ᐅ Lowering the Supply Temperature in Underfloor Heating Systems More Complex Than Expected?
Created on: 9 Mar 2023 22:07
J
JohnnyEH
Hello everyone!
We are currently discussing the supply temperature for the underfloor heating system with our prefab house provider.
The house is a timber frame panel construction and meets the KFW40 standard.
According to the construction description, the provider sets the supply temperature of the underfloor heating to 35°C (95°F). We mentioned that we consider this outdated for a new build and would prefer a supply temperature of around 30°C (86°F). We were then told that with a supply temperature of 30°C (86°F), a larger heat pump and a completely different heating system design would be required, and the additional costs could quickly reach five figures. Such extra costs obviously would not make financial sense.
Until now, I thought the supply temperature was primarily determined by the pipe spacing and would be lower if the pipe spacing was reduced.
Why could a lower supply temperature lead to a larger heat pump? What am I missing?
I should add that the heating load calculation and the exact determination of the heat pump have yet to be done. In any case, a Vaillant Arotherm Plus will be used.
Additionally, a question about the floor covering.
We know that tiles are optimal for underfloor heating but vinyl is almost equivalent. We will also have an active underfloor cooling system installed (via the air-to-water heat pump). Does either floor covering—tiles or vinyl—have advantages for cooling? Or would laminate flooring actually be the best option for cooling?
We are currently discussing the supply temperature for the underfloor heating system with our prefab house provider.
The house is a timber frame panel construction and meets the KFW40 standard.
According to the construction description, the provider sets the supply temperature of the underfloor heating to 35°C (95°F). We mentioned that we consider this outdated for a new build and would prefer a supply temperature of around 30°C (86°F). We were then told that with a supply temperature of 30°C (86°F), a larger heat pump and a completely different heating system design would be required, and the additional costs could quickly reach five figures. Such extra costs obviously would not make financial sense.
Until now, I thought the supply temperature was primarily determined by the pipe spacing and would be lower if the pipe spacing was reduced.
Why could a lower supply temperature lead to a larger heat pump? What am I missing?
I should add that the heating load calculation and the exact determination of the heat pump have yet to be done. In any case, a Vaillant Arotherm Plus will be used.
Additionally, a question about the floor covering.
We know that tiles are optimal for underfloor heating but vinyl is almost equivalent. We will also have an active underfloor cooling system installed (via the air-to-water heat pump). Does either floor covering—tiles or vinyl—have advantages for cooling? Or would laminate flooring actually be the best option for cooling?
Confusing menu navigation and operation. Pointless components. There are no truly useful control options available. Apparently, there is a wide variation in component quality (possibly indicating generally below-average quality). The service is relatively expensive but not very knowledgeable.
Too much bureaucracy; the right hand doesn’t know what the left hand is doing.
The devices are also overpriced compared to others.
If the unit breaks down after the warranty or if I can cancel the contract due to too many repairs within the warranty period, I will do like Karsten and get a Panasonic or LG and install it myself.
Too much bureaucracy; the right hand doesn’t know what the left hand is doing.
The devices are also overpriced compared to others.
If the unit breaks down after the warranty or if I can cancel the contract due to too many repairs within the warranty period, I will do like Karsten and get a Panasonic or LG and install it myself.
H
Hausbau55EE10 Mar 2023 18:13The approach to lowering the supply temperature in a NAT system is reasonable and understandable. However, you should consider whether 30°C (86°F) has to be your exact target. Maybe 32°C (90°F) would also work. When designing underfloor heating, it is common to use a standard room temperature of 20°C (68°F) and 24°C (75°F) for bathrooms. You might want to reconsider that 24°C (75°F). Using 23°C (73°F) or 22°C (72°F) can make a significant difference in these calculations. You also need to consider the location of the room within the whole house. A bathroom with two exterior walls affects the heating load differently than rooms with only one exterior wall and three interior walls at 20°C (68°F) or 21°C (70°F). Due to your desire to reduce the supply temperature, the pipe spacing will have to be closer. If you use 10cm (4 inches) spacing everywhere and 5cm (2 inches) in the bathroom, you will be approaching a very low supply temperature. In my opinion, with the Arotherm Plus, it will remain at 55/6 or even 35/6.
In any case, it is important to closely monitor the underfloor heating design and heat pump selection. This will help you avoid later frustrations with the manufacturer.
In any case, it is important to closely monitor the underfloor heating design and heat pump selection. This will help you avoid later frustrations with the manufacturer.
Tolentino schrieb:
Relatively expensive service, but not very knowledgeable.Isn't the service covered under warranty? In which cases do you have to pay for the service?
Regarding the control system, there should be some configuration options available via Modbus or EEBUS. What would you like to control on the heat pump that is currently not possible?
