ᐅ Underfloor Heating Heat Load Calculation – Explained Simply
Created on: 3 Dec 2020 13:36
H
Hamburger2020
Good day,
I have read many posts on this topic and have so far understood that room-by-room control (RBC) is no longer necessary nowadays, as it reduces the efficiency of the heat pump.
We have a ground-source heat pump with underfloor heating in all rooms.
The goal is to perform a room-specific heating load calculation so that the temperature is properly set once and never adjusted again.
Our general contractor (GC) now argued that while this is basically correct, once people reach their 60s or older and develop different habits regarding room temperatures, it is not so easy to adjust. Therefore, their suggestion is not to optimize for the highest efficiency right now but to maintain some flexibility through RBC.
I think this argument should not be underestimated. However, I suspect that with the "modern" method of a maximally efficient heating system, this might also be possible.
How would you respond to the GC on this?
Thank you very much and best regards
I have read many posts on this topic and have so far understood that room-by-room control (RBC) is no longer necessary nowadays, as it reduces the efficiency of the heat pump.
We have a ground-source heat pump with underfloor heating in all rooms.
The goal is to perform a room-specific heating load calculation so that the temperature is properly set once and never adjusted again.
Our general contractor (GC) now argued that while this is basically correct, once people reach their 60s or older and develop different habits regarding room temperatures, it is not so easy to adjust. Therefore, their suggestion is not to optimize for the highest efficiency right now but to maintain some flexibility through RBC.
I think this argument should not be underestimated. However, I suspect that with the "modern" method of a maximally efficient heating system, this might also be possible.
How would you respond to the GC on this?
Thank you very much and best regards
T
T_im_Norden3 Dec 2020 17:00You need a room-by-room calculation to determine how much heat is required to reach your desired temperature in each space. Since this is done for all rooms, you will also know the total heating demand for the entire house.
You do this for every room to prevent some rooms from being heated by others.
Under normal circumstances, the temperature differences you can achieve between individual rooms are only a few degrees.
If a room receives too little heat input, the warmth from other rooms will flow there because heat always moves toward the cooler area. Usually, the heat that arrives is not enough to reach the desired temperature. However, this heat is then missing in the rooms giving it up, since their required heat input is no longer provided, making these rooms cooler than desired. As a result, you will have to increase the supply temperature in order to provide more heat.
You do this for every room to prevent some rooms from being heated by others.
Under normal circumstances, the temperature differences you can achieve between individual rooms are only a few degrees.
If a room receives too little heat input, the warmth from other rooms will flow there because heat always moves toward the cooler area. Usually, the heat that arrives is not enough to reach the desired temperature. However, this heat is then missing in the rooms giving it up, since their required heat input is no longer provided, making these rooms cooler than desired. As a result, you will have to increase the supply temperature in order to provide more heat.
H
Hamburger20207 Dec 2020 15:16Thank you for the additional feedback! I am gradually starting to understand the importance of room-specific heating load calculations.
Our general contractor (GC) has planned either the Stiebel Eltron WPC-10 (included) or, for an extra charge, the Stiebel Eltron WPE-I-12 H 230 Premium ground-source heat pump.
They seem rather large for a KfW 40 house. However, thanks to the basement and high ceilings, we have a relatively large gross volume of 1283 m³ (45,296 ft³). Still, I often read that KfW 40 houses typically use 6 kW or at most 8 kW systems. Would it generally be a disadvantage, apart from the purchase cost, to choose a larger heating system (the WPC 10 is already included in the price)? According to the datasheets, both heat pumps seem to operate efficiently even with low kWh consumption.
The problem is that for the BAFA application, we now need to specify the exact model of the heat pump. The initial electrical work is scheduled to start soon, which, thanks to KNX, is also partially eligible for funding, so submitting the application is becoming urgent.
Our general contractor (GC) has planned either the Stiebel Eltron WPC-10 (included) or, for an extra charge, the Stiebel Eltron WPE-I-12 H 230 Premium ground-source heat pump.
They seem rather large for a KfW 40 house. However, thanks to the basement and high ceilings, we have a relatively large gross volume of 1283 m³ (45,296 ft³). Still, I often read that KfW 40 houses typically use 6 kW or at most 8 kW systems. Would it generally be a disadvantage, apart from the purchase cost, to choose a larger heating system (the WPC 10 is already included in the price)? According to the datasheets, both heat pumps seem to operate efficiently even with low kWh consumption.
The problem is that for the BAFA application, we now need to specify the exact model of the heat pump. The initial electrical work is scheduled to start soon, which, thanks to KNX, is also partially eligible for funding, so submitting the application is becoming urgent.
T
T_im_Norden7 Dec 2020 17:19If you have KfW 40, the system is way too large.
The WPC10 isn’t even modulating.
And the WPE I 12 has an even higher maximum output.
I’m afraid your general contractor isn’t really experienced with heat pumps.
Have you received a room-by-room heating load calculation yet?
For KfW 40, I would expect something around 5-6 kW.
Therefore, the 06 or even the 04 would probably be sufficient.
The WPC10 isn’t even modulating.
And the WPE I 12 has an even higher maximum output.
I’m afraid your general contractor isn’t really experienced with heat pumps.
Have you received a room-by-room heating load calculation yet?
For KfW 40, I would expect something around 5-6 kW.
Therefore, the 06 or even the 04 would probably be sufficient.
H
Hamburger20207 Dec 2020 18:36T_im_Norden schrieb:
If you have KfW 40 standard, the system is much too large.
The WPC10 isn’t even modulating.
And the WPE I 12 has an even higher maximum output.
I’m afraid your general contractor isn’t very experienced with heat pumps.
Have you received a room-by-room heating load calculation yet?
For KfW 40, I would expect something around 5-6 kW.
Therefore, probably the 06 or even the 04 would be sufficient. I suspected that 😕
Does this also apply to our larger gross room volume?
Since the heat pump is included in the price anyway, would it be a disadvantage for us if the heat pump is too large, or is it more of a problem with the general contractor, since it is basically included in the price?
H
Hamburger20207 Dec 2020 18:48Oh yes, and we have not yet received a room-by-room heating load calculation.
But what would we do with it once we have it? I wouldn’t be able to evaluate it, or is it more about us indicating the desired temperature for each room?
But what would we do with it once we have it? I wouldn’t be able to evaluate it, or is it more about us indicating the desired temperature for each room?
T
T_im_Norden7 Dec 2020 18:49Without these, you can’t plan what capacity your heating system needs.
- I would definitely not choose a heat pump that doesn’t modulate.
- The lower the minimum output of the heat pump, the better.
- I would definitely not choose a heat pump that doesn’t modulate.
- The lower the minimum output of the heat pump, the better.
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