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17kw Grant Aerona heat pump not performing

 
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Air Source Heat Pumps (ASHPs)
Last Post by AllyFish 2 years ago
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 AllyFish
(@allyfish)
Noble Member Contributor
Joined: 3 years ago
Posts: 485
07/08/2023 6:07 pm  

It really sucks Sonix, you've tried to do the right thing and been badly let down. I would be surprised if the plate heat exchanger is badly blocked, to the point the primary flow is seriously restricted. It would have to take a hell of a lot of quite large particulate contamination to do that, or some massive scale build up due to some water quality issue. Grant ASHPs don't have particulate strainers on the inlet return water connection. The magnetic sludge that builds up on ferrite magnet cores is very fine - too fine for particulate strainers, which is why magnets are used. Reverse flushing using various chemical agents should clear it. The brazed plates are stainless steel, but check compatibility of rubber hoses, plastic pump housings and impellers, etc., before chucking aggressive flushing and cleaning chemicals inside it.

My hunch is an issue with the primary circulating pump. It's relatively easy to remove for inspection change out, and a competent plumber could do that. A primary pump replacement is not new monobloc territory cost. You wouldn't change out a combi for a failed circulating pump, so surely it's not unreasonable to expect Grant to hold circulating pumps as a spare part? Even if they don't the pump will be a generic product and you may be able to source a replacement yourself. Grant are stockists of badged up Chofu units, probably with little spare parts holding in the UK. Dare say they'll probably advise changing the whole monobloc for relatively minor component failures which could and should be repairable. 


   
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 HughF
(@hughf)
Noble Member Member
Joined: 3 years ago
Posts: 488
07/08/2023 8:07 pm  

The grant pump isn’t pwm controlled so you could literally fit the cheapest one from toolstation and it would work without error codes.

Off grid on the isle of purbeck
2.4kW solar, 15kWh Seplos Mason, Outback power systems 3kW inverter/charger, solid fuel heating with air/air for shoulder months, 10 acres of heathland/woods.

My wife’s house: 1946 3 bed end of terrace in Somerset, ASHP with rads + UFH, triple glazed, retrofit IWI in troublesome rooms, small rear extension.


   
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 soniks
(@soniks)
Estimable Member Member
Joined: 2 years ago
Posts: 70
Topic starter 08/08/2023 10:19 pm  

Grant have now agreed to replace the circulating pump to see if that's that root cause of the issue this week as it's been power flushed twice with fx2 and another stronger chemical already and the water didn't look that dirty according to the heat engineer.  He was expecting it to be black and it wasn't that bad he said.  The power flush is using a Kamco flush which has a flow of 200lpm.  So fingers fingers crossed it's the pump at fault.


   
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 soniks
(@soniks)
Estimable Member Member
Joined: 2 years ago
Posts: 70
Topic starter 08/08/2023 10:21 pm  

@hughf sorry what does pwm controlled mean?  The Grant pump is a pretty powerful pump with 12m head I'm told and as it's the only pump we have now it would need to be at least as powerful.


   
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 AllyFish
(@allyfish)
Noble Member Contributor
Joined: 3 years ago
Posts: 485
09/08/2023 11:50 am  

@hughf Chofu use an end suction centrifugal pump however, not an in-line pump. Chances are only the OEM pump will fit. 

image

   
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