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Grant Aerona 3 16kW ASHP in 100 year old cottage

Air Source Heat Pumps (ASHPs)

Last Post by Prunus 4 years ago

10 Posts

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Esteii

(@esteii)

New Member Member

Joined: 4 years ago

Posts: 4

Topic starter 23/01/2022 8:48 pm [#288]

Hello,

I have recently moved into a property with a Grant Aerona 3 heat pump. The property is a three-bed, 100-year-old cottage that is well insulated. It has solar panels and solar water. All the heat pump workings, e.g. water tank, etc., are situated in the garage. The garage is not insulted. The heat pump controller is also in the garage. I also have a thermostat (within the house) that controls the heating times in the place.

I am averaging about 50 kWh of energy use per day (£12). I can have the heating set to 20 degrees all day or have it set to come on when the house is occupied, and it makes little difference to the energy use.

I'm using too much energy and have had the installer out to look at it, who change a few settings. I have also had Grant support talking me through a few settings on the phone, all to no difference.

Having looked at the 'heat pump controller', am I correct in thinking this should not be in a cold room? (cold garage). On display, it states that the room temperature is 11c and the outdoor temperature is 6.5c. Is my heat pump trying to get this 11c up to my thermostat is asking, e.g. 20c, thus using excess energy? Should the 'heat pump controller' be located inside my property?

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batalto

(@batalto)

Noble Member Member

Joined: 5 years ago

Posts: 1092

23/01/2022 9:10 pm

How big is your house? 50kw with the current temperatures might not be crazy. I'm using around 50 per day at the moment as well - but our ASHP is 12kw Vs your 16kw. Given you have a 16kw pump you probably need quite a bit of heat. It's the middle of winter so you would expect it to be cold and your heating going

12kW Midea ASHP - 8.4kw solar - 29kWh batteries
262m2 house in Hampshire
Current weather compensation: 47@-2 and 31@17
My current performance can be found - HERE
Heat pump calculator spreadsheet - HERE

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Esteii

(@esteii)

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Joined: 4 years ago

Posts: 4

Topic starter 23/01/2022 9:44 pm

@batalto Evening, my house is 163m2. I'm new to having a heat pump and don't know what a typical per day use is in winter. On a few occasions, I have had it down to 30 kWh. I wondered if the 'heat pump controller' was in the correct location or if it was ok to be in a cold environment.

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batalto

(@batalto)

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Posts: 1092

23/01/2022 9:48 pm

@esteii the first question would be, is the system using weather compensation? It should be running off your thermostat in the house given that you've said.

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Esteii

(@esteii)

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Joined: 4 years ago

Posts: 4

Topic starter 23/01/2022 10:08 pm

@batalto the system is now using weather compensation. It wasn’t using weather compensation but I got that turned on when going through settings with a Grant technician.

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batalto

(@batalto)

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Posts: 1092

23/01/2022 10:37 pm

@esteii I would suggest you whack the thermostat up to something like 22 or 23° and see if the house can get to that temperature. If it does then your weather compensation settings are too high. If you trim them down you'll start saving on power costs with no loss of comfort.

I'd suggest doing that in the day, not over night - Unless you want to wake up in a sweat

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Esteii

(@esteii)

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Joined: 4 years ago

Posts: 4

Topic starter 23/01/2022 11:14 pm

@batalto it can definitely get to 22 and more as I’ve had that on my settings before when experimenting. What would be ideal weather compensation settings? I can’t remember what I have them set at as the Grant expert changed them.

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batalto

(@batalto)

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Posts: 1092

23/01/2022 11:41 pm

@esteii I have no idea. Each house will differ as it's determined by the heat loss you experience based on the building fabric. I'd suggest just finding the current settings.

Write them down and then lower the max temperature by a few degrees and see how you get on. Just go day by day and gradually tweak down. You can see my settings as an example my signature but everyones is slightly different. If you have UFH you can go very low, rads you'll be higher.

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Derek M

(@derek-m)

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Joined: 5 years ago

Posts: 4425

24/01/2022 12:05 am

Posted by: @esteii

@batalto it can definitely get to 22 and more as I’ve had that on my settings before when experimenting. What would be ideal weather compensation settings? I can’t remember what I have them set at as the Grant expert changed them.

Hi Esteii,

A possible starting point would be a 0.8C change in water flow temperature for every 1C change in outdoor air temperature.

So, set the cold end of the weather compensation for a water flow temperature of 44C when the outdoor air temperature is -10C, and a water flow temperature of 20C when the outdoor air temperature is 20C.

As Batalto has suggested, see how the system performs over 24 hours, then if the indoor air temperature is too high then lower one of the settings, and vice versa if the indoor air temperature is too low.

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Prunus

(@prunus)

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Posts: 73

24/01/2022 4:36 pm

Posted by: @esteii

Having looked at the 'heat pump controller', am I correct in thinking this should not be in a cold room? (cold garage). On display, it states that the room temperature is 11c and the outdoor temperature is 6.5c. Is my heat pump trying to get this 11c up to my thermostat is asking, e.g. 20c, thus using excess energy? Should the 'heat pump controller' be located inside my property?

The way Grant do it, they have a traditional heating thermostat (like a boiler) to provide 'heat please' and 'hot water please' inputs to the heat pump. The (Chofu) heat pump controller is actually capable of doing its own controls being its own thermostat, running its own scheduled on/off programs, etc, but Grant completely disable all of that. By doing so, it's only the location of the external thermostat that matters. (Well, almost - the frost protection is still going to run based on the 'inside' temperature).

I plan to try using the heat pump controller instead of the awful Honeywell 'smart' thermostat I have, and to that effect have moved it out of the airing cupboard into the hall (it's just two wires), but not investigated this yet. I'm not expecting a massive increase in efficiency, but I hope it will help with things like the Honeywell unnecessarily cycling the heat pump.

Here's the full Chofu heat pump manual including the bits Grant cut out: