So here we are, brand new Grant ASHP installed…

It's ran over night, panels calibrated.  Am not seeing much promise from it, and I'm not surprised.

I'd brutally honest have thought the installer would go around and bleed rads to be sure no air (which would hamper seeing 21C) - he didn't.

I've been told to give it 24 hours from last night.  But I have a simple understanding of how heating to 21C would work - you'd expect an upward trend.

This has seemed to have currently plateaued…

So the installer set (after I was talking about noise from pump room speed, I didn't insist on changes):

• Grant ASHP at speed 1/3
• Pump room speed at 1/3
• Flow setter adjusted to get flow to around 28L/min
• Altered the WC (didn't seem to go with Grant default 45=40, changed to -3 at bottom from -4, 19 max ambient, 25 min flow, 40 max flow) - that in fairness isn't a wild W/C

Also told him multiple times that the Grant engineer for whatever reason set the UFH pump to speed 3 (seems crazy to leave it at that).

Last night I think, mmmm temps aren't really going up as expected (I'd seen on the supposedly 'broken' ASHP that it would recover faster from cold than this).

Check the flow rate, 12L/min.  I have seen up to 20L/min, but was on a defrost cycle, and the second time I saw it could have just been right after one (it's -1C outside for context).

So now we have a system running with a low water flow rate.  And underfloor pump before manifold at max speed.

I presume the temps not really going up is likely due to those factors, as saw higher temps with smaller LLH and 'broken' ASHP.

The ASHP and pump room pump, were always 2/3 both sides previously.  I'd have thought adding in 50L LLH would want them up, not down, but I have no idea tbh.

Currently seeing:

• Kitchen (UFH): 19C (Heatmiser panel)
• Yes the panel is calibrated to be -1C to match my new Testo 915i probe (I equipped myself with something accurate to ensure I was being fair to installer).  - this matches the room well.
• However, previously it would get to 21C (so say 20C - but the panel would stop it at 21C, it probably could have gotten up there)
• Hall: 18.7C (Heatmiser panel) (reminder this drives the ground front zone - 2 living rooms, 1 hall, 1 WC)
• Living Room 1 - 17.4C (temp wired Heatmiser panel)
• Living Room 2 - 17.8C (temp wired Heatmiser panel)
• Landing (upstairs) - 19.8C (Heatmiser panel)
• Utility (UFH): 21C (Heatmiser panel) - this room is tiny, and has the plant room cupboard, if it wasn't 21C, I'd be seriously worried

In about 2 hours I've seen zero upward trend.  From last night a fluctuation of maybe 0.3C from then to now (but that was at night, there's low winter sun = solar gain etc etc).

There's currently no set back either, so it's not a recover from setback situation.

Really not sure what to think anymore.  I am between a rock and a hard place.  November 26th = rumoured that the £7.5k BUS could be scrapped.

Unbelievably I'm 2 years into all this and haven't got that for obvious reasons and it's likely at serious threat.

I'm not touching anything in the system as the installer is monitoring temps.  I presume he's rather worried as asked me to move the 2 temp wired panels from near the log burner slate hearths to hang them over the doors.  Yes slight uplift, but not enough to turn sub 18C to 21C…

Posted by: @crimson

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Check the flow rate, 12L/min

So at DT 5 (the normal design DT for heat pumps) that will transport 4.2kW (assuming water, about 10% less if its glycol).

Is that sufficient, if not then DT will rise (which has the effect of reducing average emitter temperature and thus output from the emitters - just like reducing flow temperature) until the system is in equilibrium at a lower than designed room temperature.  The physics is really, really simple, you learn it at the age of about 13!

Nothing more to say.

Yeah, no idea why he thinks 12L/min is ok.  He even showed me it running to 28L-30L/min yesterday.

Going round the houses on this stuff.

Irony is - brand new ASHP heatpump + 50L LLH for the water volume issue (in a LLH, not a volumiser!!) = worse performance than before (which wasn't good enough mind, but not this bad).

Just baffles me they won't try getting the LLH off the flow.

I can see with the Amazon probes (recommended on this forum in January 2024 - that aren't far off the Testo 915i!!) - that the temp on the flow pipe from the ASHP, to the temp going to just before the heating zones (after LLH and pump room pump) - shows a drop.

