are a 2-pipe ceiling mounted cassettes with multi-speed fans
and electrical reheat in the perimeter units.

UKCS 8 – London
potential for improvement, of a comfort cooling system installed in the first
floor of a 2 storey office block. The conditioned area consists of open plans
and cellular office rooms, meeting rooms.
Installed HVAC system: 3 pipe heat recovery VRF units with roof mounted
condensers and internal ceiling mounted cassettes. The cassettes draw air
from the ceiling void that is also supplied with fresh tempered air from the
NO PHOTO AVAILABLE mechanical ventilation system. The entire building is mechanically ventilated
with a 2-duct supply and return system, within the air handling unit located in
the roof top plant room.

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UKCS 9 – London
potential for improvement, of a comfort cooling system installed in a 2 storey
office block. The conditioned area consists of open plans and cellular office
rooms, meeting rooms.
Installed HVAC system: The conditioned area has a custom Built AHU. The
packaged roof top units are VRV condensers with 3 pipe Heating/Cooling and
NO PHOTO AVAILABLE heat-recovery unit, believed to be operating as modular banks of 7 per floor.
The ground and first floor ceiling voids contain in total 56 Daikin VRV 3-pipe
heat and cooling ceiling cassettes.

PCS 5 – Porto
Case: This case is about the INESC building located in the campus of Porto’s
faculty of engineering. This is a typical 4 stories service building.
Installed HVAC system: The HVAC system is centralized and composed by
a boiler, a chiller and two ice storage tanks. The air distribution is done by
using fan coil units.
HVAC system modifications: The main tested alteration consists on the
reprogramming of the central control unit in order to provide the use of free
cooling whenever possible.
Lessons learned: The use of free cooling is estimated to offer an energy
saving potential by the order of 28% year.

Hospital Buildings

ACS 2 – Linz
Case: This case concerns with the optimization of the refrigeration plant
existent in the central hospital of Linz.
Installed HVAC system: The refrigeration plant is equipped with a 6-cilynder
2-stage compressor. The heat rejected can be collected and used for heating
water.
HVAC system modifications: The modification was basically the
replacement of the 6-piston compressor for a 6 screw compressor with 40%
more of cooling capacity.
Lessons learned: The saving potential was even higher than estimated,
achieving 30-35%.

ICS 2 – Vercelli
Case: This case intents to show the optimization of a hospital AHU that treats
the air from a surgery room. Measurements were done and the data collected
will be used to assess the system’s efficiency.
Installed HVAC system: The actual installed HVAC is a centralized system
(with AHU, chiller and water loops).
HVAC system modifications: In order to improve the system’s efficiency
several solutions were studied, such as the substitution of the chiller, the
capability to use free cooling and the heat recovery from the condenser units.
Lessons learned: Several economic and energetic analyses were done. The
use of two new chillers in partial load instead of three installed ones can
achieve savings on the order of 1460 €/yr. Savings associated to a one
degree variation in the limit temperature at which the chillers are shut off and
free cooling is adopted (23°C vs 22°C) are approximately equal to 50000
kWh/yr (with negligible differences between existing and new chillers), i.e. on
the order of 12%.This demonstrates that there is an opportunity for cost
effective energy saving measures.

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ICS 3 – Oderzo
Case: This case is about a 3-storey hospital building.
Installed HVAC system: 100% external air AHU. This unit has humidifier,
fans, HEPA filters, cooling coil and heating coil.
HVAC system modifications: In order to improve the system’s efficiency
several solutions were studied such as free-cooling with an achieved energy
NO PHOTO AVAILABLE reduction of 16% and heat recovery. The average thermal effectiveness of
the intermediate-fluid heat recovery system turned out to be on the order of
58% (based on measurements) and for an air-to-air heat exchanger 65%.
Lessons learned: This case study has allowed a quantification of the impact
of AHU operation on the electrical energy consumption of an all-air AC
system for a hospital. It shows as well that some energy saving measures
can be implemented with good results.

Commercial Building

UKCS 4 – Cardiff
potential for improvement, of a comfort cooling system installed in a small
commercial architectural practice operating as part of the Welsh School of
Architecture (WSA).
Installed HVAC system: DX splits were installed for comfort cooling. The
NO PHOTO AVAILABLE system has roof mounted condensers and wall mounted slim-line cassettes.
Lessons learned: Detail thermal simulation tool can be very helpful to predict
HVAC system consumption and consequently avoid some errors in the project
or correcting them during an Audit.

Other Service Buildings

BCS 3 – Liège
Case: This case is about a laboratory located in Liege, Belgium. The
conditioned floor area is 4000 m2. This building contents a set o offices,
meeting rooms, dinning hall and laboratories.
Installed HVAC system: The installed HVAC system is composed by Terminal
Units such as Fan coils and a AHU that supplies conditioned fresh air using
textiles diffusers. The AHU and the Fan coil units are fed by water loops. The
hot water is produced by a boiler and the cold water by chillers.
HVAC system modifications: This study only indicates retrofit opportunities no
modifications were made in the installed system.
Lessons learned: Better distribution of the hot water temperature to the actual
space heating demand and another mode of sanitary hot water production
seems to provide reduce de gas consumption.
A recovery heat pump could be used with extracted air as cold source in order
to enhance heat recovery from AHU.

