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 16/10/2025 10:52 am

Thanks both.

I’d forgot to detail that pump speeds either side of the LLH (Grant one and one in pump room). A lot of experimenting with different speeds/paired speeds was also done. Best performance so far was the Grant on mid level (can’t recall if it has 2 or 3 now) and pump room pump on mid too - I think the flow rate checked by specialist to what he wants to achieve. Increasing house side pump to 3 the flow water noise is annoying when balancing down rads, but did push temperatures up slightly. Plus I get a lot of bangs from the Eskimo rads. Installers seem to insist the buffer tank will help with that (or want to see if that helps first).

I’ll check in with them if they’re proposing to pipe this tank as a volumiser. They seemed reticent to try piping the current LLH on the return only - to avoid mixing (guess that acts as a tiny volumiser?) as kept saying we’d void Grant’s warranty (the heat specialist couldn't find that in Grant’s materials however).

I suspect there’s quite a cross fingers it works and client says all good moment going on.

What is of note is that currently (temps got down to 7-8C last night I believe), the Grant is still in 60% constant nightmode. And other than the 2 living rooms, everything is to temperature.

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JamesPa

(@jamespa)

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16/10/2025 11:13 am

Posted by: @crimson

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Plus I get a lot of bangs from the Eskimo rads. Installers seem to insist the buffer tank will help with that (or want to see if that helps first).

Im sceptical, whats the mechanism?

Posted by: @crimson

↑

I suspect there’s quite a cross fingers it works and client says all good moment going on.

I get the impression that it may be entirely that. Not a good sign.

The problem for you is that he will eventually get tired of it and find ways 'out' If by then it isn't fixed, or its been 'fixed' at the expense of running costs (because he hasn't really got a sound plan), you are left high and dry. Thats why I would try to get ahead of him!

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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