@ecodannewcastle,

that's more cycling than I've ever seen. What changes have you made?  I can see that happening if you've shut down (using thermostats/TRVs) a large portion of your house so that the volume the ASHP is heating is much reduced. 

Thanks! There seemed to be a major flaw in the set up which led to hot water from the heating system entering the radiators even when central heating turned off, and grabbing central heating water for the DHW unintentionally too (apologies for non technical speak!)

The installer fixed this by fixing the electrics to the valve that is supposed to keep the two systems separate.

At this time of the day the house was definitely being fully heated ie no thermostat/TRV throttling, but the flow temp was set manually pretty low (30 degrees-ish).

Have made a few other tweaks here and there but shouldn't be anything else major - schedule timers, playing with compensation curve.

Will keep an eye on it - unless anyone immediately understands the problem of course!

@ecodannewcastle

Do I understand correctly that you are operating your system with a fixed LWT? If so, then lower the setting by several degrees and see if that reduces the cycling.

If the cycling frequency reduces, then you should consider switching to weather compensation mode and adjusting the settings to help prevent cycling.

Thanks @derek-m

I have opened up all thermostats, lowered temp, and then switched to compensation mode - seems to have reduced the cycling (see MelCloud pic).

Does this seem acceptable now?

Some more fiddling needed to figure out which bit caused what.

Posted by: @ecodannewcastle

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Thanks @derek-m

 

I have opened up all thermostats, lowered temp, and then switched to compensation mode - seems to have reduced the cycling (see MelCloud pic).

 

Does this seem acceptable now?

 

Some more fiddling needed to figure out which bit caused what.

 

What are the weather compensation settings?

Posted by: @derek-m

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Posted by: @ecodannewcastle

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Thanks @derek-m

 

I have opened up all thermostats, lowered temp, and then switched to compensation mode - seems to have reduced the cycling (see MelCloud pic).

 

Does this seem acceptable now?

 

Some more fiddling needed to figure out which bit caused what.

 

What are the weather compensation settings?

40degrees at -10 outside; 30degrees at around +8degrees outside

Heatpump thinks it's about 8degrees outside at the moment here in Newcastle (see pic), although BBC says more like 5.

@ecodannewcastle

Try changing the warm end of the WC curve to LWT of 25C at outside temperature of 20C.

What size is your Ecodan? What is the heat loss calculation for your home? Your heat pump may start periodic cycling at warmer outside temperatures, since it will not be able to modulate down the compressor speed below the minimum allowed. This is normal, but should not be more frequent the maybe twice per hour.

Where is your tank temperature sensor located? I find it very strange that the indicated temperature is going from 48C to 10C over a short period of time.

The hot water is a few long hot showers at a time when the timer is stopping reheating (just a little experiment to see if it saves energy)

- Heat loss calculation attached (peak heat loss 13kw)

- Heat pump size: Mitsubishi W140 heat pump (MCS accredited) with a thermal output of 14kW at an outside air temperature of -7oC

I'll try adjusting the curve as you suggest.

Thanks again.

Posted by: @ecodannewcastle

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The hot water is a few long hot showers at a time when the timer is stopping reheating (just a little experiment to see if it saves energy)

 

- Heat loss calculation attached (peak heat loss 13kw)

- Heat pump size: Mitsubishi W140 heat pump (MCS accredited) with a thermal output of 14kW at an outside air temperature of -7oC

 

I'll try adjusting the curve as you suggest.

 

Thanks again.

 

 

 

The text is much too small to read, but I assume that when you state that the 'peak heat loss 13kW', this mean with indoor temperatures of 21C and an outside temperature in the -2C or -3C range. What is the size and type of your home?

What appears strange, is that your system appears to be able to supply the present heat loss with quite low LWT, with a 14kW heat pump. This would indicate that the actual heat loss is quite a bit lower than the calculated value.

A colder spell is forecast over the next few days, so it will be interesting to see how your system performs with the WC slope set for LWT of 40C at -10C and LWT of 25C at 20C.

It would be useful if you could record electricity usage along with the relevant parameters from your heat pump.

@derek-m This is what I got when I tried to "fiddle" with the system and manually control the LWT, heat pump was very unhappy, I very quickly switched back to weather compensation.