How do I check the emitter value & that the flushing value is fully closed (what does this look like / where is it positioned?)
I had wondered if you have a list of your radiator sizes and how large your underfloor heating area is since a small emitter capacity can cause cycling. The flushing valve refers to your schematic diagram.... I noticed on the drawing there was a flushing bypass valve which isn’t always fitted. And mentioned it as an aside issue. Just to check that the valve is fully closed since this could cause hot water to bypass the heating system.
Having said all that, your latest hourly graph looks better for all the changes you have made so things appear to have improved.
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Unfortunately I think the issue has not been resolved. See below hourly temps from 13h00.
I’m going to run it for a few days in the current setting to see what the overall consumption / COP figures are like - if these are still terrible I may try out auto adaptive.
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Hi @jake. I’ve started getting a bit of cycling since we have had 12c OAT. we get about 2 or 3 cycles an hour. Auto adapt does help a little by reducing the cycle size but usually adds a few degrees to the flow temp to reduce the cycling but then stops and pauses to reduce the output.
Regarding your charts... I find it easier to read the charts when I screenshot my phone to landscape. It produces a longer time line for the hourly graph. Also by adding the tank set temperature line and one of the 25c lines I get a Better proportioned graph with 5c horizontal lines. I think this helps in reading the deltaT of the Flow and Return. Here are 2 screen shots of the same chart. Does the different setup help to see the performance of the output when it’s viewed in landscape? I hope you can see how the top and bottom lines help to change the proportions of the vertical temperature scale.
Here is your chart from yesterday
This second one below, I’ve tried to copy your scale and orientation- but it’s the same chart as mine above in landscape format.
I think the flat bottom to the return temp shows how the slab temperature is preventing anymore heat being dropped from the circulation in to the UFH - so without being able to deliver heat at the rate it is being generated the flow temp rises until it reaches the set point, hence cycles. So I would read from this that the radiator circuit was not active, as otherwise the return temp would vary more.
In an ideal system the compensation curve would match the heat loss of the house at the different OATs – but if zoning is removing chunks of the house-side heat load then that equation becomes unbalanced. If you have two stats high so they are always calling, then the call from the third stat would effectively switch the entire house demand on and off. This should give you more balance, which should be more efficient.
Having UFH and radiators makes it tricky as the speed of heat transfer into the house is different, auto adapt can be too eager to put more heat in if it doesn’t register a change of temperature within a certain time, which is more likely when the heat transfer to the room is moderated and extended by the slab. But if you try auto adapt then it will refer to the temperature of the room the FTC controller is in – which looks like the second floor from the pic (I presuming you don’t have a Mitsubushi remote stat to set as the target location). When the system has the knowledge of current and desired temps it can use those to create longer runs with appropriate pauses to control the total heat delivery.
Mitsubishi EcoDan 8.5 kW ASHP - radiators on a single loop 210l Mitsubishi solar tank Solar thermal 3.94kW of PV
Ah okay so you also get some cycling when the OAT low double digits. What is your COP?
Interestingly I spoke to the installer briefly today, who said it is normal for the unit to cycle about three times an hour. We didn't have the chance to fully discuss my concerns (he was on site looking at another property) but I will try get him out to take a full look at my set up & stats.
@jaket we have decided a bit of cycling (but not too much) when it’s 10 or 12c is better at achieving a high CoP and minimise KWh consumption.
The question we faced is - what is acceptable cycling? We have decided 2 cycles per hour is stable enough and at 10 or 12c that gives us a CoP of about 4.0 sometimes 3.8. At that kind of cycling we are able to run the system at about 32c with 2 cycles per hour and 37c flow temperature without cycling. However we have about 21kw output capacity from our radiators and its a 8.5 Ecodan.
My concern is that my COP is 2.5 at best. So I’m trying to find the best set up to maximise the COP, and then understand how to minimise the kWh demand (while being at a comfortable temp inside).
100% eclectic house, Ecodan 8.5kW - PUZ-WM85VAA, 210l pre plumbed cylinder, full house UFH total floor about 120spm, part is 1920s solid wall however its been fully internally insulated, part is 1950s foam cavity insulated and part is newbuild, with new double and triple glazing and MVHR.
I have recently modified to removing zoning and unnecessary complexity in my system and like you are now looking more at optimising running conditions.
do you have a heat and electric meter or are you taking reading to calculate COP from the unit / app ? this is the way I have to and find the data as only a guide
this is the cycling I am getting today at 11-12 with OAT of 6c as you can see pretty bad but my floors just cant give up the heat pumps minimum output to my understanding
my next steps are to possibly try auto adaption or schedule in shutdowns 3h on 1h off
how are you getting on it seems you are in a similar position?
@rich I have an 8.5kw ecodan to keep cycling to 1 per hour at any temp below 10C I need to run at 32C, anything less leads to a lot of cycling.
That is with upstairs rads on and UFH downstairs all open, even then the house will heat up and thermostats will cut off the heat pump after a few hours.
You will have to run it more on and off at a higher flow temp if you want to reduce/eliminate the cycling.
@rich I have an 8.5kw ecodan to keep cycling to 1 per hour at any temp below 10C I need to run at 32C, anything less leads to a lot of cycling.
That is with upstairs rads on and UFH downstairs all open, even then the house will heat up and thermostats will cut off the heat pump after a few hours.
You will have to run it more on and off at a higher flow temp if you want to reduce/eliminate the cycling.
What range of indoor temperatures do you get when operating your system in that manner?
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