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PCS 1 – Porto:
Case: This case is about a computer center existing in the Faculty of
Engineering of Porto University. The rooms in analysis are 4 and are in function
all year to guarantee the functioning of the faculty’s computer network and
internet.
Installed HVAC system: the system installed is not centralized. Each room has
independent cooling units. The units existent are basically DX close control and
single split units.
HVAC system modifications: The proposed modification for this case consists
on the substitution of the actual DX units for a centralized system, being the
chilled water loop fed by a chiller and the hot water loop fed by a boiler. One
other fundamental change was the introduction of the possibility for the system
to free cool the spaces given favorable outdoor temperature conditions.
Lessons learned: The main achievement was the use of free cooling as well
as the savings due to the increase of the chiller efficiency (EER). These
measures result in a 70 % decrease of the compressors functioning hours and
in an overall 30% electric energy reduction.

PCS 2 – Porto:
Case: This is the case of three auditoriums existent on the Faculty of
engineering. These auditoriums are equipped with an Air-Air type system. The
analysis done to this rooms was merely acoustic.
Installed HVAC system: This air-to-air system is composed by roof-top units
(one per room) and heat pumps to provide the heating and cooling energy. This
unit mixes fresh air with return air. Given favorable conditions, the control
strategy is prepared to allow free-cooling.
HVAC system modifications: The proposed modifications are focused on the
ventilation system. Some modifications were done in order to reduce the noise
level inside the rooms. Modifications like the displacement of the mixing box or
the placement of acoustic attenuators were tested.
Lessons learned: The acoustic comfort can be achieved with parallel
improvements on the indoor air quality and energy efficiency.

PCS 3 – Porto:
Case: This case relates to library in the Porto’s faculty of engineering. This is an
8 stories building that works from Monday to Friday. This case study intents to
assess and resolve a comfort problem reported by the library users.
Installed HVAC system: the system installed is centralized. There’s a boiler and
a chiller on the roof that feed the chilled and hot water loops respectively. The
air loop is handled by an air handling unit.
HVAC system modifications: The proposed modification for this case consists
on the use of CO2 as the fresh air control indicator, the change of the lighting
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density to 8 W/m , use of vertical and horizontal shading devices on the south
facing windows and the alteration of the set-point temperatures.
Lessons learned: All these measures resulted in energy savings. By combining
some of these actions the building can archive 43 % energy reduction.

PCS-4 – Porto:
Case: These case intents to study the influence of the AHU filters conditions on
the ventilation energy consumption in a laboratory room located within FEUP.
Installed HVAC system: The studied AHU is composed by two fans, electric
resistances for heating and a DX system for cooling. The filters tested were
placed on the fresh air inlet side.
HVAC system modifications: The modification done was basically to
substitute a dirty filter by a new one, and monitor the fan motor energy
consumption.
Lessons learned: The lack of the filters maintenance reduces the indoor air
quality, and leads to energy waste by the fan motors.

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ACS 1 – Salzburg
Case: This case relates the energy consumption changes in a new archive
building along with the years and with several interventions in the system in
order to decrease the energy consumption.
Installed HVAC system: There’s no pertinent information about the cooling
system.
HVAC system modifications: The modifications done were mainly on the
system control and management.
Lessons learned: A good management of the system can, without further
equipment modification, achieve much higher energy efficiency. In this case
energy savings achieved 70%.

ICS 1 – Turin
Case: This case is about an office building in Turim that renewed the HVAC
system. However this new system seemed to be inadequate. Thermal
simulation tools were used to assess other HVAC equipments in terms of
energy consumption and thermal comfort.
Installed HVAC system: The HVAC system installed is composed by
embedded floor radiant panels and AHU’s.
HVAC system modifications: The most important simulated modification were
basically the use of AHU with fan-coil units instead of radiant floor and the
substitution of the heating oil burner for a natural gas boiler connect the system
to the gas network.
Lessons learned: The results obtained using simulation show that a 25% of
the HVAC energy saving can be spared.

ICS 4 – Bologne
Case: This case study was aimed at analyzing the performance of a water-to-
water reversible heat pump installed in a research center located in Apennine
mountain.
Installed HVAC system: The AC is an air-and-water system type (primary air
and two-pope fan coils). Hot and chilled water is produced with a water-to-water
reversible heat pump, using treated lake water that feeds the AHU and FCU’s.
HVAC system modifications: This study focus on the actual system analysis,
thus no modifications were implemented.
Lessons learned: The presence of a BEMS makes it possible to monitor and
record the main system operational parameters. The seasonal average COP for
the installed system is equal to 3.9 and a good correlation between daily cooling
energy and outdoor dry-bulb air temperature was identified.

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WELL DOCUMENTED CASE STUDIES
Twenty Six case studies were analyzed. Among these, 6 were considered to be the well
document case studies. This selection was carefully made so that we could extrapolate
AC systems in terms of typology of the buildings allover Europe. Below are the case
studies considered to be the best document examples and their location.

