Welcome to the forum and please feel free to ask any question you wish.  There are plenty of people here who are willing to help if they can.

Posted by: @barrovian1963

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It is controlled by five Heatmiser Neo Stats downstairs underfloor heating and one upstairs on the landing. The radiators upstairs  have TRVs. 

Thats (almost certainly) the problem in a nutshell  Too much control, which I think you probably realise.  Basically heat pumps are best operated with no or almost no external controls (maybe a TRV or two on a minority of radiators) and having microzoning which you apparently have is a bit of a disaster.

Can you tell us a bit more about your setup

• your house (size, construction)?
• the model?
• is there a buffer tank/low loss header?
• is there some kind of mixing down from the temperature the radiators are run at to the temperature for the UFH?
• is weather compensation enabled and if so what are the settings?
• how much energy are you using eg each season
• In addition the the heatmisers, are there any other valves that can be used to 'balance' the legs of the UFH?

If you havent already can I suggest you read this overview about heat pumps as it will introduce you to the main concepts if you dont already know them

Once we have some more information we can make some suggestions.  

F

Good morning, thank you so much for replying. You're right, I suspected the issue would be too much control. I'll try and answer your questions  as best I can but some of them are beyond me. 

Posted by: @jamespa

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your house (size, construction)?

My house is a 2022 brick built detached 4 bedroom house. Groundfloor consists of a large kitchen / diner / family area, a utility room and lounge. The hall and stairs lead up to a galleried landing with bathroom, 4 bedrooms 1 with ensuite and dressing room. 

Posted by: @jamespa

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the model?

The ASHP is a Fujitsi Waterstage WOYG160LJL. It is not connected to the internet. The only control I have over it other than the Heatmisers is via the small LCD panel on the front of the indoor unit. 

Posted by: @jamespa

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s there a buffer tank/low loss header?

I'm not sure what a buffer tank is. The is a much smaller tank by the hot water cylinder if that's what you mean. 

Posted by: @jamespa

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is there some kind of mixing down from the temperature the radiators are run at to the temperature for the UFH?

I'm not sure what you mean here (sorry) but as far as I can tell there is only one heating circuit. Radiators and UFH all run off that.

Posted by: @jamespa

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is weather compensation enabled and if so what are the setting

I'm honestly not sure. I've found settings that refer to heating curves and offsets but I'm not sure what to do with them. The manual isn't at all clear to novice like me. 

Posted by: @jamespa

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how much energy are you using eg each season

Posted by: @jamespa

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In addition the the heatmisers, are there any other valves that can be used to 'balance' the legs of the UFH?

Again, sorry but I don't know. 

Not giving you much to go on, am I? 

After a lot of time studying the manual I was able to discover that the target temp of the ASHP was 28c. Something called Heating Curve Gradient was set to 2.5 and Transferral of Heating Curve was set at 0.0. When any one of the Heatmisers started calling for heat the ASHP would start up and ramp up to full speed consuming about 6kw, then stop when the Heatmiser reached temp. If another Heatmiser called for heat the process repeats so as different rooms called for heat at different times, the ASHP runs at 6kw plus until the temp is reached. 

Having read that micro zoning was the issue I tried running the ASHP with all the Heatmisers calling for heat but that just resulted in the ASHP running at full speed. So then I tried reducing the target temp to 20c. Again, the ASHP ran at full speed. Finally, last week in the cold weather I took a deep breath and adjusted the Heating Curve Gradient from 2.5 to 0.5 (which is the manuals suggested set point for UFH) This time, with all the Heatmisers calling for heat there was a marked difference in operation. After a period of 'full pelt' running the ASHP compressor settled into a pattern of 10/15 running, 10/15 mins off. The house temp stayed around 20c By my back of a fag packet calculations this resulted in the ASHP using about 0.6Kw / 0.7Kw per hour. A lot better than 6kw per hour previously. The radiators were lukewarm warm at best but we don't like a lot of heat upstairs so I could live with that. Then I started reading about 'cycling' and how that "it is not a good thing" started to second guess myself and put all the settings back as they were. When running normally, would I expect the compressor to Start and stop? As far as I can tell, when it's not running the indoor unit is still pushing water around the system. 

Truth is, I've no idea what I'm doing and am terrified I'm going to break something. I have spoken to the installer about weather compensation but the conversation never gets very far. There is a sensor outside which shows the outside temp on the LCD display and I've noticed that when I was running the Heating Curve Gradient at a lower level, the water temps displayed varied with the outdoor temperature. Is that WC? I've no idea. 

I've got pdf copies of the installation manual which I could attach to this topic if it would be of any use.

Thanks for taking the time to read and I'm grateful for any advice you can give. 

I'll just add that this is not about the running costs. Costs are comparable to our previous annual gas and electric use. I'd just like to get it running as efficiently as I can. 

