ᐅ Who should you entrust with the room-by-room heating load calculation?
Created on: 2 Feb 2020 12:23
A
annab377
Hello everyone,
Do heating system installers know that underfloor heating is best sized and planned using a room-by-room heat load calculation?
Is the room-by-room heat load calculation also important for selecting the heat pump (in our case either water-to-water or ground-to-water), or is the "overall heat load calculation" of the entire building according to DIN 12831 sufficient?
If my architect does not offer this, who should I turn to? What should I look for in the phone directory / on the Internet to find a professional who can assist me with this?
From what I have read here in the past months, a room-by-room heat load calculation is very important. A precise calculation can save money because the heat pump selected accordingly will operate more efficiently, allowing the house to be heated more effectively.
Thank you for your answers,
Greetings from BaWü
Ann.
PS: Am I mistaken, or can the overall heat load calculation according to DIN 12831 really be verified or recalculated by oneself (assuming you have all the U-values of the building envelope, of course)? Are there already ready-made templates available on the Internet for this? Maybe also for the room-by-room heat load calculation, or is that usually too complex for the homeowner?
Do heating system installers know that underfloor heating is best sized and planned using a room-by-room heat load calculation?
Is the room-by-room heat load calculation also important for selecting the heat pump (in our case either water-to-water or ground-to-water), or is the "overall heat load calculation" of the entire building according to DIN 12831 sufficient?
If my architect does not offer this, who should I turn to? What should I look for in the phone directory / on the Internet to find a professional who can assist me with this?
From what I have read here in the past months, a room-by-room heat load calculation is very important. A precise calculation can save money because the heat pump selected accordingly will operate more efficiently, allowing the house to be heated more effectively.
Thank you for your answers,
Greetings from BaWü
Ann.
PS: Am I mistaken, or can the overall heat load calculation according to DIN 12831 really be verified or recalculated by oneself (assuming you have all the U-values of the building envelope, of course)? Are there already ready-made templates available on the Internet for this? Maybe also for the room-by-room heat load calculation, or is that usually too complex for the homeowner?
guckuck2 schrieb:
Honestly, I think it’s a bit overdramatic. Just specify a maximum installation spacing of 10cm (4 inches) everywhere, 5cm (2 inches) in the bathroom, and install as much as you can. If you want 24 degrees Celsius (75°F) in the bathroom, lay heating pipes on one wall or add an electric radiator. That’s where the issue begins... Less than 10cm (4 inches) pipe spacing doesn’t provide any significant advantage, and less than 8cm (3 inches) doesn’t add any benefit at all.
If you want to avoid using the ERR (design heat load calculation), you regulate the temperature by the sizing of the heating surfaces.
Just as you described, that’s exactly how you shouldn’t do it.
hegi___ schrieb:
This is where it starts... Less than 10 cm (4 inches) of stainless steel does not provide a significant advantage, and less than 8 cm (3 inches) is basically useless.
If you want to omit the ERR, you control the temperature by designing the heating surfaces accordingly.
Just as you described, that's exactly how it shouldn’t be done.No, you use the tacos for that.
Throttling is not a problem as long as there is generally enough flow in the system.
The problem is too little heat transfer, not too much. Increasing the flow temperature to compensate is inefficient.
Quote:
There are two important things to consider.
1. The length of the loop. The longer the loop, the higher the pressure loss, resulting in lower flow at a given pump capacity. Therefore, loops of similar length will generally carry a similar amount of water.
2. The output of the loop. This can vary greatly depending on pipe spacing, floor covering, room temperature, and other factors.
For a certain output, a specific flow rate is required to achieve a given temperature difference (which is determined by the set supply temperature and return temperature). Example: The loop is intended to deliver 100 watts with a temperature difference of 3°C (5.4°F): 100 / 60 / 1.16 / 3 = 0.56 liters per minute (l/min).
As long as the longer loops are designed to provide less output than the shorter ones, everything works fine, since they automatically get less water due to the higher pressure loss.
However, if a long loop is supposed to deliver a high output, it will need a high flow despite the high pressure loss. This means we have to increase the circulation pump speed to generate more pressure. As a result, all other loops must be throttled more. This is precisely what good design aims to avoid because it unnecessarily increases pump energy consumption — indefinitely.
Geisha Guide
There are two important things to consider.
1. The length of the loop. The longer the loop, the higher the pressure loss, resulting in lower flow at a given pump capacity. Therefore, loops of similar length will generally carry a similar amount of water.
2. The output of the loop. This can vary greatly depending on pipe spacing, floor covering, room temperature, and other factors.
For a certain output, a specific flow rate is required to achieve a given temperature difference (which is determined by the set supply temperature and return temperature). Example: The loop is intended to deliver 100 watts with a temperature difference of 3°C (5.4°F): 100 / 60 / 1.16 / 3 = 0.56 liters per minute (l/min).
As long as the longer loops are designed to provide less output than the shorter ones, everything works fine, since they automatically get less water due to the higher pressure loss.
However, if a long loop is supposed to deliver a high output, it will need a high flow despite the high pressure loss. This means we have to increase the circulation pump speed to generate more pressure. As a result, all other loops must be throttled more. This is precisely what good design aims to avoid because it unnecessarily increases pump energy consumption — indefinitely.
Geisha Guide
tomtom79 schrieb:
Shouldn't every energy consultant do that? They calculate how many heating circuits each room needs and the length of the circuits. I think our documents even specify the installation pattern of the loops. I’m not sure how it works when building to KFW standards, but if you just need an energy performance certificate according to the Energy Saving Ordinance, they do calculate the heat transfer coefficient (HT value) and so on, but for the entire building envelope. Not per room, and also no detailed design plans.
Maybe it also depends on what you specifically “order.”
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