@derek-m

Sorry not to reply before, have been offline for a few days.

Grant sent an engineer to check out our system.

No leaks found although some aspects of our installation could not be inspected (such as the conduit running from the ASHP to the house).

Pressure at the heating expansion tank was checked and found to be OK (and I was told the expansion tank pressure gauge is indeed not working).

Hot water problem fixed. Timing of heating and water has to be aligned as ASHP can't heat both at once (this is normal). Engineer set heating to go off when water is on. But he did this by setting the heating timer to off. This cuts power to the room thermostats so they no longer show the correct date and time. I think I need to cut the call for heat by leaving the heating timer always on but setting the room thermostats to a low level during periods when the water is timed to go on. I will leave for now but need to change the timing and temperature sequence on each individual room thermostat - which is a pain.

I showed engineer photos of our system being installed. He questioned the spacing (not close enough) of the heating loops in the floor. Not conclusive but even if wrong clearly cannot be changed.

He confirmed that the ASHP itself is working correctly.

Action for me:

1. Find another engineer to do regular servicing and maintenance. Grant's own man was the best yet but this was a one off and I think they normally only outsource.
2. Fix faulty gauge and a relief valve which did leak but is screwed down. Grant suggested to contact my installer but as documented before they are no longer MCS registered or do heat pump systems.
3. Get an electrician to replace the ASHP supply cable which is not external grade wiring. Also to install a meter on that supply so I can see how much power the pump alone is drawing. At present I can only measure total household usage.
4. Try and get the bathroom radiators to heat all the time (this has been the least of my problems).

Overall power usage this month has been similar to last year (about 25% more than May 2019) but it has been an unseasonally cold May. Now the weather is finally warming I see usage dropping to about 23kWh per day which is in line with May 2019. But the big savings from getting the system right come between October and March. Our rolling 12 month total usage is still distorted by the horrendous January figures. But now down to 15,300kWh  from 15,900kWh in January. But at this point in 2019 it was only 11,800kWh. With a 150 sqm house we are at roughly 100kWh per sqm p.a. As an aside I just saw some figures for a Passivhaus suggesting as little as 27kWh per sqm p.a. Scarcely believeable - must exclude power and lighting.

Mike

Hi @Mike 

Did I read that right, your avg. daily kWh for May is 23kWh? If you don't mind me asking, how many people are living at home?

Whilst May has been a bit of a damp squid for us, in our house which is approx. 130 square meters we're averaging 7.3kWh per day for May - we're due in October and no doubt will see our winter usage increase vs last year.

I was unaware that ASHP’s are incapable of heating water and radiators simultaneously.  Really?

@morgan Yes I've been told the same thing by our installers 

Since our ASHP installation on 21st April we’ve used 234kWh or 6.69kWh per day. Hot water is heated via solar PV and electric diverter. There have been a few cooler nights when the Daikin has kicked in for heating, but otherwise the ASHP is effectively off now until, I would guess September. 
Against the MCS estimates, I’ve used double the electric prediction, so perhaps April/May were colder than I thought?  Or the Estimates wrong 😳🤞

@mike-patrick I’m glad you had Grant engineer out to review your system. Can’t Grant suggest a reputable trained engineer through their network?  Did you take out or do Grant offer a support contract?  One of the reasons I picked Daikin is their annual support contract, fixed for 10 years. £234 includes annual service and all spares and labour per year. 

@julianc has your diverter been heating the hot water even tho most days have been overcast and grey?

@dant

Yes that's right.

The best figure we have ever had was avg 16kWh per day in July 2019.

That is total power usage for 2 people. So includes cooker, washing machine , tumble drier, everything.

We don't have PV  just the heat pump.

Mike

@julianc

I don't believe there is a support contract with Grant.

Our installer ( 4 years ago) didn't even register the system with Grant and I've been playing catch up.

Mike

@dant if it’s a dark or overcast day, then no, I have run the ASHP overnight on our cheap Octopus Go tariff (it is set up as such to heat to 80% if the cylinder drops below 30%). Or if my wife or daughter have a 3hr shower 🤪

But 90% of the hot water is via PV (same as before the ASHP). 
Solar thermal would be slightly more efficient at heating water on overcast days, but I’ve read previously that when they fail, it’s difficult to get parts or maintenance. One connector fused on my solar PV in 9 years and my regular electrician diagnosed and sorted it for £50. 

@julianc, that's a very low usage.  Our heating is about 17kWh per day over the same period.  What sort of temperature do you have your house?  Our ASHP has been on in the morning and evening every day so far.  Are you saying your MCS estimate was only 3-4 kWh per day for April/May.  That seems extremely low. 

We have a Nest thermostat in the hallway. Set at 17.5 in mornings. Goes to 18 to 19.5 in the evening. We have tweaked it to 20 a couple of times. And adjusted the TRVs in the dining room up when ate in there. 
The radiators haven’t got as hot as the old oil boiler days, but the Nest switches off as it has reached temperature. 
We do wear wool jumpers in the home 😉

@kev-m for the same period, so the 21st April - 25th May, we have used 275kWh, an average of 7.8kWh per day. 

The heating hasn't been on really, maybe one or two days. The house is usually between 18-20, the odd day when the heating did come on it had dropped to 17.5 degrees in the living room.