The low flow is causing distortion/mixing etc in the LLH = not enough water temp to emitters.  Simple as that.

In fairness, when installer was here yesterday - those 2 temps were pretty spot on.  However adjusting pump speeds and flow setter then leaving within 5 mins - to me seems a really bad move.

Fixing the flow rate (sorting pump speeds) - I don't believe will actually fix my issue, as the temp drop seen from ASHP, past LLH and pump rooms pump to before zones was only 0.5-1.5C anyway.  All I have is just a bigger LLH in the way.

The issue has been it seems to me, the delta with the LLH kept narrowing = cycling off of ASHP.  Avoid that by NOT HAVING A LLH!!!  NOT A BIGGER ONE!!!

So I've given him the clue the flow setter reports 12l/min, he's said it's fine.  They've got till tomorrow morning, and I can see forecast is -2C, so I'm pretty certain, it won't go up…

I truly hope the builder takes this as the installer just simply cannot get this running and he deploys the specialist.

Least if we get the LLH off the flow, we have a digital flow setter that never allows misreading, we have a smart panel that doesn't require me to report in issues (that installers ignore).

The datas there + the actual flow from the ASHP gets to the rads.

If that fails, then the rads/calcs need looking at, yet again.  I even have written record of me saying go even wider with the Eskimos, now's the time, but was assured - the rad uplift would work (that was September 2024, it helped, but didn't 'work').

I've even checked for Stelrads (only rads these guys seem to know to use) - none that fit have the output.  Grant engineer suggested their alluminium rads - none of those that fit have the output.

This is all never mind the fact that early on in this thread people pointed at the pipework being undersized (22mm/15mm plastic = smaller bore down to 15mm copper to rad = hampers flow).

So that's likely not accounted for, having 3 pumps (ASHP, pump room pump AND a pump before UFH) = lots of flow issues, plus narrow pipes to contend with.

All routes, (and it's been said by members on this thread from the get go), come to the conclusion that a LLH in this situation is just never going to work/hamper it.

I've just had an installer that won't accept that and points at every other element in the system as the fault…

Save yourself some angst.  Until the flow rate is fixed there is nothing worth speculating about. 

Once its fixed then measure the temp drop across the LLH and what happens to the rooms, and then some further deductions can be made.

Posted by: @jamespa

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Save yourself some angst.  Until the flow rate is fixed there is nothing worth speculating about. 

Once its fixed then measure the temp drop across the LLH and what happens to the rooms, and then some further deductions can be made.

Oh I know, am just raging, apologies.  2 years has worn me to the bone.

However, the temps were measured across the old LLH by the specialist (and seen on my probes), there was distortion (always has been).  That was done in July this year with the old smaller 3L LLH.

The specialist checked all this, this was why he wanted the original smaller one off the flow. 

For context he attended twice during this whole fiasco.  He said he could never really get the flow rates to what he wanted, tried different speeds either side of LLH, tried a heat dump in towel rads upstairs (to artificially add more volume).  Tried enforced 60% modulation with nightmode on constantly (tbf that helped slightly).

He suggested per Grant's spec, that a volumiser be added due to the low volume of the zone that has 5 Eskimo rads and a towel rad.  As the upstairs is hugely oversized with rads, the ground rear has UFH.  Often this smaller zone (the problem one hence the whole thread) - is only one left on, and never gets to temp.

He despaired when the installer insisted on doing the 50L LLH upgrade.  Said he didn't think it would work, likely be same, maybe less cycling, but flow would be impacted still.

But here we are, back to square one (well -1 as temps aren't as good as before…)

The current situation = installers monitor temps until tomorrow morning.  If rooms aren't 21C, they're out and specialist is instructed.

It's just hugely frustrating that their last 'fix' was the 50L LLH on the 5th, they've had 2 weeks of pointing at different ASHP components (water circulating pump, PCB, compressor), until got an entire new one yesterday.

(I honestly think the old one was impacted at the work done on the 5th, but I can't categorically say that).

Fair enough (the raging).  Try not to let it upset you (easier said than done I know). Unlike some less fortunate people you remain in control it seems.

Posted by: @jamespa

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Fair enough (the raging).  Try not to let it upset you (easier said than done I know). Unlike some less fortunate people you remain in control it seems.

