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Interpreting MelPump data / cycling?

Air Source Heat Pumps (ASHPs)

Last Post by F1p 2 months ago

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Boodgie

(@boodgie)

New Member Member

Joined: 2 months ago

Posts: 3

Topic starter 07/03/2026 11:30 am [#2871]

Hello All.

Our heat pump was installed in 2022 and I've spent this winter really trying to dial in the weather compensation settings to improve performance. I've had the MelPump app for a couple of weeks and am trying to understand what I'm seeing in the data.

I'm puzzled about the compressor frequency dropping to zero and immediately bouncing back up. Am I right in thinking this is short cycling? At worst it's every 10 to 15 mins. Thinking about compressor life / efficiency I don't think this is ideal? For context the COP during this 24hrs was 5.3 (using external metering - MelPump says 7.42!).

A bit of info about the system: It's an Ecodan 8.5KW heating a 170sqm house with UFH throughout. I've learned the UFH probably has too many controls - there are three manifolds each with a temp control valve, circulation pump and multiple zones operated by automatic actuators. I've opened the system as much as possible - all the temp control valves are fully open and one manifold runs 24/7 without any external control. The other two have digital room stats to prevent overheating.

I'd be grateful for any thoughts on the report and advice to improve cost / efficiency.

https://melpump.com/public-report/view/019cc7f6-4657-7cfe-981c-ae2288e0456e

This topic was modified 2 months ago by Boodgie

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Cycling ecodan

F1p

(@f1p)

Estimable Member Member

Joined: 6 months ago

Posts: 112

08/03/2026 3:09 pm

It looks like your flow temperature is exceeding your flow setpoint

In the curve mode you have a small permitted overshoot.

I think you would need to push a few C higher flow at that outside temperature to mitigate some of it.

It looks like your data is from MELCloud, so I can't offer you a trick available to the MELPump adapter users

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Boodgie

(@boodgie)

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Joined: 2 months ago

Posts: 3

Topic starter 09/03/2026 2:00 pm

@f1p Thanks for your reply.

Looking at the data this pattern of rapid stops and starts seems to start happening once the target temperature gets down to around the 27.5 degree mark. I hit that target at around 4 or 5 degrees outside.

I've got the heat curve down to 32 degrees at -3 and 23 degrees at 11. Is that too low for the output of the pump? It seems the compressor is only modulating down to around 36Hz before shutting itself down.

At a target of 25.5 degrees last night it had a series of these very short shutdowns. Given the COP for the day was 5.9 (externally monitored) should I try to address this or ignore it? I guess my concern is more wear to the compressor than efficiency.

https://melpump.com/public-report/view/019cd2ac-2422-7dfe-833f-6abb4b72440b

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F1p

(@f1p)

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Joined: 6 months ago

Posts: 112

09/03/2026 2:23 pm

Posted by: @boodgie

↑

I've got the heat curve down to 32 degrees at -3 and 23 degrees at 11. Is that too low for the output of the pump? It seems the compressor is only modulating down to around 36Hz before shutting itself down.

I would say yes - the floor frequency is linked to outside temperature, so for example in my 8.5kW R410a monobloc unit at 0-5C outdoor the minimum frequency is 32Hz which will increase my minimum output power.
Simularly at 5C i get another step down of floor frequency to 26Hz (But you can find this is 20Hz on other models)

I would suggest yes, you should look to address it, compressor cycles plus i think you could probably nudge up the CoP by stopping that ramp up spike in compressor freq

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Boodgie

(@boodgie)

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Joined: 2 months ago

Posts: 3

Topic starter 09/03/2026 2:34 pm

@f1p Thanks again.

Should I be looking at anything else apart from increasing the heat curve? If I push this up I'll have to use the room thermostats to prevent overheating which is going to reduce my emitters...

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F1p

(@f1p)

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Joined: 6 months ago

Posts: 112

09/03/2026 2:55 pm

Posted by: @boodgie

↑

@f1p Thanks again.

Should I be looking at anything else apart from increasing the heat curve? If I push this up I'll have to use the room thermostats to prevent overheating which is going to reduce my emitters...

I do mine dynamically - so here i start at 32C setpoint (3C outdoor) from my curve and then will increase dynamically as required up to the minimum which settles into a nice stable run around 33.6C and 32Hz freq