CICA - Informatics Center • FEUP, Porto
The building has three floors and the ground floor is the centre of informatics resources.
The function of this building is mainly to ensure and make available all the informatics
services for the FEUP community and to uphold its innovation and use.
The cooling power installed in these spaces is not enough to remove the total load that
occurs inside the building, which causes a high indoor air temperature leading to harmful
situations, causing damages and reducing the performance of the informatics hardware.
The original HVAC is a non centralized VRF system where the local cooling units are
ceiling splits and close control units with an outdoor condenser unit.

Problems

• Actual HVAC system is not adjusted to the demand
• The internal loads are higher than the installed HVAC system, causing the
damage and reducing of the performance of the informatics hardware.

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• In summer the indoor comfort is more challenging

Solutions – Major Modifications
The solution proposed is, in energetic and environmental field, the most adjusted since it
is a centralized system and has a higher efficiency. This solution also allows the power
increase without major costs.
The considered HVAC system can be defined as an air/water system. It will be
composed by a cold-water central producer (chiller), located in the building covering, and
by a cold water distribution net with two pipes, for supply and return. This circuit will
supply the existing cooling coils in the independent Close Control units. These units are
located inside the acclimatized spaces or, guarantee the indoor air quality. This system
will also include the possibility of free-cool the spaces, given the adequate exterior air
conditions.

The following equipments form the proposed system:
- Chiller with scroll compressor with 100 kW of cooling capacity;
- Four Close Control units supplied with cold water which integrates system of
humidification and electric resistance for heating;
- Ventilation, piping and control system

Accomplished improvements:
The energetic and power consumptions of the existing Close Control units in the 4
zones, obtained through dynamic simulation, are 128 MWhe/year. It should be noted that
this analyses considers the consumption of the compressor, the ventilation, the reheat
coils and humidification. Using once again the dynamic simulation, the obtained energy
consumption for the proposed solution is 87 MWhe/year.
The new system with free-cooling and electrical reheat is much more effective than the
others, except the system which uses hot water for reheat. However this system would
require a boiler so the system would consequently become more complex and
expensive.

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As it is verified the energy earnings, of the floor -1, with the substitution of the current
system for the proposed, they are of 41 MWh. This value corresponds to 2.870,00 Euros
a year of economic won (the price of the electric energy was esteemed in 0,070 €/kWh).
The proposed solution presents certain advantages when compared with the existing
system:
The cooling capacity can be increased with the connection of one or more chillers.
According to the type of equipment, it is possible to connect them and optimize its
functioning. All these systems allow a centralized management and partial loads
according to the thermal needs. The circulation fluid is water, which do not present any
restriction or danger as refrigerant fluids. When necessary, the upgrade of the indoor
power is simple and easy to implement. The terminal units could be independent of the
cold unit production, in what refers to the mark, model or type. The lifetime of this
equipment is always higher then that of splits units.

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Office Building • Maribor
The energy system of an office business building is presented, where at minimal energy
consumption, optimal working conditions are achieved. The investment costs are in the
same range as the investment costs for a traditional building. Building is heated with a
combined heat pump (water – water), which prepares heating and cooling medium for
the whole building. Heating source is ground water from a spring. Heat and cooling
energy are partly transmitted into the object by thermal activation of concrete
construction and by supplied air of ventilation units. Local regulation of temperature is
possible through local heating coils, built in special displacement air distributors. Whole
space is ventilated with high energy efficient ventilation / air conditioning units with
energy recovery more than 90%.

Problems
There are no problems reported for this building. In fact, this case study aims to report
that is possible to combine technology, comfort and reasonable expenses.

Accomplishments:
As said, the building was designed to achieve high energy performance thus reducing
the energy consumption. This global goal was approached by several sides: the building
envelope [sun exposure and wall and glazing materials] and the HVAC systems
installed.

The glazing is a two – layer glass type, argon filled. It is combined with high quality
aluminium profiles, with interrupted thermal bridges, thermal insulated. There is also a lot
of innovative details of interruption of thermal bridges at connections glazing to concrete
constructions.

Performance of the cooling system is optimized for lowest possible energy consumption.
Big amount of sensible heat is cooled with thermal activation of concrete construction it
goes on large surface area, which means high cooling medium temperature – low
energy consumption.

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The basic heat source is underground water. In winter it has a temperature around 10-
13°C,o on the other side, we have thermal activated concrete construction with large
heat areas, which means extremely low temperature heat medium of 25 – 26ºC, which
assures that the heat pump works with a excellent coefficient of performance (COP) 5-6.

Comfortable working conditions for employees are also achieved with a permanent
supply of fresh air into the rooms with three air-changes per hour. Ventilation with 100%
of fresh outside air wouldn’t be rational if it wasn’t done with ventilation and air
conditioning units that have heat recovery of 92 % and humidity recovery of 87% at the
lowest outside temperatures. In summer the air conditioning units also dehumidify the
outside - inlet air when it is necessary, which assures comfortable working conditions
even at extreme conditions of the outside air.

All these design characteristics led to a real high energy performance. The results
obtained after 24 month of operation revealed that the building is indeed efficient.

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Office Building • Brussels
Description:

This is a medium size office building (28 000 m2) erected in centre of Brussels at end of
the sixties. This building is constituted by open plan offices and (a few) meeting rooms.
The whole building has an air conditioned system with the exception of the car park.
The original HVAC system is four pipe induction units in all offices and CAV/VAV
systems in other zones.
Classical heating and cooling plant, with fuel oil boilers and vapor compressions chillers
with cooling towers.

