Question about Heating Pump Operation mode – Ecodan FTC6 v20.06

Air Source Heat Pumps (ASHPs)

Last Post by Johj45 1 month ago

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Johj45

(@johj45)

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Topic starter 18/10/2025 8:08 pm

I have a Mitsubishi Ecodan EHST20D-YM9D with PUHZ-SWM80 outdoor unit, FTC6 controller (firmware 20.06), and an external 100 L buffer tank. The system is controlled via room temperature sensor.

I would like the internal heating circulation pump to stop immediately when the compressor stops, instead of running during heating demand but compressor is off and stop only when heat pump is in standby because indoor temp is reached.

Is there any installer parameter or menu setting in FTC6 (v20.06) that allows this — for example:

Water Pump Operation

- Continuous

- During Heating Demand

- With Compressor only

or perhaps a “Delay Time before pump switched off” that can be set to zero?

the reason why i want this is that the internal circulation pump is causing distortion in the buffertank if it runs when the compressor does not heat the water.

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rhh2348

(@rhh2348)

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21/10/2025 3:22 pm

This isn't an exact reply to your question, as I don't have the same hardware as you, however if you want the primary/circulation pump to stop shortly (/immediately) after the compressor stops, on my FTC6 settings I'd adjust the following (see image - 'water pump' isn't that helpful here, it's not pump 4 that overruns, it's 1 & 2, and perhaps 3 if you've two zones) - I don't know if zero is allowed but the default is 10 mins overrun (and note the manual's commentary on the effect of reducing the time); without knowing what 'distortion in the buffer tank' means, I'd probably avoid zero if you can help it, if only to dissipate a bit of recently-generated heat [away from the outdoor unit]...

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Johj45

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Topic starter 21/10/2025 6:27 pm

Thanks, I have à split model so there is no water circulating to and from the outdoor unit. Only between the cylinder and the buffer tank, and the from buffer to radiators.

the Buffer is a 4 pipe model, ment to have the coldest water at the bottom and the warmer water at the top.

As it works for me now is that the main water pump in the cylinder does not stop until the heating goes in standby due to indoor temperatur is overreached.

in autoadapt mode it goes on and cycles the compressor several times, and each time the compressor stops at the top of a heating cycle the waterpump continues to run hence pumping colder water from the bottom of the buffer through the cylinder and then back to the warmer water at the top of the buffer. It means i am cooling the top of the buffer which i already spent energy of heating up and seems to be a waste.

That is why i would like to configure the activation of the water pump to the compressor running.

This post was modified 1 month ago by Johj45

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