And just when I think great they’re coming next week to give this buffer tank install a go. They smash my confidence yet again.

Got a call from one of the installers asking if I could check some measurements of a buffer tank unit against the plant room (they measured on their last site visit so no idea why). He’d provisionally ordered an 80L buffer tank. No way it would fit. So gave him some measurements.

Then proceeds to say ah might need a cylindrical one, will get back to you but YOU may not like the size. Ironic as I’d rather one isn’t installed as the current LLH isn’t doing me any favours…

Next document he sends has a load of options. So I send him some measurements from the plant room and tell him to confirm what one is picked himself as Ive no idea about pipes and placement etc.

How is this industry not properly regulated with these blooming grants from the government incentivising this nonsense.

Truly despair at this now.

Wish never got a Grant unit too, panel is garbage for adjustments, totally not suitable for consumers

The specialist has offered to come back when all said and done to convert a buffer tank to a 2 port volumiser on return, pull out the pump room pump and install the latest panel that works with an app. Obviously that will cost me down the line but now not even sure these guys can get a tank in anyway…

They’ve selected a 50L buffer tank.

Praying this works as at end of my tether with it all (as my last post’s tone indicates apologies).

I went back through and got water volumes together, their estimates were quite off, think they had upstairs at 100-120l, but its actually around 65l (likely forgot upstairs is Stelrad compact K2s).

Downstairs they estimated at 20-25 but thats around 60l (probably were thinking pre Eskimo rad upsize). So its not 100 v 20 but actually far closer at 65l v 60l.

Though they have said the prior smaller Eskimo hall rad that Eskimo stated at 6L was actually 4L when drained - so I’ll presume Eskimo are 33% off with their calcs. Making downstairs 40l (65 v 40).

UFH zone I don’t know water volume - it’s around 35-40sqm of UFH floor area.

I really hope the 50L buffer taking the downstairs plus that to 90l when other zones switch off will help. Obviously will in time retry getting the balancing etc down to keep all zones open but the mix of emitters and rooms v zones makes it very difficult.

It was attempted with a heat dump on the towel rad in ensuite and another towel rad and tall rad in main bathroom last year by the heat specialist - but upstairs collects so much heat in the house it can make it hard to sleep at night. Suspect I may have to literally shut off half the bedroom rads and balance half right down, to keep upstairs around 18-19C at night.

The UFH zone - about 33% of the building structure is new build extension so that warms up very easily due to significant insulation (rest of original house/walls had insulation upgrade of up to 100mm Celotex internally plus significant roof insulation etc etc).

My suspicion is in January I’ll commission the specialist to remove the house side plant room pump, convert the buffer tank from 4 port LLH/volumiser to a 2 port volumiser on the return. And get the new Grant panel. Plus work on a load of balancing etc to keep all zones open at all times to offset Grants concerns with the mixed emitters and zones. However will check that in no way affects my warranty etc.

One option could be to manually have the 2 port valves on upstairs zone open (with just towel rads pretty much fully open) and downstairs zone open. Then even when DWH comes on - those zones stay open and get 50C flow temp. Could lead to overheating in warmer months though, so might be a winter only thing to do. The hot water does seem to heat well within the 1 hour run the Grant does (wish it would run to the desired temp and not the arbitrary time!!).

Kind of points to not using zones as suggested by forums members here in previous posts. 

Posted by: @crimson

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They’ve selected a 50L buffer tank.

Praying this works as at end of my tether with it all (as my last post’s tone indicates apologies).

Can you remind me what the current problem you (or they) are expecting it to solve is?

The only thing a very slightly larger buffer tank will do is extend the cycle time a bit, probably not enough to be noticeable.  Bluntly it feels like a waste of time.  

Posted by: @crimson

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Kind of points to not using zones as suggested by forums members here in previous posts. 

absolutely, and you can do that now if you choose by adjusting the controls

Posted by: @crimson

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Then even when DWH comes on - those zones stay open and get 50C flow temp. Could lead to overheating in warmer months though, so might be a winter only thing to do. The hot water does seem to heat well within the 1 hour run the Grant does (wish it would run to the desired temp and not the arbitrary time!!).