OK  Thats actually quite a lot to go on.

My first observation is that the heat pump has way too much capacity for your house. You didnt give the floor area but unless the bedrooms are absolutely massive Im guessing its about 200 sq m.  You also dont say where you are but assuming that you are somewhere in England then I doubt you need more than 6kW and possibly a bit less, whereas the heat pump you have is 16kW.

This means that its going to cycle almost all the time and there isnt much you can do about that.  Thats not ideal but dont worry about it.  Your fridge cycles all the time (listen to it), its exactly the same technology, and fridges last a long time.

Posted by: @barrovian1963

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here is a sensor outside which shows the outside temp on the LCD display and I've noticed that when I was running the Heating Curve Gradient at a lower level, the water temps displayed varied with the outdoor temperature. Is that WC? 

Yes

Posted by: @barrovian1963

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The radiators were lukewarm warm at best but we don't like a lot of heat upstairs so I could live with that.

expect that, lukewarm is good as long as it heats the house sufficiently.  'Low temperature heating' (where the water in the radiator circuit is lukewarm) requires a different mindset to the high temperature heating we are used to with boilers (which, incidentally, are also capable of low temperature heating and indeed more efficient if used that way).  Once you get used to low temperature heating you wont want to go back.

The experiments you did are definitely heading in the right direction, but before we circle back to those can you post a picture of the small tank next to the DHW tank (and another of the plumbing and any other equipment near the DHW tank) so we know what we are dealing with.  

If you haven't already can I suggest you read this overview about heat pumps as it will introduce you to the main concepts.

Finally don't worry about breaking it.  Heat pumps are nearly indestructible and tend anyway to complain before anything serious happens, as long as you proceed methodically taking a note of anything you have done its will become less scary.

@jamespa Thank you for your reply. I'm in Norfolk UK and you're almost spot on with the floor space. Having dug out the plans its about 210 sq m.

There are actually about 8 similar properties on our development, all built at the same time and with the same make and size of ASHP. Everyone else seems quite happy. It's just me that wants to delve deeper into it. I guess there is nothing I can do about it being oversized. You just hope when you're buying a new place with new tech (to me anyway) that's it's the right thing for the job. I certainly can't afford to replace it so will have to make the best of it. I'll take some photos of the plant room and pipework when the laundry is dry. It's quite a warm spot and Mrs. B likes to dry the washing in there at this time of year. 

I take comfort in what you say about not worrying about cycling too much. I was concerned that the compressor switching on and off would be a bad thing. If I understand, it's not ideal but not disastrous. It's certainly nicer than having it running at full pelt for two or three hours. 

So my plan is to put all the Heatmisers on to call for heat, open up the TRVs then reduce the temp set point on the ASHP down from 28c to 21c and reduce the heating curve to the Fujitsu recommended value for UFH to 0.5, down from 2.5 which is the setting for classic radiators and see how it goes. What do you think? I mean, what's the worst that could happen .... 

Posted by: @barrovian1963

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So my plan is to put all the Heatmisers on to call for heat, open up the TRVs then reduce the temp set point on the ASHP down from 28c to 21c and reduce the heating curve to the Fujitsu recommended value for UFH to 0.5, down from 2.5 which is the setting for classic radiators and see how it goes. What do you think? I mean, what's the worst that could happen .... 

 

You clearly have 'got' it.  You dont really need me!

The only thing Im not sure about is this

"then reduce the temp set point on the ASHP down from 28c to 21c"

Ideally you want the ASHP ignoring its own room temperature setpoint at this stage, so you get the heating curve optimised (= as low as possible).  There is probably as setting for 'adaptive', 'room influence', AI, Intelligent mode or the like which you want to disable so its purely running on weather compensation. 

Them, as you say, set all heatmisers well above the target, open the TRVs, reduce the WC (heating) curve as low as it will go whilst still heating the house.  Do this slowly, making changes no more than twice per day.  The aim is to get it to the point where the house is comfortable with the ASHP 'on' 24*7 and all TRVs and Heatmisers continually calling for heat AND the WC curve as low as possible.  Allow several days of iteration.

You may need to 'balance' the zones to get them all at the same temperature which you ideally do using lockshield valves on the radiators or some sort of restrictive (but not thermostatic) valve on the UFH.  On the other hand you may find this isnt necessary.  If you find you need to do this do post again and I can give you some tips how best to go about.

The worst that could happen is that you slightly overheat for a few days and get slightly too cool for a couple of days.  

Please do post about how you get on and do post if you have any questions.

Once the WC (heating) curve is optimised you may want to reintroduce the room influence, or not.  With My Vaillant I found that the house temperature was significantly more stable running purely on weather compensation, so having turned off what Vaillant call 'room influence' it has not gone back on again.

@jamespa Good morning, and thanks again for your time.

