I've got an Ecodan that I''m trying to configure to work it's best based on all the useful information here.
It seems to work fine during the really cold weather but at the moment (6C) I seem to get a lot of short cycling:
It's currently set to a target temp of 32 for 6C using WC.
This morning when it was about -3C it was running as following:
Generally the delta is always around 2 so I thought maybe it was this causing the short cycling. The pump speed was on 5 so I've dropped it to 3 (still within the flow limits) and heard the pump sound drop, but has had no impact on the delta.
I have Octopus Go and so run it at 45C for a couple of hours to take advantage of the cheaper rates. When I do this the delta is roughly between 5-10.
What could be causing this short cycling? Am I running the flow too low, and the fabric (it's heating up screed with UFH) can't actually take in any more heat?
I've got an Ecodan that I''m trying to configure to work it's best based on all the useful information here.
It seems to work fine during the really cold weather but at the moment (6C) I seem to get a lot of short cycling:
It's currently set to a target temp of 32 for 6C using WC.
This morning when it was about -3C it was running as following:
Generally the delta is always around 2 so I thought maybe it was this causing the short cycling. The pump speed was on 5 so I've dropped it to 3 (still within the flow limits) and heard the pump sound drop, but has had no impact on the delta.
I have Octopus Go and so run it at 45C for a couple of hours to take advantage of the cheaper rates. When I do this the delta is roughly between 5-10.
What could be causing this short cycling? Am I running the flow too low, and the fabric (it's heating up screed with UFH) can't actually take in any more heat?
Many thanks!
Do you have any room thermostats? If so then set them 2C higher than the desired room temperature.
@derek-m Sorry, should have mentioned that - I have the Mitsubishi wireless controller but it's already set higher to avoid interfering with the actual running. It's 5C higher than current temp.
@derek-m Sorry, should have mentioned that - I have the Mitsubishi wireless controller but it's already set higher to avoid interfering with the actual running. It's 5C higher than current temp.
If your controller is set to operate in WC mode, then you would normally have a large '0' (zero) shown on the display, which indicates that there has been no offset applied to the WC curve settings. If you have increased the offset to +5, then you are setting the required LWT to be 5C higher than the value calculated by the WC curve. If this is the case then reset the offset back to zero.
It is only 3rd party thermostats that need to be set slightly higher than the desired temperature, because they are on - off devices that can keep switching the heat pump on and off.
Is your UFH zoned, if you have different zones calling for heat at different times then you wont lose enough heat and the return temp will be too high causing cycling.
Although it doesn't sound like that is that is the case as you only talk about 1 thermostat that is set above the desired temperature.
What are the flow rates on the UFH, could there is too little flow to the emitters and that is causing the high return temperature.
Are all your rooms getting to the desired temperature?
@derek-m The WC is set to 0, I meant the Mitsubishi wireless room thermostat is to +5 of the current temp.
I do have UFH controls, but these are all set to +10 of the current room as I don't want them interfering with the general controlling of the HP - I want it done from a single source. In fact, the UFH controls aren't even wired up to be able to turn the HP on/off, they can only open or close their actuator.
@derek-m The WC is set to 0, I meant the Mitsubishi wireless room thermostat is to +5 of the current temp.
I do have UFH controls, but these are all set to +10 of the current room as I don't want them interfering with the general controlling of the HP - I want it done from a single source. In fact, the UFH controls aren't even wired up to be able to turn the HP on/off, they can only open or close their actuator.
Your heat pump, when it is operating, is producing more heat energy than that required to heat your home, so the Leaving Water Temperature (LWT) will start to increase and eventually will stop the compressor. When the LWT reduces sufficiently the compressor will restart, hence the cycling.
What are your WC curve settings? Do you have a buffer tank, lower loss header or plate heat exchanger installed?
Initially try changing your controller to fixed LWT mode with a LWT setpoint of say 30C. If your heat pump still cycles then lower the LWT setting by 1C at a time, and monitor the result.
@derek-m The WC is set to 0, I meant the Mitsubishi wireless room thermostat is to +5 of the current temp.