Control Strategy:

The building is equipped with a classical BEMS with two levels: a set of local control
units and a PC for supervisory management.
The comfort must be satisfied from 7 am to 8:30 pm, five days per week.
The BEMS is imposing an earlier re-start, according to weather conditions.
There are also some special requirements for the (prestigious) ground floor: the air
conditioning is required there all along the year in order to protect the (exotic wood)
decoration!
Indoor air temperatures are measured at three different locations of each floor (except
for floors 5 and 6). The average of all these temperatures is used by the BEMS in order
to fix the primary air temperature.
The primary air is only supplied during pre-heating and occupancy time.
Outside that time, if the weather is very cold, the induction units are still used in free
convection mode, by supplying hot water to the heating coils.

20

Accomplished improvements and Retrofit Opportunities:

An attempt of free chilling was done sometime ago, by adding a water-to-water heat
exchanger between the condenser and the evaporator circuits (in parallel to the chillers).
For reasons still to be investigated, this experience failed and the system was
dismantled.
The AHU’s were partially renovated and the replacement of all induction units and
thermostatic valves is now projected.
The replacement of existing induction units by more efficient devices (other induction
units or fan coils), if fitting in the small space available, should make possible to run the
system with higher chilled water temperature and therefore better COP.
The environmental control should also be made more accurate.
More indoor temperature sensors will be installed in the occupancy zone for better
control of set-points.

But much other retrofit potential should be considered:

- Variable rotation speed for pumps and fans
- Optimal control of chilled water temperature
- Energy recovery loops between supply and exhaust air circuits
- Air recirculation
- Optimal control of cooling towers
- Free chilling (again!)
- Chiller condensers heat recovery
- Use of chillers in heat pump mode (when no more used for cooling)

21

Archive Building • Salzburg
Description:

This case study relates to a building built in 2003/04. This building has it the energy
consumption measured online by an energy monitoring system. In the first months high
energy consumption was registered. It was thought that this high energy consumption
was due to the fact that the building had been recently constructed.
Optimization measures were taken in order to reduce the energy consumption. It was
possible to reduce the consumption by about 40%. During August and September the
regulation and cooling system companies cooperated in order to increase energy
efficiency in the system. From this cooperation resulted a 60% reduction in the energy
consumption. The year of 2005 brought the evidence that is possible to reduce the
consumption by more than 70%

Problems:

The main problem detected in this building was the high energy consumption. The
systems were not functioning properly. It was realised that the range for the air was too
small. When the room temperature was too high, the climate cabin started to cool the
room. The result was that the room became too colt and than the heating system had to
start heating the room. The system was continuously cycling between on and of mode.

Accomplishments:

After the detection of the problem several modifications were made. The combined work
of both regulation systems and cooling system companies resulted in an energy
consumption decrease of about 70%

22

Cultural Building • Turin
Description:

The building of the culture department is situated in the historic centre of Turin has five
floors, building houses administration offices of the City Council and a library. The old
building was renovated in 1996 when a new HVAC was installed, but over the years this
system has been seen to be inefficient and not adequate for the building’s needs.
The actual HVAC system is constituted by: primary air plant, embedded floor radiant
panels supplied with warm water in winter and cold in the summer.

Problems:

The HVAC system is formed by embedded floor radiant panels that cool the
environment, without relative humidity control. The humidity is controlled by different
AHU’s in the building. In winter this system works well, in fact the air is heated and
humidified by the AHU and the embedded floor radiant panels function correctly. In
summer, however, the temperature of the water circulating in the panels cannot go
under 18°C or there are problems of condensation and mildew and the single primary air
plant cannot maintain the correct environmental conditions.
The distribution of air produced by the various AHU, located on each floor of building,
passes through rectangular or circular channels with run in the corridors. In summer, the
distribution of air in areas distant from the AHU’s is not enough to guarantee
maintenance of optimal temperature and air control conditions, in fact the people that
work inside these offices experience some problems.

23

Proposed Solutions:

Change the embedded floor radiant panels to fan-coils. The new HVAC system can still
be defined as air/water system but, it will be composed of AHU’s for ventilation, and cold
– hot water distribution for the fan-coils.

Use a suitable BMS, the system is already predisposed with a specific control console
and suitable software.

Strengthen the fan of the various AHU’s because the existing fans are insufficient to
force air to the offices distant from the AHU

Intensify the maintenance of the fittings that is currently performed by an external firm
and the inspection of the components by the administration.

Use electricity meters to download electric consumption on an hourly and daily basis, in
order to collect further information for an effective audit of the building.

Change the burner that is currently installed (heating oil) to a methane model and
connect the system to the gas distribution network.

24

Archway House – Office Building • Cardiff
Description
This building, located in Cardiff-Wales, is an office building with the respective office
functioning profile. This case studied intents to assess whether or not thermal simulation
tools can provide an interesting and reliable tool in energy auditing. The building here
presented is equipped with VRF multi/split systems with the capability to use free/cooling
whenever possible.

Electrical energy consumption data was collected for June, July ad August. The aim is to
simulate the building in a thermal simulation tool and then compared the simulated
values with the real ones. To see if values obtained by simulation are reliable, and thus

The software used was the EnergyPlus and the weather data used was real data for the
same period as the electric measurements.

