Non-Default Flow Temperatures in DEAP This will be the 3rd in a series of documentary evidence webinars for registered BER assessors. This webinar for registered BER assessors and will cover the following: 1. The effect of Flow Temperature on heat pump operation 2. The Designer/Installer sign-off workbook 3. BER Requirements where a non-default flow temperature is used.

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DEAP Heat Pump Webinar 3
Non-Default Design Flow Temperature
September 14th, 2021
David Bevan

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Overview
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Design Flow Temperature
Documentation overview
Designer/Installer sign-off sheet
Heating Design sheet
Radiator Specifications & Output Conversion
Assessor Checks

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1 – Design Flow Temperature
Why is the flow temperature important to the heating design?
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Design Flow Temperature
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• The Flow Temperature is the temperature of the heated water as it leaves the heat pump and
enters the distribution system
• Why do we care about the flow temperature?
– The efficiency of the heat pump depends on the difference in temperature between source
and the sink - the smaller the temperature difference, the more efficient the system.
• Example: An Air-to-Water heat pump system:
– The efficiency depends on the temperature difference between the external air and the
heated water leaving the heat pump.
• You can’t change the temperature of the external air, but you can change the temperature of the
water leaving the heat pump

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Design Flow Temperature
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• Therefore, using a low flow temperature will increase the system efficiency.
– This is why underfloor heating, typically operating at a flow temperature of 35°C, is so well-
suited to heat pump systems
• However, it is important to ensure that the distribution system in the dwelling is capable of
delivering sufficient heat to the dwelling at the lower flow temperature.
– This is a particular concern in retrofit scenarios, where, e.g. a heat pump is installed in place
of a gas/oil boiler.

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Heat Emitters
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Underfloor Heating

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Heat Emitters
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Convector Radiators
Aluminium Radiators
Fan Coil systems

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Design Flow Temperature - Defaults
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Emitter Description Default Design Flow
Temperature
Radiators Small surface area, high water temperature
required to deliver heat
55°C
Fan Coil Radiators Small surface area but the fan leads to more
effective delivery of heat so a reduced flow
temperature is possible
45°C
Underfloor Very large surface area allowing a lower flow
temperature to be effective in delivering heat
35°C

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Non-default Design Flow Temperature
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• A non-default Flow Temperature can be used in a BER where it is supported by all required
evidence
• Why is there a requirement for supporting evidence?
– A lower flow temperature will lead to an improvement in efficiency so, as per the DEAP
methodology, this requires supporting evidence.
– The details of the heating system design are required to show that the system will operate
correctly using a lower flow temperature.

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2 – Documentation Overview
The documentation required to support the use of a non-default flow
temperature in a BER
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Documentation for NDFT
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• A non-default Flow Temperature can be used in a BER where it is supported by all required
evidence – as supplied by the Designer/Installer of the heating system.
• Documentation List
– Designer/installer sign-off sheet;
• First page of the Designer/Installer excel file
• Ideally, it should be provided for all heat pump installations as it has details on Daily
Operation Hours, etc.
• May not be available for existing installations where defaults will have to be used -
though non-default Ecodesign/test efficiency data can still be used in this case
– Heating design sheet;
• Second page of the Designer/Installer excel file
• Required where a non-default flow temperature is used.

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Documentation for NDFT
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– Radiator specifications
• Manufacturer’s document providing details of radiator heat output, including conversion
factors where necessary
• Required where a non-default flow temperature is used.
– Radiator Output Conversion sheet
• Third page of the Designer/Installer excel file
• Required where the radiator outputs specified in the Heating Design Sheet are not taken
directly from the manufacturer’s brochure.

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3 – Designer/Installer Sign-off
The first page of the Design/Installer Sign-off workbook
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Designer/Installer Sign-off
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• General Information
– Address must clearly identify the dwelling
• Purpose of Installation
– Is the system providing space and/or water heating?
• Heat Pump Selection
– Manufacturer,
– Model,
– Type of heat pump (up to 3 heat pumps)
– No. of hours per day the heat pump is designed to run
– Temperature of the water leaving the individual heat pump for,
• Space heating
• Water heating

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Designer/Installer Sign-off
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• Heat Emitter Design
– Emitters present
• Radiators, fan coil units, underfloor, warm air
– Temperature of the water leaving the heat pump system for space heating
• Hot Water System
– Maximum flow temperature of water
– Type of DHW store
– Manufacturer, model of DHW store
– Immersion present
• Confirmation
– Name, Company, Email, Job Title, Signature, Date

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Designer/Installer Sign-off
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• This sheet should be completed by the Designer/Installer in either hardcopy or softcopy format, and signed
using one of the following methods:
– Hardcopy signed by the Designer/Installer, or,
– Softcopy format with an electronic (e.g. scanned) signature from the Designer/Installer, or
– Softcopy format accompanied by an email from the designer/installer confirming that the data with the
sign off sheet is correct.
• If the signed designer/installer sign-off sheet is not available, default values must be used for installation data,
namely:
– Default flow temperature for the distribution system present, as per Table 28 of BER Guidance Doc;
– No of Hours per Day Heat Pump has been designed to run = 8 hours;
• Ecodesign/test data relating to the heat pump may still be used in this situation to calculate a non-default
efficiency.

