Posted by: @fleurcules

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It was sitting at 35 for a bit, now up to 36. Although oddly the rads have just gone from feeling about as warm as they ever do to feeling noticeably colder.

OK well so far as I can see there are now only three possibilities

1. The heat pump is unable to get up to the set temperature because of a fault

2. The heat pump is unable to get up to the set temperature because too much energy is being dissipated even though there is no fault.

3.  The heat is unable to get up to the set temperature because something else is stopping it even though there is no fault and its not dissipating a load of energy.  However I can see what condition would caused this.

In case (2) then something (eg the house) would be getting pretty warm with perhaps 14kW flowing into it.  In case (3) you would at least expect it to cycle.

You could check return temp and flow rate in the UI to calculate how much heat the heat pump is generating, and electrical power consumption to check how that corresponds.  This would unequivocally differentiate the cases above.

I would say 95% probability there is a fault with the unit itself.  I would do those final checks (when its running obviously), summarise and approach your installer/Grant to fix.  Im surprised the A1 error isnt constant unless there is in fact another internal fault as yet unrevealed. 

Ok think I'm done tinkering, have gone back to WC mode. Under fixed temp settings the highest it got to was 36, then dropped back to 35/34.

@jamespa thanks for all of your help so far! 

Edit: just seen your most recent reply. Energy consumption is pretty much steady at around 2kW whenever it's on (only higher if e.g. the kettle is on, occasionally drops lower).

Posted by: @fleurcules

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Ok think I'm done tinkering, have gone back to WC mode. Under fixed temp settings the highest it got to was 36, then dropped back to 35/34.

@jamespa thanks for all of your help so far! 

Edit: just seen your most recent reply. Energy consumption is pretty much steady at around 2kW whenever it's on (only higher if e.g. the kettle is on, occasionally drops lower).

Noted.  Its a pity you didnt capture the flow rate and return temp when it was in fixed FT mode, but you could capture it now or just go for the 95% case that there is a fault (unless of course Im missing something!) and get Grant in.

Assuming you do do that don't let the engineer tell you its working until he/she has demonstrated operation at 55C or thereabouts, ie sufficient to heat DHW!  Good luck!

First time posting so bear with me. Some bits that have helped me with my bodged grant install. Note that I haven’t necessarily correlated this with your issues so please pick and choose and YMMV

1. Balance your heating emitters. For my money this does not get spoken about enough, insane how much this can benefit your system for free. This includes any UFH that was running on reactive controls (room thermostats).

2. The unit you have has a pump that has three speeds set by dip switches inside the external unit. This means the oft repeated 5 degree dt does not necessarily apply. The unit can probably modulate to about 25% output. You want roughly 2 degree dt at this point and 8 degree dt when it’s outputting at its max. I note you have seen the flow does not get high enough, I wonder what your dt was at that point. Perhaps a useful experiment might be to set your flow to 45 as before and check your dt when it seems to “stall” if this is above or at 8, maybe up your pump speed.

3. As mentioned before do inflate your thermostat temp way past the  desired point, salus thermostats do have TPI by default which means that it will turn itself off and on without you noticing.

4. Advanced, consider running a wire to the modbus ports on the outside unit. I have done this and there is a helpful guide on the web which i will try and find if you are happy to do some tinkering. This, mapped into home assistant, will give you all the data about what your heat pump is doing that you should need.

Sorry about your experience with grant. I’d be minded to get a general heat pump installers opinion as the issue is likely the install and not the unit themselves which are actually quite capable.

The units are rebadged Chofu units from Japan which is a well regarded company shipping to quite a few countries i believe. 

@adamp thanks. I've now spoken to someone from Grant and they are going to send someone out to replace the discharge temperature sensor. He seemed confident this would fix my issues and is also likely the cause of the A1 error code. Fingers crossed!!

@fleurcules thats great news.  My advice is to make sure he demonstrates high temperature operation and if you can note the cop when he does it (difficult I know for a short run).  Then he cant easily leave saying 'its fixed' if, in fact, its something other than the sensor!

Just to update the thread, I now have a new heat pump!! The Grant engineer came last Monday, and found that there wasn't enough gas in the system so likely a leak. I'm away on a work trip but my husband was then left without any heating for a week, but luckily we were able to demonstrate that the previous owners had serviced it so Grant came today and fitted a new one. Hopefully that's the last of the issues!

@fleurcules thanks for posting an update and I’m glad you were able to get to the bottom of it.

On a semi-related note, I’ve been genuinely surprised by the number of comments we’ve had on our YouTube channel (and a few on the forums as well) this winter from homeowners reporting heat pump failures that, on investigation, turned out to be refrigerant loss. That’s interesting, because both installers and manufacturers consistently tell me that refrigerant leaks are extremely rare.

It does rather underline why the industry is pushing towards refrigerants like R290 with a much lower global warming potential… if leaks do happen, the consequences are at least far less severe.

@editor We come across about 4 leaks per year on sealed heat pump systems out of about 200 we see. This is why the service must be carried out by an F Gas engineer so it can be leak checked. As for R290 if installed poorly without adequate ventilation the damage caused to the environment is zero until it maybe it ignites, then it could be catastrophic.   Generally though leaks are rare and nothing that escapes would ever compare to the damage by air travel or another rocket to the moon!