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Grant 10kW versus Samsung 12kW - sizing dilemma with ECO4 installation

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(@allyfish)
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@tobyg provided they sit the unit on the rubber crumb support feet there won’t be an issue. They absorb nearly all vibration, not that there is much from the units anyway, as fan impeller & motor and compressor are all resiliently mounted.

@tobyg, if you can afford it, specify the Grant Smart Controller just launched. I have one here, awaiting fitting, which isn’t just a straight swop out for the existing Chofu controller, so I’ll need to get Grant in to do it.

It looks like you can set back the weather compensation curve up to 3degC on night time scheduled setting based on the installation manual provided with the controller kit. (Literature not yet released on Grant’s web site) If you can that’s a major step forward and kudos to Grant.

https://www.grantuk.com/about/news/introducing-the-grant-aerona-smart-controller/

 


   
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(@peterrsaltings)
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@tobyg Grant 10KW most likely a good call. Supplementary heating always an option in rare severe weather. Make sure heat pump is level (otherwise it may create unwanted resonance's) and remember during defrost cycles lots of water runs off and in the winter, you want that going to a soak away (gravel). Mine sits on a concrete base, surrounded by gravel. Otherwise a slip hazard may be created around the heat pump.


   
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(@iancalderbank)
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@tobyg sounds good to me. much more likely your house is under 10kw heat loss than over  and the lower modulation capability of the grant will help you control it when its mild. as per allyfish if there's an option to get the more sophisticated controls - do. re the outdoor part, the rubber feet take care of most things but it does need to be level.  drain wise you either need a gravel soakaway, or in my case its on paving slabs, but there is a rainwater drain about 70cm away. The base of the samsung has the facility to fit a condensate drain pipe to take all water away from the unit, which I have done, the grant may well have the same.

focus your efforts now on getting the radiator sizes right. really try to push for the lowest design temp you can / largest rads that will fit.

My octopus signup link https://share.octopus.energy/ebony-deer-230
210m2 house, Samsung 16kw Gen6 ASHP Self installed: Single circulation loop , PWM modulating pump.
My public ASHP stats: https://heatpumpmonitor.org/system/view?id=45
11.9kWp of PV
41kWh of Battery storage (3x Powerwall 2)
2x BEVs


   
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(@allyfish)
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Posted by: @iancalderbank

the grant may well have the same.

Yes it has, my Aerona drain has a plastic drain elbow designed for push-fit plastic tubing. The elbow fitting has worked loose somehow, but the locking nut is under some metal covers in the base of the Aerona which protect the trace heating element in the base, and also which cannot be removed easily. So I can't tighten it! The unit leaks a little onto the paving, but it drains through into the substrate and has never formed an ice pool. I could get some silicone seal onto it from under the unit and bodge it I suppose in the summer when it is dry.... 😉

 


   
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(@tobyg)
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both units are supported by a 3rd party control system called Homely , custom developed in the UK for heat pumps, which seems to be a good way to bring a really user-friendly control system into the picture, have a read of their stuff, there are write ups by users of it on this forum.

Thanks @allyfish, I’ll certainly request the new Grant smart controller. How would this interface with the Homely system recommended by @iancalderbank, is it a case of one or the other, and Grant’s upgrade should do away with the need to use Homely, or would you use them in tandem?

 


   
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(@tobyg)
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Posted by: @iancalderbank

Posted by: @tobyg

@iancalderbank:

on this , although you say you aren't a natural techie, try downloading and reading the manuals for the user-facing controller for each. For samsung, its this. I don't think either has a reputation for being that user friendly to be honest. however both units are supported by a 3rd party control system called Homely , custom developed in the UK for heat pumps, which seems to be a good way to bring a really user-friendly control system into the picture, have a read of their stuff, there are write ups by users of it on this forum.

Thanks @allyfish, I’ll certainly request the new Grant smart controller. How would this interface with the Homely system recommended by @iancalderbank, is it a case of one or the other, and Grant’s upgrade should do away with the need to use Homely, or would you use them in tandem?