Dont do that, it will suck heat from your DHW and risks damaging flooring.  This is unnecessary and a diversion from fixing the problem.

I think I may have lost the plot (which is better than your installers who never found it).  Following various mods you have made what is the actual problem now that you want to solve?

Posted by: @jamespa

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Posted by: @crimson

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They’ve selected a 50L buffer tank.

Praying this works as at end of my tether with it all (as my last post’s tone indicates apologies).

Can you remind me what the current problem you (or they) are expecting it to solve is?

The only thing a very slightly larger buffer tank will do is extend the cycle time a bit, probably not enough to be noticeable.  Bluntly it feels like a waste of time.  

 

Posted by: @crimson

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Kind of points to not using zones as suggested by forums members here in previous posts. 

absolutely, and you can do that now.

Posted by: @crimson

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Then even when DWH comes on - those zones stay open and get 50C flow temp. Could lead to overheating in warmer months though, so might be a winter only thing to do. The hot water does seem to heat well within the 1 hour run the Grant does (wish it would run to the desired temp and not the arbitrary time!!).

Dont do that, it will suck heat from your DHW and risks damaging flooring.  This is unnecessary.

 

I think I may have lost the plot, and your installers never followed it.  What is the actual problem now?

The problem is the downstairs front zone.

so for context there’s 3 zones:

Zone 1: UFH ground rear

1x 40sqm kitchen/dining

1x small utility room

(this was done as mostly extension - doing UFH to ground front would have had significant cost involved)

Zone 2: upstairs zone

consists of:

4 bedrooms (2 stelrads per room)

1 bathroom (1 tall rad + 1 towel rads)

1 ensuite (1 towel rad)

1 landing (1 stelrad - undersized)

Zone 3: ground front

2 living rooms (2 eskimo horizontal column rads per room)

1 WC (1 towel rad)

1 hall (1 eskimo vertical rad)

problem:

Zone 3: ground front zone doesn’t get to temperature, Zone 1 and 2 do and switch off.

Heat calcs have the rooms in Zone 3 at 30-170% oversized versus calcs with delta 16.5 (so well accounting for the flow temps etc). Note hallway one is 170% oversized versus delta over sized to account for undersized landing rad. Living rooms 30% and 45% over over sized, so emitters should suffice (calcs have been done 4x).

Appears due to short cycling of Grant ASHP 13kw.

Attempted resolutions:

EARLY 2024:
LLH back to front: installers realised had the LLH back to front - was observed by 4 probes on all ports (per suggestion of forum members) and mixing was very apparent

rooms were at 14C… after correction (it had arrows on the FRONT) - rooms go to 18C

LATE 2024:

rad upsize - eskimos doubled in height, hall triped in width. Original calcs were wrong, rooms 20% undersized rads. Now over over sized. Got 18c to 20c (sometimes 19C) Short cycling still happening, no 21C per system design.

EARLY 2025:

as emitters more than doubled and only gained 2C no one seemed to be able to pinpont issue - builder consulted a heat specialist.

heat dump upstairs - increasing volume active by having towel rads run constant 

Recently:

heat specialist enforced nightmode to see if ASHP is simply oversized hence cycling. Has improved things but still not to temp.

Current thinking

installers: water volume is the issue due to low volume of Zone 3 when only zone calling for heat. So take 6l LLH up to 50L buffer tank. However I’m skeptical as they had water volumes way off.

heat specialist: 

a) water volume - Grant specifiy a volumiser, one isn’t present. During frost weather defrost cycles did kill room temps (as no volume for the defrost).

b) LLH is causing mixing - remove it plus house side pump and just have 2 port volumiser on return

Regards to DWH:

Was just proposing upstairs and downstairs rads, not UFH. But wont do that if an issue.

Hope that all makes sense. Its been a 2 year journey so far.

Other context: I didn’t pick installers. Builders did. It’s under a JCT contract. Catch 22 is outstanding payments to builders and thus plumbers. But I’m beholden to say system works to get £7.5k grant.

