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

Created on: 6 Aug 2020 11:45
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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
L
lesmue79
16 Nov 2020 19:23
I am currently working on the hydraulic/thermal balancing access and trying to minimize short cycling because it simply isn’t cold enough yet to push the system to its limits. And yes, we do have controlled mechanical ventilation, although not from Vaillant.

Heating control: left total heating efficiency 5.5; right auto 19.5°C (67°F).
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T_im_Norden
16 Nov 2020 20:20
Didn't you have a mechanical ventilation system with heat recovery? Because ventilation loss is fully included there.
T
T_im_Norden
16 Nov 2020 20:21
17x2 pipe is better than 16x2.
Tolentino16 Nov 2020 20:26
I understood that as well. But better in relation to what? Do I then need less airflow? Less supply temperature? Less piping?
OWLer16 Nov 2020 20:47
T_im_Norden schrieb:

Didn’t you have a mechanical ventilation system with heat recovery? Because ventilation loss is fully included there.
If you meant me, then yes. I have no idea what the energy consultant calculated or what the heating engineer used from those calculations as a basis for my system design.

I don’t really care, I just want him to agree to the small heat pump now. 🙂 Let’s see what Vaillant suggests for my needs. As long as it stays with the Arotherm plus, it can only be the 75 model, due to eligibility for subsidies. My heating engineer is also not very keen on installing split units, since he wants to switch to R290 refrigerant in the future.
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T_im_Norden
17 Nov 2020 06:34
A larger pipe diameter mainly means less pressure loss, so the pump has to work less.
Both 16mm (0.63 inches) or 17mm (0.67 inches) can be suitable; it also depends on the calculation.