Posted by: @crimson

↑

Cycling has always been stated as happening by the specialist and by the installers. S

It will inevitably.  If your heat pump capacity is perfectly matched to your house loss you can expect the heat pump to cycle from an OAT of roughly 11C and above.  If your heat pump capacity exceeds your house loss the onset of cycling will be lower.  It may also be lower if there is distortion in the LLH.  Added system volume will increase the 'on' time for the cycling, but not the on/off ratio which is determined by the ratio of min output of the heat pump to demand.  There are some other tweaks which can change the on or the off time, but again not the on/off ratio.

Posted by: @crimson

↑

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

It will be, there is no reason for it to change materially unless the house loss changes or you change one of the parameters that affects the cycling period!  Given you are operating open loop cycling is not the cause of your rooms not getting to temp, and at current mild temps is almost inevitable anyway.  Thus recommend you ignore cycling for now

Posted by: @crimson

↑

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

That will be night mode AKA quiet mode, which imposes a cap on compressor modulation.  This may have the effect of reducing cycling for the reason stated in my post above and will definitely cap the max output of the heat pump, which may or may not be what you want!

Posted by: @crimson

↑

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.

I recommend we just get new data following recent changes (both deltaTs and absolute Ts), and then work out from that whats happening. 

Heating is a matter of energy generation and energy transport, the temperatures tell you about both of these (if you had flow rates it would tell you everything).  Failure to heat is because either energy generation is failing or energy transport is failing or both.  Given how long it has taken to track down the problem the fact your installers never bothered to measure anything merely proves that they don't understand heating.

Thanks James, will get back to you.

as a reminder theret 3 zones. Ground floor front (5 rads), ground floor rear - UFH and first floor (rads - 8 Stelrads, 2 towel, 1 tall).

so I dont think open loop. Its first floor and ground rear stop calling leaving 5 Eskimos and a towel rad calling for heat in Ground front.

Posted by: @crimson

↑

Thanks James, will get back to you.

 

as a reminder theret 3 zones. Ground floor front (5 rads), ground floor rear - UFH and first floor (rads - 8 Stelrads, 2 towel, 1 tall).

 

so I dont think open loop. Its first floor and ground rear stop calling leaving 5 Eskimos and a towel rad calling for heat in Ground front.

 

Thanks.  I had forgotton that particular feature.  I presume the call for heat switches secondary pumps on/off not the heat pump.

All of this is going to be much easier to diagnose if its treated as a single zone fully open by setting all thermostats and TRVs to max.  The heat loss calculations are, after all, done on this basis. You will also reduce your cycling by doing this, engaged system volume is key!   The state of the zones (open/closed) will change the characteristics of the LLH, which could easily confuse measurements unless we know exactly what is happening when any measurements are made, and when any problems occur.  Is there any material reason not to do that?

@jamespa 

i think the challenge is in the house, its an existing 1970s structure thats been highly insulated, basically gutted and celotex up to 100mm on internal walls and a tone of loft insulation and other works.

But the rear is underfloor and extended, with 1 new bedroom on first floor (as 2 floor extension). Thats largely “new” construction.

Upstairs just doesn’t even need heating it seems, passively it gets a lot of warmth to get to 20+C. In actuality its hard to make it keep to 18-19C for sleeping.

There’s a large hallway in ground floor that adjoins the upper landing and that’s where heat flies up.

So in effect you have 40-45sqm underfloor at rear ground being easily heated. Upstairs getting tonnes of passive heat. Then 2 large ground floor front rooms struggling as the other zones just don’t need the heat. Balancing those down is very difficult it seems. I honestly tried and tried and got nowhere. The living rooms have the most external wall space in effect with 2 slight overhang roofs (also replaced and insulated).

The way the specialist put it upstairs is hugely oversized as smaller rooms, so is the rear with the underfloor. Leaving the front ground as the unique challenge. As the most external wall space in ratio to the room. So the heat pump in effect becomes almost oversized due to often solely that zone needing heat. Hence him attempting the 60% forced lower power via nightmode.

His thought was the LLH could be effecting the delta to point that ground front just keeps meaning it cycles off. It seems Eskimos cant function a very low delta. Hence him wanting the LLH off the main flow.

However the installers had this design so should have thought this through.

Posted by: @crimson

↑

i think the challenge is in the house, its an existing 1970s structure thats been highly insulated, basically gutted and celotex up to 100mm on internal walls and a tone of loft insulation and other works.

But the rear is underfloor and extended, with 1 new bedroom on first floor (as 2 floor extension). Thats largely “new” construction.

Upstairs just doesn’t even need heating it seems, passively it gets a lot of warmth to get to 20+C. In actuality its hard to make it keep to 18-19C for sleeping.

There’s a large hallway in ground floor that adjoins the upper landing and that’s where heat flies up.

