The document compares and discusses three HVAC system alternatives for a villa project: individual split units for each room, a semi-central VRV system for each block, and a fully central chilled water system for the whole building. It provides details on the components, operation, advantages and disadvantages of each system. A table then directly compares the three systems according key factors like initial cost, maintenance cost, effect on building design, flexibility, and indoor air quality.

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HVAC SYSTEMS COMPARISON
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APPLIED HVAC SYSTEMS.
There are more than one system can be selected to air conditioning for the buildings.
-Individual system.
-Semi-central system.
-Central system.
In the following pages a briefly description of the different systems can be applied in our project.
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FIRST ALTERNATIVE (INDIVIDUAL SYSTEM).
-This system consists of indoor unit (inside space) suspended above false ceiling and outdoor unit
It composed of one split unit for air conditioning for each room, and also one fan for exhaust air
suspended outdoor (outside space) .
from each toilet
Heating shall be directly by using electric heaters.
-The main advantage of that system is the easiness of installation and dealing with technicians
-Very cheap comparing with other systems.
-That system requires an outdoor space to install the outdoor units (condensing units) like the
faced of building or the roof in case if existing, and the number of outdoor unit is proportional
with the number of rooms served, so in case of block A for example we will need a free space to
handle 37 condensing units.
-incase of operation of all units in the whole zone the area will be liable to noisy effect.
-Very simple in maintenance but need large number of technicians to check the whole units.
Mechanical - HVAC
Individual split unit (indoor-outdoor unit)
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SECOND ALTERNATIVE (SEMICENTRAL SYSTEM).
This system composed from central station for each block, and provide cooled air to each room of the block by a terminal unit .
-there are one central unit feed the block by required fresh air treated
a central fan to exhaust the air from the each toilet.
-heating could be attained by reverse acting of the system in addition to electric heaters.
The proposed system to fit that alternative is VRV system.
The VRV System comprises of :
1-Outdoor air cooled condensing units
2-Indoor units
3-Simple refrigerant copper piping
4-Power and control cables and
5-Remote and centralized controllers for operating the system
-Outdoor air cooled condensing units are easily located on roof tops of the building. They can also be located on each floor, in case of a high rise buildings.
-There is therefore no need for a separate machine or equipment room as is the case with Chiller based system.
Variety of VRV Indoor units are available to suit the requirements at individual locations in a premise and to meet the clients' special needs. Floor mounted, wall mounted, ceiling suspended, ceiling cassette
as well as ceiling built-in type models are available in various cooling capacities.
-very complicated system need to well trained technicians
Mechanical - HVAC
VRV system including (indoor-outdoor unit)
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THIRD ALTERNATIVE (CENTRAL SYSTEM).
This system composed of main central station for generation the chilled and hot water for whole
buildings through an insulated piping network which will be connected to air distribution
equipments inside each room.
-the generated chilled water is circulated to the chilled water network through two set of pumps
installed in series, first one is primary pumps which circulate the chilled water inside the chiller
plant and second one is secondary pumps which deliver and circulate chilled water in the different
buildings.
-and a central feed by fresh air and central fan to exhaust air from toilets.
-water cooled chillers.
-Tow chillers selected (water cooled chiller 1x330T.R+1 standby) are proposed to offset the
Water cooled chiller
calculated load.
-chilled water circulating pumps:
1-primary pumps(1 working+1 standby)
2-secondary pumps(1 working+1 standby)
- A preliminary selection for cooling tower have been made and the flowing in fig are the
dimensions of cooling tower area.
Mechanical - HVAC
FAN COIL UNIT
Cooling tower
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COMPARISON BETWEEN SYSTEMS.
Comparison Elements:
1) Initial Cost:
It is the cost of construction of the system until reach of regular operation.
2) Maintenance and Operation Cost:
It is the cost of system operation includes the material, power consumption cost and the labors salaries and any spare parts expenses.
3) Effect on Architect:
It is the influence raised by use of the system on the shape, faced and internal spaces utilization and special requirements needed by machines.
4) Effects on Structure:
It is the impact on the structure be weight of the machines and equipment and the effect of opening & provisions on the structure.
5) Effect On Environment:
Includes the heat emission, humidity, noise vibration and chemicals propagation.
6) Estimated Operation Life:
It is the life of the system from start up till become not able to form continuous operation.
7) Effect On Utilities & Others:
It is the system effect due to the nature of demand of the power, drainage and connection to other equipments located for serving it or part of its equipment.
Mechanical - HVAC
8) Flexibility During Construction:
It is the measure by which that the system facilitates partial and quick construction plans.
9) Development Capability:
It is ability of the system to be connected with other systems and complying with addition of other facilities in future.
10) Operation Facilities:
It is the measure of how the system is operating and treats for trouble shooting during operation.
11) Coordination Needs:
Contain the needs for engineering activity to be needed to assure proper installation and how much it would be essential.
12) Quality of Inside Air Conditions:
It is the measure of indoor air quality been produced by the system.
13)Time For Delivery:
It is the factor that shows the system expected time delivery to cope with time program for the project construction.
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Order Of The Comparison Element
The comparison element shall be arranged from our side as a mechanical engineer in the following form:
The elements given points
1. Quality of inside air conditions. 20
2. Effect on architect and structure 18
3. Power consumption . 16
4. Effect on environment. 15
5. Estimated operation life. 12
6. Initial cost. 11
7. Maintenance and operation cost. 11
8. Flexibility during of construction. 10
9. Time for delivery. 10
10. Operation facilities. 9
11. Development capability. 8
12. Effect on utilities and others. 6
Mechanical - HVAC
13. Coordination needs. 4
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INDIVIDUAL SYTEM VRV SYSTEM CENTRAL SYSTEM
POINTS ITEM EVALUATUIN POINT ITEM EVALUATUIN PIONT ITEM EVALUATUIN
QUALITY OF INSIDE AIR CONDITIONS 20 LOW 10 HIGH 20 HIGH 20
EFFECT ON ARCHETICT AND STRUCTURE 18 LOW 14 LOW 14 HIGH 10
POWER CONSUMPTION 16 HIGH 6 LOW 10 MODERATE 9
EFFECT ON ENVIRONMENT 15 HOT AIR / NOISE 5 HOT AIR 10 HUMID AIR 13
ESTIMATED OPERATION LIFE 12 7-10 YEARS 5 13-17 YEARS 8 18-20 YEARS 11
INITIAL COST 11 LOW 10 MEDIUM 7 HIGH 5
MAINTENANCE AND OPERATION COST 11 2% OF INITIAL COST 10 3% OF INITIAL COST 8 5% OF INITIAL COST 6
FLEXIBILITY DURING CONSTRUCTION 10 HIGH PER ROOM 9 LIMITED 7 LIMITED 7
TIME FOR DELIVERY 10 FAST 9 LONG 8 LONG 7
OPERATION FACILITIES 9 EASY 8 SEMI-COMPLECATED 7 COMPLECATED 6
DEVELPOMENT CAPABILITY 8 LOW 4 LIMITED 6 HIGH 7
SINGLE PHASE / 3PHASE /
EFFECT ON UTILITIES AND OTHERS 6 UNBALANCED 3 3PHASE / BALANCED 6 BALANCED 6
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COORDINATION NEEDS 4 LOW 4 MEDIUM 3 MEDIUM 3
150 97 114 110
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COST & CONSUMPTION CAOMPARISON
COST (LE) POWER CONSUMPTION (KW) KWH (1year)
SPIT UNIT 192,500 52.5 1,379,700
VRV 442,500 39.5 1,038,060
Mechanical - HVAC
CENTRAL 505,500 49 1,287,720
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