@crimson Hi,

Been dragged in by @editor 😀 

I have not had time to read the whole thread, but, from what I can see, it is a typical Grant disaster.

Heat pump system design is not difficult and as long as 2 basic principles are followed, reasonable performance will be achieved.

1:--As heat pumps use energy to move energy up the temperature scale, the lower the temperature, the lower the bill.

2:--We are moving heat with water, heat pumps require a difference in temperature between the flow and return of 5 Deg C to about 8 Deg C for best performance. This is 4 times the water flow of a fossil fuel boiler to move the same amount of heat energy.

If you run at high temperatures (45 Deg C +) you WILL have high bills and probably an undersized heat pump and a cold house.

If you do not move the water, you do not move the heat, you do not heat your house.

It is really as simple as that. A little common sense, tells you that if you reduce the flow temperature, (low loss header, thermostats, zoning) reduce flow (high temperature valves, magnaclean type filters, undersized secondary pumps, double pumping water, and other fittings) you will get very poor performance, huge running costs and a cold house.

As your installation includes

• Low loss header
• Secondary circulators
• Double pumping the water
• No Delta T control
• Possibly low flow
• On-Off thermostats
• zoning
• Low flow, high temperature valves
• Extremely high delta t (difference between flow and return) of 13 Deg C (flow is far too low)
• Weather compensation set very high
• In addition to vertical radiators that are a high temperature product and do not work with low temperature due to lack of convection (low temperature only works with radiators 600mm and below)

You really do not stand a chance.

It is no wonder the system is not working. This is the fault of the manufacturers (nearly all of them) who recommend this type of design as, with this method of installation, it is impossible to affect the operation of the heat pump (low flow issues) and therefore not their problem. It is also the fault of the training industry, MCS and all the CPS bodies who regulate the industry who take the easy path and operate with vested interest that are at odds with customer protection. 

It is not the fault of the installers, most are doing the best they can, and believe they are doing the right thing because the manufacturers, training industry and MCS are all in a cartel against them and you, the customers who should be the bos. There are a few in the industry that are trying to break this cartel, but to do so, mass public support will be needed, they are too powerful.

I have started a training centre, at my own expense, to try and correct this and help you the end user to have the installation you deserve, I have had support from Panasonic but no other manufacturer, government, CPS, training certification body or anyone else as, I fear, it goes against their native.

To sort your system, you need to remove the low loss header, thermostats, zoning, low flow valves, possibly the secondary pumps, timers, setbacks and anything else that is in between the heat pump and the radiator. The system then needs to be run on weather compensation only, preferably with delta T control (without Delta T control the COP will be limited to 3.5-4). Remove the TRV's from all common area radiators and only control the bedrooms with TRV's. I would suggest you run the weather compensation to low-  -3 ----  45 and high 15----- 25. Use the heat pump controller to do the hot water with a 5 Deg Delta T. With this setup, you will significantly improve your performance and comfort levels.

It is bonkers. Especially when the plumber says oh don’t have too big a difference between off and on temps on the zones keep to 2C diff. Sometimes keeping zones between each other similar is better. And keep the TRVs on max. Which we’re pretty much doing other than upstairs lower temp than others - but begs the question why bother having them? Its like presenting customers with a false choice. I get run it like that but then just remove it all, it’s all decorative. TRVs basically being things saying Max throughout the house (never touched them).

As for vertical rads, there’s 1 in hall, 1 in en-suite (towel rad) and 1 in downstairs toilet (towel rad) and 2 in bathroom (1 towel, 1 vertical) the bathrooms never really that cool as smaller spaces anyway. The living rads are short - 200mm Eskimo column style rads 1.5-1.7m wide. They’ve never been remotely warm or hot.

Something is now clearly very wrong as not a single radiator has any notable heat and zones are sitting at 18c with no movement up.

I’m very frustrated. All the setting tweaking (brutal honesty having a consumer device you have to hold 3 keys to program codes is nonsensical - I work in tech and would never expect a device like that for an end user - it’s laughable). The grant items experiencing a supposed power surge and wiped out fuses for the ASHP itself and the hot water panel just broken. That leaves me at mercy of having electrician or plumber coming.

Just lucky the plumber was a certified electrician so is happy to touch electrical items, others wouldn’t bother.

Yet the simplest thing is, the pipe bringing in hot water isn’t passing said water across a LLH that’s no wider than my hand is tall. That seems just common sense. Heat not getting to heating system means no heat coming out the rads. They don’t have a chance.

its 10c outside and we’ve had zones to 20c a few weeks ago and I think it was similar/lower temp outdoors so something is just broken now.

I’ll see what Grant say and report everything back.

Back to hot water. 4x a day for an hour a time. Effectively wiping out the heating for 4 hours of the day. How is that their reccomendation. I changed that to twice a day, will see over time what works for our demand.

Overall concept of recommending this to people in its current state seems utter madness. To have an experienced plumber just seem flummoxed by something and call a manufacturer to change settings reeks of something I’d rather not have had in the house. Am sure once it works it works and will be happy. But can’t say I’m singing praises for ASHPs

I think Grant have recognised how unfriendly the controller is, with bringing out (soon) there own 'smart' controller, but I'm not expecting this to be retrofitted to existing installs.

Some of the issues are because Part L of Building Regulations is still very focused on conventional boilers - and that insists on zoning, and TRVs. There's scant mention of heat pumps.

The Grant is particularly stupid (or more precisely, the wiring of the Grant's) with respect to DHW. When it's in DHW mode (which is a fixed time, typically set to one hour at a time) it isolates the CH side for that entire period. On most days, my HW has reached its target in 30 mins; but the HW controller stays 'on' so it just sits there idling for another 30 mins, with nothing going to the CH. I've taken to hitting the 'advance' button on my HW controller, which stops the HW cycle, and gives the CH the heat again, but this ought to not require manual intervention.

@crimson The fault is at Grants and MCS's door, the installer was, I presume, trained by them, I think you have every right to legally demand that you get the performance level stated on your MCS certificate (I presume you have one) and if you cannot get that level of performance, or they refuse to deliver it, you could have a case for miss selling, breach of contract with MCS and a breach of the building regulations.

The Law states:

(b) providing fixed building services which—

(i) are energy efficient to a reasonable

standard.

(ii) have effective controls; and

(iii) are commissioned by testing and adjusting

as necessary to ensure they use no more

fuel and power than is reasonable in the

circumstances.

One can reasonably assume that the MCS certificate can be considered the reasonable level of fuel and power usage. Therefore, if the annual performance and estimates are not there about, it may be considered that the installation is not compliant with the building regulations and therefore is illegal. The homeowner has 6 years to lodge a claim. This claim must be to the local building control or installers Competent Persons Scheme. If the installer has followed the manufacturer's guidelines, the liability would possibly fall back on them.

You are right, it is bonkers, frustrating and wrong, but if people do not stand up and challenge the system then nothing will change. Maybe it is time for the no-win no-fee lawyers to get involved. The manufacturers, training industry and MCS are taking nearly every installer and hone owner to the cleaners for their own selfish gain.

I’ll be honest if Grant don’t sort it with plumber I’ll demand a different manufacturers ASHP. I’ve no interest in dealing with something like this long term.

im definately seeing nothing going to rads now of any real temp. Will raise again to plumber tomorrow. This is very unusual now. The hall tall rad was usually a good indicator. Eg warm when things running, cool when hot. Now it’s never warm nor any other rads. I suspect zones sitting as they are is just the heat retention in the house pretty much with a tiny bit of help from heating. Will ask them to change too temp down from 50c as it’s worthless running that high for no benefit

@crimson You do not stand a chance of getting any reasonable performance with your current system design, regardless of heat pump installed. You have changed heating technology, you do not treat an electric car like a diesel one, you cannot fill it up at the petrol station, you cannot treat a heat pump like a boiler. If you try, you will fail, you are currently trying to do it and failing dismally.