Thats a great analysis and |I doubt any heat loss calculations adequately deal with this.  Put another way there is an (probably) unaccounted for loss from ground floor and equal gain to top floor which is exacerbated by the desire to keep the top floor cooler than the ground.  I have seen a couple of posts by owners of 'low loss' houses commenting that they simply cant keep the upstairs cool enough even with no designed heating, this is potentially a variant on the theme.

Posted by: @crimson

↑

The way the specialist put it upstairs is hugely oversized as smaller rooms, so is the rear with the underfloor. Leaving the front ground as the unique challenge. As the most external wall space in ratio to the room. So the heat pump in effect becomes almost oversized due to often solely that zone needing heat. Hence him attempting the 60% forced lower power via nightmode.

I can buy that analysis

Posted by: @crimson

↑

 It seems Eskimos cant function a very low delta. 

Based on the physics I dont believe that, all they care about is the temperature of the water not how much the deltaT is across them.  They would be really happy with really fast flowing water and essentially zero deltaT

Posted by: @crimson

↑

His thought was the LLH could be effecting the delta to point that ground front just keeps meaning it cycles off. Hence him wanting the LLH off the main flow.

but I do believe and agree with this!

Posted by: @jamespa

↑

Posted by: @crimson

↑

i think the challenge is in the house, its an existing 1970s structure thats been highly insulated, basically gutted and celotex up to 100mm on internal walls and a tone of loft insulation and other works.

But the rear is underfloor and extended, with 1 new bedroom on first floor (as 2 floor extension). Thats largely “new” construction.

Upstairs just doesn’t even need heating it seems, passively it gets a lot of warmth to get to 20+C. In actuality its hard to make it keep to 18-19C for sleeping.

There’s a large hallway in ground floor that adjoins the upper landing and that’s where heat flies up.

Thats a great analysis and |I doubt any heat loss calculations adequately deal with this.  Put another way there is an (probably) unaccounted for loss from ground floor and equal gain to top floor which is exacerbated by the desire to keep the top floor cooler than the ground.  I have seen a couple of posts by owners of 'low loss' houses commenting that they simply cant keep the upstairs cool enough even with no designed heating, this is potentially a variant on the theme.

 

Posted by: @crimson

↑

The way the specialist put it upstairs is hugely oversized as smaller rooms, so is the rear with the underfloor. Leaving the front ground as the unique challenge. As the most external wall space in ratio to the room. So the heat pump in effect becomes almost oversized due to often solely that zone needing heat. Hence him attempting the 60% forced lower power via nightmode.

I can buy that analysis

Posted by: @crimson

↑

 It seems Eskimos cant function a very low delta. 

Based on the physics I dont believe that, all they care about is the temperature of the water not how much the deltaT is across them.  They would be really happy with really fast flowing water and essentially zero deltaT

Posted by: @crimson

↑

His thought was the LLH could be effecting the delta to point that ground front just keeps meaning it cycles off. Hence him wanting the LLH off the main flow.

but I do believe and agree with this!

Sorry James a typo there. Eskimos CAN perform at a low delta t. Sausage fingers here. The 8C expected delta set by the Grant ASHP by default may be too high is what I was trying to get at. Combined with the LLH perhaps distorting the delta means its cycling when the Eskimos could draw out heat

Posted by: @crimson

↑

Sorry James a typo there. Eskimos CAN perform at a low delta t. Sausage fingers here. The 8C expected delta set by the Grant ASHP by default may be too high is what I was trying to get at. Combined with the LLH perhaps distorting the delta means its cycling when the Eskimos could draw out heat

Definitely.  8C DT is higher than the default design DT for most heat pump systems which is 5  This has the effect of reducing the average flow temp by 1.5C, which will of course reduce output if the correction factor was calculated assuming DT5 (which it probably was, since thats what software is likely to do by default).

However DT is really just a function of flow rate and actual emitter output, and DT5 (or 8) will be reached only at design OAT unless your heat pump modulates its pump speed and thus flow rate to maintain a fixed DT.  Yours cant as far as the eskimos are concerned, because the DT at the rads is determined by the secondary not the primary.  

That said we don't know much about what is happening as regards DT on the primary and its just possible that something is happening to restrict power transfer across the LLH (that blasted LLH again).  You dont seem to have a problem with total power output so I don't suspect this, but measuring temperatures will (yet again) confirm.  There is absolutely no point IMHO in fiddling with any settings related to this until we understand whats going on.

So its clear temps are downward trending. Suspect nightmode off is the cause.

its relatively cooler temps now outsife over night so I wouldn’t expect this (eg flow temp would have gone up on the WC)

I return today so will see whats up (praying no disaster leak or something lol)

Am putting together a case to builder to really get installer agree with Grant to isolate off the LLH to just tick it off as being an issue. They can try the PCB replacement first. And if not that then look at the LLH. Be it adding digital flow setters either side to confirm, then trialing as a volumiser. Seeing as the old one back to front caused such an issue am inclined to think this itself could be the cause.

