The maximum flow temp has always been within a degree of what the WC curve has called for.

Coldest day here since it was installed was between minus 1 and plus 1. Average flow temp on that day was 43 degrees according to Melcloud. I didn't have the Shelly temperature sensors or Home Assistant back then, just the Shelly energy monitor and app, so I have no detailed info to check for cycling.

I had the heat curve set to 44 degrees at zero OAT, so pretty much spot on.

Shelly energy consumption historical data is only sampled hourly - one of the reasons that I started using Home Assistant.

I've not seen it run a defrost cycle at all. Is there a way of knowing, apart from seeing the flow temp drop below the return temp? I've not seen it do that, except when the ASHP is off and everything is cooling right down.

I've got 10 radiators. I've looked up the manufacturers' specs for each one at deltaT50, applied a correction factor of 0.41 to get the deltaT25 number, and added them all up.

In theory, they should be able to output around 5.8kW at a flow temp of 45 degrees, and 20 degrees ambient - close to the rated 6kW of my heat pump

@clockworks The only way to detect defrosts from the data is as you say to see the flow temp drop below the return.  You should be getting defrosts when its low single figures as it was a couple of weeks ago when it was cold and damp.

Unfortunately Home Assistant only stores detailed historical data for 10 days, then it saves hourly data long term. I need to tweak the system to store detailed info for longer, but the machine I'm running it on doesn't have enough "disk" space for that. New mini PC with 256gb is on order!

Looking back at the last 10 days of detailed data, at no point did the flow temp drop below the return temp - except when everything was off for 3 hours.

@clockworks I don't know if this help ....

We have a Stiebel Eltron WPL25AS (installed Aug23).  I have also been looking at how to minimise cycling due to the lower modulated output limit, on the warmer days. 

This eventually led me to a control parameter buried deep within the system: "Controller Dynamics", within "commissioning".  This parameter influences how quickly the heat pump output controller switches up or down a stage in output.  The stages seem to be 100W changes.  Values for this parameter range from 10 to 500, default is 100.

It also influences the point at which the heat pump switches on in relation to the difference between the set temperature and the actual temperature (buffer temperature - we have a 100 litre buffer).  So it can effectively delay switching on.  Today it switched on with a set temp of 28.7 and an actual temp of 24.1.  The delta (4.6 in this case) becomes higher for a higher setting of the controller dynamics parameter.

It is currently set to 200 and the heat pump is cycling less often, compared with the 100 default setting.  For a setting of 30, cycling is significantly increased. 

We have an old property with uninsulated solid stone walls (high thermal mass) so we don't notice any difference in comfort temperatures inside.  The solid stone walls are performing better than the heat loss calcs suggest.   

Sorry, I don't know whether there is an equivalent parameter for the Ecodan - but perhaps someone here does?

I hope this is of some use.

I don't know where you are in Cornwall - as it happens we are organising a community meeting on 06Feb25.  There will be an impressive amount of knowledge and expertise in the room.  Via 'visit a heat pump' (Nesta), I have also arranged a site visit earlier in the day.  There are still a few tickets for both.       

Interesting. I'll have a trawl through the installation manual for the Ecodan, see if there's anything similar.

I'm right down west, between Helston and Penzance, so quite a long way. I wonder if similar events are being held in my area....

Posted by: @clockworks

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Interesting. I'll have a trawl through the installation manual for the Ecodan, see if there's anything similar.

 

I'm right down west, between Helston and Penzance, so quite a long way. I wonder if similar events are being held in my area....

Community Energy Plus cover your area - you could ask them?

i have the same problem Clockworks , 12kw ashp cycling every 20 minutes ..

 so i am following along to see if there's a solution , other than replacement .

In a thread on here  i did a bit of research about the economical effects of running a higher FT , say 32c , and less cyling, 1 per hr , compared to 29c FT and once per 20 m , it seemed that i used 30% less power with the faster cycling .

It doesn't help that my AsHP is made by harnitek , who seem to be unknown .

regards

robert

@clockworks   Looking at your flow temperature graphs, the rise before the pump stops is not particularly big. You could try this: Under Operation setting > Heating operation > Heat pump thermo diff adjustment; if I remember correctly this sets a temperature range around the target flow temp for the pump to work within. By default this is 5° either side (might have been altered by your installer) and can be increased to a total range of 15°. 

@harriup I believe these offsets only work in autoadapt mode and not in weather compensation mode which is why I were suggesting @clockworks gets his wireless controller set up.

I was going to look at Thermo Diff, but it said I had to shut down before I could even see what the current settings were.

Would you suggest lowering the lower limit, so it stays off until the flow temperature drops further away from the target before restarting?

Posted by: @gary

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@harriup I believe these offsets only work in autoadapt mode and not in weather compensation mode which is why I were suggesting @clockworks gets his wireless controller set up.

That sounds feasible. Assuming it's currently set at the default (-5 to +5), then it doesn't appear to be working in WC mode - it's currently stopping at the target temp, and restarting at around -5.

I've watched a couple of videos about fitting the wireless controller, and read through the manual to see where it plugs in. I've not taken the cover off the FTC6 to have a look though.

It's currently set up to be controlled by the Evohome boiler relay, which is just a "zero volt" on/off relay.

I'm guessing this will have been wired to the "room stat 1" terminals on the FTC6 (TB1.1 terminals 7&8).

When I connect the wireless remote to the CNRF socket, will I need to disconnect the Evohome relay, or does flipping SW1-8 and selecting "Room RC1" as the zone controller effectively disable the Evohome relay?

@clockworks I have never tried to use a wireless controller before so will be interested to find out how it goes.

I would hope the dip switch change would mean it ignores the Evohome connections, I would just try it and see what happens, you cant' break anything.

Just turn off the mains power to the FTC before you open the cover, you don't need to do anything on the main controller, that will power off when the FTC power is off.

Set the evohome to a low temp so its not calling for heat then see if you can get the HP to fire up from the wireless controller would my first experiment.

If you need to disconnect the evohome as you say it will just be two wires into 2 terminals on the bottom left of the FTC, these just screw in,  its easy to remove just take a picture beforehand so you know where they went incase you have to revert back.