Heat Pumps and Zones (or not?)

[Ivor Windybottom]

Thanks for all the replies. Good to know that there are as many opinions as I've had ideas. I do understand that heat pumps will run more efficiently if all the system is open, but it does seem incredibly wasteful to heat rooms where nobody will enter for the rest of the day, even if it does do this efficiently.

The place is a big sprawling bungalow, all internal walls are brick. So heating an unused room will not provide any benefit to upstairs and little to adjoining rooms. It would just dissipate through the loft into the sky and vanish.

I think I'm concluding that I'll ask the installer to plumb in the zones, and fit zone valves. But don't wire anything to them, and manually lock them all open using their little metal levers. Also install a buffer tank, I believe this eases things if it ends up with restricted flow rates(?). Then just install the standard controller from Vaillant, Daikin or whatever and run it exactly as the manufacturer intended, with everything open.

Once I get a baseline for how well it works then I can start playing games. I can manually open and close the zone valves, see how the COP and power consumption looks. If all goes smoothly then I will add some controls that will drive the zone valves in whatever way makes sense. Or if it all starts cycling or turns terrible in any other way then I just leave things as they are.

We should be looking at about a 10-12kW heat pump. So a bit bigger than average therefore possibly more prone to cycling if driving a smaller number of radiators.

I could look at modulating controller(s) that probably haven't been invented yet, that would fully take over the system. Alternatively (more likely), I'd leave the heat pump doing its own thing based on weather compensation and the controllers just each open and closes its own valve. Then the signal to the boiler would just be the sum of them all, i.e. if any one or more zone wants heat then the heat pump gets the signal to switch on. Hopefully this is easy to achieve by just wiring the microswitches on the zone valves in parallel.

We're installing big radiators that should enable it to be reasonably responsive. I'd rather the odd room is a bit cold sometimes than we constantly throw power at it and never feel the cold. We own jumpers!

 

[Mister Banks]

If not heating rooms make sure the doors are closed or the cold rooms will suck the heat from the heated rooms.

 

[vulcancontinental]

Great in theory but so very difficult to make comparisons due to differences in temperature over the periods you are monitoring.

If you factor in degree days and ensure occupancy, hot water use and the same for workday/weekend/door opening etc are in line you have a chance but few people do all this.

People in my experience heat to their budget so if it's affordable opened valves you'll never try it out the other way and manually go round opening closing valves.

You may be an exception, who knows.

You may be even more exceptional and actually keep data and let us know your findings.

 

[Ivor Windybottom]

I'll definitely do it, and will report back. It may take a year or so though.

It seems bizarre that we've gone from enouraging or even mandating zoned heating, to suddenly discarding them and some even suggesting leaving all TRVs set to max.

Building regs still require that zones are used for homes that are over 150sqm floor area. Ours is currently just under this but will be over when later extended. So if not zoned then, in theory, building control could demand that this is added later if not fitted from the start.

It definitely costs less for the installer to not bother with zones, which makes me wonder if this could be a motivator here. Along with heat pumps having that air of new mysteriousness.

I'm willing to listen to Heat Geek's videos. But I definitely don't accept his often controversial opinions. He's definitely confident and not afraid of saying he's right. But I don't think he's accredited by any heat pump manufacturer, and does seem to have built something of a cult following.

 

[MNW67]

Do you have some idea of how far in temperature you might want the unheated zones to fall below the heated zones? That might give you an idea of the sort of saving in terms of heat loss you might be able to make. This thread has made me think again about my own setback temperatures and do some sums of my own. Some of it seems counter intuitive. I ended up last night trying to work out the cost of heating fifty tonnes of masonry through 1.5C!

 

[SimonH2]

From what I have read online, i have read a lot, heat pumps should be installed utilising weather compensation, room thermostats are not required.

Which anyone with a few brain cells to rub together should be suggesting is "not good advice". Absent a very detailed knowledge of the needed parameters and a crystal ball to understand how they are going to change and how the occupants are going to use the building, then it's impossible to effectively control a system based only on weather comp.
Get a group of people in one room - less heat needed, weather comp overheats it, users open window to get rid of excess heat.
Have different rooms with different requirements - either users find some rooms too cold at times, or some rooms too hot at times, or more likely both.
Like the OP, I mostly work from home, so it's nice to be able to shut the door to my little room and get it warm enough that I can work without my fingers freezing. But if I were to turn up the heating for that, SWMBO would be throwing open the window in the other room to let the heat out. When I'm not working from home, it makes no sense to be heating the room beyond avoiding damp problems.
I've just completed a (temporary) individual room zoning exercise using wireless stats and thermo-hydraulic actuators as it's "not convenient" at the moment to run all the cabling to do it as I eventually want it to work. When complete, my intention is to control the flow temperature to suit the most demanding room - and controlling the rest of the rooms by their rad valves. Oh yes, the CH doesn't run direct from a boiler (there's a thermal store as a buffer) so I don't need to consider minimum flow rates.
Hearing that HPs can't cope with such variable loads is "not inspiring".

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.

