Thanks both.

I’d forgot to detail that pump speeds either side of the LLH (Grant one and one in pump room). A lot of experimenting with different speeds/paired speeds was also done. Best performance so far was the Grant on mid level (can’t recall if it has 2 or 3 now) and pump room pump on mid too - I think the flow rate checked by specialist to what he wants to achieve. Increasing house side pump to 3 the flow water noise is annoying when balancing down rads, but did push temperatures up slightly. Plus I get a lot of bangs from the Eskimo rads. Installers seem to insist the buffer tank will help with that (or want to see if that helps first).

I’ll check in with them if they’re proposing to pipe this tank as a volumiser. They seemed reticent to try piping the current LLH on the return only - to avoid mixing (guess that acts as a tiny volumiser?) as kept saying we’d void Grant’s warranty (the heat specialist couldn't find that in Grant’s materials however).

I suspect there’s quite a cross fingers it works and client says all good moment going on.

What is of note is that currently (temps got down to 7-8C last night I believe), the Grant is still in 60% constant nightmode. And other than the 2 living rooms, everything is to temperature.

Posted by: @crimson

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Plus I get a lot of bangs from the Eskimo rads. Installers seem to insist the buffer tank will help with that (or want to see if that helps first).

Im sceptical, whats the mechanism?

Posted by: @crimson

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I suspect there’s quite a cross fingers it works and client says all good moment going on.

I get the impression that it may be entirely that.  Not a good sign. 

The problem for you is that he will eventually get tired of it and find ways 'out'  If by then it isn't fixed, or its been 'fixed' at the expense of running costs (because he hasn't really got a sound plan), you are left high and dry.  Thats why I would try to get ahead of him!

Sorry but the more I think about this the more its shouting RED FLAG.  The work is, you say going to be done in a day.  He is probably going to fit a Grant 17kW and retain a buffer tank.  There is so far no diagnosis of the actual problem.

What he is planning to do is to fit a larger than necessary heat pump so that he can whack the flow temperature up as high as is necessary to solve the transport problem by brute force, dealing with mismatches through the buffer.  Basically he is going to emulate the old oil system.  He isnt allowing any time for 'discovery', careful thought or re-commissioning, so his intention is to leave it at a very high FT with no concern for your running costs.

It will very likely work in the sense that the rooms will be warm so he can say he has done the job.  Expect the electricity bill to be double a reasonable amount.  If you are happy with this please do proceed.  If not you had better hope I'm wrong!

Posted by: @jamespa

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Sorry but the more I think about this the more its shouting RED FLAG.  The work is, you say going to be done in a day.  He is probably going to fit a Grant 17kW and retain a buffer tank.  There is so far no diagnosis of the actual problem.

What he is planning to do is to fit a larger than necessary heat pump so that he can whack the flow temperature up as high as is necessary to solve the transport problem by brute force, dealing with mismatches through the buffer.  Basically he is going to emulate the old oil system.  He isnt allowing any time for 'discovery', careful thought or re-commissioning, so his intention is to leave it at a very high FT with no concern for your running costs.

It will very likely work in the sense that the rooms will be warm so he can say he has done the job.  Expect the electricity bill to be double a reasonable amount.  If you are happy with this please do proceed.  If not you had better hope I'm wrong!

@jamespa - the Grant ASHP isn’t being replaced, the 13Kw will remain, apologies if I wasn’t clear. The heat specialist was experimenting with the current 13Kw in nightmode to see if it’s “oversized” currently not undersized if that makes sense. Currently in nightmode at 60% its  normal power rate - it’s still heating rooms same as before (mind you its 8C coldest lately, no sub temps). The short cycling is still happening however.

It’s just the LLH header thats being replaced.

Attached is a photo explaining the works.

The heat specialist felt it’s physically too small and like to be mixing (hence him wanting to temp bypass it to prove to installer)

The day’s work is to also do some snags:

• replace a TRV - actual valve - not head,
• replace 2 clogged bleed valves in one of the Eskimos.
• fully drain system and add back glycol

I won’t be signing off the job until am happy the system performs at the designed flow temp of 40C with a weather curve.

Hope that makes sense. I’ve probably used incorrect terminology somewhere.

Posted by: @crimson

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It’s just the LLH header thats being replaced.

Attached is a photo explaining the works.

The heat specialist felt it’s physically too small and like to be mixing (hence him wanting to temp bypass it to prove to installer)

He is right.  Better to eliminate it altogether.  Is the Grant the R290 or the R32?  The instructions for the R290 (which as it happens I was reading just yesterday) are very clear that buffer is not mandatory.  Not sure about the R32.

Posted by: @crimson

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• fully drain system and add back glycol

Better to fit antifreeze valves!

Posted by: @crimson

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I won’t be signing off the job until am happy the system performs at the designed flow temp of 40C with a weather curve.

Very sensible precaution.  Check COP as well during the test period.  

I’ll check which version the Grant is, suspect like you thats what the specialist is seeing - that there’s no requirement.

Antifreeze valves the installers suggested against their use as one offs? And cost per refit? Also they mentioned as glycol already in system it wouldn't fully be gone anyway. (I have no idea on that stuff). I did query did they use an inhibitor per Ekimo’s requirement.

Not sure how to check the COP with the Grant I’ll be honest.

To clarify heat specialist’s observations were (was writing this then saw your reply):

Due to space constraints Grant’s recommended low loss header / volumiser couldn't be used. LLH in place currently is very short. Upon running the system he could see temps at the 4 inlet/outlets on the LLH indicated mixing was occurring - meaning the 5 delta wasnt maintained and system cycled off.

