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?
Basti2709 schrieb:
I have done the same now... I’m currently at 17 liters flow rate... unfortunately, I can only observe this evening how long the heating cycles actually last...
On what basis does the boiler modulate? In other words, which parameter tells it to operate at lower output? In my case, does it make sense to reduce the maximum heat output? According to the default settings, it was:
Minimum heat output: 36%
Maximum heat output: 84% (now I have it at 50%)
So, would it make sense to set Min (36%) = Max heat output (36%)? That would still be 7.3 kW…Nowadays, the output is primarily controlled via the heating curve. Other parameters also play a role (and indeed do), such as setpoint versus actual flow temperature, return temperature, temperature drops, and more.
In your heating system, as mentioned, the minimum heat output is already an issue because it is simply too high for the house. Therefore, in my opinion, you don’t need to worry much about limiting the maximum output. Most likely, you can’t even set Min = Max (but this is just an assumption).
With a minimum output of 7 kW, the system will continue to cycle on and off frequently unless technical modifications are made. Even less powerful systems commonly have cycling problems, so with the capacity in your house, this behavior is almost built-in. Something will need to be adjusted.
Best regards,
Thorsten
Despite having an open flow and 17 liters/min (4.5 gallons/min), the unit only heats continuously for a maximum of 10-15 minutes before shutting off... it is now heating from 23 to about 34 degrees Celsius (73 to about 93 degrees Fahrenheit).
The problem now is that I only manage to reach around 19 degrees Celsius (66 degrees Fahrenheit) in the living area, and the consumption has increased to around 9-10 m³ (318-353 cubic feet) (previously, with cycling, it was 22 degrees Celsius (72 degrees Fahrenheit) and about 6-7 m³ (212-247 cubic feet))... so I have for now turned the ERR down again and raised the design temperature because my partner felt it was too cold... I spoke to the heating technician by phone, and he said everything is fine and working as it should...
Would installing a buffer tank help (300 or 500 liters (79 or 132 gallons))? That way, the boiler could fire fully into the tank, and I would always have heat available immediately when I need it... and the boiler would only start 2-3 times to heat the buffer...?
The problem now is that I only manage to reach around 19 degrees Celsius (66 degrees Fahrenheit) in the living area, and the consumption has increased to around 9-10 m³ (318-353 cubic feet) (previously, with cycling, it was 22 degrees Celsius (72 degrees Fahrenheit) and about 6-7 m³ (212-247 cubic feet))... so I have for now turned the ERR down again and raised the design temperature because my partner felt it was too cold... I spoke to the heating technician by phone, and he said everything is fine and working as it should...
Would installing a buffer tank help (300 or 500 liters (79 or 132 gallons))? That way, the boiler could fire fully into the tank, and I would always have heat available immediately when I need it... and the boiler would only start 2-3 times to heat the buffer...?
Your heating technician is trying to talk their way out of it. What they installed simply does *not* work optimally.
Please look up Wikibooks/Optimization of Small Heating Systems/Measures Against Heat Loss.
You should stop wasting time complaining with the people involved (especially your heating technician) and start establishing clear facts.
Why is it too cold now?
Because the flow is not continuous. The supply temperature rises, but the heat does not transfer to the floor that quickly. The burner turns off again and waits (it often has a hysteresis of 5 to 15 minutes before it starts again).
If the oversized heating system remains, in my opinion the buffer tank is the only option. I don’t think the buffer needs to be as large as 300 liters (that’s a huge tank). Off the top of my head (a professional should confirm): 70 to 120 liters.
Are you currently consuming 7 to 10 cubic meters of gas per day?
Good grief. That’s way too much. We have a similarly sized house and only use about 2.7 cubic meters per day. When it’s -10°C (14°F) outside, I use just under 4.
Best regards,
Thorsten
Please look up Wikibooks/Optimization of Small Heating Systems/Measures Against Heat Loss.
You should stop wasting time complaining with the people involved (especially your heating technician) and start establishing clear facts.
Why is it too cold now?
Because the flow is not continuous. The supply temperature rises, but the heat does not transfer to the floor that quickly. The burner turns off again and waits (it often has a hysteresis of 5 to 15 minutes before it starts again).
If the oversized heating system remains, in my opinion the buffer tank is the only option. I don’t think the buffer needs to be as large as 300 liters (that’s a huge tank). Off the top of my head (a professional should confirm): 70 to 120 liters.
Are you currently consuming 7 to 10 cubic meters of gas per day?
Good grief. That’s way too much. We have a similarly sized house and only use about 2.7 cubic meters per day. When it’s -10°C (14°F) outside, I use just under 4.
Best regards,
Thorsten