Not sure I’m trying to here, I’ve contracted a builder and a plumber to design a system as part of a full renovation extension project. They’ve had full reign here, full service access, every wall was striped back, battoned and replastered/re insulated etc so they could put in what they needed I don’t think an original pipe is used in the end or if was minimal amount. The entire property has been re plumbed etc. not simply tacked on, but I agree that not sure why so much added to complexity of it if it’s simply in effect don’t use the TRVs and don’t use the heatmiser panels.  But far as can tell like you say it’s a Grant install that’s just not running well due to manufacturers odd insistence of elements. I’ll reach out to architect and ask if they’ve had this on similar projects with these plumbers.

I’ll report back how it goes over next few days.

The fact it was working better at one point would indicate to me it’s not entirely hopeless. I don’t recall when there was a frost in November that zones dropped to 18c. And at that point it was 19-19.5c downstairs but the programme had effectively huge sets back of 21 to 16c quite often (eg come on 7am off 9am, back 12-2, back 5-8. Then nothing for 11 hours at 16c). Its not being run like that now and it simply can’t get that high. it would seem there’s another factor potentially in play, that something has changed/gone wrong. There has been some sloppy mistakes from plumbers on the project and a lack of continuity of who’s here. The power surge issue is in back of my mind too. The ASHP completely lost power.

…or it’s a complete dead duck. If it is - they’ll have to rectify it. Thank you for sharing that info above as useful for any recourse with them. Seemingly the architect is very much it doesn’t get sorted they don’t get paid.

Apologies if I’m come across exasperated, but at the end of a 9 month project I’ve lost patience.

Further observations.

6:30pm zones last night hit their required temp other than downstairs (log fire running with living room doors open, likely heat goes up to landing etc so not entirely ASHP driven).

Checked the main panel. Pump icon flashing, ASHP off for a while. Odd as downstairs was still calling for heat. I found this happening 2-3x. Eventually fan cames back on. I’ll prompt plumber to check that valve as seems odd it could potentially not be calling for heat when supposed to. Will ask also if possibly replace that valve. It not having a light on it compared to the other 2 zones makes it somewhat harder to check if zones are working as intended.

Top left pipe warmer than ever been outside hot water cycle lately.

This morning similar situation (6:30 is 2 hours after a 1 hour hot water cycle which is sitting at 45C atm). Only zone calling for heat is downstairs. Hall rad warm, living room rads similar.

Checking the out and return temps on Grant panel:

00 - 37C

09 - 44C

7C difference compared to much larger that has been when all zones on.

if I have time today and plumber not here I’ll play around with zones demanding heat/not demanding heat to see if there’s a particular problematic one.

Posted by: @editor

↑

All manufacturers do, and it's becoming an increasingly divisive topic among installers.

Finally Grant is waking up and smelling the coffee and, when they offer their 'smart controller' option pack (which monitors primary flow rate), they are now saying open circuit system is possible using primary pump in the ASHP with no need for a low loss headers. Up until very recently they've included a LLH in all their circuit diagrams regardless of how small and simple the circuit might be.

The Grant LLH is not a buffer, Grant separately offer a buffer tank, but this is seldom fitted. The LLH adds a few litres of capacity, and a buffer would only be needed to increase exceptionally small volume systems due to the Grant ASHPs propensity to defrost frequently and needing sufficient thermal capacity to achieve this. One of the barriers to getting rid of buffers is the reversing valve defrost method most ASHPs use. They draw heat energy out of the hydronic circuit (i.e. from your emitters) and dump it outside to defrost the unit. When you think about this principle it's a pretty dumb idea - you want the ASHP to be heating your home, not your patio. It's done this way simply for the convenience of the ASHP manufacturer - reversing valves are fitted to most ASHPs as they can be configured to heat or cool, but in the UK nearly all are heat only appliances per MCS requirements. Most air to water ASHPs are derived from air to air ASHPs, and air to air ASHPs are heat/cool appliances that have used reversing valves for decades. No-one is thinking out of the box and coming up with a more suitable defrost method for A2W heating systems.

