Heat Pumps and Zones (or not?)

[wannocks]

The fundamental with a heat pump is the flow rate.
If too many zones are closed, or the system is restrictive the flow rate will drop.
Slightly too low will lower the COP (efficiency), if its too low the heat pump wont run at all.
This can be mitigated with a header or buffer, with some loss of efficiency. (Some heat lost due to mixing, and additional pumps required)

The traditional method is to have a boiler that makes too much heat, and throttle it back with thermostats.
Heat pumps use modulation and weather compensation to match the heat output to the building losses.
On/ Off controls do not work well with heat pumps.

 

[Ivor Windybottom]

Heat pumps use modulation and weather compensation to match the heat output to the building losses.
On/ Off controls do not work well with heat pumps.

This is what I thought previously. Does the heat pump supplier's own internal controller feed back the temperature to allow this modulation? If so then a lot of efficiency could be lost as a result of replacing it with a simple on/off timer/thermostat.

But I'd expect the cost of blindly heating the entire building all day and evening would be higher than selectively heating different zones even if that does reduce the COP.

My work area is three decent sized rooms, about the size of a small bungalow. Basically an annexe that's attached. There is absolutely no value to us in heating it beyond 4pm, I won't be there and none of the heat would remain the next day.

The reverse applies to heating the living areas while I'm at work.

There's a cavity wall and heavy fire door between the living and working areas. They're pretty much separate semi-detached buildings.

 

[Ivor Windybottom]

Daikin's reply to my query is just as expected...

Thank you for reaching out to us with your query. To ensure the most efficient and accurate resolution, we recommend contacting the installer directly. They possess the specific expertise and insights into your installation and can address your concerns promptly.

If you have the installer's contact information, kindly reach out to them directly. Should you need any assistance in obtaining their details or have further questions, please don't hesitate to let us know, and we will do our best to assist you.

... Just the sort of reply that makes you want to buy elsewhere.

 

[Ivor Windybottom]

My concern is that a lot of fitters at the moment are ex-gas people who've recently converted to heat pumps. So there may be many who are still doing the job how it was always done without understanding of the issues of cycling and more subtle controls than simple on/off switches.

I suppose the worst case is that I could in future just leave all the zones open and run it in pure weather compensation mode. But I very much doubt this would make sense. I would be getting greater efficiency but heating lots of rooms that didn't need it.

It probably will make sense to heat half the space with less efficiency. I've read various threads here and elsewhere and I'm guessing that many heat pump early-adopters are retired, or at least home all day. So heating the entire house efficiently is probably desirable for them anyway.

I often open all the windows in the living zone to get some air through while shutting myself in the heated work zone.

 

[Mister Banks]

My concern is that a lot of fitters at the moment are ex-gas people who've recently converted to heat pumps. So there may be many who are still doing the job how it was always done without understanding of the issues of cycling and more subtle controls than simple on/off switches.

I suppose the worst case is that I could in future just leave all the zones open and run it in pure weather compensation mode. But I very much doubt this would make sense. I would be getting greater efficiency but heating lots of rooms that didn't need it.

It probably will make sense to heat half the space with less efficiency. I've read various threads here and elsewhere and I'm guessing that many heat pump early-adopters are retired, or at least home all day. So heating the entire house efficiently is probably desirable for them anyway.

I often open all the windows in the living zone to get some air through while shutting myself in the heated work zone.

Have a look for a Heat Geek, preferably Elite status, in your area. They will be a much safer option with helping to design a system that is tailored for your specific environment. I have read too many times how heat pumps are installed by untrained gas/oil heating engineers and left in the default configuration with a poor design.

 

[MNW67]

I often open all the windows in the living zone to get some air through while shutting myself in the heated work zone.

You mentioned a third heating zone. Is that bedrooms?

 

[Ivor Windybottom]

I'm now looking at EPH and Honeywell controls. Thankfully it looks like OpenTherm may be the sort of thing I'm looking for. It just depends on how this could work with multiple zones.

We'll have 4 zones. Living, Sleeping and 2x Work zones. Plus a hot water cylinder so 5 in all.

I have seen several Heat Geek videos. There's some useful info there, but my conclusion is that he's obsessed about COP almost to the exclusion of all else. He seems to miss that it's less expensive to heat half the house at 300% efficiency than it is to heat the whole house at 400% efficiency. Also I suspect his knowledge may be based on small/open-plan homes, where heat is very free to move around anyway - in which case zones make little sense.

 

[BlueLoo]

I'm now looking at EPH and Honeywell controls. Thankfully it looks like OpenTherm may be the sort of thing I'm looking for. It just depends on how this could work with multiple zones.

We'll have 4 zones. Living, Sleeping and 2x Work zones. Plus a hot water cylinder so 5 in all.

I have seen several Heat Geek videos. There's some useful info there, but my conclusion is that he's obsessed about COP almost to the exclusion of all else. He seems to miss that it's less expensive to heat half the house at 300% efficiency than it is to heat the whole house at 400% efficiency. Also I suspect his knowledge may be based on small/open-plan homes, where heat is very free to move around anyway - in which case zones make little sense.

I think "Trust nobody, do your own research" is the motto for most things these days.

 

[MNW67]

I'm now looking at EPH and Honeywell controls. Thankfully it looks like OpenTherm may be the sort of thing I'm looking for. It just depends on how this could work with multiple zones.

