ᐅ Heat pump LWZ 403 Sol: high supply and return temperatures with solar thermal system. Underfloor heating system is not working...
Created on: 10 Apr 2023 21:23
P
Phansol
Hello dear forum,
When our LWZ 403 Sol solar thermal system is active, the underfloor heating does not seem to work properly – at least the heating circuit pump does not appear to run.
(Room temperature 18.6°C (65.5°F))
Flow temperature: 58.7°C (137.7°F) (normally, of course, much lower, but this fits since the hot water is being heated intensely)
Return temperature: 54.6°C (130.3°F)
Setpoint HK1: 25.2°C (77.4°F)
Actual value HK1: 59°C (138.2°F)
Setpoint HK2: 25.3°C (77.5°F)
Actual value HK2: 59.2°C (138.6°F)
The heating circuit pump does not run at all during the day as long as the sun is shining and the temperatures are high enough to charge the domestic hot water (max. 65°C (149°F)).
Since the actual temperatures of the heating circuits are so high, the pump probably does not start either?! What could be the problem here?
When our LWZ 403 Sol solar thermal system is active, the underfloor heating does not seem to work properly – at least the heating circuit pump does not appear to run.
(Room temperature 18.6°C (65.5°F))
Flow temperature: 58.7°C (137.7°F) (normally, of course, much lower, but this fits since the hot water is being heated intensely)
Return temperature: 54.6°C (130.3°F)
Setpoint HK1: 25.2°C (77.4°F)
Actual value HK1: 59°C (138.2°F)
Setpoint HK2: 25.3°C (77.5°F)
Actual value HK2: 59.2°C (138.6°F)
The heating circuit pump does not run at all during the day as long as the sun is shining and the temperatures are high enough to charge the domestic hot water (max. 65°C (149°F)).
Since the actual temperatures of the heating circuits are so high, the pump probably does not start either?! What could be the problem here?
KingJulien11 Apr 2023 16:46I don’t know how it works with the SOL, but in principle, you can adjust the cycles of the heating circuit pump on the LWZ. You could try setting the "AT cycles max" (or something similar) to 19°C (66°F) and the "max cycles" to the highest value, for testing.
Oh, and make sure you’re not in summer mode, meaning heating operation is off because of AT. That can be configured as well.
Oh, and make sure you’re not in summer mode, meaning heating operation is off because of AT. That can be configured as well.
The system has been in place since 2013, but we only purchased the house this month.
Summer operation is currently set to start at 20°C (68°F) ambient temperature, which should still be fine.
Minimum and maximum cycles are 0 / 100, with corresponding temperatures at 25 / 0°C (77 / 32°F).
In other words, at an ambient temperature of 25°C (77°F) (due to solar use), the heating pump no longer cycles, and at 0°C (32°F) and below, it runs 50 cycles.
Would the following be possible?
Because of the low ambient temperature at night (e.g., 0°C (32°F) → 100 cycles) and the early morning hours, a few pump cycles are needed there (for example, 45).
If the ambient temperature rises and the sun shines, then at around 18°C (64°F), only 40 cycles would be allowed (assuming this adjusts dynamically), so the pump would stop running.
Is this a flawed approach, or is it possible? If possible, I would probably need to increase the minimum cycles for the ambient temperature...
Summer operation is currently set to start at 20°C (68°F) ambient temperature, which should still be fine.
Minimum and maximum cycles are 0 / 100, with corresponding temperatures at 25 / 0°C (77 / 32°F).
In other words, at an ambient temperature of 25°C (77°F) (due to solar use), the heating pump no longer cycles, and at 0°C (32°F) and below, it runs 50 cycles.
Would the following be possible?
Because of the low ambient temperature at night (e.g., 0°C (32°F) → 100 cycles) and the early morning hours, a few pump cycles are needed there (for example, 45).
If the ambient temperature rises and the sun shines, then at around 18°C (64°F), only 40 cycles would be allowed (assuming this adjusts dynamically), so the pump would stop running.