The heating was not assessed; the aim is only to assess the cooling performance.

Only one of the spaces, AC_zone, has a cooling system. It is intended an internal
temperature of 24 ºC, during the labor hours. There is a 2-pipe cooling Multi-split DX
system with the following known characteristics:
Rated Power Consumption: 35.4 kW
Total Cooling Capacity: 75 kW

There is also a free-cooling system, on whenever the outdoor temperature is lower than
17.5 ºC. This system allows a great energy saving, especially in locations with low
summer temperatures, as it is the case of Cardiff.

Solutions encountered using simulation software:

25

From the breakdown analysis it can be concluded that the following ECOs could be used
to help reduce the cooling energy demand in the building:

- ECO E4.5 – Replace electrical equipment with Energy Star or low consumption
types.
- ECO E4.9 – Move equipments (copiers, printers, etc.) to non conditioned zones.
Electrical equipment loads are the highest loads among the internal gains in this
case, therefore any possibility to reduce the amount of energy they use and
release should be considered. Most of the copiers and printers, etc in this case
are in the conditioned zone, relocation to non conditioned areas could also be
considered to reduce the cooling loads.

- ECO E4.7 – Modify lighting switches according to daylight contribution to different
areas.
- ECO E4.8 – Introduce daylight/occupation sensors to operate lighting switches.
Electrical lighting seems to be on all the time according to the survey and its
contribution to the cooling demand is considerable.

- ECO E2.1 – Generate possibility to open/close windows and doors to match
climate. Ventilation should be used as much as possible as a free cooling source
as the outside air temperature tends to be lower that the inside air temperature.

- ECO E1.1 – Install window film or tinted glass.

- ECO E1.3 – Operate shutters, blinds, shades, screens or drapes.
Solar control should be used to reduce the cooling loads, even though it is not
the highest contributor to it.

- ECO O2.2 - Shut off A/C equipments when not needed.
The ancillary equipment to the A/C system is apparently consuming 3kW even
when then system is providing no cooling. The relatively short period of time that
this system provides cooling means that this load becomes a very significant
component of the overall energy use, and reduces the overall COP dramatically.

26

RESULTS AND ENERGY POTENCIAL IMPROVES
General energy Improves

In general overview, the observed potential energy savings in different real examples
can be subdivided in a few audit strategies, such as:
1. management system control optimization
2. efficiency control of the equipment energy consumptions
3. lighting efficiency control
4. new strategies of recovery energy
5. free-cooling strategy implementation
6. simply chiller equipment replace

To achieve a good Potential Energy savings strategy the building’s owner (or auditor)
must to know well the energy utilization such as:
• running hours of AC and the length of pre-cool period;
• internal comfort conditions, ie temperature, humidity, lighting levels;
• localization of the unnecessary AC and lighting, I e unoccupied zones;
• chillers/pumps schedules and settings;
• specific equipment energy consuming
• lighting energy consuming
• the areas of high energy consumptions
In Europe, and in particular countries, it is possible to have an idea of the energy
utilization for the office building sector. Therefore, the auditor know, in the first approach,
how is the potential energy saving that can achieve if applied different strategies that
presented above. The figure shows the average energy end-user breakdown typical for
the European office building sector.

HVAC
27%
Lights
33%

HVAC 25% - 30%
LIGHT 30% - 45%
Equip 25% - 40%
Average Energy end-user breakdown for EU office
building
Equipments
40%

Energy end-user breakdown from Belgium CS1

27

Some audit cases had energy improvements only with a new lighting strategy control, for
example the PCS-31 the reduction the light to 8 W/m2 it had have double effect on the
energy consumption, first in direct electricity consumption and second in the reduction of
internal loads, ie peak cooling power. At the end, with global strategy control for the AC
system, the global system achieves 43% of energy reduction. Of course it is not only the
lighting effect but all control strategy.

Good control and management of the system in same cases can reaches a high save
energy. This was happen in the ACS-12 case study when the total save energy it was up
to 70%. This is an excellent example but the average control management has less
energy efficiency indeed.

The use of free potential energy (free-cooling) is used in some cases with excellent
results in same cases the energy profits can achieve from 30% to 60% reduction of the
total energy consumption. This solution is well dependent fro the weather conditions and
the countries with cool climates are more suitable for this kind of solution.

Equipment Replacement

There are a significant number of examples, in AdiBAC, based in replacement cool
equipment, ie change the old chiller by a new one with high efficiency. The CS shows
some examples were the energy saves can be up to 35% of total energy (ACS-2)4, and
other when the energy saves reach 56% of the energy used for the cooling system
(FRCS-1)3.

It is quite possible to make an idea how energy we can save if we make chiller
equipment replacement, in average point of view. Based upon the EER evolution in the
last ten years, that means ± 30% increase efficiency on average (EECCAC), therefore it
is possible to forecast the potential energy save for the next days in the AC systems.

The "cases" in the data base are real installations which are described under the format
that the various existing reference frames request in order to make them comparable.
For part of the existing case studies it will be necessary to supplement information
available by complementary measurements and / or by calculations so that all the
methods become applicable. Besides their use in further work packages, the case
studies in the data base will allow for the first time to estimate on a statistical basis the
magnitude of the gains possible on European A/C installations.