Do the heat pumps you are considering work with OpenTherm? In fact, do any heat pumps? I've just been reading this discussion. It's a bit above my head, but it seems to include a discussion as to whether OpenTherm, or indeed any type of load/room compensation, works with heat pumps.

Getting the best out of a heat pump - is Homely a possible a...

Homely, currently only available for Samsung and Midea heat pumps, claims to be a 'smart' control system for these heat pumps, smart insofar as it can...

renewableheatinghub.co.uk

 

[BlueLoo]

Do the heat pumps you are considering work with OpenTherm? In fact, do any heat pumps? I've just been reading this discussion. It's a bit above my head, but it seems to include a discussion as to whether OpenTherm, or indeed any type of load/room compensation, works with heat pumps.

Getting the best out of a heat pump - is Homely a possible a...

Homely, currently only available for Samsung and Midea heat pumps, claims to be a 'smart' control system for these heat pumps, smart insofar as it can...

renewableheatinghub.co.uk

Good question.

HPs and UFH is already low temp

 

[Mister Banks]

Do the heat pumps you are considering work with OpenTherm? In fact, do any heat pumps? I've just been reading this discussion. It's a bit above my head, but it seems to include a discussion as to whether OpenTherm, or indeed any type of load/room compensation, works with heat pumps.

Getting the best out of a heat pump - is Homely a possible a...

Homely, currently only available for Samsung and Midea heat pumps, claims to be a 'smart' control system for these heat pumps, smart insofar as it can...

renewableheatinghub.co.uk

In general the online opinion from various sources is not to use third party controls on heat pumps.

 

[MNW67]

In general the online opinion from various sources is not to use third party controls on heat pumps.

I have been reading similar. The point I was making, though, was even if you wanted to use third party load/room compensation, does such a controller even exist which is compatible with heat pumps? I have been ploughing through that link again, and there seems to be a fair bit of discontent at how well the built in controls actually work. Some seem to be saying that built in load/room compensation is not currently available on heat pumps, but that it would really help. There is apparently a device called Homely which seeks to make the built in weather compensation work better by using weather forecasts and other data. Funnily enough, the manufacturer I chose at random above, Worcester Bosch, actually do seem to have a controller which can use a degree of load/room compensation to vary the built in weather compensation.

 

[vulcancontinental]

I haven't read all replies and studied them however I'd mention that the reheat time using a heat pump is a longer than with a boiler so the setback temperature in the rooms you want to put less heat into will be by necessity and practicality not much lower than your occupied areas.

Your suggestion that its cheaper to heat half the house at a COP of 3 than all at a COP of 4 doesn't seem to make sense. Your heat pump is the only thing with a COP so you believe you're reducing it by running the property in a condition that limits the optimum efficiency of the appliance. All you're doing to the heat pump is reducing the load and as long as that is within it's modulation range and doesn't create cycling it will cope.

Your description of the property suggests it will exceed the minimum system volume required by the heat pump, over 10kW usually 40-50 litres. If you zone you will reduce the minimum primary circuit possibly below that figure as zone volumes should not be included in the heat pump primary circuit for the simple reason they will turn off and become isolated from the heat pump capacity creating cyling. Even radiators with TRV's become isolated from the heat pump required minimum flow rates.

From the info I skimmed through here my reaction would be to simply leave it open loop.

 

[robinbanks]

Is there a fundamental issue with zoning with a heat pump?

Not that I've seen with mine, but I've ceased using the zones, and the third party heatmiser stats. Father in law still uses his zones but seems to have more complaints with his system in general.

My HP controller in the hall does the thermostatting; if a heatmiser stat was doing it, it would just be an on/off call for heat (as I suspect the Vaillant controller also does) and then the HP's problem to modulate based on stuff like the delta T of the flow and return, but my HP just carries on supplying water at a requested temperature. If I was zoning for different temps I'd ask it for higher then mix down with a TMV on a manifold, but as noted i binned the zones, turned the upstairs off and run a 28 degree flow temp to the downstairs with control mostly by just the flow rates to different heating loops. The system seems to mostly self balance as warmer days result in warmer rooms, warmer return temps and the HP works less hard to reheat the flow. To what's degree the HP controls use the external temp beyond a few preconfigured set points for when to activate booster heaters, I've never checked

Did you say your walls were solid brick and therefore well insulated? What U value have you assigned to your walls and roof?

 

[Mister Banks]

I have been reading similar. The point I was making, though, was even if you wanted to use third party load/room compensation, does such a controller even exist which is compatible with heat pumps? I have been ploughing through that link again, and there seems to be a fair bit of discontent at how well the built in controls actually work. Some seem to be saying that built in load/room compensation is not currently available on heat pumps, but that it would really help. There is apparently a device called Homely which seeks to make the built in weather compensation work better by using weather forecasts and other data. Funnily enough, the manufacturer I chose at random above, Worcester Bosch, actually do seem to have a controller which can use a degree of load/room compensation to vary the built in weather compensation.

Drayton Wiser has a heat pump mode but I have no idea how well it works. Vaillant seem to be getting very good reviews on the their heat pump controls. Some reviews are saying not to use third party controls on Vaillant heat pumps or boilers.