Hausbau55EE schrieb:
You should reconsider that 24°C (75°F). Using 23 or 22°C (73 or 72°F) makes a big difference for this calculation. Then you need to consider the location of this room within the entire house. A bathroom with two exterior walls affects the heating load calculation differently than rooms with one exterior wall and three interior walls at 20 or 21°C (68 or 70°F). Because you want to reduce the supply temperature, the pipe spacing will be smaller. If you choose 10cm (4 inches) everywhere and 5cm (2 inches) in the bathroom, you will be close to a very low supply temperature. In my opinion, it will remain at the Arotherm Plus 55/6 or even 35/6.
In any case, it is good to closely monitor the design of the underfloor heating and the choice of the heat pump type so that you don’t end up frustrated with the manufacturer later. What raises some doubts for us is that the building specification states that the system is generally designed for 35°C (95°F). Our bathroom has two exterior walls. We will definitely ask whether lowering the room temperature in the bathroom could be a way to reduce the supply temperature. In any case, I take away that a supply temperature of 35°C (95°F) wouldn’t be the end of the world 🙂.
H
Hausbau55EE10 Mar 2023 20:13If possible, have the heating load calculation done for your project (room by room). This way, you can consider your options more effectively. Most importantly, you can understand why the builder is asking for a five-figure surcharge 😉.
In your bathroom and two other wet rooms, it might be sufficient to design the system for 32°C (90°F) with 5 cm (2 inches) pipe spacing (please also install under the bathtub and in the shower a floor heating system). A wall heating system can also help.
The proper design of the underfloor heating system is absolutely essential.
In your bathroom and two other wet rooms, it might be sufficient to design the system for 32°C (90°F) with 5 cm (2 inches) pipe spacing (please also install under the bathtub and in the shower a floor heating system). A wall heating system can also help.
The proper design of the underfloor heating system is absolutely essential.
R
RotorMotor10 Mar 2023 20:21JohnnyEH schrieb:
Does the service not fall under warranty coverage? In which cases do you have to pay for the service?
Regarding the control system, there should be several adjustment options via Modbus or EEBUS. What would you like to control on the heat pump that currently isn’t possible? "Service" is provided through a maintenance contract.
The energy integral thing is more of a hassle.
The system cycles a lot.
JohnnyEH schrieb:
Could you ask if lowering the room temperature in the bathroom would be a way to reduce the supply temperature? In my opinion, that’s a very bad idea.
It’s just a gimmick that doesn’t make the house or bathroom any warmer.
It doesn’t improve efficiency either.
Hausbau55EE schrieb:
(please also install underfloor heating under the bathtub and in the shower). If the bathtub is in a polystyrene (styrofoam) enclosure, underfloor heating underneath is more of a disadvantage, since the heating loops reduce the flow without adding any heat.
Hausbau55EE schrieb:
A wall heating system can also help. That makes a significant difference.
The warranty doesn’t last forever. After that, you’ll have to pay at least 400 EUR (about 430 USD) for a replacement part.
In my case, the issue was commissioning without consulting the installer first (technically debatable, but since I still needed a document from him for the BAFA subsidy, and considering the more than 13,000 EUR (about 14,000 USD) funding, I didn’t complain about the 450 EUR (about 490 USD) cost). I had destroyed the safety temperature limiter because the hot water valve was closed, but I had activated hot water production. The heat couldn’t dissipate and then it went brzzffft...
The technician actually told me I can turn on the hot water anytime. There are two valves—he showed me one, but not the other...
So, I’m a bit behind because I have an incorrect calculation of yield and efficiency figures and haven’t really gotten into it properly yet. But seeing what the other members in the neighboring thread do with all the workarounds across so many pages, I imagine there should be more straightforward options.
For example, via the eBus, you can do simple things like, if there’s excess photovoltaic power, heat up my hot water storage a lot and also warm the screed a bit—though this is very complicated to set up. You actually need programming skills, proper scripting knowledge, not just clicking together some Alexa routines.
In my case, the issue was commissioning without consulting the installer first (technically debatable, but since I still needed a document from him for the BAFA subsidy, and considering the more than 13,000 EUR (about 14,000 USD) funding, I didn’t complain about the 450 EUR (about 490 USD) cost). I had destroyed the safety temperature limiter because the hot water valve was closed, but I had activated hot water production. The heat couldn’t dissipate and then it went brzzffft...
The technician actually told me I can turn on the hot water anytime. There are two valves—he showed me one, but not the other...
So, I’m a bit behind because I have an incorrect calculation of yield and efficiency figures and haven’t really gotten into it properly yet. But seeing what the other members in the neighboring thread do with all the workarounds across so many pages, I imagine there should be more straightforward options.
For example, via the eBus, you can do simple things like, if there’s excess photovoltaic power, heat up my hot water storage a lot and also warm the screed a bit—though this is very complicated to set up. You actually need programming skills, proper scripting knowledge, not just clicking together some Alexa routines.
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