The rad upsize was a significant cost to builders and plumbers (I only paid rad cost difference).

So it’s all at an impasse basically. Hence no real control here to say just do X Y and Z.

I even requested they get different installers back in 2023 when they wouldn’t select rads for Zone 3 and I had to suggest the Eskimos (which they signed off).

And to add at all stages the installers have blamed Eskimos for:

not performing at Eskimo’s stated specs (when the non Eskimo rad WC room in the zone is also not performing - and thats 200% oversized..)

Having low water volume (though seems similar to upstairs)

MCS only guarantee Stelrad performance:

However no Stelrads that fit under the windows in the living rooms meet the calc’s watt output requirements at delta 16.5. Hence me suggesting Eskimos as they were holding up downstairs finish - costing me rent as project overran.

Accused me of selecting purely on aesthetic basis - but was for performance as per note above…

Overall it’s a constant blame game, even though I always ask them to approve/confirm things. Hence why so far no extra costs (other than difference in rad costs) have laid with myself.

They also never once take any temp measurements, check deltas across rads, balance rads, check flows either side of LLH. They seem to operate to the Grant install pack (but missed volumiser due to space in plant room). So in my eyes they can’t diagnose anything. They’re not a small outfit either and do 100s of installs. So this seems to be that one time it doesn’t just work and they don’t know how to fix…problem is I’ve caught them out on some somewhat mistruths - Eskimos require a flow of 45C (rubbish) plus banging up the Grant flow temp to 50C to try and mask the problem, plus telling builder Stelrad would have worked (when none fit).

Only progress so far has been from forum members suggesting temp probes and the specialist being brought in (who they keep ignoring).

Treble post apologies.

To be clear - myself and specialist have said why not just remove the LLH and the house side pump, keep zones open etc and have a volumiser. Seeing as the LLH has been a consistent issue it would be logical.

However installers insist Grant specify the LLH as part of the install pack they use and state I’d lose the warranty.

Builder won’t allow any works other than directed by installers so that they cannot point fingers at external involvement and thus risk loss of MCS and grant.

Posted by: @crimson

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MCS only guarantee Stelrad performance:

 

Thats simply a lie!  MCS guarantee very little and certainly do not guarantee radiators or specific models of radiators.  If you wish ask for the written evidence of this statement.

There is a question that it is worth being clear on here, did you specify eskimos against installer advice or did you express a preference which was accepted by installer?

Posted by: @crimson

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To be clear - myself and specialist have said why not just remove the LLH and the house side pump, keep zones open etc and have a volumiser. Seeing as the LLH has been a consistent issue it would be logical.

However installers insist Grant specify the LLH as part of the install pack they use and state I’d lose the warranty.

Swapping the buffer for a slightly larger one wont make any difference to the problem whereas doing the above would (which is not to say it will fix it entirely)

Can I suggest you ask for written evidence of the statement about the LLH?

Unfortunately you will have to let the installers do what they propose to prove that it wont work.  In the mean time can I suggest you get the answer to the question about the eskimos clear in your own mind (so you know what you can and cant argue) and also take some temperature measurements of the flow pipework (so you can work out whats happening).  I can be more specific about the latter, but Im not going to describe at length what needs to be dome unless you are actually going to do this.

The problem is soluble but needs to be done methodically.  Your choice, in practice, is probably

• Work it out yourself with the help of people on the forum, by taking measurements, then either adjust settings if that will fix it or prove it to your installer and ask them to show you documentary evidence for the things that they claim are stopping them doing what needs to be done
• Get a third party to do it who knows what they are doing (you appear to have one), but this may invalidate your warranty and will cost money
• Waste a lot of time and get frustrated with an installer who clearly doesn't understand heating systems. 

Of course the first of these choices could still lead to the third, but it would at least put you in a position of solid understanding which is never a bad thing.

I’m letting them proceed.

will look into other aspects once confirmed its working/not working.