I do have UFH controls, but these are all set to +10 of the current room as I don't want them interfering with the general controlling of the HP - I want it done from a single source. In fact, the UFH controls aren't even wired up to be able to turn the HP on/off, they can only open or close their actuator.
Your heat pump, when it is operating, is producing more heat energy than that required to heat your home, so the Leaving Water Temperature (LWT) will start to increase and eventually will stop the compressor. When the LWT reduces sufficiently the compressor will restart, hence the cycling.
What are your WC curve settings? Do you have a buffer tank, lower loss header or plate heat exchanger installed?
Initially try changing your controller to fixed LWT mode with a LWT setpoint of say 30C. If your heat pump still cycles then lower the LWT setting by 1C at a time, and monitor the result.
Report back your findings.
Can't give you an exact answer on what's installed unfortunately, but I do have the preplumbed cylinder from Mitsubishi and then there are two cylinders on the wall (one of which I assume is the expansion vessel?):
There is no other equipment after this though, it goes straight to the manifold.
WC settings: it is set to 35C at -5C outside, down to 25C at 15C outside:
But I do currently have this set to +2 at the moment, been meaning to readjust the curve to reflect this.
I'll do the trial tomorrow that you mentioned, I won't play about with it right now as I don't want to make the house cold overnight!
I understand the idea behind it, lower the LWT till it matches or less than the heat loss (if I am understanding it correctly). But then, if I ramp up the LWT like I do overnight (45C) then it works fine?? Shouldn't this still not work?
@derek-m The WC is set to 0, I meant the Mitsubishi wireless room thermostat is to +5 of the current temp.
I do have UFH controls, but these are all set to +10 of the current room as I don't want them interfering with the general controlling of the HP - I want it done from a single source. In fact, the UFH controls aren't even wired up to be able to turn the HP on/off, they can only open or close their actuator.
Your heat pump, when it is operating, is producing more heat energy than that required to heat your home, so the Leaving Water Temperature (LWT) will start to increase and eventually will stop the compressor. When the LWT reduces sufficiently the compressor will restart, hence the cycling.
What are your WC curve settings? Do you have a buffer tank, lower loss header or plate heat exchanger installed?
Initially try changing your controller to fixed LWT mode with a LWT setpoint of say 30C. If your heat pump still cycles then lower the LWT setting by 1C at a time, and monitor the result.
Report back your findings.
Can't give you an exact answer on what's installed unfortunately, but I do have the preplumbed cylinder from Mitsubishi and then there are two cylinders on the wall (one of which I assume is the expansion vessel?):
There is no other equipment after this though, it goes straight to the manifold.
WC settings: it is set to 35C at -5C outside, down to 25C at 15C outside:
But I do currently have this set to +2 at the moment, been meaning to readjust the curve to reflect this.
I'll do the trial tomorrow that you mentioned, I won't play about with it right now as I don't want to make the house cold overnight!
I understand the idea behind it, lower the LWT till it matches or less than the heat loss (if I am understanding it correctly). But then, if I ramp up the LWT like I do overnight (45C) then it works fine?? Shouldn't this still not work?
Thanks for your help so far!
The heat loss, and hence heat demand, will be greater overnight, which means that the heat pump is unlikely to be operating at minimum output. The cycling occurs when the heat pump is operating at minimum output and cannot go any lower, but is still producing more heat energy than required to meet demand.
@derek-m Using MELCloud, I have a schedule to change it to flow temp mode which is set to 45 on the local controller, and then at the end of the cheap period the timer triggers it again and sets it back to WC mode.
@derek-m Using MELCloud, I have a schedule to change it to flow temp mode which is set to 45 on the local controller, and then at the end of the cheap period the timer triggers it again and sets it back to WC mode.
What happens to the LWT and RWT measurements during the boost period?
@derek-m Using MELCloud, I have a schedule to change it to flow temp mode which is set to 45 on the local controller, and then at the end of the cheap period the timer triggers it again and sets it back to WC mode.
What happens to the LWT and RWT measurements during the boost period?
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