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
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
With most general contractors or prefabricated house companies, you usually have little chance of contractually fixing something like this in advance. The sales representatives you deal with at this early stage generally lack the technical expertise regarding building services engineering.
I managed to get my builder to the point where he himself suggested reducing the level of completion so that I could arrange the building services separately.
Regarding the waiver of individual room control, they didn’t even know that according to energy saving regulations, it is allowed to skip this for rooms smaller than 6 meters squared (about 65 square feet). Otherwise, they would have wrapped 10 meters (33 feet) of underfloor heating pipe in my 1.5 meters squared (16 square feet) pantry and installed a separate heating circuit.
I managed to get my builder to the point where he himself suggested reducing the level of completion so that I could arrange the building services separately.
Regarding the waiver of individual room control, they didn’t even know that according to energy saving regulations, it is allowed to skip this for rooms smaller than 6 meters squared (about 65 square feet). Otherwise, they would have wrapped 10 meters (33 feet) of underfloor heating pipe in my 1.5 meters squared (16 square feet) pantry and installed a separate heating circuit.
Joedreck schrieb:
- Room-by-room heat load calculation according to DIN
- 30/27/21 (flow temperature/return temperature/room temperature) or 30/27/23 in the bathroom
- Heating circuit length fixed at 80m (262 feet) per circuit ±10%Now we're getting to the core of the matter. So far, I have only discussed a 30°C (86°F) flow temperature with the general contractor. The heating installer wants to use the standard 35°C (95°F) with a 15cm (6 inches) pipe spacing. When I told him that 30°C (86°F) flow temperature was agreed upon, he immediately referred to 30/22 (flow/return).How exactly are flow and return temperatures related? Does it have something to do with the flow rate and pipe length that allows you to influence this?
D
Daniel-Sp8 Sep 2020 13:06The supply line determines the heating curve. You can consider the return line and thus the temperature difference either as a whole or for each heating circuit individually. The return temperature results from the amount of heat delivered and can therefore be influenced by the flow rate. Other influencing factors include screed/room temperature and the lengths of the heating circuits.
However, modern heat pumps typically operate with a smaller temperature difference than the 8°C (14°F) suggested by your heating engineer.
However, modern heat pumps typically operate with a smaller temperature difference than the 8°C (14°F) suggested by your heating engineer.
T
T_im_Norden8 Sep 2020 13:25This is heating engineer Reflex, suggest 30/26 or 30/28 to him.
Also keep an eye on the heating circuit length as well as the pipe diameter of the connection and the circuits.
Also keep an eye on the heating circuit length as well as the pipe diameter of the connection and the circuits.
Thank you for the feedback.
First, I will call the general contractor again. Then we’ll see how to proceed. I have regularly discussed "room-by-room heating load calculations (DIN 12831)" and a supply temperature of 30°C (86°F) with the general contractor. However, the contract now states that all planning is to be done according to KFW 55 standards. I apparently didn’t pay close enough attention to that.
However, I have documented several contract discussions with him in writing, pointing out the above-mentioned points. His response was that the calculations will of course be done and that a supply temperature of 30°C (86°F) is no problem. He did not contradict this.
Let’s see what he tells me later.
There are various service providers online who also offer these calculations. Does it make sense to commission this independently and then present a counterproposal to the heating installer? I assume the heating installer mainly wants to minimize the amount of piping installed and complete the installation in the shortest possible time, while still complying with energy-saving regulations/KFW 55 requirements, right?
First, I will call the general contractor again. Then we’ll see how to proceed. I have regularly discussed "room-by-room heating load calculations (DIN 12831)" and a supply temperature of 30°C (86°F) with the general contractor. However, the contract now states that all planning is to be done according to KFW 55 standards. I apparently didn’t pay close enough attention to that.
However, I have documented several contract discussions with him in writing, pointing out the above-mentioned points. His response was that the calculations will of course be done and that a supply temperature of 30°C (86°F) is no problem. He did not contradict this.
Let’s see what he tells me later.
There are various service providers online who also offer these calculations. Does it make sense to commission this independently and then present a counterproposal to the heating installer? I assume the heating installer mainly wants to minimize the amount of piping installed and complete the installation in the shortest possible time, while still complying with energy-saving regulations/KFW 55 requirements, right?
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