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 09/11/2025 9:18 pm

In a way I’m glad the water heating shows this up. As least then its not something beyond the plant room, but perhaps having a bigger LLH further exaggerates what was going on before.

Builder said the installer has been radio silent though said he was monitoring house temps over the weekend. Am sure them going down didn’t give him opportunity to say he’d fixed it lol.

Another odd thing. I still get the metallic bang in one of the living rooms on an Eskimo rad. And thats happened during a hot water cycle when the zone is shut. I know that would seem a smaller issue amongst all this, but any ideas what it could be? I think its the non TRV side of the rad…

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JamesPa

(@jamespa)

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09/11/2025 10:01 pm

Posted by: @crimson

↑

Also realised hot water tank was sitting at 35C…

I do run that to the bare min, 1 cycle a day for an hour. If no one has a shower etc, it will sit lowest 44C, so fine for using.

probes show 45C on pipework flow into plant room from ASHP into LLH, 34C top left of LLH and 34c just before 2 port valves - heating/water tank.

so no wonder thats struggled.

would seem secondary pump is now buggered

With that drop its clear that very little hot water is getting from the primary into the secondary so either pump problem or piping problem. Has he plumbed the LLH back to front eg with primary and secondary going in opposite directions. That would cause all sorts of interesting effects none of which are good.

It beggars belief that the installer didn't check this before he left. Id be tempted to lock the door next time!

This post was modified 1 hour ago by JamesPa

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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Topic starter 09/11/2025 10:18 pm

Posted by: @jamespa

↑

Posted by: @crimson

↑

Also realised hot water tank was sitting at 35C…

I do run that to the bare min, 1 cycle a day for an hour. If no one has a shower etc, it will sit lowest 44C, so fine for using.

probes show 45C on pipework flow into plant room from ASHP into LLH, 34C top left of LLH and 34c just before 2 port valves - heating/water tank.

so no wonder thats struggled.

would seem secondary pump is now buggered

With that drop its clear that very little hot water is getting from the primary into the secondary so either pump problem or piping problem. Has he plumbed the LLH back to front eg with primary and secondary going in opposite directions. That would cause all sorts of interesting effects none of which are good.

It beggars belief that the installer didn't check this before he left. Id be tempted to lock the door next time!

This is what the specialist thought but looked at the specs of the tank and it has no baffles which he said would mean you can’t really pipe it wrong. All the labels are on the front, no arrows this time. I tried to get my phone round the back but couldn’t see anything.

I was shocked he left so quickly. Either he realised it was buggered so rather than be there any longer thought he’d chip off or something has ramped down after he left.

He did place the flow probe and probe thats just before the heating zones next to each other. I wonder if he thought the one just before zones was actually the return and was happy that there was a lovely delta and not however something completely wrong lol. I thought I was going a bit mad when saw them next to each other but theyre definately on the pipe work that runs above the 3 zone valves and just under the hot water valve so they can’t be a return.

Let me know if I am bonkers though have attached a photo. However the black probe temp is very close in temp to another that’s top left of the LLH (so the flow after the LLW).

This post was modified 47 minutes ago by Crimson

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