Posted by: @cathoderay

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will monitor and minimally adjust the others and see what happens, and report back in due course.

Interim report back: not much to report. I have now got all the uptairs radiators to within a degree of each other, all rooms same temp except bathroom which is a degree or so warmer. Upstairs is generally slightly over temp, around 20 when it should be 18. I can't get it to cool down (with a view to diverting the heat to downstairs, which is too cold) using the lockshields. Some of them are in the last quarter turn before full closure, and the adjustment in this range is just too coarse. I am in effect in an on/off range, the rad is either off, or slightly over-heating the room. I have avoided using the TRVs, which are all fully open, to keep things simple. I have also made a point of always setting the lockshield valve position by turning clockwise ie going from more open to more closed, as at the almost closed end of the scale slack in the valve might lead to incorrect assumptions about exactly how open/closed it is. Example: I find valve is closed at 3 o'clock, then open it anticlockwise to 9 o'clock, then close it clockwise to 12 o'clock to have a valve that is a quarter turn open.

Downstairs: as noted above, despite clamping down on upstairs flow, downstairs remains cooler than it should be eg the kitchen at 0700 this morning was 15.5 degrees. All lockshields are fully open, and LWT temps are generally about where they should be eg 54 yesterday am (ambient -3) and 53 this morning (also ambient -3).

I suppose all I can do is more upstairs tweaking...     

Posted by: @bretix

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@lucgw Hi, I'm quite new to this forum and an finding a similar problem.

We had 2 10kw grant Aerona installed last January with 11 new oversized radiators.

Since November our usage has gone up dramatically anywhere between 30-80kw per day in November, and 60-140kw through December.

Through the summer the system had been a dream used primarily for hot water with the flow set at 60 degs (since turned down to 45) Our use has also risen so much due to EV needing more frequent charging due to the freezing conditions.

The house is warm with the heating on manual and thermostat set at 20 (tweaked from 22 in the last week).

What I did discover was that my use was spiking after my water heating schedule finished as I was heating my cylinder overnight on a cheaper tarrif to top up for an hour through the day. I've adjusted this since to heat water more frequently (as suggested by somebody on this forum), for shorter periods, thus hoping there's still enough ambient heat that I don't get 2 or 3 kw spikes the following hours for heat. So far I think this is helping...

I am fortunate to get RHI and awaiting SEG from the PV which should reduce my bills anually £2200 for the next 7 years for so far yearly use of approx 17000 kw! 

On reflection I do wonder if I should have invested in more PV, diverters and a decent battery size and installed infrared panels to heat individual rooms instead to have more control over my heating.

You should have moved to a smaller house 🤣 and not installed a grant, or in your case two of the darn things…

They're good units, made in Japan by Chofu, but they’re crippled by grant installing them like an oil boiler.

By making changes to your installation, you should see improvements in system efficiency. But be aware, we’ve just had two weeks of unseasonably cold weather, everyone is spending tons of money on their heating. I’ve burnt 250kgs of coal and countless amounts of timber, my wife has been spending £12/day on gas in her 98m2 home…. It’s cold, energy is expensive.

Posted by: @lucgw

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@oswiu 

thank you for responding. I’ll reply to each of your points above:

1) all got changed to UFH. Bathrooms and ground floor are all tiles and the rest on the house is engineered wood. We put an undelay under the wooden flooring as the company we bought from assured us that it was compatible with UFH.

2) how do I check the flow temperature an LWT? Are these the same? Sorry I find the whole pump, cylinder, pipes, manifolds and thermostats overwhelming. 

3) the weather compensation is at 0 degrees. 

4) I think as it’s trying to reach a target temperature it does come on when it’s not meant to in the day. I’ve tried to lower the target temperature in each room to either 17 (or in some rooms 14) as the temperature just won’t get above those levels.

---

5) I’m not sure. But we have spent a small fortune or putting new double glazed Aluminium windows around the whole house as well redoing the lofts and putting more insulation in them. Where there is no wooden boarding in the loft it’s 270mm insulation, where there is boarding there’s 200mm.

Thank you for the advice too.

---

 

1) That's great that you've got UFH, it works great with heat pumps as it allows for low water temperatures whilst still being comfortable. You will have noticed that unlike radiators it is generally very slow to react when you turn the heating on. You're better off putting lower temperature water through it for longer.

