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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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JamesPa

(@jamespa)

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13/11/2025 9:57 pm

Posted by: @crimson

↑

Other half informed me exact changes by engineer:

flow temp max up to 45

UFH manifold - speed 3 (no idea why!!)

connected loose wire

So now of course installer will have a get out of jail free stating manufacturer made changes.

They cant get away with this argument, all three changes are easily reversible if the installer thinks the wrong thing was done!

Putting the flow temp up should make a difference (at the expense of efficiency) and is a good 'test' move IMHO. If it works it proves that there is no fundamental problem, and leads directly to a discussion about efficiency and how removing the LLH would maintain both house temperature and efficiency.

Is there any possibility that the reason its not currently heating is just air in the system/no system pressure? Bleeding/topping up are things that householders are going to do/have to do and, unless they are reckless, its not reasonable to void warranty if householders carry out this basic piece or ongoing maintenance, particularly just after a system has been filled and is thus quite possibly full of dissolved air (you know it is, you can hear gurgling).

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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Posts: 290

Topic starter 13/11/2025 10:06 pm

Posted by: @grantmethestrength

↑

@crimson mate you have proper been through the wars, I really hope you get some resolution, and soon.

thanks. Just heard a big clunk.

secondary pump is now off.

P1 error on the Grant panel

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Grantmethestrength

(@grantmethestrength)

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Posts: 147

13/11/2025 10:09 pm

Yup that will be your lack of pressure

Kind Regards
Si
——————————————————————————
Grant Aerona3 13kW
13 x 435w + 13x 480w Solar Panels
Sigenergy 10kW Inverter
16kW Sigenstor battery

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Crimson

(@crimson)

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Topic starter 13/11/2025 10:15 pm

But why did pressure plummet?

on Monday gauge didn't read 0. But flow setter did.

so much for the hydraulic separation of the LLH…

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JamesPa

(@jamespa)

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13/11/2025 10:30 pm

Pressure will be same either side of llh. Llh gives some separation of flows but it's the same body of water at same pressure.

Assuming you mean static pressure, ie measured when water pumps are off, it could plummet because of

Dissolved air coming out of solution (air is more compressible than water)
Dissolved air coming out of solution and then being vented through the auto bleed.
A leak
A faulty expansion vessel

The last is the least likely, but not impossible. There may be other reasons but these are the ones that come to mind.

The first recourse sofaik is simply to top it up via the filling loop and manually bleed any points where air is obviously collecting. That's certainly what I have been doing with my central heating for the past 30 years!

Flow setter could possibly read zero without pressure being zero if the air in the llh goes below the port which feeds the flow setter. Again there may be other reasons eg pump has run dry because of air in system or airlock.

This post was modified 44 minutes ago by JamesPa

This post was modified 43 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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