@harriup Thanks for responding.  

The L9 error we are pretty confident was resolved.  One question that I have just asked myself was whether the unit was behaving like this prior to the L9 error.  I need to think back.

Re: the ASHP behaviour - when the random calls are made, the ASHP is active - fan spinning.  Not sure I have seen it run enough yet to know how hard it is working, but it seems fairly full tilt.  It then stops when the temp gets up but the circulating pump in the loft keeps running for 10 mins once the ASHP shuts down.

Thanks for the Facebook idea - I have found the link and requested to join the group.

Most of the noise seems to be coming from the circulating pump, which is a Grindfors UPS3 A attached to the ASHP Outlet just before the splitter between DHW and Heating.

Hi there,

Apologies if this point has been covered before.  What is the connection between your ASHP and your underfloor heating?  We had this with ours where there was no connection so they were running independently of each other which caused all sorts of strange noises.  If the underfloor heating isn't calling for heat and the ASHP thinks it needs to you will only be heating a relatively small amount of water.  

Many thanks

Drew 

@crustydoodle

On first assessment I believe that the problem may be associated with one or more of the temperature sensors and possibly the settings within the controller itself.

Your graphs show that the heat pump is being started at approximately the same LWT and then being stopped at approximately the same higher temperature. This indicates some form of control by the controller.

I would suggest that you start by recording the readings from each temperature sensor, at say 10 minute intervals, to identify which of the sensors may be initiating heat pump operation.

Then locate each temperature sensor and confirm that it has good thermal contact with the pipework and that it is adequately insulated.

I assume that your loft area is not insulated at the roof?

Do you have anti-freeze within your system?

@derek-m no anti-freeze I think.  And the loft is not insulated at the roof.  Is this likely to be an issue?  We were told it shouldn’t be.

when you are referring to the sensors,  I assume you mean the thermistor readings?  I think checking the contacts may be getting beyond my skill set though.

As an added symptom, I just set our stats to trigger the heating to come on.  This time it didn’t trigger any activity for the ASHP.  I am now wondering if the two systems are not talking properly. 
when we ran it for the trace I originally posted, the flow and return temps were already low and so it came on to heat the heating loop but the UFH actuators were open and then it didn’t get to temp to switch it off until we turned off the heating - you can see it does what I thought was an abnormal cycle immediately after the heating was turned off.

Today I’ve turned on the heating when the flow/return temps were already at 45degC and nothing has triggered.

i will try again later when the temps for the probes on the heating loop indicate something lower and see what happens.

What underfloor heating control system is it that you have fitted?  Are you sure the two are connected?  

Many thanks,

Drew

@drew-pa it’s a Heatmiser control system.  They are supposed to be connected but I am starting to wonder…….

We had a similar issue with our system. It certainly sounds like you have something similar.  It would be a good starting point for you for sure.  Having two different control systems didn’t work for us.  It will be intersting to hear how this works out, good luck.  

Drew 

Posted by: @crustydoodle

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@derek-m no anti-freeze I think.  And the loft is not insulated at the roof.  Is this likely to be an issue?  We were told it shouldn’t be.

when you are referring to the sensors,  I assume you mean the thermistor readings?  I think checking the contacts may be getting beyond my skill set though.

Yes, the sensors are the thermistors.

When I refer to 'good thermal contact', I mean is the thermister either fitted in a suitable pocket or clamped to the pipework such that it is measuring the true temperature.

Did the recording of the thermistor temperatures indicate which may be initiating the starting of the heat pump?

@derek-m I did some checking, not every 10 mins as I couldn’t get to the loft that often.  However it is THW1 and THW2 that seem to be driving the response.

I also ran another heating test, this time turning up all the stats just before an expected ‘abnormal’ heat pump activation.  The heatmiser system opened and the ASHP did not activate.  Then when the Flow temp fell to 30degC the circulator kicked in and shortly after the ASHP.  This then seemed to heat the UFH, and there was a differential between Flow and Return suggesting that some heat was being dissipated into the house.

When the heating ended its 1 hour run, the flow and return temps returned to being identical (at around 32DegC).  I’m expecting the temps to shoot backup to 60degC now the heating circuit is closed but will see.

@crustydoodle

Just to clarify if my understanding is correct.

You started the heating system by raising the setting on one or more thermostats. The UFH pumps started but not the ASHP. Did the primary water pump start with the heatmiser or when the heat pump started?

After some time the LWT cooled to the point where is started the heat pump and the primary water pump. Is this correct?

If that is the case then you need to get your installer back, since any call for heat from your heating system should also initiate your heat pump.

How competent would you consider your installer?

@derek-m that’s more of less right.

When I turned on the heating, the actuators opened but no pump came on.  Only 20 mins later the primary water pump and then the ASHP came on. 

i had considered the installer competent - they were recommended by someone we know and most of the work they have done seems good.  There was a loose cable to a pump, but things happen.  However, not being able to diagnose this issue is a concern, especially if it does turn out to be the UFH control connection to the Mitsubishi control.

the other area that has knocked my confidence in them is there being no flagging of noise concerns with the tank location.  Even if it does get sorted, I think the noise from the circulating pump is going to be an issue.