I'm only seeing 22l/min on the flow setter with the hot water cycle running but I'm none the wiser if that's good or not…

This is what I'm seeing during the DWH cycle currently.

Will check again from 4pm when heating is running

Ok he's told me he'd like to see depending on what it's doing between 18l/min - 28l/min.  Have asked what it was like before

He showed me a photo of 5-10l/min.

However am not convinced this pump was the issue.  Realised I have photos of the flow setter from early 2024, and it sat at 28l/min, and was before rad upsize.  So I don't think this has been like this for all that time.  Unless post LLH being swapped round and post heat specialist coming it's had a fault.  As I recall the heat specialist that the builder employed looking at the flow setter constantly when he attended when he was trying different ASHP pump speeds and secondary plant room pump speeds either side of the LLH.  I'd be certain he'd have clocked that.

Have an irksome feeling this is again the installers chasing a gremlin.

Seeing no effect from circulating pump replacement and no positive effect from 50L LLH upgrade

To summarise history of this saga:

LLH back to front - room temps at 14c

LLH back to front fix - room temps at 18C

Calcs confirmed wrong/rad sizing wrong. Rads more than doubled in output - room temps at 18-20C

Water volume indicated as issue. LLH from 5L to 50L. No change

Primary circulating ASHP pump indicated as faulty. Replaced

No change

I’m going to contact builder and installer and suggest following

1. if Grant gave PCB. Just replace it, confirm no change, ticks that off list
2. Installer speak to Grant - get them to agree 4 port 50 LLH conversion - top 2 ports capped, acts as 50L volumiser on return only. Flow from ASHP is direct to before heating zones with secondary plant room pump removed and appropriate settings are changed. With no impact to 7 year warranty
3. If Grant refuse. Install digital flow setters/monitors either side of LLH to see if flow is distorted
4. If distorted - re ask point 2

All I can see is that at all issues point to the LLH that has always been indicated here as a problem and at no point has the system been tested without it to just confirm. I get installers don’t want to deviate/lose warranty but why not just trial it??

What I’m trying to do is lead installer to put the onus on Grant, if the installers refuse to deviate from Grants specification/direction with their install pack - only route I can see, is to get them to get Grant to agree a change.

I’ve checked and checked the heat calcs.

If they are correct. The Eskimo rads in the problematic front ground zone are 30-140% oversized even to the watt requirement at delta 16.5, when using Eskimo’s correction factor. Ignoring Eskimo’s correction factor and using the installers heat calc software one. 2/3 of the areas are still oversized. 1 is 7% under (but performs better).

Eskimo strongly stand by their correction factor so I don’t think thats the issue.

However I note that 2 living rooms on the calcs are at delta 50 - 40 watts apart (X at delta 16.5). The reality is one adjoins the plant room and has less external wall space. Maybe the other room should require more watts, but again thats X percent oversized.

Both have log burners installed in the project that due to HETAS requirement, had external vents installed. These do get cooler air near them. So perhaps calcs need revisit, but going by the percentage oversized Im just not convinced. The ASHP cycles so much too.

However the downstairs WC is 20% oversized (non Eskimo) and is worse performing room in house. Its XXm.

In my head emitters could be ruled out. And the LLH needs to just become a volumiser on return in order to isiolate the LLH being the issue before emmiters and calcs are looked at again. Least this way its ruled out as the cause and other investigations can be done.

You are doing a splendid job of cornering the installers, well done. 

I have a couple of comments which may or may not help

Posted by: @crimson

↑

To summarise history of this saga:

LLH back to front - room temps at 14c

LLH back to front fix - room temps at 18C

Calcs confirmed wrong/rad sizing wrong. Rads more than doubled in output - room temps at 18-20C

Water volume indicated as issue. LLH from 5L to 50L. No change

Primary circulating ASHP pump indicated as faulty. Replaced

No change

Just to add one more thing - there are no surprises in any of the above, it was all predictable, at least qualitatively

Posted by: @crimson

↑

And the LLH needs to just become a volumiser on return in order to isolate the LLH being the issue before emitters and calcs are looked at again.

Completely agree.  This is likely to make a difference, try it, if it works you have found the solution assuming Grant will stop being idiots.

All that said I personally would still measure some temperature drops across LLH, from LLH to problem emitters and across problem emitters, even if I kept the results to myself!  At least then I would understand whats going on even though the installers evidently don't and probably never will.  But thats just me.

Posted by: @jamespa

↑

You are doing a splendid job of cornering the installers, well done. 