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4 – Heating Design Sheet
The second page of the Design/Installer Sign-off workbook
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Heating Design Sheet - Introduction
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• Where a non-default flow temperature is used, the Designer/Installer must fill out the Heating
Design sheet.
• The information provided here should show that,
– the heat emitters are capable of providing sufficient heat to bring the house to the required
temperature
– the heat pump is appropriately sized for the dwelling
• The heat output for a given emitter is based on the design temperature difference, ΔTdesign for
the room:
∆𝑇𝑑𝑒𝑠𝑖𝑔𝑛=
Flow Temp+Return Temp
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− Room Temp

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Heating Design Sheet
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1. Address copied over from the Designer/Installer page
2. Design Flow Temperature copied over from the Designer/Installer page
3. Return Temperature – the temperature of the water as it returns to the heat pump
– Specified by the Designer/Installer
– Used to calculate the average temperature of the water in the distribution system

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Example – Room heated by a Radiator
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• Room Heat Loss – It is the responsibility of the designer/installer of the system to carry out these
calculations in accordance with the following:
– S.R. 50-1:2021 Building services - Code of Practice - Part 1: Water based heating systems in dwellings;
– S.R. 50-4:2021 Building services - Part 4: Heat pump systems in dwellings;

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Example – Room heated by a Radiator
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• Radiator Details –
– Manufacturer, Model / size
– Design Room Temperature - taken from SR 50 documents
– ΔTdesign – calculated by the excel workbook
– Single heat emitter output at ΔTdesign – from radiator documentation – additional calculations may be
required

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Example – Room heated by Underfloor
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• Mostly as per the previous example
• Total Heat Emitters Output – total room output from the u/f emitter

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Example – Room heated by an Air System
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• Mostly as per the previous example
• Total Heat Emitters Output – total room output from the air system
• Supply Air Temperature
– Limited to 35°C
– Calculates the air flow rate needed to provide that level of heating

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Example – Room heated by a Fan Coil system
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• Mostly as per the previous examples
• Total Heat Emitters Output – total room output from the fan coil system

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Completed Heating Design Sheet
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Completed Heating Design Sheet
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• Summary of heat loss details provided
– Total Heat Loss
– Total Heat Output
– TFA used to calculate the HLI of the dwelling
– Heat pump output at design conditions – worksheet will show warning message if the heat
pump is undersized compared to the Total Heat Loss.

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Summary – Data Checked by the Assessor on Heating Design Sheet
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• Dwelling address of the heat pump installation has been provided.
• The design flow temperature and return temperature have been provided.
• For each room in the dwelling that is heated by the heating system, all the required heating
design data has been provided.
• The total heat emitter output (Watts) is greater than the total heat loss (Watts)
– i.e. the heat emitters provide enough energy to heat the house to the required temperature
• The name and contact details of the Designer/Installer have been provided.

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Summary – Data Checked by the Assessor on Heating Design Sheet
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• The HLI stated on the heating design sheet should be within 10% of the HLI calculated in DEAP,
i.e.
0.9 * HLI DEAP < HLI DesignSheet < 1.1 * HLI DEAP
• Where HLI DesignSheet is less than (HLI DEAP * 0.9) there is a risk that the heating system is
undersized.
– In such a case, the default flow temperature must be used.

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Summary – Data Checked by the Assessor on Heating Design Sheet
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• The HLI stated on the heating design sheet should be within 10% of the HLI calculated in DEAP,
i.e.
0.9 * HLI DEAP < HLI DesignSheet < 1.1 * HLI DEAP
• Where HLIDesignSheet is more than 10% larger than HLI DEAP, the BER Assessor must ask the
Designer to confirm in writing that they followed the SR 50-4 standard for heat loss calculations
and sizing.
– If the Designer provides this confirmation then the non-default flow temperature can be used,
as long as all other conditions are met.
– If the Designer does not provide this confirmation, then the default flow temperature must be
used.

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5 – Radiator Specifications &
Radiator Output Conversion
The source of data for the heat output from the radiators
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Radiator Output Conversion sheet
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• The ‘Single heat emitter output at ΔTdesign‘ needs to be supported by evidence – radiator
manufacturer’s brochure

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Radiator Specifications
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• The radiator output data used by the Designer/Installer in Column F of the Heating Design sheet
must be supported by documentation from the manufacturer.
• In many cases, the manufacturer’s brochure may not have the radiator output for each of the ΔT
values used in Column J of the heating design sheet.
• However, the manufacturer is likely to provide a table of Conversion Factors for all ΔT values in
the radiator’s operational temperature range,
• Both will allow the Designer/Installer to convert the stated radiator output at a reference ΔT,
usually for ΔT = 50 °C, to the radiator output at the ΔT values used in the dwelling.
• In cases where the radiator output information is not available from the manufacturer, the
Designer/Installer can follow guidance in SR 50-4.

