@kenbone I’m Suffolk based

@crimson I have worked up there, but it is a long commute from Basingstoke.

As a summary I had numerous issues with the heat engineers/plumbers on a project that was an extension and full re wire/re plumb and re insulate project with heating system fully replaced with under floor at rear ground floor of property, radiators front ground floor and first floor of property.

Issue were installing a LLH back to front and getting calcs wrong so ended with undersized radiators. Long story short - after almost 11 months of back and forth it was agreed to replace undersized radiators.

This entailed:

First floor: changing K1 Stelrad compact horizontal line rads to K2 type.

Downstairs: doubling the height of 200mm living room raadiators to 400mm (2x 1450 wide, 1x 1694 wide and 1x 720mm wide doubled in height.)

Tripling width of vertical hall radiator from 240mm wide by 1800mm tall to 720mm wide by 1800mm tall I had tried to push making 3 of the living room rads wider to over oversize but cost agreements between builders and plumbers wouldn't allow it.

So here I am trying to get the system performing and so far within front downstairs second living room is stuck at 20C, other living room hits 21C and hallway 20.5C, so almost there.

Similar issue to before, ASHP turns off before zone gets to temp. It's quite mild (8-14C) and the Grant Aerona3 is on WC with:

2102 (max flow temp): 40C

2103 (min flow temp): 30C

2104 (min ambient temp): -3C

2105 (max ambient temp): 20C

This puts the system at 7C running approx 35C. Think that was a guide someone here gave as a good start. So now I'm a little under I'm trying to up the min flow temp to 31C, puts it at around 36C at 7C ambient.

Next steps I"ll take are balancing the rads (hasn't been done by plumbers...). I've bled the rads and experimented with secondary pump speeds. Mid speed of 3 always ran better but will try slowest and mid every few days and this is so borderline. Frustrating that it just hasn't worked straight away but a vast improvement.

Sorry to hear your problems but it sounds like you are now on the right track. It also sounds like you have learned a lot about heat pumps during your journey so I will keep my comments short on the assumption that you are well informed but please feel free to come back for more explanation.

If you are going to balance the rads then I would turn any TRVs up to full and balance for same (or desired) room temperature not for same deltaT; there is a Heat Geek video about this.  The ideal way to run a heat pump is with no TRVs at all or all TRVS in main living rooms fully open and used only to limit temperature not to control it.  The closer you can get to this the better and balancing the rads for room temperature helps achieve this.

The LLH is a concern, in most houses these shouldn't be fitted as they inevitably reduce efficiency by around 15%.  However as you appear to be running at a fairly low flow temp the hit might not be too severe and so is probably not be your first priority to do something about this.

Grant installations, from repute, include a thermostat controlling a 'call for heat' signal to the ASHP.  This should ideally be turned up above the desired temp (ie used as a temperature limiter) so that the system is run most of the time on WC.

Hope that gives you some food for thought.

Thanks James,

I do wonder about that LLH.

It appears the challenge Ive always had still remains. The Eskimo rads seem to work very well at low temps. But the issue is always the ASHP seems to stop running when the delta is low, which it is with these rads, yet they still kick out heat but get cut off by the grant ASHP.

Right now the zobe is around 19.5C-20c, one living room at 20.4C, which has been warmer at 21C. Now the underfloor zone has hit its temp and not calling for heat its just downstairs. There’s such an imbalance in zones that I cant leave the underfloor on as that simply gets too hot and the other half will open doors windows to crash it down.

I’m first attempting to bring down the warmest living room with balancing, not with TRVs against the cooler living room.

One learning has been the drayton TRVs have a very useful hidden/not widely known feature in that when removing the top of the TRV if you have Drayton’s key you can balance numerically on the TRV side and very accurately. So I’ve dropped the warmer living room down to 5/6 on smallest rad and 4/6 on larger.  I’ll have to keep tweaking this to try and get both living rooms equal. But suspect upstairs will need to have that zone on but keep bedrooms so low they dont get above 18C via balancing (not TRVs), so that 3 towel rads upstairs still use heat and the ASHP runs more for downstairs. A huge faff that could have been avoided if the plumbers just went with way oversizing of downstairs which I in vain pushed for.

Another challenge is the front downstairs zone has a hallway which shares with the first floor landing. And keeping upstairs not too hot and downstairs warm enough is a challenge with my wife as she hates upstairs too warm. Suspect the landing rad will need to get out a bit of heat to stop it all drawing from down to up.

