Hello,
After the first few days in my new home, I’m having some issues with the heating system. Somehow, it feels like something isn’t working 100%... it heats very irregularly. In my experience, it only heats properly when as many rooms as possible are set to flow. Once most rooms have reached their temperature and only 1 or 2 are open, the system quickly cycles on and off...
- We have about 140 sqm (1507 sq ft) of floor area
- Underfloor heating throughout the entire house
- A Junkers Cerapur ZBS 22/100 S-3 MA gas boiler with hot water generation (22 kW)
- 17.5 cm (7 inches) calcium silicate stone + 14 cm (6 inches) external thermal insulation composite system (ETICS) (no special energy-saving regulations)
As mentioned, when only a few heating circuits are open, the boiler turns on (starting at about 25°C (77°F) flow temperature), heats up quickly (up to about 45°C (113°F) flow temperature), then drops off rapidly and starts again. So the heating circuits are only heated sporadically...? If I turn on more heating circuits, the warm-up time is longer and it gets warm... is the boiler oversized, since it heats single rooms poorly?
After the first few days in my new home, I’m having some issues with the heating system. Somehow, it feels like something isn’t working 100%... it heats very irregularly. In my experience, it only heats properly when as many rooms as possible are set to flow. Once most rooms have reached their temperature and only 1 or 2 are open, the system quickly cycles on and off...
- We have about 140 sqm (1507 sq ft) of floor area
- Underfloor heating throughout the entire house
- A Junkers Cerapur ZBS 22/100 S-3 MA gas boiler with hot water generation (22 kW)
- 17.5 cm (7 inches) calcium silicate stone + 14 cm (6 inches) external thermal insulation composite system (ETICS) (no special energy-saving regulations)
As mentioned, when only a few heating circuits are open, the boiler turns on (starting at about 25°C (77°F) flow temperature), heats up quickly (up to about 45°C (113°F) flow temperature), then drops off rapidly and starts again. So the heating circuits are only heated sporadically...? If I turn on more heating circuits, the warm-up time is longer and it gets warm... is the boiler oversized, since it heats single rooms poorly?
According to the energy saving regulation, my heat transfer coefficient (Ht) is 0.285. What is yours?
This also explains why everyone says to do a heating load calculation and not to rely solely on energy saving regulation documents.
However, aside from that, there are many assumptions in the calculation that don’t really hold true; for example, standard values for thermal bridges, it states "windows with Uw <1.00" (we are actually well below that), perimeter/foundation insulation is 0.035 instead of 0.038.
I calculated using the actual materials, dimensions, etc. from the planning for the construction site, based on the bids, so it was naturally more accurate.
This also explains why everyone says to do a heating load calculation and not to rely solely on energy saving regulation documents.
However, aside from that, there are many assumptions in the calculation that don’t really hold true; for example, standard values for thermal bridges, it states "windows with Uw <1.00" (we are actually well below that), perimeter/foundation insulation is 0.035 instead of 0.038.
I calculated using the actual materials, dimensions, etc. from the planning for the construction site, based on the bids, so it was naturally more accurate.
wpic schrieb:
It makes little sense to keep a low-temperature radiant heating system turned off in large areas. The entire house should be heated evenly. The system is not designed for short-term operation. Besides, the heat produced must be delivered by the heat generator either into a buffer tank or the water reservoir of the entire underfloor heating system. If these heat stores are no longer available, the heat generator must shut down. Either the heat generator is not suitable for your system (oversized) or your usage behavior does not match the system. I think both could be the case if the gas condensing boiler cannot modulate down to a significantly lower output.I don't have many options to influence this... there is a thermostat in every room set to about 20 degrees Celsius (68 degrees Fahrenheit)... once this temperature is reached, the flow is automatically stopped by the controller and actuator, right? The only option would be to set all thermostats to maximum... then they stay fully open... and it gets too warm...
T21150 schrieb:
I didn’t see in your heating system documents the minimum modulating output. I probably missed it, but I’d estimate it at around 4-5 kW.
That is too much for a modern house the size of your property.
Best regards,
ThorstenHeating capacity kW
22
Modulation range kW
7.3–21.8
Max. flow temperature °C
88
Domestic hot water capacity kW
28
Storage volume l
100
Performance coefficient (DIN 4708) NL
2.8
Weight kg
108.3
Basti2709 schrieb:
Only option = set all the valves to maximum... then they stay fully open all the time... and it gets too warm... Then adjust the heating curve on the heat pump (set the flow temperature lower) until it only reaches your desired temperature. That way, it will work properly, and your heat pump will only use the energy it actually needs.
Although, in my amateur estimation, the heat pump is oversized.
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