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Radiator Output Conversion sheet
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• A new sheet in the Designer/Installer excel file, introduced to facilitate a change in guidance
• To be completed by the Designer/Installer in cases where the radiator output at ΔTdesign cannot be
read directly from the brochure (i.e. a conversion factor calculation must be done)
• This sheet has been introduced so as to put the onus for verifying the radiator output onto the
Designer/Installer and to remove the need for Assessors to do these calculations
• The Assessor still has to perform checks to verify that the data in the radiator brochure ties in with the
data entered in this sheet and in the Heating Design sheet

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Radiator Output Conversion sheet
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• ΔTdesign: taken from the Heating Design sheet
• Radiator Make, Model/Code: taken from the Heating Design sheet
• Radiator dimensions: taken from the radiator manufacturer’s brochure
• Heat output (manufacturer): the heat output at a reference temperature (usually ΔT = 50°C),
taken from the radiator manufacturer’s brochure

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Radiator Output Conversion sheet
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• ΔT (manufacturer): the reference temperature (usually ΔT = 50°C), taken from the radiator
manufacturer’s brochure
• Conversion Factor: the heat output at ΔTdesign is calculated by multiplying the heat output at the
reference ΔT by a conversion factor taken from the manufacturer’s brochure. It usually has a
value between 0 and 1.
• Heat Output at ΔTdesign : the heat output from the radiator at the non-default flow temperature.
This will need to be checked against the values used in the Heating Design sheet.

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Radiator Specifications – Assessor Checks
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• The Assessor’s job is to check that the information presented by the Designer/Installer ties
together, i.e.
– The ‘Single Heat Emitter Output at ΔTdesign’ values from Column F of the Heating Design
sheet
are clearly linked to
– The ‘Heat Output at ΔTdesign’ values from Column J of the Radiator Output Conversion sheet
• The Assessor does not have to check the calculations done by the Designer/Installer to convert
from the reference radiator output to the actual radiator output.
• However, the Assessor does have to check that the radiator manufacturer’s document does
contain the information that allowed the Designer/Installer to carry out the calculation

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Radiator Data – Example 1
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• The Designer/Installer has supplied the workbook. The data in column F of Heating Design,
matches the corresponding data in the Radiator Output Conversion sheet:

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Radiator Data – Example 1
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• The Designer/Installer has supplied the radiator manufacturer’s document which states the output
at ΔT = 50°C and provides a table of conversion factors,
• These match the values used in the excel file
• On that basis, the information can be used in DEAP.

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Radiator Data – Example 2
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• The Designer/Installer has again supplied the workbook.
• Here is the Radiator Output Conversion sheet:
• Let’s check the Conversion Factors in the Radiator Manufacturer’s brochure…

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Radiator Data – Example 2
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• This shows the heat output at ΔT = 50°C but it does not give conversion factors used in the
workbook.
• So where did the D/I get the values used in the workbook?
• Assessors should ask the D/I to clarify – defaults from SR 50-4 are acceptable

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Other Scenarios
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Scenario Meet
Requirements?
Assessor Recommended Action
No radiator brochure No. Request the information – if it isn’t provided, use
the default flow temperature
Radiator brochure provided – it has no
technical data
No. Request the information – if it isn’t provided, use
the default flow temperature
Conversion factors in the rad brochure do
not match the values used in the D/I
workbook
No. Ask the D/I to change the workbook – if it isn’t
provided, use the default flow temperature
Heat output at ΔT = 50°C in the brochure
don’t match the value(s) used in the
workbook
No Ask the D/I to change the workbook – if it isn’t
provided, use the default flow temperature
‘Single heat emitter output’ in Heating
Design sheet does not match value
calculated in Rad Output Conversion
sheet
No Ask the D/I to change the workbook – if it isn’t
provided, use the default flow temperature

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6 – Assessor Onsite Checks
On-site verification of information in the Design/Installer Sign-off
workbook
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Assessor Onsite Checks
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• Heat Emitter Type:
– Check that the installed heat emitter in each room matches the heat emitter type specified in the
completed heating design sheet.
• Radiator Size:
– Check that the radiators specified in the heating design sheet match those installed in the dwelling.
– The radiators installed in the dwelling should be within ± 50mm of the size specified in the heating design
sheet.
• The heating design sheet must reflect what is installed in the dwelling.
• If an assessor finds something different in the house, they should request the designer/installer to amend the
documents to reflect the installation in the dwelling.
• If this is not done, the default flow temperature should be used.

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References
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References
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• Section 13.1 of the BER Guidance Document

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Questions?

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End of presentation