ᐅ Sizing of Air-to-Water Heat Pumps for New Construction

Created on: 6 Aug 2020 11:45
P
Pixelsurium
Hello everyone,

we are planning a prefabricated house using timber frame construction. It will have 180 sqm (1,937 sq ft) of living space with underfloor heating, and about 230 sqm (2,475 sq ft) of usable area.
So far, the offer included an air-to-water heat pump from Daikin (Altherma 3R, formerly Rotex HPSU compact Ultra).

Now it seems that this unit might not have enough capacity (?) and as an alternative (additional cost around 4,000) we have been offered a "Wolf heat pump CHC Monoblock 10/300-35".

The Daikin is available in the 4-9 kW version—would that really be insufficient for this size? And what do you think about this offer?

I have the energy-saving regulation heat protection certification and a renewable energy heat law document available, if any information from those is needed.

Thank you very much!
Best regards
T
T_im_Norden
14 Oct 2020 11:19
That shouldn’t have anything to do with facing brick.
If you have facing brick, you’ve likely planned a cavity wall with insulation placed between the facing brick and the interior wall.
This achieves the same insulation values as external thermal insulation composite systems (ETICS).
Tolentino14 Oct 2020 11:31
What kind of walls do you have?
OWLer14 Oct 2020 11:53
No idea. Ytong blocks, insulation, facing bricks; inside, calcium silicate bricks. The energy consultant really had to put some effort into addressing the thermal bridges to meet the transmission heat loss requirements for KFW55. We might have fewer issues with different windows or more/different insulation, but this is how it is now, and we are running a flow temperature of 33°C (91°F).

Heating load is 5.9 kW.

Now the focus has to be on proper planning of the heating circuits.
D
Daniel-Sp
14 Oct 2020 13:28
Which heat pump was finally chosen?
N
nordanney
14 Oct 2020 14:47
OWLer schrieb:

in KFW55
So it really has to be 33 degrees supply temperature? Unbelievable. I would invest some money and have it calculated externally.
T
T_im_Norden
14 Oct 2020 15:17
Who performed the calculation, the heating engineer or an external party?

Is it the room-by-room heat load calculation or the calculation for the underfloor heating?

If it is for underfloor heating, what pipe diameter was used in the calculation, what spacing, and what are the lengths of the loops?
How many heating circuits?