Ecodan Melcloud Temperature Change

Air Source Heat Pumps (ASHPs)

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Gruff2001

(@gruff2001)

New Member Member

Joined: 2 years ago

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Topic starter 26/10/2025 12:07 pm

Long time lurker, first time poster

5kW Ecodan, FT6 controller

Yesterday, Octopus energy had a 3 hr free electricity session. Thought a cunning way to take advantage of this was to heat the house up significantly so we wouldn't need to have heating on in the evening. (Normally the system looks after itself very nicely, weather comp set etc)

I used the app to increase temp, up from 18C to 22C; forgot to boost flow temp so plan was never really going to work in3 hr window.

My issue, the ASHP stopped heating when 19C was reached and not the new target temp. I’ve not been able to find any info online as to how the app controls the temp, whether there are timing limits etc etc or was there a ghost in the machine

I would be grateful if someone could point me in the direction of some useful literature or perhaps explain how the app works (or doesn’t)

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downfield

(@downfield)

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Joined: 1 year ago

Posts: 103

26/10/2025 8:33 pm

Posted by: @gruff2001

↑

or was there a ghost in the machine

I also find my Ecodan's response to input temperature changes to be very slow, and sometimes non-existent.

Sometimes it will stay off at a room temp of 20C when the set temp is 21C for long periods.

I think there is a delay in turning the pump off to allow residual heat to be removed from the outside unit - at least mine seems to run for about 10 minutes after the temp is set back in the evening.

But I don't understand why it doesn't turn on quickly in response to an increase in the room stat.

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ASHP-BOBBA

(@ashp-bobba)

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Posts: 313

26/10/2025 9:42 pm

@gruff2001 - if set on WC, the app is only communicating to the controller and reading the stat against the weather curve, there are so many settings but a popular way to set the system up is on a WC as follows (max design flow temp @-2 min design flow temp @+20) so if for example your WC was at a peak V external temperature then the stat when moved 2℃ would only dynamically influence this by a small amount 0.5℃ for example. Next time you could just change the WC curve, mitsi have this nice -5 to +5 button right on the front screen of the FTC6 when in WC mode, this shifts the WC up by 5 points or down by 5 points moving the whole compensation control.

The above is a balance of input heat V heat loss, it may be the system stopped heating "assuming you mean the ASHP evaporator and compressor stopped running " due to the fact that to chased and caught up with its DT6 on the flow against its WC value at the time. If you are running your WC design to chase 19/20 it will not just raise to 22/23 by changing the set point ion the app, this will just act as the stop point.

Unless in fixed mode and in room control the stat is only part of the calculation of control and has an influence rather than operates like a total start stop.

BTW Havenwise automatically does exactly what you are trying to do but every day all day all year, additional weather station input, tariff tracking, optimising and so on, worth a look if its something you would like to track all of the time.

Hopefully I managed to explain this nicely complicated setup, forgive me for making a lot of assumptions above as it may be your system is not set up in this way.

AAC Group Ltd covering the Kent Area for design, supply and installation of ASHP systems, service and maintenance, diagnostics and repairs.
Professional installer. Book a one-to-one consultation for pre- and post-installation advice, troubleshooting and system optimisation.

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