ᐅ Shutdown differential of the heat pump?

Created on: 12 Dec 2014 11:16
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seiler-1
12 Dec 2014 11:16
Hello,
I have a problem with my heat pump.
Here is the situation:

Lately, my heat pump has been exceeding the target setpoint. This setpoint is predefined. For example, the controller sets a target supply temperature of 30°C (86°F) and switches the heat pump on. However, the temperature keeps rising until it reaches the current cutoff differential at 43°C (109°F), and only then does it start to go down again.

Why can’t this heat pump meet and maintain the target setpoint?
Or is this behavior inevitable?

Thank you very much for any advice.
J
Jonas-1
13 Dec 2014 09:52
Hey Seiler,
I'm not an expert in this field, but usually a constant control setting is not possible.
For example: The house has a heating load of just 0.85 kW, which is the lower limit for the heat pump. However, this is enough to heat the water to 30 degrees Celsius (86°F). The pump, however, delivers 2 kW, so the water gets warmer than 30 degrees. If the controller were to switch off at this temperature, the water would cool down too quickly. This cycle would then repeat continuously.

Regards
S
seiler-1
13 Dec 2014 14:41
Hi Jonas,
Thank you for your explanation. If I understand correctly, it wouldn’t be advisable to lower the cut-off differential. Otherwise, the heat pump will short cycle, right?
Best regards
L
Luca-1
19 Dec 2014 14:11
In my opinion, this depends on the heating system and the heating demand of the house. It can make sense to turn it down slightly. However, the heating system and the house should be coordinated with each other.

In cold winter conditions, when higher temperatures are needed, the setting can be higher. But it is quite challenging to find the best adjustment here.
R
Roman-1
1 Jan 2015 14:20
Hello,
this could get really interesting when it gets very cold. If the heat pump currently has to deliver 43°C (109°F) in the supply line, that already seems questionable to me.

Does the heat pump also control the return flow?
S
seiler-1
3 Jan 2015 15:57
Hello,
Thank you for the responses.

Here is some additional information.
These are the two settings that control the behavior of the heat pump:

1x the differential cutoff of the heat pump
1x the temperature boost of the heat generator (i.e., heat pump) on the buffer tank – I have now set this to 0, meaning "target value buffer = target value heat pump" instead of "target value buffer + boost = target value heat pump."

Let’s see what effect this has.

Best regards