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
N
netuser
8 Nov 2021 11:39
Alessandro schrieb:

I’m missing room labels, heat demand per room, over/under coverage, design temperatures, heating circuit lengths, temperature difference, etc.

Attached is a new overview for one of the rooms. The heating circuit length would be 106 m (348 feet), unfortunately installed with a spacing of 15 cm (6 inches).
However, I still can’t determine the over/under coverage from this, or perhaps different terms are being used!?

Technical table with room data: geometry, volume, temperatures, air exchange, losses.
A
Alessandro
8 Nov 2021 12:14
this is for the ventilation...............
H
Hausbau 55
8 Nov 2021 15:15
Alessandro schrieb:

this is for the ventilation...............
How do you come to that conclusion? This is the heating load calculation for a room, which is probably next to the bathroom. However, this calculation is only a small part of the overall heating load calculation for the entire house.
A
Alessandro
8 Nov 2021 15:27
Well then, your heating technician should set everything according to these values.
B
Benutzer200
8 Nov 2021 15:43
netuser schrieb:

I still can’t determine an over- or under-coverage from this, or are different terms being used?!

You have posted a heating load calculation. Simply put, it means a certain amount of heat is required. Depending on the system design, you can achieve this with a 15cm (6 inches) pipe spacing and a 45-degree Celsius (113°F) supply temperature, or with a 5cm (2 inches) pipe spacing and a 28-degree Celsius (82°F) supply temperature. Or it may not fit, resulting in over- or under-coverage.

As a summary, it should look like this or something similar:


Excel spreadsheet with ground floor rooms (hallway, kitchen, WC, bathroom, bedroom) and numerical values.
N
netuser
8 Nov 2021 16:37
Benutzer200 schrieb:

You posted a heat load calculation. Simply put, it means that a certain amount of heat is required. Depending on the heating system layout, you can achieve this with a 15cm (6 inches) pipe spacing and 45-degree flow temperature or with a 5cm (2 inches) pipe spacing and 28-degree flow temperature. Alternatively, it might not fit, resulting in over- or under-delivery of heat.

In summary, it should look something like this:

Thank you!
I understood the "functional principle" and the connections well enough to follow your overview accordingly.
My only issue was that when I asked for the heat load calculation, I was only given the per-room calculations shown above, and there was no information about pipe spacing or over- or under-delivery rates. That confused me again, and I thought either I’m simply not able to correctly interpret all the technical abbreviations and units, or there must be another overview with the relevant information 🙂