Can DEAP be trusted to size a heating system?

Chimpster

A major part of my business is doing heat loss reports on houses where the occupants were cold over the winter. We use a mix of thermal imaging, air tightness testing and plain old heat loss calculations to report on the various reasons why the house is cold.

We do all our heat loss calculations manually based on proven engineering formulas. My question is this, the DEAP software appears to be pretty accurate when it comes to these heat loss calculations, I am wondering can the DEAP software be used to calculate and sign off on sizing of heating systems accuratly? Have SEI any guidance on this?

sinnerboy

Yes but contradictory as usual . Section A3.5 of the manual refers


A3.5 Estimating the required boiler size While DEAP should not to be used to size the heating system (this is usually up to the system designer or heating system supplier/installer) the following method can be used to estimate the required heat system power output. Note that sizing the heating system is not the responsibility of SEI and is entirely between the client and the assessor or system designer. Maximum recommended dwelling heating load: Expressed in kW. For dwelling heat load, the maximum space heat demand is calculated by multiplying the heat loss coefficient by the desired maximum temperature differential (deltaT usually -1 to 21 degrees C). The heat loss coefficient is the heat loss in W/K of the dwelling when accounting for fabric and ventilation losses. The heat loss coefficient is called the "Total Heat Loss" in the DEAP. 2 to 4 kW should be added to the space heating demand for water heating depending on occupancy or floor area. The total of space and water heating requirement should then be multiplied by 1.1 to account for distribution losses giving the following maximum recommended dwelling heating load: Dwelling space and water heat requirement (W) = dwelling space heat loss + dwelling DHW requirement = Total Heat Loss*22 *1.1 + 4000*1.1

d'Oracle

I would strongly advise against using DEAP for sizing or heating design.

Some defaults and constants in DEAP are unreliable, and it was not designed with a view to heating system design.

sydthebeat

d'Oracle wrote: »

I would strongly advise against using DEAP for sizing or heating design.

Some defaults and constants in DEAP are unreliable, and it was not designed with a view to heating system design.

i would agree....

however, when compared to other 'rules of thumb' applied when sizing boilers.... its my opinion that the DEAP method as per SBs post above is actually more accurate than most.

sinnerboy

d'Oracle wrote: »

I would strongly advise against using DEAP for sizing or heating design.

Some defaults and constants in DEAP are unreliable, and it was not designed with a view to heating system design.

What would you do lieu ?

d'Oracle

sinnerboy wrote: »

What would you do lieu ?

I probably wouldn't.....:D
I suppose it could be of some use, but the user behavior assumptions, or in some ways lack of, would put me off it.

Id probably stick to the formulae for signing off purposes.

sydthebeat

d'Oracle wrote: »

I probably wouldn't.....:D
I suppose it could be of some use, but the user behavior assumptions, or in some ways lack of, would put me off it.

Id probably stick to the formulae for signing off purposes.

mind me asking what formula this is??

its not the old (ft3 x 5 + 20%) is it??

homewardbound11

Sorry to bring up an old post and i had already started a new thread so i apologise.
I have done deap calcs on the house and now have my plumber awaiting to start but he is lost as to what to apply. (4 or 3.5 or even 5 to the standard calcs).
I have e-mailed my BER assessor and I had hoped to get a reply but i still have not got one.
How do you spec the btu's for each room/radiator to a low energy house A2 or even any low energy house,
Can a reasonable assessment be made from the heat loss calculations .