Grant 13kW Aerona3 - issues getting zones to temp

Crimson · 2024-01-16T07:17:28Z

Hi all, New here and looking for some advise. I have a 220sqm property with a Grant 13kW (I need to check if it’s 13 or 17) Aerona 3 ASHP installed as part of a full renovation/extension heating and plumbing redesign. We moved in on 1st December and have never quite had the heating be up to scratch. There are 4 zones each with Heatmiser panels (mainly floor space measures listed not total room sizes) 1 underfloor heating open plan kitchen/dining area approx 44sqm 1 utility with underfloor approx 8sqm Ground floor heated by radiators (Eskimo) - consists of 2x 28sqm living rooms, 1 hall at 16.5sqm, 1 downstairs wc 2 sqm - approx 74.5sqm First floor heated by radiators (Stelrad/towel rads in bathrooms) - consists of 2x 20sqm bedrooms, 1x 18.5 sqm bedroom, 1x 16sqm bedroom, 1x 9.5 sqm bathroom, 1x 3.8 sqm ensuite, 1 Wc 2 sqm, 1 storage cupboard 1sqm - approx 93sqm The downstairs area seems to never hit the desired temp of 21c. I have set it at 21c on and 19.5c off on the heatmiser oanel. Every morning it’s not even sitting at 19.5c. Of note the hall and landing essentially same space so I always wonder if that is an issue as it’s serviced by just 2 radiators between them. All rads were sized according to heat calcs performed by the plumbers. The Grant is running with weather compensation. The plumber/installer came other day and set: 2101: 50c (not sure why set this as that’s the fixed point but keeps referring to the weather curve) 2102: 50c 2103: 35c 2104: -4c And on the panel set to 40c. This improved zones by I reckon 1c but I still never see the downstairs zone hit its desired temperatures. Of note in mornings the rads downstairs never feel as warm to touch as later in the day so I wonder if the system is struggling at coldest points of the day? All radiators have TRVs opened to max. hot water has been an issue too but panel for that has lost power. Seemingly the second time with a power cut. Am awaiting electrician to come and get that back on and check what settings that has. im concerned as can see the electricity meter is flying up and we’ve not got a system working as it should. Can provide more info if needed and photos etc. be good to have some advice as I’m at the mercy of the plumbers who so far on this project have made some blunders so don't quite trust their setup. To clarify this is a Aerona 3 13kW.

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Crimson

(@crimson)

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Topic starter 25/11/2025 2:47 pm

Posted by: @jamespa

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Posted by: @crimson

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It's likely that I'll need to find my own independent Heat specialist, as not pleased they (installers, builder and specialist) all converse with one another and suddenly out of nowhere get to no availability.

Or just commission a plumber to do the replumbing?

As soon as you touch it your installer will argue that it voids the warranty and I doubt any third party will warranty a system largely installed by someone else (why would they?). Therefore if you are going to bypass the LLH you have already accepted the risk of a warranty argument (mad I know). If you are going to do this you might as well cut to the chase and get a regular plumber to change the pipework.

Sorry I didn't explain the situation fully, the agreement was the work would be done with the installers agreement and no warranty void, as they've worked together before (and get advice off him). e.g. it's "fix this issue" not the entire install is at fault scenario.

I was considering the other option if BUS fails (e.g. our esteemed Government pulls it), but looks like that's going through now in hope if it's pulled tomorrow, our application is in the system…

So now it's a waiting game until next year (again!!)/hope specialist gets a free day and comes over before then.

I have managed to pull the top of the WC down to 42C now the house material seems to be back to a decent state.

So I'm now fully back to where I was before works done on the 5th of November, a situation totally unavoidable had the installer followed the specialist's advice laid out in July.

Least got movement on the BUS (only taken 2 years!)…

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JamesPa

(@jamespa)

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Joined: 3 years ago

Posts: 4164

25/11/2025 2:56 pm

@crimson

Noted. At least you now have a confirmed route forward and a warm house. That, in itself, is a step forward however frustrating the wait. Installer needs to go back to school!

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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Crimson

(@crimson)

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Joined: 2 years ago

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Topic starter 25/11/2025 3:09 pm

Posted by: @jamespa

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@crimson

Noted. At least you now have a confirmed route forward and a warm house. That, in itself, is a step forward however frustrating the wait. Installer needs to go back to school!

Oh the installed needs to go somewhere, that's for sure! But unfortunately with them contracted by the builder/the BUS etc I've still got some overarching presence of them (ghost of 2 Christmases past now…).

As ever I'll report back on how things go.

My final thought on this, is as it's 48 pages of waffle from me, back and forth. It would be good to create a summary post, if an admin wouldn't mind - once all is solved.

I could list how conclusions were made, the sorts of things found etc. In some hope that should this happen to someone, all the mad points are listed (LLH with arrows on back to front etc, strainers blocked, primary circulating pumps, PCB F5 fault, bizarre warranty statements).

And as ever, appreciate everyone's input and suggestions, wouldn't have got this far without them!

👍

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