 

I have a couple of comments which may or may not help

Posted by: @crimson

↑

To summarise history of this saga:

LLH back to front - room temps at 14c

LLH back to front fix - room temps at 18C

Calcs confirmed wrong/rad sizing wrong. Rads more than doubled in output - room temps at 18-20C

Water volume indicated as issue. LLH from 5L to 50L. No change

Primary circulating ASHP pump indicated as faulty. Replaced

No change

Just to add one more thing - there are no surprises in any of the above, it was all predictable, at least qualitatively

 

Posted by: @crimson

↑

And the LLH needs to just become a volumiser on return in order to isolate the LLH being the issue before emitters and calcs are looked at again.

Completely agree.  This is likely to make a difference, try it, if it works you have found the solution assuming Grant will stop being idiots.

All that said I personally would still measure some temperature drops across LLH, from LLH to problem emitters and across problem emitters, even if I kept the results to myself!  At least then I would understand whats going on even though the installers evidently don't and probably never will.  But thats just me.

Thanks James.

Am back Sunday night. Will put probes in. I do have probes on the 4 ports of the LLH, neglected to take a photo as the heating cycle didn’t even happen lol. Genuinely can’t fathom how he let it run a DWH cycle for 30 mins, then barely witnessed a heating cycle and was so confident it was done. It just doesn’t make sense, hot water was never an issue!!!

Ironically checking on the Neo app. It shows the house temp is starting to gradually drop…so it may be the 50L has made things worse than before.

I’ll give them the benefit of the doubt, but Monday will check the temps and send the mail to builder.

I’ve no interest it letting this run 1 more or 2 more weeks as there’s clearly no change. So want them getting this resolved before temps drop outside.

OK, couple more questions

At these relatively mild temps, how certain can you be that its not just a WC setting problem that would be resolved by leaving the cold OAT end of the curve where it is but increasing the warm end a tad

Given mild temps, probe variability may matter when measuring the various DTs.  You should either check calibration or reverse  pairs of probes so you can take out any variability.  I think you need temps at

• output from heat pump (optional if you know that there is little loss between heat pump and LLH)
• input to LLH
• output from LLH
• input to problem rad
• output from problem rad

The DTs, combined with the absolute temperatures, will tell you precisely what's going on

It would be useful to have primary flow rate when the temperatures are measured.  Secondary flow rate would be even more useful but I guess you dont have that.

Posted by: @jamespa

↑

OK, couple more questions

At these relatively mild temps, how certain can you be that its not just a WC setting problem that would be resolved by leaving the cold OAT end of the curve where it is but increasing the warm end a tad

Given mild temps, probe variability may matter when measuring the various DTs.  You should either check calibration or reverse  pairs of probes so you can take out any variability.  I think you need temps at

 

• output from heat pump (optional if you know that there is little loss between heat pump and LLH)
• input to LLH
• output from LLH
• input to problem rad
• output from problem rad

 

The DTs, combined with the absolute temperatures, will tell you precisely what's going on

It would be useful to have primary flow rate when the temperatures are measured.  Secondary flow rate would be even more useful but I guess you dont have that.

 

Thanks will do. Don’t expect a huge uplift in temps but looking at the at the app its clearly dropping and dropping. The WC we ensured was same as before.

I’d expect rooms that weren’t a problem to keep similar temps but now they’re sliding downwards. Keep in mind that at the 50L install they removed the enforced night mode running constant at 60%. The nightmode did seem to reduce cycling so it could be that variable is what is causing the slide downwards. And perhaps the 50L hasnt impacted anything.

Again will recheck Monday just to see if its not an anomaly, but its dead clear if the temps are going down, its likely cycling a tonne. Which the installer said was caused by the primary circulating pump. Again I don’t take anything they say as gospel as this is after emitters and water volume - the 3rd incorrect conclusion.

Really puzzling @crimson. I have a 'text book' Appendix B Grant 10kW Aerona install scheme with secondary pump, 4 port low loss header, all original 22 & 15mm CU pipework on the secondary radiator side and 20 system rads. 28mm CU primary pipework. The primary circulator is set to speed 2, indicating at 21 litres/min on the Grant flow setter, the secondary pump, a Grundfos UPS-3 also set to speed 2. It pushes water around all the radiators with TRVs open (used to prevent overheating in rooms subject to solar gain), and lock shields adjusted to get reasonably consistent delta T temperature drop across each radiator.

Towel rails lockshields in wet rooms x3 are almost completely closed, as compared to panel radiators they have very little flow restriction and always a lower delta T. Using digital thermometers, plus my Testo pipe clamp meters either side of the LLH, I've got almost zero distortion, <0.5degC. Flow and return delta T maxes out about 6degK during pre-heat or DWH cycle, down to 2.4degK on minimum turn down. The ASHP only ever cycles on very low load. I've had to invest some time manually balancing radiators, optimising WC and ASHP controller parameters, all the stuff Grant should have done during commissioning but didn't. It all works reliably with decent SCOP. Furthest radiators upstairs and downstairs have supply temperatures a degree or two cooler than the primary supply temperature, but with fairly long uninsulated 22mm CU pipe under the floors that's to be expected. Nonetheless the rads off them give enough heat output. System max weather compensated flow temperature is 45degC, minimum 30degC. Design temperature was 50degC but I've never needed to run it at 50.

