@allyfish the system was flushed maybe 6-8 months before the install happened.  I did ask at the time and the installer said the system was already clean and didn't need another flush.  Maybe another example of cutting corners

When the heating started after the summer this year I got an FU fault a couple of times but has been good for a while now.  This is when Grant said there is a flow issue somewhere in the piping.

Posted by: @soniks

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@derek-m 

You just reminded me I have a pizza oven thermometer which I can use

In my lounge 

There are 4 radiators.  I took the readings from 

2m K2 radiator new - top : 32c,  bottom : 24.8c

1m K2 radiator new - top : 34.1c, bottom : 29.8c

1.6m K2 radiator new - top : 22.3c, bottom : 17.1c

low height 43cm double radiator existing - top: 35.7, bottom : 32.9

 

Did you get warm water to the cold radiator? If not then remove the TRV actuator head and ensure that the valve plunger moves freely.

@derek-m

@allyfish No I don't have a flow setter/guage AFAIK - where would it be installed normally.

The pump is a Wilo 25/80 pump attached image.  Can't see the model number anywhere but I think it may be a Wilo-Yonos Pico pump.  I think it's on the highest setting at the moment.

I do agree with you the flow rate needs to be resolved first before balancing.  From the discussions the discussions on the forum perhaps it is a piping issue as the property has been extended a couple of times by the previous owners and I wonder whether the piping has been done properly.  Are there are any heat detectors that could show where the pipes are layed if I turned on the heat pump to the max and potentially give an indication of the pipe size based on the heat emitted from pipes.

There is a Mag one filter installed.  How can I tell if the heat pump heat exchanger is blocked?

@soniks thanks for that, the in-built pump in the Grant Aerona 17kW can provide 50l/min at 5m head on the highest speed setting. A Wilo Pico RP25/80 in series with that can provide 50l/m at 3m head. (25/80 is a common fixed speed CH pump badged up by various manufacturers) Pumps in series raise the head, so in combination you have 50l/m at 8m head. That's more than enough pumping capacity. I would recommend a specialist heating engineer is brought in to investigate further.

Flow gauge and flow setter. For properly commissioning a Grant ASHP setting the flow is essential. The grant units have fixed speed pumps and no internal flow sensing, so they rely on the installer commissioning this to suit the make/model and design water leaving temperature. If you don't have one installed I would recommend fitting one. You can DIY but it's probably a system drain down job.

The condition of the MagOne filter might give you some idea as to how clean or not your system pipework is. You can open that up for inspection & cleaning without drain down, but stop the system first. If there's a lot of build up of black sludge on the magnet and/or evidence of other contamination, then a power flush of the piping system may be a good idea. 

You can't really check the plate heat exchanger without a full drain down, disconnection of the outdoor unit flow and return pipes, and reverse flushing to see what comes out! A competent heating engineer who has power flushing equipment could do that for you at the same time.

When the system is being power flushed the engineer would be able to look further into the circuit pipework for any obvious issues.

@hughf Thanks have PMs @heacol to check availability and area he covers.

Are there any other reliable Heating Engineers that have experience with Grant heat pumps that anyone would recommend?

Sorry I should have clarified in my last post - reliable heating engineers that covers the Surrey region

Posted by: @soniks

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Sorry I should have clarified in my last post - reliable heating engineers that covers the Surrey region

Adam Chapman of heatgeek is based around Guildford, he should be able to advise on any local engineers who are competent.

@derek-m I measured the temperatures on the radiators again the I can see the following readings.  Slightly higher than before without changes.  Perhaps it's because it's not as cold at the moment.

               Top       Bottom 

K2 1m      36.7     31.1

K2 1.6m   33.1     25.5

K2 2m      31.2     23.9

Out of interest what sort of temperatures would be considered normal for radiators with a heat pump.  I set the flow temp to 50c at the moment.

@hughf Thanks have contacted him and the company he is linked with is not taking on any new work until next year.

Posted by: @soniks

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Out of interest what sort of temperatures would be considered normal for radiators with a heat pump.  I set the flow temp to 50c at the moment.

Over the last 24 hours, mine have ranged between 28 and 38 degrees while heating. If you set the flow to 50, I expect at least one radiator should be achieving near that (45+?) at the top. There's a discussion on here somewhere where people with temperature sensor guns pointed them at their radiators, which you might find by searching.

Posted by: @soniks

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@derek-m I measured the temperatures on the radiators again the I can see the following readings.  Slightly higher than before without changes.  Perhaps it's because it's not as cold at the moment.

               Top       Bottom 

K2 1m      36.7     31.1

K2 1.6m   33.1     25.5

K2 2m      31.2     23.9

Out of interest what sort of temperatures would be considered normal for radiators with a heat pump.  I set the flow temp to 50c at the moment.

If the temperature of the water coming out of your heat pump is in the region of 50C, then you should be seeing temperatures not much below that at the top section of your radiators. If you are not getting such temperatures then there must be some mixing and cooling of the water within your system. If that is the case then it can seriously reduce the overall efficiency.

I would suggest that you measure the temperatures on the pipework around your system to try and locate any problem areas.