2) The terminology can get a bit much, I know. Yes LWT and flow temp are the same thing, I just didn't know what it would be called in your manual so I referenced both. I don't have a Grant heat pump, and I've just cross referenced a video to the manual @HughF linked in this post https://renewableheatinghub.co.uk/forums/postid/12327 with a Grant video on Youtube and they have slightly different values, so I can't wholly help you find the flow temp, but I suppose it doesn't matter anyway because of the next point.

3) 0 means weather compensation is off. It should be on, so set it to 1. The default curve in the above manual looks fine as a starting point to me, so I suggest you turn this on as long as you bite the bullet and turn up all the thermostats to call for heat during the day. I know this sounds counter intuitive, but if you get a really good weather compensation curve going and leave the heating on all day, then you will both be more comfortable and have smaller bills. You can feel free to schedule the thermostats off at night should you so wish, although I'm not sure it would help with UFH. If bills are a major concern, I would suggest not doing this today as it's really cold, but perhaps on Monday when it warms up, and thereafter you should see significant benefits to steady state low temp heating.

5) I would encourage you to ask your installer for details on your heat loss and design flow temp since it will help set up the weather compensation curve correctly first time. If you had an MCS accredited install (eg if you got the BUS grant of £5k) then they will have done these things, so it should just be a case of sending you an email.

@hughf Yeah the installers seemed to know what they were talking about ('just done 2 hotels down south' etc), but still not convinced they did the best installation despite 3 days time think they were rushing due to people wanting installs before the RHI cut off!

Our heat loss survey was for 31000 kw so I am a bit more optimistic that we are about 17000 inc EV. I'm hoping new windows will help.

Saying that I've got a minimum 6 years to recoup some costs and improve further my heat losses...hopefully.

Looking at the installation I'm new to this so not sure what I can improve on apart from further insulating pipes etc? The installers did mention maybe an idea to put a small surround in front of the pumps approx .5m (?picket fence), but not sure how that would benefit. The plant room is in the garage under the annexe where the piping leads so I am thinking about constructing a surround to stop any further heat losses.

We could make the house air tight but as we live in an area where radon is prevalent would then have to install a decentralised heat recovery ventilation. It just goes on and on 😂

@bretix they told you you'd use over 31,000kWh on your heat pumps and you're on track to use 17,000kWh of electricity including your general usage and an EV?! That is a serious miscalculation. What was your heating usage like before you got the heat pumps?

@oswiu I assume that 31,000kWh was the total CH+DHW demand for the year. At a SCOP of 3.5, that would be 8857kWh of Electricity to run the ASHP.

A seasonal average of 3.5Miles/kWh at 10k miles/annum would add on another 2857kWh onto the above figure...

My 5 day moving average electricity use is 85kWh, and median outdoor temperature -1, but dropping to -8 at night.

Although the timer is correctly set so that the ASHP is only heating the water or the house  (but not both at the same time) the pump is failing to get the water up to a usable temperature. I have now switched space heating to continuous plus the immersion heater to come on during the cheap rate overnight. This hasn't saved any money but at least we now get a tank full of piping hot water in the morning.

Heating engineer visited earlier in the week, fixed a faulty pressure gauge and eliminated the air in the system. Towel rails now both work properly for the first time in months.

This, too, hasn't reduced the electricity consumption but pipework is no longer noisy.

Until last week our electricity consumption has been lower every month this year than in the same month last year. So all was looking good.

Given that our current experience with very cold weather is no different from the freeze in January 2021 (when our ASHP was not correctly configured to only heat the water or the house), leads me to conclude that either our system was not installed/still isn't configured properly, or that ASHPs cannot run efficiently at outside temperatures close to and below Zero. There are lessons for either or both ASHP installers and manufacturers.

We are properly insulated and have underfloor heating. ASHP or not it should be possible to heat it and the hot water sufficiently on 85kWh per day.

Mike

@lucgw, I really feel for you as this was us last year having moved from old house with GCH to ASHP with UFH on both floors.  We have an ecodan but am sure some of the learnings will apply!

the heating engineers that installed the system were pretty new to heat pumps so had set it as manufacturer recommended which would probably been fine had electricity not been so costly!  We have dramatically dropped the compensation curve, currently running flow temp of 35 even with overnight lows of -8.  We have effectively one zone, with a remote sensor in one room controlling all the other rooms, the others don’t switch on unless main one is calling for heat to stop the cycling. The thermostats are used as limiters rather than controlling when the room calls for heat. As we work from home we have the heating set to run constantly.  In the shoulder months we had it running less as was very mild.

