ᐅ Modulating Heat Pumps / Temperature Differential / Excessive Start Cycles
Created on: 23 Feb 2024 14:22
J
jx7
A modulating heat pump can adjust its kW output to match the demand.
With my modulating heat pump, you can set the differential, that is, the difference between the supply temperature and the return temperature.
Is this the parameter that controls the power output? In other words, does the kW output adjust so that a certain value of the differential is maintained?
What changes if I adjust the setpoint from 5°C (41°F) to 2.5°C (36.5°F) or to 8°C (46°F)?
If I have the problem that the heating turns off too quickly and causes too many startups—although all individual room thermostats are open and the heating curve has been minimized—can adjusting the setting for DHeizen (differential) positively influence this situation?
With my modulating heat pump, you can set the differential, that is, the difference between the supply temperature and the return temperature.
Is this the parameter that controls the power output? In other words, does the kW output adjust so that a certain value of the differential is maintained?
What changes if I adjust the setpoint from 5°C (41°F) to 2.5°C (36.5°F) or to 8°C (46°F)?
If I have the problem that the heating turns off too quickly and causes too many startups—although all individual room thermostats are open and the heating curve has been minimized—can adjusting the setting for DHeizen (differential) positively influence this situation?
I can’t explain it clearly, and I’m not sure whether heat pump controls actually work this way. But generally, it is said that you should keep the temperature difference (spread) low and maintain a high flow rate. This way, you can work with lower target supply temperatures. A lower target supply temperature automatically means the compressor requires less power. If the compressor only reaches a certain minimum, which is actually already too high for the target supply temperature, then the question is how your specific heat pump detects this. Vaillant units have an energy integral that builds up or decreases over time based on the difference between the target and the actual supply temperatures.
However, that doesn’t mean all manufacturers do it this way (from what I’ve read, this seems to be more of a Vaillant-specific feature).
For you, the best option would be if you could set a desired room temperature and at the same time a minimum runtime or a lockout period after a heating phase. Then, the supply temperature and flow would be adjusted in such a way that the desired room temperature is achieved. A minimum runtime (for example 2 hours) would ensure that a heating cycle is worthwhile, and if the desired room temperature is exceeded a bit, that’s just how it is. A lockout period (for example 3 hours) would prevent the pump from starting again immediately after the desired room temperature is undershot and would also limit the maximum number of cycles (in this example, 6 per day).
How you implement that on your system, I have no idea… Sorry.
However, that doesn’t mean all manufacturers do it this way (from what I’ve read, this seems to be more of a Vaillant-specific feature).
For you, the best option would be if you could set a desired room temperature and at the same time a minimum runtime or a lockout period after a heating phase. Then, the supply temperature and flow would be adjusted in such a way that the desired room temperature is achieved. A minimum runtime (for example 2 hours) would ensure that a heating cycle is worthwhile, and if the desired room temperature is exceeded a bit, that’s just how it is. A lockout period (for example 3 hours) would prevent the pump from starting again immediately after the desired room temperature is undershot and would also limit the maximum number of cycles (in this example, 6 per day).
How you implement that on your system, I have no idea… Sorry.
Tolentino schrieb:
I can’t really explain it, and I’m not sure if heat pump controllers work exactly like this. But generally, it’s said that you should keep the temperature difference (delta T) low and maintain a high flow rate. This way, you can work with lower target supply temperatures. Lower target supply temperature means the compressor’s required capacity is automatically reduced. If the compressor can only reach a certain minimum, which is actually too high for the target supply temperature, then the question is how your specific heat pump detects this. Vaillant uses something like an energy integral that builds up or reduces over time based on the difference between target and actual supply temperature.
But that doesn’t mean all heat pumps work like that (from what I’ve read, this seems to be specific to Vaillant).
For you, the best approach would be if you could set a desired room temperature and at the same time define a minimum runtime or a lockout period after a heating cycle. Then supply temperature and flow would be controlled so that the desired room temperature is achieved. Having a minimum runtime (e.g., 2 hours) ensures that each run is “worthwhile,” and if the desired room temperature gets a bit too high, that’s just how it is. A lockout period (e.g., 3 hours) would ensure the heat pump doesn’t restart immediately after the room temperature falls below the target again, while also limiting the maximum number of cycles (in the example, 6 per day).
How you could implement this on your system, I have no idea…. Sorry (1) Thanks for the info. So Vaillant controls based on the temperature difference, but not directly—it uses the integral over time.
(2) Unfortunately, with the Ecoforest you cannot set a minimum runtime. There is a fixed 15-minute lockout period between starts, but it can’t be changed.
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