Downstairs WC not being on Eskimo. Not having draft from log burner vents and performing the worse yet being 20% oversized. To me that indicates its not an emmiter or calc issue leaving something in the plant room/pipework as the cause.

Back at (my now colder) house.

Barely seen any heating cycles. Realised pressure had dropped to 1 bar, when installers want 1.5. Bled 2 tall rads in downstairs zone, both had a lot of air.

Texted the specialist (just dropped him a note to say house temps dropping and he’s responded - suspect a lot of curiosity his side as to what on earth is wrong here, didnt expect messages back on a Sunday)

the probes show some really odd behaviour. On a cycle the temp seen right showed 36C. Top left 27C!

So now not sure if secondary pump has an issue or this new 50L LLH is distorting flow like crazy. Hence ASHP cycling off big time.

i really want the 50L as a volumiser now just to get the actual floe to the bloody zones!

Posted by: @crimson

↑

Back at (my now colder) house.

 

Barely seen any heating cycles. Realised pressure had dropped to 1 bar, when installers want 1.5. Bled 2 tall rads in downstairs zone, both had a lot of air.

Texted the specialist (just dropped him a note to say house temps dropping and he’s responded - suspect a lot of curiosity his side as to what on earth is wrong here, didnt expect messages back on a Sunday)

the probes show some really odd behaviour. On a cycle the temp seen right showed 36C. Top left 27C!

So now not sure if secondary pump has an issue or this new 50L LLH is distorting flow like crazy. Hence ASHP cycling off big time.

 

i really want the 50L as a volumiser now just to get the actual floe to the bloody zones!

 

Really sorry to hear this, I was expecting no change not a deterioration and I must therefore eat humble pie following my comment that swapping a small volumiser for a larger one wouldn't make things worse.  It shouldn't so far as I can see, but of course it could, and it seems it has.  Like you I suspect poor setup/pump problems and, like you, would just love to see what the system does without this incumbrance.  It sounds like your heat specialist is similarly surprised so I perhaps should take some comfort.

What does "right showed 36C. Top left 27C!" refer to?

Posted by: @crimson

↑

i really want the 50L as a volumiser now just to get the actual floe to the bloody zones!

 

As I am sure you can imagine I cant agree more!

Also realised hot water tank was sitting at 35C…

I do run that to the bare min, 1 cycle a day for an hour. If no one has a shower etc, it will sit lowest 44C, so fine for using.

probes show 45C on pipework flow into plant room from ASHP into LLH, 34C top left of LLH and 34c just before 2 port valves - heating/water tank.

so no wonder thats struggled.

would seem secondary pump is now buggered

Posted by: @jamespa

↑

Posted by: @crimson

↑

Back at (my now colder) house.

 

Barely seen any heating cycles. Realised pressure had dropped to 1 bar, when installers want 1.5. Bled 2 tall rads in downstairs zone, both had a lot of air.

Texted the specialist (just dropped him a note to say house temps dropping and he’s responded - suspect a lot of curiosity his side as to what on earth is wrong here, didnt expect messages back on a Sunday)

the probes show some really odd behaviour. On a cycle the temp seen right showed 36C. Top left 27C!

So now not sure if secondary pump has an issue or this new 50L LLH is distorting flow like crazy. Hence ASHP cycling off big time.

 

i really want the 50L as a volumiser now just to get the actual floe to the bloody zones!

 

Really sorry to hear this, I was expecting no change not a deterioration and I must therefore eat humble pie following my comment that swapping a small volumiser for a larger one wouldn't make things worse.  It shouldn't so far as I can see, but of course it could, and it seems it has.  Like you I suspect poor setup/pump problems and, like you, would just love to see what the system does without this incumbrance.  It sounds like your heat specialist is similarly surprised so I perhaps should take some comfort.

What does "right showed 36C. Top left 27C!" refer to?

 

Posted by: @crimson

↑

i really want the 50L as a volumiser now just to get the actual floe to the bloody zones!

 

As I am sure you can imagine I cant agree more!

 

 

 

Temps quoted refer to:

1. Temp on pipe flowing into house from ASHP (Flow)
2. Temp on pipe just before 2 port valves and thus before the 2 port valve for water heating (Flow after LLH and secondary pump)

So I’ve just sat there watching 30 mins of a hot water cycle. And it went up 1C lol.

1. Flow on pipe - 46C
2. Flow after LLH and secondary pump- 34C

Insane drop of 12C

Changing the pump room pump speed to 3/3 closed it to 46C/38C but clearly something is very wrong.

Specialist checked Grant docs and pump speed 2/3 on the grant (which i think installer said he set it to) - should handle a buffer tank of 30L or more.

The old LLH Would lose around 1-1.5C but nothing like this.

So perhaps the ASHP needs to go to 3/3 or something is very wrong.

Specialist checked the new 50L tank specs and said no ‘baffles’ so this time they couldn’t have piped it wrong way round lol.