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Melpump Users Anywhere?

bontwoody · 2025-10-27T15:53:52Z

Ive just installed a dongle that allows me to monitor and communicate with an Ecodan through Melpump. Its a snip at £35 but there isnt a lot of documentation I can find. Does anyone on here use it? Here is an example of its reports for anyone interested.

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Air Source Heat Pumps (ASHPs)

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Majordennisbloodnok

(@majordennisbloodnok)

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13/03/2026 11:44 am

Posted by: @f1p

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I don't think either will take precedence, it is last received.

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Thanks, @f1p. My issue with understanding is a matter of what's being changed and how - something I don't know, so in need of illumination.

It seems to me a matter of whether we're talking about an event or a state, and forgive me if I oversimplify my explanation for the benefit of non-coders who may also be reading.

If there's a schedule to trigger an event - like "start heating the hot water" - then understandably that action will start when the trigger is hit either by the local schedule or the Internet one, whichever happens first if both want to try controlling it. If that schedule is only an Internet one and the trigger can't be sent to the heat pump for some reason (e.g. Internet connectivity issues), the heat pump won't do anything when it and the Internet can see each other again. However, if that event puts the heat pump in a particular state (e.g. holiday mode), when the heat pump can talk with Melpump/Melcloud again the two will synchronise that state in one way or another so that either Melpump/Melcloud recognises the pump should be in holiday mode and updates the state retrospectively or the heat pump knows it's not in holiday mode and tells Melpump/Melcloud to sort itself out to reflect this.

For various schedules, I simply don't know if it's events or states that matter (probably sometimes both) and, if it's a state needing to be synchronised how the precedence will work.

Of course, I may be overcomplicating things here. It wouldn't be the first time.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

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F1p

(@f1p)

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13/03/2026 8:03 pm

Posted by: @majordennisbloodnok

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when the heat pump can talk with Melpump/Melcloud again the two will synchronise that state in one way or another so that either Melpump/Melcloud recognises the pump should be in holiday mode and updates the state retrospectively or the heat pump knows it's not in holiday mode and tells Melpump/Melcloud to sort itself out to reflect this.

Okay, thanks for explaining - it would be the former. The heat pump current state is always reported actual, regardless of attempts to change it.

Both in my adapter and the official MELCloud adapter there is retry logic, to compensate for potential write failures caused by a rejection in the FTC as it could reject the command when "busy" or a malformed packed in the serial communication (due to electrical interference for example) and it is limited to a fairly conservative quantity.
MELPump and Home Assistant both work in a optimistic approach, where the change is considered successful until proven otherwise (confirmed by the next read)
I don't have evidence to suggest that MELCloud has any retry logic if the command was unable to reach the heat pump due to a connectivity issue
MELPump has retry logic, where if that optimistic state was proven unsuccessful shortly after it will perform another attempt

This post was modified 23 hours ago by F1p

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