I would suggest as a check, that you set your system into fixed Leaving Water Temperature (LWT) mode, with an approximate setting for the weather conditions, and then check and record the readings of all the various parameters on the display screens. This will hopefully confirm that the various sensors are providing correct information.

If you post the results or provide photo's of the screen displays it may then be possible to provide some assistance.

Hi there

It’s certainly an odd situation. First question from me is do you know where the temperature sensor is located that is reading the 25.5 degrees room temp from? Is it a remote Mitsi controller, a 3rd party sensor or is located in the plant room by any chance?

Posted by: @hjd

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Hi there

It’s certainly an odd situation. First question from me is do you know where the temperature sensor is located that is reading the 25.5 degrees room temp from? Is it a remote Mitsi controller, a 3rd party sensor or is located in the plant room by any chance?

It's most likely from the Main RC, the only other options are the Mitsi portable RC or a wired thermistor. The Ecodan doesn't take temperature info from 3rd party thermostats. I can't see the Main RC box in the plant room photo so I presume it has been wired through to another room.

In some ways it doesn't matter as only Room Temp mode uses the set temp to control its behaviour. Flow Temp and Heating Curve modes will only use the outside temp to set the flow temp, and will continue to keep going unless told not to by the 3rd party thermostat. So this would explain why changing the value of the set temperature has no effect when running in Compensation/Heating Curve mode.

You are playing with the heating curve and making it as low as you can but not seeing much effect. In the Service menu there is a setting (Service > Operation Settings > Heating Operation > Flow Temp Range) that controls the minimum flow temperature for the system to produce, the default is 30°, so unless that has been altered by your installer you might just be hitting that base temp despite being able to change the curve on screen below that value. The minimum you can set is 20°.

I don't know much operationally about UFH but I know it doesn't play well with Room Temp control as there is a lag between the heat being put into the slab and it then heating the room. I wonder if you have a big slab that can absorb a lot of heat it would take a long time for the slab to stop reducing the return temps enough for the Ecodan to pause its input. Perhaps keep an eye on the relationship between the flow and return temps as you run it.

Posted by: @hjd

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Hi there

It’s certainly an odd situation. First question from me is do you know where the temperature sensor is located that is reading the 25.5 degrees room temp from? Is it a remote Mitsi controller, a 3rd party sensor or is located in the plant room by any chance?

Hi, I didn't know where it was as I've always assumed the only sensors were either the Heatmisers around the house, or the outdoor sensor of the ASHP itself. But I've now determined that the FTC panel is a sensor in itself and this is located in the plant room which having put an independent electric temperature reader in that room, its also 25.5 degrees. This room is different to everywhere else as it holds all the house electronics so lots of units running and very warm, almost airing cupboard like.

Just had a look at the options of using a different sensor on the control panel, it was set to MAIN RC, also have Room/Zone of which there are 8 of those and also have TH1 which being the temperature reads -39c when I choose that, can only assume its something that isn't connected.

I wonder, if you go into the settings menu and look at the thermistor settings, what is TH7 reading? which should be the outdoor ambient temperature.

Posted by: @mcwatson1974

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Posted by: @hjd

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Hi there

It’s certainly an odd situation. First question from me is do you know where the temperature sensor is located that is reading the 25.5 degrees room temp from? Is it a remote Mitsi controller, a 3rd party sensor or is located in the plant room by any chance?

Hi, I didn't know where it was as I've always assumed the only sensors were either the Heatmisers around the house, or the outdoor sensor of the ASHP itself. But I've now determined that the FTC panel is a sensor in itself and this is located in the plant room which having put an independent electric temperature reader in that room, its also 25.5 degrees. This room is different to everywhere else as it holds all the house electronics so lots of units running and very warm, almost airing cupboard like.

Just had a look at the options of using a different sensor on the control panel, it was set to MAIN RC, also have Room/Zone of which there are 8 of those and also have TH1 which being the temperature reads -39c when I choose that, can only assume its something that isn't connected.

 

@mcwatson1974

can you explain how you normally use the system?  What's on the FTC screen, how do you set the zones and switch the heating on and off, are you using WC or fixed flow, etc.? 

In your current experiments, I assume the FTC screen is set to WC, i.e. like this:

Posted by: @harriup

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You are playing with the heating curve and making it as low as you can but not seeing much effect. In the Service menu there is a setting (Service > Operation Settings > Heating Operation > Flow Temp Range) that controls the minimum flow temperature for the system to produce, the default is 30°, so unless that has been altered by your installer you might just be hitting that base temp despite being able to change the curve on screen below that value. The minimum you can set is 20°.