1
AuditAC Case Studies Brochure: Case studies: Portuguese, n3
2
Auditac Case Studies Brochure: Case studies : Austrian, nº 1and nº2
3
Auditac Case Studies Brochure: Case Studies: French , nº1

28

DETAILED INFORMATION FOR AC CASE STUDIES

Austrian Case Study 1
ACS1
City Archive
Georg Benke
Austrian Energy Agency – Austria

Date: December 2006

There’s no pertinent information about
the cooling system

Introduction
The new city archive was built in 2003/2004 and started to “operate” in March 2004. As
all buildings owned by the city of Salzburg, the energy consumption was measured
online by an energy monitoring system (EMS), measuring the energy and water
consumption in 15 minutes intervals. In the first months (until End of July) it was thought,
that the high energy consumption was due to the present situation, the building was new
and the materials were just brought in, causing the constant opening of the doors.
In the last week of July 2004 the installers of the ventilation systems were order to
optimize the system. It was possible to reduce the energy consumption by about 40 %.
During August and September two teams (one for the regulation system and one for the
cooling system) tried to optimize the system but only achieved the expected result, a 60
% reduction at the beginning of November.
The year 2005 brought the evidence that it was possible to reduce the consumption by
more than 70 %.

Building Description
The Building was built in the year 2003-2004 to be the official Archive for all the
information, documents and papers of the City of Salzburg. It is situated in the north –
west of the Kapuzinerberg hill and is usually in the shadow of this small hill. (See map
and also pictures below). About 20 people work in the building. The building is heated by
the district heating system.
The working places are situated in front of the four floors high storage area

29

Design Details
The regulation system of the company controls 9 different storage areas and provides
this information to the air climate cabin. If the air is outside a certain range (f.e. 18°C / 50
% Humidity) the air climate cabin or the heating system starts to operated.
It was acknowledged that the range for the air was too small. When the room
temperature was too high, the climate cabin started to cool the room. As a result the
room became too cold and the heating system had to start heating the room. The
system was continuously cycling between on and off mode

Building Energy Performance
The energy consumption (electricity) for the whole building:

2004 2005

kWh kWh
January - 7.282
Energy Comsumption (KWh)

25
February - 5.125
March 13.270 4.110 20
April 17.805 4.009 15 2004
May 20.129 4.233 2005
10
June 18.014 4.684
5
July 23.522 4.723
August 13.360 4.859 0

ce e r
M y
Fe a ry

ne

r
A ly
ch

ril

ve r
O er
pt s t

September 10.008 3.161
ay

be
e
r

De mb
Ju
ua

Ap

Se ugu

ob
b
Ju
ar

M
nu

m
em
br

ct
Ja

October 10.342 4.773
No

November 10.008 3.197
December 5.871 -

142.329 50.156

Cooling and Ventilation Performance
There is a Central Ventilation system – situated on the roof which brings the air to the
nine Climate storage areas, each have a different temperature (between 14-21°C). The
heating / cooling is done decentralise for each area, which have also 9 heat exchangers.
The humidity should be 50% (45% - 55%).
There is no CO2 sensor in the storage area.

Summary
It was not so easy to solve the problem previously described because in the beginning
the companies did not try to solve the problem together. Each company tried to find a
solution on his own.
When they start to cooperate, they realized that the range for the quality of the air was
too small. The range was made larger an the energy consumption could be reduced by
70 %.

30

Austrian Case Study 2
ACS2
Hospital
Georg Benke
Austrian Energy Agency – Austria

Date: December 2006

The refrigeration plant is equipped
with a 6-cilynder 2-stage compressor.
The heat rejected can be collected and
used for heating water.

Introduction
This case study is aimed at optimizing the operation of the refrigerating equipment
present in the General Hospital of Linz, a general hospital with 1000 beds, serving
188,968 inhabitants. There are 6 Piston compressor engine
(Kolbenkompressormaschinen) in two station (three per station) from the year 1985 and
1987, Refrigerant R22) which were on their cooling limit (2500 KW). It was made a
forecast for the year 2008, and as a result of this study the cooling needs would reach
the 3600 kW. A decision was made in order to replace all 6 engines with 6 Screw
compressors (Schraubenkompressoren), which have up to 40 % more cooling capacity
and need less energy.

Building Data

General Hospital Linz / Upper-Austria
1000 beds
Space Activity 45.000 ambulant patients (year)
28.000 operations per year
Nr. of employees 2000

Design Details
Initial Situation
There are 6 Piston compressor engine (Kolbenkompressormaschinen) in two station
(three per station) from the year 1985 and 1987, Refrigerant R22) which were on their
cooling limit (2500 KW).
The system was designed in the way, that the waste heat of the compressor could be
used to heat hot water or the Reheating register of the ventilation system. But in the
situation, when the highest amount of heat was available, nobody need it. During
summer, when the temperature outside was higher than 30 °C, the inlet temperature
was 48°C and the outlet temperature was 54°C in this case the COP was less than 2,5.

Implemented Situation

31

The 6 piston compressors were replaced by 6 Screw compressors
(Schraubenkompressoren), which have up to 40 % more cooling capacity and need less
energy.