Posted by: @jamespa

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The only thing Im not sure about is this

"then reduce the temp set point on the ASHP down from 28c to 21c"

When the room temp setpoint  was 28c on the ASHP, it seemed as though it was running hard trying to get a high flow temp presumably to get to 28c. When I reduced the room setpoint target to 20/21c the ASHP didn't try to achieve these high flow temps and consequently didn't run anywhere near as hard. So that was my uneducated logic. 

In the settings menu, there is something called 'Room Influence:

It mentions "room thermostat" but I don't have (a Fujitsu) one, only the heatmisers. It's currently set at 1%. It says if the setting is set to 100% then the settings are based on ambient temperature. Trouble is, I don't know if it means ambient outside or ambient in. Previously when I've asked about it I was told that it wouldn't work as the temp in the plant room (which is always higher ) would influence to ASHP into thinking it was at say, 20c and shut off leaving the rest of the house cold. I guess there is only one way to find out. 

I'm going to give it a week or so with the new adjustments to see how the things go. Again, thanks for your time and I'll keep you posted.

PS. I

Posted by: @barrovian1963

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It says if the setting is set to 100% then the settings are based on ambient temperature.  Trouble is, I don't know if it means ambient outside or ambient in

This is indeed ambiguous!.  One would expect, since this is in a section called 'room influence' that it means ambient in, but it is unclear.

the background is that the Fujitsu controller will almost certainly have a temperature sensor in it and, if it is in the plant room the room influence function.  So you need to disable it (you have been told it wont work and whoever told you this was right that it wont work properly, but it does need to be disabled). 

Its unclear whether that means setting it to 0% or 100% but its one of the two.  When its disabled it shouldnt make any difference what you set the 'room temperature' setpoint to on the ASHP (and if it does then another setting needs to be changed in addition).  You may need to try both to find out how to interpret this ambiguous definition.

@jamespa Trying to think this through. The ambient temperature in the plant room stays fairly constant at around 25c. The room influence setting is currently at 1% and the ASHP's target temp is 20c and the ASHP gets to a temp and then starts cycling, presumably to maintain the set temp. Does that mean the room influence is disabled, i.e. the ASHP is running as expected on WC? Who knows. I'll have to rely on how hot the house 'feels' after a day or so I guess. Having looked at the manual again it looks as if the room influence setting cannot be set to 0%. It's 1% to 100%. So I'm going to leave it at 1% for the time being and see what happens. It's frustrating not having any online monitoring of the ASHP, I have to rely on looking at the spikes and troughs of my electric consumption to get a rough idea of how much it's cycling. Either that or I sit outside and watch it. And I'm not that dedicated (yet) 

I'm starting to wonder if the system may not be the best of installs, but I've got to make the best of it. I'm actually quite jealous of my neighbours who seem quite happy with their identical systems. 

Posted by: @barrovian1963

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. The room influence setting is currently at 1% and the ASHP's target temp is 20c and the ASHP gets to a temp and then starts cycling, presumably to maintain the set temp. Does that mean the room influence is disabled,

I think that's very likely.  Thus if you set all external controls to be permanently on you should be able to optimise the wc curve to the lowest possible consistent with your house being warm enough. 

Please post back with how you get on.

@jamespa Will do. I'll be honest, I'm still worried about the compressor turning on and off all day. To my old head, still living in the gas boiler age, it just seems wrong. But I've just got to remember. your earlier fridge analogy and to get Mrs. B to realise that the ASHP running all the time is how it's supposed to work. I'll be honest, I wish I knew what I know now about ASHPs when we moved in three years ago and I'd have challenged the builders and the heating engineers who put the system in. But now I'm stuck with it and have to make the best of it. Either that or save up, rip it out and get a different system installed. Thank you for your time this weekend. It's very much appreciated.

Posted by: @barrovian1963

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@jamespa Will do. I'll be honest, I'm still worried about the compressor turning on and off all day. To my old head, still living in the gas boiler age, it just seems wrong. But I've just got to remember. your earlier fridge analogy and to get Mrs. B to realise that the ASHP running all the time is how it's supposed to work. I'll be honest, I wish I knew what I know now about ASHPs when we moved in three years ago and I'd have challenged the builders and the heating engineers who put the system in. But now I'm stuck with it and have to make the best of it. Either that or save up, rip it out and get a different system installed. Thank you for your time this weekend. It's very much appreciated.

Once its running at lowest possible FT you might be able to reassess the operating mode when its mild.  Depending on your house, when its mild (which is when it will cycle most) it may OK (from a cost perspective) to have it on 'part time'.  Definitely something to do once the operation is optimised though.

Boilers, incidentally, frequently cycle like mad!  Although they have much greater modulation capabilities than heat pumps, they tend to be even more oversized.

If you can, get some statistics out of it on how much heat it delivers, then you know for definite what size you need should you ever come to replace it.