I don't think LLHs are particularly inefficient or troublesome if they are in balance with stable and well matched flow rates on primary and secondary sides. Ok, a secondary circulator is needed, which is added power consumption & running cost, but for larger properties with original 15-22mm CH pipework, the ASHP primary circulator might not have sufficient capacity to achieve the recommended flow rate range for the kW rating of the heat source so a second pump might be needed anyway.

Question: (and apologies for not reading through this long thread as it may have been asked before.) Have you tried disabling WC, running the system at a set flow temperature, and seeing if you still get excessive cycling or large thermal distortion and temperature difference at emitters?

Posted by: @crimson

↑

I’d expect rooms that weren’t a problem to keep similar temps but now they’re sliding downwards. Keep in mind that at the 50L install they removed the enforced night mode running constant at 60%. The nightmode did seem to reduce cycling so it could be that variable is what is causing the slide downwards. And perhaps the 50L hasnt impacted anything.

re 'enforced night mode running constant at 60%' are you saying that the heat pump was previously forced on (at 60% modulation) at night.  If so thats significant because this would dump heat into the house which, if you have turned it off, is now not happening.  Normally however night mode is noise reduction by limiting compressor modulation to 60%.  This could well reduce cycling if the normal behaviour of the Grant is initially to ramp up to full (to get flow temp up to full as soon as possible) and then back off.

Posted by: @crimson

↑

Again will recheck Monday just to see if its not an anomaly, but its dead clear if the temps are going down, its likely cycling a tonne. Which the installer said was caused by the primary circulating pump. Again I don’t take anything they say as gospel as this is after emitters and water volume - the 3rd incorrect conclusion.

Cycling happens because the minimum continuous output of the heat pump is greater than the demand that the heat pump sees.  The heat pump then cycles so that on average the output matches the demand.  Its as simple as that.   

With the current mild temperatures cycling is more or less inevitable.  Its unlikely this is responsible for a room temp drop assuming the emitter circuit is fully open and always calling for heat, although it could easily, depending on how it has been set up, be responsible for significant room temperature fluctuation.

Posted by: @crimson

↑

Thanks will do. Don’t expect a huge uplift in temps but looking at the at the app its clearly dropping and dropping. The WC we ensured was same as before.

Another possible explanation is that the water pumps are now acting differently increasing the temp drop across the LLH.  

If you measure the temperatures I suggested it should give a much clearer idea what is going on.

Not able to keep up with both posts but:

Night mode was forced constantly. So not just at night but at 60% constantly, assume that's 60% modulation or whatever the manual states. This was done with a wire on the terminal and setting. So nothing in the terminal stating night or not if that makes sense.

I’ll look at the 4 probes across the LLH when get back but am pretty sure top right (flow from ASHP), to top left (through LLH) to just before heating zone, to just before first rad in run would see temp drops. Likely readings further back in thread. Installers havent once looked at temps. Literally never.

Cycling has always been stated as happening by the specialist and by the installers. Specialist thought due to lack of volume and distortion across the LLH, could never with secondary and primary pump get what he wanted but do mind there’s no flow setter/meter after the LLH before heating zones so was hard to tell, so simply looking at the delta reported by ASHP was what he was trying to manipulate.

The zones get warmer then cycles off.

Pump speeds always set at 2/3 both side produced best results.

I’ll see when am back if disabling WC and running at constant temp indicates anything.

In regards to pipework my frustration is - its all new. So them choosing 22mm down to 15mm seems a mistake. They could have used whatever they wanted as it was all replaced. At all points they seem to have different people at different steps in their own company. So its highly frustrating.

Previously I’ve just increased the min or max temp beyond the system design to compensate but the cycling is always consistent.

My only other thought is to adjust the delta down from the grants default 8C that determines when the ASHP cycles off.

To summarise the project allowed full scope of pipe design, and rads. The only restriction was no underfloor in front ground One (problem one) due to having to re-establish damp proof layer and therefore cost. Theres zero reason original pipe work would be used (and it wasn’t) as the placement of the ASHP is a location the prior boiler was nowhere near placed.

What’s frustrating here is Ive never seen anyone look at temps on pipework or across rads etc. its literally hand touch - its on and theres no flow rate indication both sides of the LLH, just one side (which was blacked out…).

So far it seems the installers just trial and error stuff then say they didn't think the factor changed was the issue (volume, emitter sizing etc). It’s woefully hard to deal with them as they assure me they’ve found it out, but it never comes to light.

All i can say is the builder has a specialist stating to try the LLH as a volunsier on the return solely with no secondary pump to ensure the flow rate is consistent. But the grant direction that plumber quote blocks it.