I am however more hopeful as at least have the worse room downstairs now be performant, just a case of slowly tweaking and finding a workable balance.

as before it is annoying to have so much equipment installed thats basically useless, heatmiser panels etc. hopefully in years to come ASHP installations will just be single loop and less gear saving customers money.

@crimson 

As Im sure you know there are various things that stop ASHPs (and boilers) running including but by no means limited to

• Flow too low (shouldn't be a problem with your llh)
• Flow temp too high, cant modulate down (likely at mild temps and possibly made more likely by the LLH)

From what you say you may have times when only a small part of the circuit is open.  That means only a small amount of heat is lost from the emitters and the ASHP will go into cycling mode.  You wont necessarily notice this because the rad side circulating pump will still be circulating.  Im guessing this may be what you have.  You dont mention the size of your ASHP, is there a possibility its oversized which would exacerbate the problem.  Ideally you dont want zones at all, just to balance everything.

The more you can balance so that you can leave as much of the circuit open, the better.  If the first floor landing is a rad, turning that well down might solve the problem with upstairs overheating.

Posted by: @crimson

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as before it is annoying to have so much equipment installed thats basically useless, heatmiser panels etc. hopefully in years to come ASHP installations will just be single loop and less gear saving customers money.

Indeed.  I have been on this journey for two years now and I do have the impression that there are more installers that install single loop, no add ons, but its still not universal. Buffer tanks/LLHs are still, it seems, added to avoid low flow problems causing call outs, but they are really masking not solving a problem and costing the customer in both capital and running costs.

Unfortunately we have been suckered by the heating industry into buying lots of stuff to control our fossil systems in ever finer granularity is search of efficiency.  It would have been much better if fossil systems had been properly installed to condense (as they are all designed to do - but rarely in fact do) and run on weather compensation.  This would have saved us all more money than the various add-ons that the industry has shoved our way, and we would all have ben more comfortable.  Sadly the behaviour is now entrenched in the industry and the customer and it will take a while to unlearn.  

Thanks James, it’s a 13Kw.

It’s definitely cycling. Only difference this time is hits 20c rather than 18.5c after radiator upsizing was done recently.

The discussion of it being oversized was had. The property is 240sqm with a large portion still the original late 1970s building with a lot of insulation upgrading done (10cm of insulation boards inside, reinsulation of loft, triple glazing etc etc) but can’t compare to new part. Plumbers reassured it could modulate down enough though based on the calcs (but I don't trust them).

I’ll try and keep the upstairs open but low. A heat specialist did come last year and talk about having effectively a heat dump by using the towel rads (which is useful for drying towels so not just useless heat). - meant to add, he actually manually opened the valve but oversight there is theres no separate calve for the water heating mode. Theres 3 zones - downstairs rads, downstairs UFH and first floor. They all switch off when direct water heating happens. Ideal would have been valve between water heating and heating to leave them all open but usual over zoning of ASHP mistake)

Will see where I get with that.

Next week I’m working from home so should have time to tweak and tweak.

Frustration is if I go to installers they’ll just run it hot as anything else is time consuming.

Going to be a struggle, already complaints upstairs is too hot at 19-20C. Ive now had to turn all the hidden Drayton balancing down to 2/6. And have the actual visible TRVs on 2 to basically turn them off…before windows are opened etc.

Good news is main living room is 21.6 (too hot), so I’ll dial that back on the balancing. Other living room stuck at 20C. So almost there. 20.5-21 “feels right” if that makes sense, any more and get complaints it too warm.

Once I get a good balance in front downstairs, I think next step is to actually dial back the temp via the WC.

I’m hopeful not that at least on not too high flow temps with the rad upsizing (36c at 7C ambient, or in actuality it was 11C ambient and running at 34.5c), the system CAN perform. Its just the quirks of the WC and having another zone running to prevent the ASHP cycling that will be a journey to complete

Posted by: @crimson

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Frustration is if I go to installers they’ll just run it hot as anything else is time consuming.

I think that's a fundamental limitation with weather compensation, and probably why we didn't adopt it (unlike many other countries).  Balancing radiators takes 'too much time' so installers would, as you say, prefer to run everything hot, charge us for fancy controls, and walk away.  Same with turning down the flow temp of a condensing boiler so it actually condenses, its not worth the hassle for the installer and the customer wont know that their gas bills are 10% higher (and they are less comfortable) for the next 15 years.

