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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 13/11/2025 5:41 pm

I’m probably at my mental limit with this.

Queried builder that specialist has in fact been booked in tomorrow and he’s sent a message along lines of change of plan due to MCS and BUS requirement, will call me tomorrow…

If he’s delusional enough to think he can wrangle original installers back he’s out of his mind.

My understanding is MCS isn’t installer tied (just need a MCS certified company to certify the install, doesn't need to be original installer?) and is tied to the installation itself? Want to prepare myself for the call tomorrow. Sick of people trying to deceive me.

Obscene at this point and people are still being obscure with me.

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JamesPa

(@jamespa)

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13/11/2025 5:54 pm

Posted by: @crimson

↑

My understanding is MCS isn’t installer tied (just need a MCS certified company to certify the install, doesn't need to be original installer?) and is tied to the installation itself? Want to prepare myself for the call tomorrow. Sick of people trying to deceive me.

Thinking about it BUS is installer tied I believe. As a householder you have to consent to a particular installer claiming the BUS grant. I dont know the ins and outs of this needless to say, for that it would be necessary to read the regulations and probably detailed documents on operation of the BUS.

This post was modified 1 hour ago 2 times 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 13/11/2025 6:09 pm

Seriously doubt they've even applied for it as it has a 120 day period by looks of it.

Utter lunacy this has got to this point.

Specialist tells me been told to come next week to let system run over weekend.

So now the builder is lying to me. He told me yesterday had booked specialist in to come Friday.

Not home yet but no idea if hot water has run. Temps still aren't 21c, rooms at 19c. No way over weekend they’ll get warmer as panels had them around 18.6C last night so clearly its still buggered with a poxy 0.4C increase.

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JamesPa

(@jamespa)

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13/11/2025 6:33 pm

Really sorry to hear that.

The building trade is just dodgy, the world over it seems. Did you see the video of that vast bridge in China that collapsed earlier in the week. Now thats a serious case of dodgy builders!

Your issue should have taken half a day to fix or a day tops, it just needs someone present who understands what they are doing. What I don't understand is why your builder is incentivised to persist in asking the hopeless installer to return unaided by someone who actually understands heating. Presumably he is somehow incentivised to do this otherwise he wouldn't.

This post was modified 43 minutes ago by JamesPa

This post was modified 39 minutes 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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