Control Strategy
There were also smaller changes within the control system of the cooling centre. There
was no change in the kind of cooling consumption all over the hospital.

Date of the new screw compressor:
Type: 30HXC190-PH3
Cooling capacity: 622 kW
Electricity consumption: 130 kW
Evaporator capacity: 622 kW
COP: 4, 78
Performance levels: 6
Minimum level: 21 %
Refrigerant: R134a

Within the control systems of the cooling centre the following changes are possible:
An own program make a calculation about the energy consumption (Cooling, heating)
within the next 24 h. Based on these results, it is possible the change the cooling
demand in time.
If the outside temperature is less than 18°C and the enthalpie about 45 kJ, it is possible
to raise the Cooler outlet temperature to 7 or 8 °C. (Otherwise it is 6°C). This goes hand
in hand with the weather forecast.
To optimize the efficiency of the cooling engine, they try to operate always with 100 % or
50% per engine.

Cooling Performance
Characteristic data from the screw compressor

Performace Condensor inlet Cooling Electric
COP
level temperature Capacity Capacity
% °C kW KW
100 31°C 622 130 4,78
86 31°C 532 123 4,33
71 31°C 436 109 4,00
50 31°C 316 67 4,72
36 31°C 218 54 4,04
21 31°C 155 47 3,30

To optimize the production of cool on a hot summer day, an extra Heat exchanger unit
was fixed on the roof. With this heat exchange unit it is possible to reduce the inlet
temperature from 48°C to 38 – 40°C. During winter they will use free cooling, when the
outside temperature is less than 8°C. The heat exchanger on the roof should be enough
the offer a cooling demand of 150 to 200 kW (reduction).

Summary
The first part of the renovation was done in May 2003. Concerning to calculation it was
expected that the electricity consumption will be reduced by about 20 to 30 %. The
maximum power load will be reduced by about 180 kW and the energy saving is up to
500.000 kWh. First result showed that there is a saving even between 30 to 35% - in this
happened in the hot summer 2002.

32

Belgium Case Study 1
BCS1
Office Building
Corinne ROGIEST-LEJEUNE
Philippe ANDRE
University of Liège - Belgium

Date: December 2006

Heating – three gas boilers with variable flow
to feed radiators and AHU’s.
Cooling – two chillers with reciprocating
compressors and air condensers with variable
flow to feed AHU’s and fan-coils.

Introduction
The building is located in the center of the town of Namur where it must be integrated in
the city landscape. The building has been defined in modules in order to take into
account the slope of the street.
The commissioning and the management of the HVAC system have been monitored by
the University of Liège.

Building description
Project Data
Location: Namur (Belguim).
Altitude: 90 m
Year of construction: 1997/1999
Costs in €: 52 500 000

Number of working spaces: 884
Degree days: (15/15) 2240 Kd
Heated floor area: 31440m2
Heated space: 105000 m3
Inst. heating capacity: 3150 kW
Inst. cooling capacity: 1825 kW

Brief description of the type of building in study:

Big size (68000 m² with 32000 m² offices) office building.
Modular architecture: 11 blocs.
Most of the useful area of the building consists in offices.

33

Figure 2: sketch of the building at design stage

Description of the building layout:
Two big (300 meters long) rectangular buildings (South wing and North wing)
connected together by an atrium except for the central bloc that is the entrance
hall.
3 levels under ground (parking and road tunnel).
3 levels in the North wing and 5 levels in the South wing, for offices.
The atrium has no level and is covered by glass.

Figure 3: lateral facades of the building Figure 4 : building section

Design Concept

Building Envelope
Detailed description of the building envelope:
Per office: South: 0.08 m² heavy opaque concrete structure
3.02 m² triple glazing
0.76 m² wooden frame
North: 7.35 m² heavy opaque concrete structure
5.21 m² double glazing
Atrium North and South: 4.87 m² heavy opaque concrete structure
1.76 m² insulating metallic panel
5.78 m² double glazing

Physical properties of the walls, slabs and roofs layers:

external North wall (ventilated): natural stone +insulation (polystyrene)

34

+ reinforced concrete U=0.47 W/m²K
office floor: heavy reinforced concrete +light concrete +linoleum U= 1.07 W/m²K
office ceiling: linoleum +light concrete +heavy reinforced concrete U= 1.07 W/m²K
internal wall: plaster +acoustic insulation (rock wool)+plaster U= 0.35 W/m²K
corridor ceiling: paving (gres)+light concrete+reinforced concrete U= 1.89 W/m²K
corridor floor: reinforced concrete +light concrete +paving (gres) U = 1.89 W/m²K
atrium wall: natural stone (pierre bleue)+ air+reinforced concrete U= 1.80 W/m²K
external wall South: crepi +insulation (polystyrene)+reinforced concrete U= 0.43 W/m²K
simple glazing (to interior street): U=3.88 W/m²K
double gazing (North):glazing + air +glazing U=2.81 W/m²K
external wooden frame: U=2.86 W/m²K
internal wooden frame: U=2.45 W/m²K
atrium frame: U=2.86 W/m²K
atrium glazing: glazing +air +glazing U=2.83 W/m²K

Solar and Overheating Protection
Passive technology: Atrium between the two buildings to increase solar gains during
winter.
In North façade, windows are large because of no noise from the road. In South façade,
windows are smaller to limit solar gains and noise from the station. There is an external
metallic structure to shade the top of each level in the South facade.