You can of course get auto balancing TRVs, but they balance for flow not temperature, thus assuming that the rads are perfectly sized, which is obvious nonsense.  Not sure what the real point of these is, but doubtless someone will know.

Its pretty clear that, with the right firmware, 'smart' TRVs have the hardware to do the balancing job properly and indeed Adia Thermal are working on just this. The system they are developing has a central controller which measures flow and deltaT at the heat pump, and smart TRVs that talk with the central controller and balance for room temperature.  The central controller also optimises the flow for cost of electricity.  Basically its the job automated, so everything is optimised specifically for a heat pump. 

It seems to me that installing this technology before fitting a heat pump also has legs, as it knows exactly how much each rad is emitting and the room temp so could size the house and rads without resorting to the GIGO spreadsheet malarkey.  Currently they don't seem to be targeting that market, which I understand from a commercial PoV as it involves persuading MCS to be more flexible about the sizing methodology.  Technically however it clearly makes sense.

Currently Adia only support control of Samsung and Midea derivatives (of which there are many), so not much use if you don't have one of these  Both of these are modbus based so hopefully other modbus enabled makes will be supported relatively soon.   In the mean time manual balancing is all we seem to have.

So now I’ve come to the conclusion the rads are now correctly sized (did hope so as according to calcs they’d be very much oversized, just purely physical space meant doubling height of rads was easiest route than making wider).

This is now very much a balancing exercise. So far almost there, end of the day it’s only 5 Eskimo and 1 towel rad in this zone I need to think about. Upstairs over performs so much that its mostly off.

Ironically prior to rad upsizing the worse performing room is now the hottest. I have 1 radiator, the smallest in the room on 4/6 on balancing (via the hidden drayton presetting key - this is not via TRV setting) and the largest on 2/6. Bizarrely turning these down seemed to have the opposite effect at first of making the room warmer…I’m wondering now if the ASHP side the flow speed is set too high as inside theres a pump I’m running at its slowest. 

That room sits at 20.5C which is plenty as when we’re in the rooms it hits 21C, very comfortable.

the other living room sits around 19.8-20C depending when the ASHP is cycling on and off. So is slightly off and noticeably so. Rather than just chasing numbers I’m looking at comfort.

Upstairs is a bit of a pain, having to keep that zone open. All bedroom rads are at 2/6 on the balancing, and the TRVs at 2/6 too. They’re off effectively. Leaving just the landing rad on, towel rads and office rads on, landing sits at 20.5C - I’d say thats too warm as our main bedroom is next to that. Bedrooms range from 18.8C to 20C. I think 19c is max we want. Does show the effect of heat rising. My office which is bedroom 4 is nice at 20.5C. On paper the bedrooms are very much over over sized now especially my office.

Main bedroom has a towel rad in it, which I’m going to look at turning that down a bit to avoid heating our bedroom up too much.

To break the task down my goal is to get both living rooms downstairs at same temp. Then alter the WC on the Grant panel to bring overall temp down to bring up stairs down to just the point downstairs is ok (downstairs relying on upstairs running to avoid cycling too much and not coming to temp)

currently I’m at

max ambient ashp runs - 20c

min ambient ashp flow rate  - 29.5C (this is what I’m tweaking down)

max flow rate - 40C

ambient temp max rate runs at: -3C

WC looks good so I think system is in a good place, I just need to get a handle on the balancing and temps.

overall do wish this sort of thing was automated. You had a temp probe in each room, set desired temps of each room and the ASHP works out balancing and WC for you - that would be a dream.

Posted by: @crimson

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overall do wish this sort of thing was automated. You had a temp probe in each room, set desired temps of each room and the ASHP works out balancing and WC for you - that would be a dream.

The Grant R290s (if thats what you have) may just be Midea based.  If so then you could contact Adia (see my post above).  They are looking for test sites.

That said it sounds like you are almost there and anyway you probably have the R32 as the R290s only came in very recently.  So its almost certainly not worth it/not feasible.

Posted by: @jamespa

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ou probably have the R32 as the R290s only came in very recently.

Yup, must be the R32 model. The larger R290s are not available wholesale yet... https://www.grantuk.com/professional/products/air-source-heat-pumps/r290/

Trying to find out who the Chinese OEM is of the Grant badged R290s, and whether it's available branded up elsewhere.