Eskimos - I suggested as they couldn’t find Stelrads to meet the room requirements - as it was holding up project myself and architect were at a loss with them not sending anything. This was after they sent a heat calc doc and after endless prompting the entire stelrad catalog. Asked them at time to confirm they’d work and they did. Sorry if it seems fluffy, this went on for about 6 months and I suspect they wanted the architect or client to take the hit.

They’ve just at multiple times tried to accuse me of forcing them. However architect acting as design manager looked back through emails and it was confirmed installers gave go ahead. They just chose to try and pull one over the builder when it suits.

Posted by: @crimson

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I’m letting them proceed.

Eskimos - I suggested as they couldn’t find Stelrads to meet the room requirements - as it was holding up project myself and architect were at a loss with them not sending anything. This was after they sent a heat calc doc and after endless prompting the entire stelrad catalog. Asked them at time to confirm they’d work and they did. Sorry if it seems fluffy, this went on for about 6 months and I suspect they wanted the architect or client to take the hit.

They’ve just at multiple times tried to accuse me of forcing them. However architect acting as design manager looked back through emails and it was confirmed installers gave go ahead. They just chose to try and pull one over the builder when it suits.

All good then, installer has no excuses.

Re the eskimos, I looked for them and I cant immediately see why they would have an output that is substantially different to any other panel radiator of the same size.  It might be worth a double check on specs, if you would like to tell me model, size, output required at what FT I am happy to do an independent check as well as calculate the effect of any departure from that FT.  I have spreadsheets already set up to do this sort of thing for my own install.

I really do think that, coupled with the above, taking a few temp measurements would seal the question of where the problem lies.  Its definitely what I would do.  No point in waiting for your installer who is obviously totally out of his depth (not surprising, there arent many people who actually understand heating - the whole domestic heating industry has dumbed down in past years -with of course some stellar exceptions - and resorted to fixing all problems by brute force).

In summary what I said 4 pages ago remains my thinking.  I hope, for your sake, I am wrong.

The blame game is more or less standard practice in the building industry in my (rather sad) experience; the only solution is to get ahead! 

Thanks,

I’ll try and send docs and soreadsheets next week, away currently.

the Eskimos in regards to performance were their correction factors, off top of my head at delta 16.5 it was 0.33 factor instead of 0.237. Even at that rating I think theyre fine for that too.

have to remember i wasnt on site so installers were suggesting Stelrad Concord Lolines but said they also needed tall rads in the rooms (which the architect said sounded bizarre), and just wouldnt suggest actual items, kept sending entire catalog. I think i worked off their heights at around 30cm as being the max and found a radiator site that gave me ability to search by outputs and heights which led to the Eskimos. Builders were being useless as well at time not confirming the height could have actually been 40cm, installers wouldnt confirm either (so the first round of short rads could have been avoided…).

all amongst the huge project itself as well so heating wasnt my top item at the time

Posted by: @crimson

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16.5 it was 0.33 factor instead of 0.237.

Thats strange.  Then output of convection radiators is always, so far as I was aware, proportional to DT^1.3.  There are minor variations in the exponent, perhaps 0.02 either way of 1.3, but these are obviously just rounding.  The physics is the same after all.

I suppose its possible eskimo have some clever tubework for the airflow, but if so why dont others also do this?

That said the table here is definitely not ^1.3, its ^1.  

I would personally be suspicious until I had heard a convincing explanation of why eskimo is materially different!  I would go so far as to say that personally I wouldnt believe it without solid corroborating evidence.

Forgot to say a few pages back, i got them to send me written evidence from Grant for the LLH. Was some conditions Grant wanted to account for due to mixed emmitters and zones (again, why not just not have the zones lol).

Here:

• Protection against low system volume in oversized or zoned radiator systems
• Balanced flow rates across mixed emitters (radiators, UFH, etc.)
• Improved air and dirt separation when combined with appropriate magnetic filtration
• Compliance with hydraulic separation guidance for heat pump installations

also mentioned volume for defrost cycle (not sure why a 6L LLH was used originally…).

I’ll have to find out when the Grant warranty commenced, assume late 2024.

Believe its 2031 then that it would expire. I guess have to weigh up warranty over being warm. Or use log burners and get works done once warranty is over.