Is this a flawed approach, or is it possible? If possible, I would probably need to increase the minimum cycles for the ambient temperature...
KingJulien11 Apr 2023 18:12Phansol schrieb:
Summer mode is set to start at 20°C (68°F) outdoor temperature What hysteresis is used? In summer mode, the pump runs normally at the minimum value.
Phansol schrieb:
Cycle minimum and maximum are 0 / 100, with temperatures at 25/0. I wouldn’t set it to 0. Running the heating water once through the system certainly won’t hurt.
Phansol schrieb:
If the outdoor temperature rises and the sun is shining, for example at 18°C (64°F), only 40 cycles would be allowed (if this adjusts dynamically) and the pump would stop running. I don’t think it works like that, with a 24-hour accumulated total and a “remaining quota.” The pump usually interpolates based on the current outdoor temperature.
Just increase it for testing. Trial and error is better than theory.
288 cycles should be the maximum and thus continuous operation.
1/100 was set, I made a mistake while writing. Sorry.
I’m now running FHEM and have a clearer overview of the system (including winter/summer settings). However, I’m now struggling with many short compressor cycles that I can’t explain:
Yesterday (in the evening I briefly switched off the ventilation, which explains the “pause” in the 4th graph):
Today:
You can see that the heating pump (3rd graph, black line) runs continuously from a certain point on, no longer just short pulses to “test”. Meanwhile, the integral value keeps resetting — the compressor only runs for a very short time (0.5–1 sec) and then immediately switches off again. This resets the integral value, but since the temperatures haven’t changed, the integral value drops right back down.
What possibly incorrect setting could cause this? Is this normal? The flow is present as mentioned, and normally the compressor runs and heats well.
I’m now running FHEM and have a clearer overview of the system (including winter/summer settings). However, I’m now struggling with many short compressor cycles that I can’t explain:
Yesterday (in the evening I briefly switched off the ventilation, which explains the “pause” in the 4th graph):
Today:
You can see that the heating pump (3rd graph, black line) runs continuously from a certain point on, no longer just short pulses to “test”. Meanwhile, the integral value keeps resetting — the compressor only runs for a very short time (0.5–1 sec) and then immediately switches off again. This resets the integral value, but since the temperatures haven’t changed, the integral value drops right back down.
What possibly incorrect setting could cause this? Is this normal? The flow is present as mentioned, and normally the compressor runs and heats well.
KingJulien24 Apr 2023 08:46Wow, you’re throwing some real puzzles out here. But nice curves! 😉
I have no idea if this behavior is related to the solar system, I’m not familiar with that.
What do you mean by the compressor running for 1 second? Do you mean it twitched every time the integral was reset? Have you seen that live? I’ve never seen the integral reset like that before.
The only thing I notice now:
During the cycles in the morning, the return flow rises quite quickly. It’s hard to tell from the scale, but somehow it looks too fast.
Can you rule out a hydraulic short circuit? What about ERR and ÜSV?
Does the Vd always run for a normal length of time with the solar pump? Or is that just coincidence?
Are you running 100% return flow control?
What I and P values have you set?
Maybe you can also check out the FingerHaus forum, where most people discuss ground source heat pumps and FHEM.
Or also the HTD forum.
I have no idea if this behavior is related to the solar system, I’m not familiar with that.
What do you mean by the compressor running for 1 second? Do you mean it twitched every time the integral was reset? Have you seen that live? I’ve never seen the integral reset like that before.
The only thing I notice now:
During the cycles in the morning, the return flow rises quite quickly. It’s hard to tell from the scale, but somehow it looks too fast.
Can you rule out a hydraulic short circuit? What about ERR and ÜSV?
Does the Vd always run for a normal length of time with the solar pump? Or is that just coincidence?
Are you running 100% return flow control?
What I and P values have you set?
Maybe you can also check out the FingerHaus forum, where most people discuss ground source heat pumps and FHEM.
Or also the HTD forum.
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