Heat pump per calcs is to size however underfloor zone hits temps quickly, upstairs doesn’t call for 21C, which leaves the small front downstairs zone on and that has very small volume with the Eskimo rads. Cycling then occurs further.

Suggestion was to use an external Grant volumiser (30L capacity) - this wasn’t gone for due to a) they’re not convinced 30L will add enough and b) requires shifting the ASHP forward (additional works as its on a slab essentially - that would need to be extended)

Other suggestion was to also remove LLH altogether, plus house side pump, leaving just the Grant WSHP pumping water.  wasn’t gone for as installers insist a LLH is required by Grant and there’s concern the Grant pump solely would cause further rad noise

Posted by: @crimson

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Antifreeze valves the installers suggested against their use as one offs?

They arent one offs, but they will empty the system in part if they go off.  Better than making it work less well by filling with Glycol.  Some argue not to bother with either on the grounds that prob of freezing very small.  Not sure I would do this I have a/f valves

Posted by: @crimson

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also they mentioned as glycol already in system it wouldn't fully be gone anyway

BS assuming they flushed it properly.  And if they didnt then they should have

Posted by: @crimson

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Suggestion was to use an external Grant volumiser (30L capacity) - this wasn’t gone for due to a) they’re not convinced 30L will add enough and b) requires shifting the ASHP forward (additional works as its on a slab essentially - that would need to be extended)

Really dont, why would you want to put a volumiser outside where it gets cold

Posted by: @crimson

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Other suggestion was to also remove LLH altogether, plus house side pump, leaving just the Grant WSHP pumping water. 

Correct answer!

Posted by: @crimson

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 wasn’t gone for as installers insist a LLH is required by Grant and there’s concern the Grant pump solely would cause further rad noise 

First part - check if its the R290 or R32.  ask for proof.  Second part semi BS.  Yes it could do this in principle, but only because its pushing the amount of water through the system that is needed to transfer the heat!  If the system cant take it then something needs to be done with the system!

Conclusion: Heat specialist is almost entirely correct, installer is out of his depth and a BS merchant who just wants to fob you off with a quick fix which, in reality, he doesnt know will work because (a) he hasnt done enough work on diagnosing the problem and (b) he probably doesn't really understand it anyway

Thanks @JamesPa, I think the external volumiser suggestion - supposed to be insulated - was on assumption no space inside but yesterday’s visit it was drawn the conclusion that moving the expansion tank meant a buffer tank could replace the LLH without affect access. I think the whole Grant specify a LLH excuse statement has caused this impasse as it were (in convos the heat specialist’s was keen to just remove it)

I’ll dig out the manual, and identify the ASHP version/get it confirmed.

I wouldn’t be surprised if a lot of BSing is happening, these are the same installers that got the problematic LLH installed by one if their staff the wrong way round (it even has bloody arrows on it…on the front side).

These guys also seem to not want to do any real diagnosing of the issue hence relying on myself to provide observations.

To add to this, I did raise before the rad uplift fix attempt (double height of 4 Eskimo rads and trippled width of 1) - if they should go over over over sized with them based on them keep saying they’re low water volume. But they didnt. We’re now past that point as the builders had to shoulder original Eskimo rad prices, so that I only pay the difference for bigger ones plus they shouldered the non plumbing work costs of this (decorating etc)

A quick google states the Grant Aerona3 requires a low loss header as a mechanical break as part of Grant’s install package - I suspect they’re using the install package and not opting to not have the LLH.

Posted by: @crimson

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A quick google states the Grant Aerona3 requires a low loss header as a mechanical break as part of Grant’s install package - I suspect they’re using the install package and not opting to not have the LLH.

R290 has an explicit installer setting for 'no buffer'.  It couldn't be clearer!

Not sure then, I’ve been reading the manual and it does state it needs a volumiser, and even suggests options for low volume systems (why they didn’t think to go with that I don’t know). However having a volumiser is a prerequisite, it doesn’t state that it needs to be on the flow UNLESS it has an element to supplement heating (which this wouldn’t).

References to a Low Loss Header are only included when its states you don’t need a volumiser if you use a combined volumiser and low loss header.

I’ll try to prompt the installers to think upon that as thats effectively what the specialist was suggesting, use the buffer tank/LLH as a volumiser on the return as per your notes and the specialists.

Just don’t get why they cant get passed having this LLH, when clearly when first installed wrong way round caused issues and even after a hugely significant emitter uplift (upstairs went from K1-K2 along with the Eskimo increases), we see mixing indicated on the probes and temps not showing huge increase. Just obvious something other than the rads is causing this.

Overall it seems they’ve gone - client picked eskimo, they only want Stelrad, so point fingers at Eskimo (even though they approved them). They should have checked system volume with the install.

I’m at point now of reaching out to Grant directly for them to confirm if its required on the flow, or if it can just be put on the return.

Posted by: @crimson

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sure then, I’ve been reading the manual and it does state it needs a volumiser, and even suggests options for low volume systems (why they didn’t think to go with that I don’t know). However having a volumiser is a prerequisite, it doesn’t state that it needs to be on the flow UNLESS it has an element to supplement heating

Volumiser totally different to buffer or llh.  Volumiser 2 ports, buffer/llh 4, volumiser doesn't cause system distortion, doesn't penalise COP, buffer/llh does.  Either solves defrost issues and mitigates short cycling.  I have no problem with fitting a volumiser!

Best to put volumiser on flow but it's ok on return, something of a discussion on this earlier in the year with a difference of opinions at start but convergence at the end but also general agreement it doesn't matter that much in the absence of an integral heating element.