A LLH can have uses - as it enables different hydraulic characteristics on primary and secondary side, but it has efficiency losses, and requires a second circulating pump so has a running cost penalty. In @crimson's case, the issue seems to be a very low primary side flow, meaning the LLH is very imbalanced. Low primary flow compared to secondary is not good, as the secondary side flow temperature ends up lower than the primary, reducing the system heating capacity and requiring the primary side to be set to a higher temperature to compensate, reducing COP and increasing running cost. HeatGeek has done an excellent article on this.

The root cause of so many problems with ASHPs is poor installation and lack of competency in the trade. It seems Crimson has this issue, with a plumber not spotting blatant deficiencies such as very low flow and imbalanced LLH. Multiple zones is another area where ASHPs are not well suited, as the ASHP has to cater for a wide variance in flow & load - that probably means a LLH is unavoidable. People like @heacol are trying to educate the trade about not designing overly-complex systems with multiple zone control and multiple pumps, but old habits die hard it seems. If the heat and mass flow balance is properly worked out, and the emitters properly sized, no zone control is required. Perversely SAP calculation method still advocates adding zone control of heating systems as one way to increase energy efficiency in the home, but in the case of ASHPs that's a poor recommendation best avoided. ASHPs are happiest when they run low and slow with stable load, constant flow, and weather compensated flow temperature.

I’ve now upped are upstairs zone during day to stop that just switching off. As that thermostat is on the landing above a staircase that’s in a large hall by a large front door that when opened can suck out a degree or 2, that’s likely suddenly needing to go on every now and then. Will see how downstairs fares with that brought up a bit. Downstairs zone is approaching 20c now. Not seen that in weeks.

Perhaps the option of dropping down some TRVs to keep bedrooms from being too hot at night might be an option, leaving the landing rad on max and 2 rads in bedroom that is my office.

this is the first time since issues a couple weeks ago seen that top left pipe have much temperature. With pre the hot water panel being broken I do wonder if that was intermittently demanding a hot water run but likely loopy theory.

At 9am a hot water cycle runs. I’m shifting that to 1-2. As the tank is showing 44c still from a 3am-4am run, least letting the heating zones come up before warmest part of day. Then having it do a 5-6pm run. Will see how we got on with hot water only having the 3 slots in the day v 4. Just feels like if zones finally get towards temp, blitzing them off to do hot water that’s not needed is a waste

@crimson temperatures- for the sake of 10 quid buy yourself a set of these , tape them tightly to the pipes either side of the LLH, cut a bit of 28mm pipe insulation and put it over the top of it. just so you can see better than a hand test.

Changing heat pumps isn't going to sort this - any other brand, if its trying to drive water into a system that has whatever the unsolved issue on your system is, will be crap as well. Even if the issue gets solved so that you get a half-decent flow rate, and a warm house, it will still be less inefficient than it could be . The LLH is a fundamental non-movable cause of inefficiency.

On the other hand, if you at this stage are able to get your system design changed to one that moves the water in the most thermodynamically and hydraulically efficient way (no LLH, no buffer), then any decent heat pump will get the job done.

Thanks @iancalderbank , I'll order those today.

Was on a bit of a rant other day, I'd just had enough this weekend.

Plumber is apparently in contact with Grant to see what can be done.

Over the weekend all that's really changed is now heat panel replaced, we're getting hot water.  Secondary pump changed down from speed 3 to 1, but I've changed to speed 2.  I'm tinkering with when the hot water runs so it's not too often.

Things seem to have improved.

I'll keep reporting back what's done by plumbers/Grant incase this is useful for others.

I keep racking my brains back, but I swear I've seen the hot water tank reading be higher than the nominal 19c ish it was sitting at other day.  Which is odd as outside the once a week run for legionella by immersion itself, (before I was boosting via the immersion itself so we could shower etc) - it shouldn't have in theory got any heat.