@cathoderay I agree with cathoderay, my Mitsubishi does not use it's thermistor (in it's control panel) when on Weather Comp mode. If WC is set too high, it uses more power, but if it is set too low, it cycles. I do not want it cycling more than occasionally as I believe that risks premature breakdowns as well as reducing the heating efficiency. So I set the WC a little higher and usually mid morning my room thermostat stops calling for heat and the HP should shut down. I may have to turn the room thermostat up in the afternoon to restart the HP as we have UFH in concrete floors which take a while to warm up, especially on sunny Winter days when the living room is very warm but the floors are cold. At night I program my room thermostat to set back by not more than 2C so the floors will warm up enough by the morning. At the moment, the HP mostly draws approx 1 kW, per our smart meter. I could relocate the control panel into the living room and then use Auto Adaptation in the future but first I would really like to know how that would affect cycling.

Posted by: @sliderule

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@cathoderay I agree with cathoderay, my Mitsubishi does not use it's thermistor (in it's control panel) when on Weather Comp mode. If WC is set too high, it uses more power, but if it is set too low, it cycles. I do not want it cycling more than occasionally as I believe that risks premature breakdowns as well as reducing the heating efficiency. So I set the WC a little higher and usually mid morning my room thermostat stops calling for heat and the HP should shut down. I may have to turn the room thermostat up in the afternoon to restart the HP as we have UFH in concrete floors which take a while to warm up, especially on sunny Winter days when the living room is very warm but the floors are cold. At night I program my room thermostat to set back by not more than 2C so the floors will warm up enough by the morning. At the moment, the HP mostly draws approx 1 kW, per our smart meter. I could relocate the control panel into the living room and then use Auto Adaptation in the future but first I would really like to know how that would affect cycling.

@Sliderule, I wouldn't become too concerned by some cycling.  As @cathoderay has explained, it's what ASHPs do.  You fridge cycles all the time and never comes to any harm.  The sort of cycling that tends to happen at the right hand end of the WC curve, 2-4 times per hour, is OK.  The rapid cycling, 6 plus times per hour that happens when something is wrong or you only have one radiator open isn't, but can usually be fixed. 

The way you are running your ASHP sounds fine.  AA will have a similar result but without manual intervention.  In my case, it pretty much eliminates cycling, even at warmer OATs. 

As an alternative to relocating your control panel you can connect a remote temp sensor Mitsubishi Electric PAC-SE41TS.  These are about £20 off eBay.  You can also use the wireless controller but these are expensive and hard to find right now.  

What Ecodan do you have? 

@kev-m Hi kev-m, We have an 11.2kW R32 model PUZ-WM112VAA, just installed replacing a 13 year old 14kW Ecodan which had a refrigerant loss last year and again this year with a compressor failure, which is why I am paranoid about cycling. In the early years it wasn't until we got a smart meter that I realised it was cycling and put in some programmable thermostats to help reduce the cycling. I know now that it cycled an average of 4 times a running hour over its life, more in the  early years and less later. This time I did the heat loss calculation and went down in power. I am still waiting for the installer to fix a few bugs, but it's running well, and cycles less than once per hour, often only once or twice a night.

I don't think much of the fridge comparison, HPs are much more complicated with variable speed compressors working at much higher power levels and with greater lubrication challenges, lots of soldiered joints in the heat exchanger exposed to greater temperature ranges, let alone the electronics, inverter, plate heat exchanger, reversing valve etc.

It's nice to know that AA works well. I'll probably give it a try when I get time, thanks for that.

Posted by: @bontwoody

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@guthrie Moving the Samsung controller is quite easy, just two wires. This would be suitable to extend it.

https://midsummerwholesale.co.uk/buy/renewable-heat-accessories/cy-2-core-comms-cable

I think I shall leave that alone for now until I understand if it affects any warranty or suchlike.  Probably the easiest long term option.

Posted by: @guthrie

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2) Would it make sense to just run the hot water tank heating once a day, say 3 to 5pm or so?

I have a similar Samsung and have found a hot water mode that works for me. I am on an Agile tarif and so I force the hotwater to heat up at 2pm-3pm and 2am-3am when electricity is cheap.

I had mixed success with this to start with as I had the schedule set to Off for the remaining time and On only in those time windows. The problem was that if the tank temperature didn't drop to the bottom of its hysteresis band at 40 during that On period, it wouldn't charge. That sometimes left me with water at 41 at 3pm, that wouldn't last until 2am. I found that if I changed a DHW mode setting I could force it to ignore the hysteresis band and charge up when it was turned On. This was much better. However I still had the occasional issue when lots of hot water was used that it wasn't heated on-demand. I also didn't want it heating at peak times due to cost.

I ended up with two time windows where it will be On and forced to heat, two peak times it is Off and won't heat. The rest of the time is in economy mode which is 5c cooler, which has the effect of not heating unless the tank cools a lot. This worked an absolute treat in the summer. I might get rid of the 2am charge in the winter, although the COP hasn't been too bad overnight right now.

Regarding the heating, I do wonder how effective set points are, given they require setting the flow temperature/water law higher to be able to recover. I have been dropping my water law down to a point where around 8c is modulated right down and running continously. It was cycling before. I am gauging this by looking at the operating time measurement in the energy consumption on the control panel. Mine is a slighly different case though as I have a third party controller and no solar panels/battery. I hope to get some panels soon though!

Good luck with your adventures with the Samsung unit. I am enjoying mine overall, but the data exposed thought the controller is minimal. e.g. I can't work out COP of hotwater and heating individually.

@olly That makes sense for the water tank.  When our smart meter gets sorted out so it actually works (no signal) it would definitely be worth using an agile tariff.

I am also irritated that it isn't really possible to work out the COP without adding more measuring gubbins. 

I am looking at the MCS handover checklist and thinking hang on, we don't have all of that.

We have the invoice, MCS certificate, not necessarily insurance backed warranty details but at least the paperwork for the equipment which contains the usual warranty stuff.  Also manuals.

But I do't seeheat loss calculations for each room, internal and design temps, and the duty of the heat emitters in each room.  I suppose the design max heat emitter flow temp is in the quote, but I don't see any details of maintenance requirements beyond what the manuals say.

Also no sign of comissioning control values...

I take it this is quite normal. 

@guthrie

My installer left me the entire package from soup to nuts but from what I read here that does not seem to be the norm.  May I enquire what part of central Scotland you are in? I ask because in my corner of eastern Perthshire we are a group of 16 house none of whom get any mobile signal whatsoever and the few brave souls who have attempted smart meters have very dumb meters. I very much doubt that the Arqiva signal from Durris, near Banchory,  can get us. 

@abernyte Biggar, where there are many iffy mobile signals due to the strange siting of the local masts plus ups and downs in terrain.