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17kw Grant Aerona heat pump not performing

soniks · 2022-12-11T17:30:24Z

Hi I have a 17kw Grant Aerona heat pump to heat a large 4 bed detached property and I have to say the installation has left me wishing I never embarked on the heat pump journey. I went through Green Match who put me in touch with a couple of installers of which I selected the one that said I would get a Grant manufacturers MCS install - this was the primary reason I went ahead with the install. As it turns out the person I spoke with was really just a middle man/sales person who seemed knowledgeable about heat pumps and even said at one point he was involved in setting up the MCS scheme himself which gave me some confidence that they would so a good job. The work was actually done by an independent installer (ex Grant engineer) who started the install and then half way through went on holiday leaving us without a working system requiring us to resort to using the immersion heater for hot water. Thankfully it was summer and we didn't need the heating. I can live with that if we were to get an install that worked. He completed the install and the system didn't warm any of new radiators they was cold and at best tepid. We also had a number of radiators oversized in the rooms based on the heat loss calcs but most didn't even come to temperature. I said the system can't be commissioned in the state it was left as it was just not working as per the design. I had a new born on the way and said this would never work in the winter. They made all sorts of excuses saying it's a piping issue and nothing to do with the install and trying to absolve themselves of any responsibility. They they went on to say it because we had a one pipe system which was total rubbish as it turns out after speaking with other plumbers. In the end they would not give me the MCS certificate until I made the final payment and was left with no option to pay given new born was due. MCS were pretty much useless too and I really don't understand why they exist as they do not protect the consumer at all. In the end I got another heat engineer in and he suggested putting in a circulating pump funnily in the same location as the one they took out because the heat pump circulating pump should have been powerful enough. This helped distribute the heat a little better although not to the levels expected. In short, 3 years on I would say the system isn't performing and my bills have increased significantly as opposed to being cheaper as I told when all the calculations were performed. About a month or 2 after the install the compressor failed and the whole unit had to be replaced and I've had several blockage faults which shuts the unit down. Grant have been in a couple of times and they have told me the flow rates should be a lot higher than they in my system - 35 litres which I thought seemed high given my incoming flow rate from the mains is only 23lpm. I looked at the documentation and for the heat pump I have it mentions a minimum of 15lpm. Wondering if anyone else has their flow rates for when the heating is on and when the hot water is on? I also installed the metering and monitoring option and can see that my efficiency looks to be 2.4 at the moment for December so far which is far lower than what Grant advertises. The highest I had is 3.26 in Aug when I wouldn't have been using the heating at all and only warming the hot water. One of the things I'm now considering is putting under floor heating to remove any possibility of piping issue although I'm sure this will be pretty expensive. I would love to hear from anyone else suffered similar issues and what they have done to resolve. What I've learnt is to use established companies showing a good track record of designing a system properly and good after care as when things go wrong because they will inevitably. Sorry for the long post.

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Air Source Heat Pumps (ASHPs)

Last Post by AllyFish 3 years ago

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AllyFish

(@allyfish)

Prominent Member Contributor

Joined: 3 years ago

Posts: 518

07/08/2023 5:07 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)

Honorable Member Member

Joined: 4 years ago

Posts: 489

07/08/2023 7:07 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)

Trusted Member Member

Joined: 3 years ago

Posts: 70

Topic starter 08/08/2023 9:19 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)

Trusted Member Member

Joined: 3 years ago

Posts: 70

Topic starter 08/08/2023 9:21 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)

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Joined: 3 years ago

Posts: 518