 


   
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(@tobyg)
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It sounds like we don't need to lay concrete then, but some sort of soakaway is a priority. Thanks.


   
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(@tobyg)
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Posted by: @rupes

Posted by: @tobyg

There isn't a set back function on the Grant controller, you can't knock the LWT down 2 or 3 degrees overnight, which is a shame. If you could I would do that. If you turn a master room control thermostat down you start cycling the ASHP on and off, and that's not good or efficient control.”

 

The Grant does in fact have a couple of potentially interesting features which could offer set back and boost functionality:

Night Mode - which will reduce the compressor frequency (essentially dial down the power a bit) to reduce noise and power consumption.

Low Tariff Mode - which will increase the target temperature by a set amount over whatever the current value is.

Both of these modes are configurable (you can set the max compressor frequency for night mode and the target temperature adjustment amounts) but unfortunately these modes can only be enabled by closing an electrical contact which therefore needs to be physically wired up to some sort of time-switch or smart switch.  So you either need to get the installer to do it or you need to open up the wiring panel on the heat pump and start tinkering around in there yourself.

I don't have these connected up on my system so I've no idea how effective or useful they might be in practice. 

I could potentially see some benefit though - I have the Octopus half hourly tariff which has expensive electricity between 4pm and 7pm every day - that's when I would trigger the night mode - at present (if it's not too cold) I just programme lower thermostat temperatures for that period which tends to switch off the heat pump completely.  It might be better to keep the heat pump running at a lower compressor frequency rather than have it switch off and then on again - but who knows.  

 

 

@rupes, thanks for your message above. Just to be clear, if I can get these two functions wired up at installation it'll mean I'll have the option of activating them, or not - it's not that they'd then be on all the time?

 


   
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(@allyfish)
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Hi @tobyg, sounds like you’re all clued up on controls. Homely is probably the most sophisticated and future proof ASHP control, the Grant Smart controller is a half-way house from what I can tell. It has some very good features, and a nice touch screen graphical control interface, but it doesn’t have the option of customised control based on flexible and variable time of use tariff like Homely. I guess it’s a question of how much automation and sophistication you want. I’ve got the basic Grant/Chofu controller running very efficiently. I’ve not dabbled with quiet mode or night time mode, but as @rupes says these are useful features to turn down the compressor. I think the Grant smart controller has adopted this functionality. Offset adjustment of the weather compensation curve does much the same thing, reducing capacity not cycling the unit on and off.


   
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(@peterrsaltings)
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@tobyg 

You might also be interested in this link:

https://energy-stats.uk/what-size-heat-pump/

Definitely HTC gave me the best measurement of heat loss and was at 4.5KW @-2C, way below the MCS estimate of 7.5KW. Quite why they sized the heat pump at 12KW is a bit of a mystery but at least I am using long cycling on off peak tariffs to get the most economical way of running it and still achieving SCOP around 3.5 for combined heating, hot water and weekly pasturisation.

As Ian stated, get the radiators as large as you can but do match the room heat losses to the rad output at the set flow temp for a given outside temp, otherwise some rooms won’t get up to temperature at a given flow rate, whilst the rest of the house will be fine. Weather compensation and modulation will take care of the rest.

And watch out for pipe sizing, as I think this is a limiting factor in my house and huge disruption required to upgrade. I have 28mm from the heat pump, 22mm splits upstairs and down, but quite a few long 15mm runs with several rads connected at the end. Upsizing them may not give me the benefits I hope and the guidance of how much heating power can be delivered by each pipe size is useful.


   
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(@rupes)
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@rupes, thanks for your message above. Just to be clear, if I can get these two functions wired up at installation it'll mean I'll have the option of activating them, or not - it's not that they'd then be on all the time?

That’s right. You would have a pair of wires for each feature - connect the two wires of either pair together (e.g. with a timeswitch or smart switch) to activate either feature. 

I would hope that the new Grant smart controller has a built in means of doing this without additional switching hardware - but I don’t know. 

 

Grant Aerona3 13kW


   
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