Figure 6: view of solar protections

Design Details
Global description of HVAC system type:
Central heating production by 3 natural gas boilers (operating in cascade) with hot water
loop with variable flow (to feed radiator circuit and AHU).
Central cooling production by 2 chillers (reciprocating compressors with air condensers)
with cool water loop with variable flow (to feed AHU and fan-coils).

Heating and cooling power is distributed through huge collectors feeding the substations.
There are 5 groups (substation) for each set of two architectural modules.
Substations feed terminal units in offices, meeting rooms and atrium.

The terminal units are VAV boxes (cooling and ventilation), fan-coils (heating and
cooling in the meeting rooms) or radiators (only in the offices). Thermostatic valves or
VAV terminals provide local control.

Terminal units

35

In the offices:

Figure 7: view of the terminal units

About 1 500 terminal units with VAV (Variable air volume) installed in the ceiling of
all offices. These ventilation boxes are used for both air renewal and cooling. The
temperature set point is selected by the occupants.
Radiators with thermostatic valves installed in each office. The supply water
temperature in to the radiators is regulated by a three-way valve in function of the
ambient temperature

In the atrium:
Terminal units with CAV

In the meeting rooms:
Some rooms (meeting rooms) are provided with fan-coils which supply air, pre-heated at
20°C.

Air handling units
There are 5 AHUs (substation) for each set of two architectural modules (example G-H):
- “S1” for offices in South wing
- “S2” for the atrium, South side
- “N1” for offices in North wing
- “N2” for atrium, North side
- “N3” for meeting rooms (located between the 2 modules in the North side).

Figure 8: organization of the AHUs distribution

36

For group S1 and N1, the AHU feeds the offices with fresh air at fixed air volume (4300
m³/h) and re-circulated air with variable air flow (8600 to 18900 m³/h).
For group S2 and N2, a fixed (constant air volume) part of the air extracted from the
offices (3400 m³/h) is injected in the atrium after cooling and-or heating in the AHU.
Difference between fresh air and air injected in the atrium air is extracted through the
corridors to the sanitary by extraction fans.

M.E.T. Namur P Ventilation Rue Intérieure Bloc
p
Atrium t t h
t
Cde
Etat CAV Cde
Dis. Etat
Dis.

p
VAV
p p
t h Offices

Fresh Cde Cde p
Etat Cde Etat
Air Dis. Dis.

Figure 9: detailed view of a typical Air Handling Unit

GS1 is constituted from: GS2 is constituted from:
Register Register
Filter Filter
Heating coil (68 kW) Heating coil (16 kW)
Cooling coil (123 kW) Cooling coil (22 kW)
Humidification battery Fan with constant flow (3400
m³/h)
Fan with variable flow (8600 - 18900 m³/h)
GN1 is constituted from: GN2 is constituted from:
Register Register
Filter Filter
Heating coil (54 kW) Heating coil (18 kW)
Cooling coil (83 kW) Cooling coil (23 kW)
Humidification battery Fan with constant flow (3400 m³/h)
Fan with variable flow (8600 - 18900 m³/h)
GN3 is constituted from:
Register
Filter
Heating coil (17 kW)
Fan with constant flow (1600 m³/h)

Cooling plant
The cooling plant is composed of two chillers, which have nominal capacity of 869.5kW
and 956.5kW respectively.
Each chiller is composed of:
3 or 4 screw compressors
1 water heated evaporator
2 air-cooled condensers
2 electronic expansion valves (one per condenser)
3 or 4 oil separators (one per compressor)

37

3 or 4 oil cooler (one per compressor)
3 or 4 filters (one per compressor)

Both chillers use two independent refrigerant circuits, which are connected to the same evaporator

Figure 11: scheme of the chiller circuits Figure 12: distribution of cold water

Chiller 1 is located in the west side of the building and chiller 2 at the opposite in the
East side of the building.
Chiller 1 has 4 twin screws, direct drive compressors, 2 for each refrigerant circuit; chiller
2 has 3 screw compressors, 2 for the first circuit and one for the other.
The cold water circuit is divided in “primary” and “secondary” water networks.

Control Strategy
Global control
Electricity and HVAC are controlled separately.
Supervision software is used to
- adapt the hourly settings
- manage automatic cut off of electrical circuits
- visualize process control
- manage the alarms
- record electrical consumptions
The management of HVAC system is based on one central unit and several control
stations.
central unit: - supervision of all of the HVAC system in DCC
- collection information from collect units, analyze
- optimize HVAC performance to reduce energetic costs
- facilitate maintenance
control station: - function modules
The control system is different for heating and for cooling and, for both cases, shows a
hierarchical nature, starting from the control of the rooms, then considering control of the
secondary units (HVAC) and ending with control of the primary plants (boilers and
chillers).

Specific control systems:
Boilers: - set point temperature in relation with external temperature
- cascade operation activated by temperature sensor on in and out water

38

Technical guides for successful air conditioning audits: volume 10 case studies

Technical guides for successful air conditioning audits: volume 10 case studies

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