We heat the water once a day, with a 300l tank this gives enough for 2 of us. The secondary pump which sends hot water to the taps are timed to when we wash up or shower.

Including everyday electricity usage we are currently using 55-60kWH a day but it’s a 5 bed house & everywhere is warm all day/evening. Next week this should drop to below 40kWH with the mild weather. 

We watched countless YouTube videos and have done some tweaks to get it as low as possible. Hope you can figure out how to get it working more efficiently soon

@mike-patrick You've got a Grant Aerona 10, the chances are it will be installed indirectly with a LLH and all the associated inefficiencies that come with that. It's just the way Grant do things.

Here's some performance data for a properly configured direct system:

http://emoncms.org/samsung5kw/app/view?name=Samsung5kWASHP

Posted by: @oswiu

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Posted by: @lucgw

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@oswiu 

thank you for responding. I’ll reply to each of your points above:

1) all got changed to UFH. Bathrooms and ground floor are all tiles and the rest on the house is engineered wood. We put an undelay under the wooden flooring as the company we bought from assured us that it was compatible with UFH.

2) how do I check the flow temperature an LWT? Are these the same? Sorry I find the whole pump, cylinder, pipes, manifolds and thermostats overwhelming. 

3) the weather compensation is at 0 degrees. 

4) I think as it’s trying to reach a target temperature it does come on when it’s not meant to in the day. I’ve tried to lower the target temperature in each room to either 17 (or in some rooms 14) as the temperature just won’t get above those levels.

---

5) I’m not sure. But we have spent a small fortune or putting new double glazed Aluminium windows around the whole house as well redoing the lofts and putting more insulation in them. Where there is no wooden boarding in the loft it’s 270mm insulation, where there is boarding there’s 200mm.

Thank you for the advice too.

---

 

3) 0 means weather compensation is off. It should be on, so set it to 1. The default curve in the above manual looks fine as a starting point to me, so I suggest you turn this on as long as you bite the bullet and turn up all the thermostats to call for heat during the day. I know this sounds counter intuitive, but if you get a really good weather compensation curve going and leave the heating on all day, then you will both be more comfortable and have smaller bills. You can feel free to schedule the thermostats off at night should you so wish, although I'm not sure it would help with UFH. If bills are a major concern, I would suggest not doing this today as it's really cold, but perhaps on Monday when it warms up, and thereafter you should see significant benefits to steady state low temp heating.

 

I think that you may find that the 0 is showing on the controller display, which would normally indicate that the system is in weather compensation mode, with the temperature offset at 0C.

Posted by: @derek-m

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I think that you may find that the 0 is showing on the controller display, which would normally indicate that the system is in weather compensation mode, with the temperature offset at 0C.

This may or may not be the case, I was just going off what it said in the above Grant manual. It seems to have a 1 (on) or 0 (off) control, then a two point WC curve. That's assuming the correct setting was being looked at which I cannot guarantee.

The Grant/Chofu ASHP controller does not show if Weather Compensation is enabled or not from the 'home screen' display, you need to enter installer level and check parameters in the attached 'WC settings'. The defaults here are a good starting point, let them chug away for a few days and then adjust to suit.

Grant have made a right pigs ear of their installer manual, cutting and pasting bits of the Chofu document, and it makes for very hard reading. Here's a much simpler guide showing how to enter install and service level parameters. Make a note of any changes. There is a restore factory defaults option if all else fails.

WC should be enabled at handover, it might even be a MCS requirement. However, my system was handed over with it disabled and it seems others were as well. Makes you wonder why...

If you ever need to boost the house temperature, for example, after a holiday, you can set the fixed outgoing water set point 2101 to, say 50 or even 55degC, and then disable WC with parameter 2100 set to 0. The heating system will try to supply water at whatever temperature is set in 2101. It'll burn some electricity doing so, but for a few hours it could be useful. Enable WC again (2100 set to 1) as soon as possible! Ideally, WC supply temperature should be providing enough heat to just overcome steady state seasonal heat loss, but it's hard to get it right and is a process of trial and error.