Settings of the Flow Temp Range

Posted by: @hjd

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I wonder, if you go into the settings menu and look at the thermistor settings, what is TH7 reading? which should be the outdoor ambient temperature.

Thermistor Readings as below

Posted by: @kev-m

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can you explain how you normally use the system?  What's on the FTC screen, how do you set the zones and switch the heating on and off, are you using WC or fixed flow, etc.? 

In your current experiments, I assume the FTC screen is set to WC, i.e. like this:

So I've tried the treating it as a boiler (ie. heat up in mornings and evenings), tried the method of using all the Heatmisers to control the max temps around the house, tried the ramping up the temp to zillion degrees during the low overnight tarrif and hoping it was sufficient for the day. Now wanting to achieve the method of using Weather Compensation to control flow temp, sticking room stats on max and letting the flow temp do the work.

I thought I had it cracked yesterday. Put the curve back to normal curve, but did the minus adjustment on the FTC controller to -9 and I heard it click the heating off. Left it like that and thought all was good. Only to wake in the night finding our bedroom going past 22c, past 23c and heading for 24c before I had to shut it off. I looked at Mecloud (at 2am) and it didn't suggest the ASHP was actually heating, but the temps were still going up. And the ASHP must have been doing something as my hot water didn't achieve anything (its set to heat to 50c between 2.30am and 4.30am whilst I'm on a cheap tarrif but doesn't do this very well in the heart of the winter when my ASHP is heating the house). So I have to put a timer in so the heating turns off for a couple of hours whilst the ASHP deals with the hot water. See below for some of my FTC controller settings. I've cycled the sensor options just to show what options I've got, which are Main RC (says its 25.5c when this is used which is the temp of the plant room where the controller is), TH1 (which says its -39c so can only assume this isn't a sensor that is connected) or Time/Zone (which no idea what this is or does but I have 8 room/zones to choose from).

What is strange is that since putting it on weather compensator, the stats on max but with the house boiling up, my COP is much improved. Was generally less low 2's but last two days, it was 4.2 two days ago and 3.8 yesterday. 

If I could just stop the house over heating, I'd be happy!

Thanks for sharing. I had just wondered whether there was something wrong with TH7 and it was misreading the external temperature, thinking it was much lower than it was and hence never reaching the point where the ASHP was switched off. But looks OK to me. 

I am stumped I am afraid.

Although, I did just go an look at my own system. Even when in WC mode, my TH1 still displays the temperature from the Main RC - which should be 25.5 rather than the -39 you are seeing. When a thermistor is not connected it just shows blank. So perhaps there is something wrong the -39 in WC mode, which is convincing the system to just keep running as it must think the house is freezing!

@mcwatson1974

TH1 is the remote room temperature sensor (hardwired or wireless), which is an optional extra. I suspect that you do not have this installed, hence the display showing -39C.

Try each of the different options in turn under 'room sensor settings'. I can't remember if it is on Ecodan's, but I think that on some of the controllers it is necessary to switch them off, and back on again, for certain setting changes to take effect.

In your system do you have a 3-port changeover valve to select CH or DHW heating, or do you have two 2-port valves? I would suggest that you check that the valve or valves are operating correctly, and not supplying hot water to the heat emitters when heating the hot water cylinder.

Posted by: @derek-m

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In your system do you have a 3-port changeover valve to select CH or DHW heating, or do you have two 2-port valves? I would suggest that you check that the valve or valves are operating correctly, and not supplying hot water to the heat emitters when heating the hot water cylinder.

I have been wondering if there is any link between the DHW and the UFH as I've been watching it for the past couple of days and I've had the downstairs calling for heat but left the upstairs isolated. The downstairs as warmed up despite the CH function of the ASHP not heating at all. The DHW has been heated to 53c overnight each night so not sure if the UFH is utilising any of this heating or temperature although, and here is a comment of a complete amateur, I'm assuming there is no sharing of the UFH water with the CH / tank water as the former has antifreeze within so I've always assumed they were kept separate and therefore heated separately. But I'm assuming they pipes pass through the same heating functionality within the ASHP and so could still share the heating process. Or I'm talking complete rubbish.

Anyhow, no idea on the whole 2 port v 3 port thing but I do have the Diamond Cover maintenance with Mitsuibishi and I've only ever used them for the annual maintenance so maybe I'll make use of calling them out to have a look at the problem.