Thanks James, its honestly hard to keep it together, especially as we’ve slipped into a cold spell. It would have been great to check a fix worked but alas no.

I’ll keep reporting back in hopes that the end fix may help someone here.

Honestly appreciate everyone’s input here. I’ve not ignored it, always relay it to the installers but have been brushed away as some mad client who expects hot rads on a low and slow system.

So this morning marked 24 hours up for installer. Rooms weren't to temp as I expected.

I instructed builder that I no longer wanted the installers on site - as in - you don’t instruct someone else, I will.

Not a situation I wanted to get to, had hoped installers would do the job correctly.

The specialist kindly offered to attend site today as he said he was really worried myself and family this weekend again would be without heating and didn’t think it right, especially with misty conditions and sub zero temp combination being quite hard for ASHP.

So he emptied the strainer again. So seems stuff is still in the system blocking the flow and started to see temps rise again as flow rate shot up. Suspects will have to repeat a few times if flow drops.

He then got his Testo clamps out to check temps across the LLH, and to check actual delta on flow and return with different pump room speeds again to maintain a decent delta and flow rate. And then temps started to rise again more steadily. No champagne yet however. (I know this has time and again been suggested here - just never had the position of someone on site to do it in detail - I probably should have invested in a pair of Testo clamps).

He has 100% confirmed what has been thought here all along, in black and white. This plant room setup loses 3-4C from flow into LLH from ASHP, before gets to heating zone ports. He was a bit surprised in fairness, but it confirmed his July recommendations. I think tbh the smaller LLH had more a 1-3C drop but didn't have accurate clamp meters of course.

He then confirmed at one of the Eskimos the temp seen, and said thinks should they get the actual design flow temp, we’d be seeing 21C temps in the rooms.

I’ve asked him to put a report to the builder which outlays this.

I mean this is not all new, its just from a different position now installer is no longer involved.

My hope is we go ahead with the works and get this finally done and dusted after 2 years.

He even proved the pump for the UFH (so I have one after LLH and another for the UFH) - disconnecting it, get expected flow rates on the manifolds. So that is pretty pointless. So we’re talking rip 2 pumps out, LLH as 2 port volumiser on return only = direct heat to emmiters. Only concern is Grant unit pump if hefty.

I will likely attempt a day of looking at the WC calc doc previously shared here, what the flow temp is on the WC based on ambient temp. And use a fixed flow temp of that +3C or +4C. Then confirm with a probe the rads get the actual flow temp (eg say its -3 outside, flow temp would be 40C, set fixed at 43 or 44C, to account for the drop in plant room, check probe at flow to rad shows 40C) and see if get 21C.

All in all painful it takes 2 years to get here and STILL not got works done that a lot of members said needing doing but contracts etc get in way. I could be here with works done after July report and just be confirming the system works…

In terms of kit I wish I got early on:

(have this recently) Testo 915 - that made it clear to installer, the Heatmiser panels weren’t accurate and forced him to calibrate - £100

2-3x Testo 115i Clamp thermometers (£90 each)

I’d have put clamps:

1 on flow pipe from ASHP in plant room.

1 on return pipe from LLH in plant room.

those two would prove actual delta

then:

1 keep flow pipe location

1 after LLH and plant room pump, just before 2 port heating zones = proof of drop due to distortion in LLH

1 on pipe to radiator in problem zone = proof emitter not getting flow

I think brutally honest having that kit would have removed any notion I’m some mad client with inaccurate probes. They all use this kit.

So again am in midst of lunacy it seems.

Tested system with an inflated W/C of 3.5-4C higher than the installers design.  Rooms got to temp (was slow as house had completely bottomed out).  A little bit of balancing needed mind, but I've said it's on a professional to do that.

That - proved that without the temp drop across the LLH (still uncertain why - competing pump rates etc etc distortion, gremlins, no one who's been on site can confirm) - the system could in theory run at system design flow rates with the emitters etc etc to the design of 21C at 40C max flow.

The next problem becomes - due to all the faffing about, sandbagging, people crossing fingers something would just work and I'd say lets call it a day - the specialist is saying no longer has capacity.

Proposal was a temp bypass from ASHP flow to heating zone 2 port valves (turning off the pump room pump, and avoiding the LLH) - to see if in fact, the LLH becomes a volumiser fixes it - without capping/numerous pipe work changes.