Yeah, it's a bit annoying when you contact the manufacturer for information and they just fob you off with carp like that. Especially when, like you, you don't feel you can trust the installers (noting the comments about many of them having done the "learn to fit HPs in a day" sort of conversion course) to be fully au-fait with everything the kit can do.

 

[Mister Banks]

Which anyone with a few brain cells to rub together should be suggesting is "not good advice". Absent a very detailed knowledge of the needed parameters and a crystal ball to understand how they are going to change and how the occupants are going to use the building, then it's impossible to effectively control a system based only on weather comp.
Get a group of people in one room - less heat needed, weather comp overheats it, users open window to get rid of excess heat.
Have different rooms with different requirements - either users find some rooms too cold at times, or some rooms too hot at times, or more likely both.
Like the OP, I mostly work from home, so it's nice to be able to shut the door to my little room and get it warm enough that I can work without my fingers freezing. But if I were to turn up the heating for that, SWMBO would be throwing open the window in the other room to let the heat out. When I'm not working from home, it makes no sense to be heating the room beyond avoiding damp problems.
I've just completed a (temporary) individual room zoning exercise using wireless stats and thermo-hydraulic actuators as it's "not convenient" at the moment to run all the cabling to do it as I eventually want it to work. When complete, my intention is to control the flow temperature to suit the most demanding room - and controlling the rest of the rooms by their rad valves. Oh yes, the CH doesn't run direct from a boiler (there's a thermal store as a buffer) so I don't need to consider minimum flow rates.
Hearing that HPs can't cope with such variable loads is "not inspiring".

Yeah, it's a bit annoying when you contact the manufacturer for information and they just fob you off with carp like that. Especially when, like you, you don't feel you can trust the installers (noting the comments about many of them having done the "learn to fit HPs in a day" sort of conversion course) to be fully au-fait with everything the kit can do.

I can see the benefits of using weather compensation, I understand how it would work regarding flow temperatures, but how this works in practice with keeping a space heated without using room thermostats needs more investigation on my part.

 

[Ivor Windybottom]

Thanks all, really good to hear I'm not the only one who's a bit baffled and not entirely trusting of the various largely self-appointed experts.

The temperature difference between adjacent rooms could be pretty big. One heated, the other not. Unheated rooms here seem to settle at about 12 degC at the moment, so a difference of 10 would be a maximim. But if a heated room raises the temperature of an unheated one slightly I really don't see the issue with that. If the rooms we're not using are only slightly cooler than those in use then that's definitely heat saved. The question is whether the efficiency reduction more than wipes out the heating saved. I do get all the arguments about it then needing more heat later, but taking things to extremes, nobody would claim you would save money by leaving the heating on while you go away on holiday. We effectively go on holiday every day, selectively from different rooms.

I have absolutely zero experience of using a heat pump, but I find it hard to believe that less heating could result in higher bills. What I'm seeing on youtube is people obsessing about COP while taking less notice of actual spend. It's like driving 100 miles further to the local shop because the high speed driving will improve your overall mpg. Yes it will, but you'll still have wasted a load of fuel on a pointless journey.

I'm pretty confident I'm hopefully going down the right tracks by leaving my options open and just trying it out. I'll start with the simplest possible system, i.e. all zone valves fitted but permanently open, then add complexity. This will take weeks or months of experimentation after it's all installed.

I want to see for myself exactly what happens if, in the most extreme situation, you shut off all except one radiator. Start from there, if it turns out it's absolutely fine then I'll stop mucking about and just add the full zoning control.

My feeling is that I'll end up with the heat pump's own system setting the flow temperature according to the weather. Simple on/off timer/thermostats will open and close each valve and, overall, tell the heat pump whether to run or not. I have seen multiple zone controllers, but I may actually prefer to get four one-zone timer/thermostats, one in the most used room for each zone. Hopefully those with smartphone integration have apps that can cope with multiple units, so your phone then becomes the overall control panel.

 

[Ivor Windybottom]

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[robinbanks]

It would just dissipate through the loft into the sky and vanish

I think I'd be sorting the insulation out so that possibility is vastly reduced, before installing a heat pump

taking things to extremes

You have an odd way of looking at the system as a whole. If your warm rooms are poorly insulated from your cold rooms and your cold rooms are poorly insulated from the world then there isn't much conventional different between your cold room and the world.
Heat pumps aren't intended to be used in a fashion where you blast the heating on and off to just rapidly warm up the parts of the box you're interested in and hope for lower bills by trying to make some smaller amount of heat "follow you round" before it disappears through a poorly insulated fabric

people obsessing about COP

All that aims to do is put it on par with the gas boiler they're demonstrably already happy to pony up for. If electricity is 3x the price of gas, and a heat pump can be made to produce 9 units of heat for 3 units of electricity, it compares favourably to using a gas boiler to generate 9 units of heat from 9 units of gas, where the gas unit is a third of the cost of an electricity unit.

