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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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KenBone

(@kenbone)

Estimable Member Member

Joined: 2 years ago

Posts: 44

17/10/2025 6:33 pm

@crimson it all depends, on how many rads/ufh are fully open (no actuators or TRVs, a volumiser won't hurt the system (i have 420l worth), that i can bring in and out of my system, but my system i use for testing products.

Is it the older Aerona 3 unit.

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JamesPa

(@jamespa)

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Joined: 3 years ago

Posts: 3143

17/10/2025 8:30 pm

Posted by: @crimson

↑

I’m looking at the diagram in the manual and nowhere is there a LLH, item 6 is a volumiser, on the return.

No idea why they’re insisting on the LLH. Should put in a volumiser (80-100 litres) on the return in place of the LLH. Run the flow direct from ASHP to the heating system and DWH, obviously to the valves etc.

And remove the internal pump room pump thats on that, as with no LLH don’t see why would need it.

Very frustrated with these guys.

You are correct you dont need the second pump if there is no LLH/Buffer (unless there is a 'head' problem with your downstream system)

Its entirely understandable that you are frustrated. Sadly, in my work life as well as my home life, I have been there several times with tradespeople of various sorts (but generally plumbers or electricians).

Its very difficult, in my personal experience, to reason with tradespeople who don't understand what they are talking about. There are two ways to rationalise this:

a) conscious incompetence

They know they don't understand what they are talking about, but daren't admit it. So they try to cover themselves by using technoBS. This works on most people because most people are either not capable of challenging them with logical arguments or don't care to do so.

b) unconscious incompetence

They don't even realise that they don't understand what they are talking about So they say what they believe even though its BS. This works on most people because most people are either not capable of challenging them with logical arguments or dont care to do so.

In either case arguing with them is difficult. Perhaps a psychologist would do better than I do, because its probably more a psychological problem than a technical one. Bizarrely its much easier to argue with someone who does know what they are talking about than with someone who doesn't.

That said they all know the power of the pound. Dont pay until you are happy (but make sure you keep a paper trail) but at the same time make sure they remain responsible. Tricky balance, but the one you somehow need to strike as I know you appreciate.

This post was modified 3 days ago 3 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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Posts: 230

Topic starter 19/10/2025 8:21 am

I hope out of all of this that I can run the system at a much lower flow temp.

Checked back through endless mails on calcs and it looks like rad wise (this is in addition to ASHP oversizing rads at delta 16.5, so rad output divided by 0.237 for non Eskimo and 0.33 for Eskimo - against the room watt requirements- hence me stating over-oversized as its versus those watt calcs)

Bedrooms range from:

15-115% over-oversized (only the office I like at 21C and thats 115%, others we have at 18C)

Living rooms (Eskimo)

30-45% over-oversized

Still have a main bathroom 14% undersized and an en-suite 24% undersized. But I suspect they’ll be fine as both have electric underfloor in addition to those rads/not really rooms we spend time in.

This makes me glad at least that the rad uplifts works seemed a sound thing to have done.

The substantial oversizing was due to simply doubling heights/K1-K2 changes to minimise non plumbing works (removing skirting/decor etc etc)

This post was modified 2 days ago 2 times by Crimson

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