So now I'm stuck, again, for another winter, running hot.  Now at 44C max flow instead of 42C, as this bigger LLH seems to cause more distortion.

It's got to point I wonder if people hope I just give in and pay up and live with a compromised system…

Posted by: @crimson

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That - proved that without the temp drop across the LLH (still uncertain why - competing pump rates etc etc distortion, gremlins, no one who's been on site can confirm) - the system could in theory run at system design flow rates with the emitters etc etc to the design of 21C at 40C max flow.

So sort of progress, but...are you certain its going to be OK when it gets cold again?

Posted by: @crimson

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It's got to point I wonder if people hope I just give in and pay up and live with a compromised system…

Obviously thats the case, it always is!

Posted by: @crimson

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So now I'm stuck, again, for another winter, running hot.  Now at 44C max flow instead of 42C, as this bigger LLH seems to cause more distortion.

OK well at least you have a warm house.  2C is 'worth' about 5-6% in terms of efficiency, 4C about double that.

Posted by: @crimson

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Proposal was a temp bypass from ASHP flow to heating zone 2 port valves (turning off the pump room pump, and avoiding the LLH) - to see if in fact, the LLH becomes a volumiser fixes it - without capping/numerous pipe work changes.

Sensible.   

Alternatively just measure the temp drop across the LLH, because for sure thats how much you could reduce your FT if it weren't there.  Of course this doesnt prove that the water pump will suffice whereas the plumbing suggested would.

Posted by: @crimson

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It's got to point I wonder if people hope I just give in and pay up and live with a compromised system…

Obviously thats the case, it always is!  The installer is now more confident that his hope will pay off because you are now warm!

Assuming you are certain its going to be OK when it gets cold again, the question now becomes, can you hold the installer to the design flow temp.  Thats devil in the detail of the agreement which only you will know.

Alternatively @toodles went to some considerable effort to balance flow rates across his buffer tank to minimise distortion.  Of course this means that it serves no purpose, but we know that to be the case anyway.  You could go down that route, maybe reduce the penalty to 1-2%, at which point its probably best to give up!

I think over the 2 years a lot of pump speeds either side have been experimented, in aim to get solid delta and less distortion, never worked as too many variables.

Temps were measured across the LLH - specialist saw 3-4C drop with 2 Testo clam meters.  I've looked back at my notes, it used to be 1.5-2.5C with the smaller LLH.

Problem I'm seeing is that the drop (on my cheapo probes) - can range from 2-4C, depending on actual flow temp and how many zones open/shut = will never be able to account for it fully…this might explain my curve had a greater deviance from the Grant default as ambient went up (e..g hotter flow = less drop across LLH, cooler flow = greater drop across LLH) - but I may be coming to a bad conclusion of what I did over that year.

I was running 2C hot since rad uplift fail back in September 2024 through to early this month, so already had a year of 5-6% of increased running costs.  Like you say it's now 12% more (said to builder, I'm in worse state now than before the ill advised LLH upgrade - instead of a volumiser).

Temps have been down to 2C here, and it seems to have held, of course be good to see -3C.

But I wanted to see that without the LLH, not best try W/C inflation…

The specialist highly suspects the primary circulating pump within the Grant ASHP will be sufficient enough to run on its own.  He was thinking (of course) - remove plant room one - as no more LLH (just volumiser), plus remove one at UFH manifold.  He tested unplugging UFH pump, flow rates remained same (another pointless part in this system).

I'm afraid I'll probably be messaging here until I retire about this garbage system…

It's likely that I'll need to find my own independent Heat specialist, as not pleased they (installers, builder and specialist) all converse with one another and suddenly out of nowhere get to no availability.

Posted by: @crimson

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It's likely that I'll need to find my own independent Heat specialist, as not pleased they (installers, builder and specialist) all converse with one another and suddenly out of nowhere get to no availability.

Or just commission a plumber to do the replumbing?

As soon as you touch it your installer will argue that it voids the warranty and I doubt any third party will warranty a system largely installed by someone else (why would they?).  Therefore if you are going to bypass the LLH you have already accepted the risk of a warranty argument (mad I know).  If you are going to do this you might as well cut to the chase and get a regular plumber to change the pipework.