Yes yes, efficiency this, that, the other, gas and electricity prices blah, solar panels blah, but they're minor distractions - your heat pump should be largely on cost par with a gas boiler most of the time but your initial focus should be in stopping your paid-for heat escaping. It's useful to you while it's trapped inside your house and you only need to top it up slightly to offset a low loss. If you have a high loss, you might not succeed with a heat pump because they just don't generate units of heat rapidly.

want to see for myself exactly what happens if, in the most extreme situation, you shut off all except one radiator

What implosion are you expecting? If the one rad doesn't cool the return flow sufficiently to get a reasonable delta T at the heat pump, the heat pump will stop trying to produce heatSo

 

[Ivor Windybottom]

I think I'd be sorting the insulation out so that possibility is vastly reduced, before installing a heat pump

What makes you think the loft isn't insulated? It already is, very much so, along with the cavity walls. I'm just stating what actually happens - with the best insulation in the world, it ends up making its way out one way or another.

You have an odd way of looking at the system as a whole. If your warm rooms are poorly insulated from your cold rooms and your cold rooms are poorly insulated from the world then there isn't much conventional different between your cold room and the world.
Heat pumps aren't intended to be used in a fashion where you blast the heating on and off to just rapidly warm up the parts of the box you're interested in and hope for lower bills by trying to make some smaller amount of heat "follow you round" before it disappears through a poorly insulated fabric

You have an odd way of discussing things but let's try and keep this thread nice.

We currently have pretty much no heating. We use plug-in electric heaters, we just heat the rooms we're in. I can absolutely promise that, from actual real-world experience, it's very much possible to have adjacent rooms with a huge difference in temperature. There's only a single brick wall between them but it's actually a pretty good insulator. Obviously there will be some transfer through the wall, but it doesn't make a huge difference.

As stated above, I haven't stated that anything is poorly insulated, you're the only one who's said this.

What implosion are you expecting? If the one rad doesn't cool the return flow sufficiently to get a reasonable delta T at the heat pump, the heat pump will stop trying to produce heatSo

Cycling is the issue. It takes time and energy to get going, runs for a short time, then uses more time and energy to shut down again. So it reduces the efficiency.

I want to find out for myself just how much of an issue this really is. My first step will be to create the worst possible situation, by having a 12kW heat pump driving just a 1kW radiator. See what happens and just how bad the numbers are. If it all gets handled reasonably elegantly then perhaps it isn't a problem. If it runs terribly then I'll start experimenting to find the point at which things do turn bad. But I don't know, I'd really appreciate first-hand knowledge that other heat pump owners have. But I suspect that different makes and models behave differently, perhaps I just need to get one installed and find out what I'm lumbered with.

 

[vulcancontinental]

Well there's loads of advice in these pages and whichever method you end up using will be the right one for you.

The worse that could happen is you spent a few hundred pounds on zone valves you might not need or a few hundred on fuel bills that were not necessary. In the long run you'll be warm and comfortable.

Personally I tend to view unheated rooms as not being warmed usefully by an adjacent room you do want warm but a loss added to a room you need warm. It's your opinion that pays the bill.

 

[Ivor Windybottom]

Perhaps I've got more of an insight into just how isolated the rooms are as a result of heating with portable heaters for a few years. There really isn't much leakage between adjacent rooms.

Perhaps those who think otherwise live in open-plan or plasterboard homes. Bricks are a pretty good insulator.

The main point of the zoning effort is my work area, which is more or less a semi-detached separate property. I'm not usually there at all after 5pm, so there's no point in running the heating after 3pm. If it was heated in the evening then a tiny, tiny percentage of that heat would still be there the next day. It would be literally money thrown into the sky for about half the time the heating was on.

But if I'm going down the zoning route then I reckon splitting living and sleeping areas also makes sense. It should also mean that the living area needs less time to heat, partly as the heat will be shared between fewer radiators, but also because I'll be less worried about setting it to switch on earlier in the afternoon, as it should be using less power.

 

[MNW67]

I have just been reading something which, if I have understood it, may contradict part of the Heat Geek presentation.

Heat Geek says:

One more variable to add to this, is that the compressor is most efficient at maximum output. When the compressor speed slows, it actually drops in efficiency.

There are two ways we can ensure this sits at the maximum output as much as possible.

But this thread appears to say the opposite and includes the chart below. Can anyone clarify?

Heatpump output vs efficiency dilemma

Hi All, We're in the process of specifying a ducted A2A system for our house, for heating only (hot water supplied via a separate system). System setup is a little unusual and restricted because we are using the existing ground floor ductwork from a gas warm air system, with the upstairs/1st floo...

forum.buildhub.org.uk

 

[Ivor Windybottom]

That's extremely useful, and adds to my conclusion that the only way is to get the stuff installed and actually try it. With your own system in your own building.

The additional cost is a few zone valves and some extra pipe runs, it will be insignificant when installing a new system. We're looking at about £16k in total, so it should be a trivial difference.

If they all end up permanently jammed open then fine. But I suspect that I'll actually get back many times more than that additional cost in electricity savings by using them.

In parallel, I'm also going to buy some timer/thermostats, wire them up on my bench and start playing with the phone app. See if they're nice to use as a cluster together. So by the time I conclude that they're a good idea then I'll have already tested them and know that they'll work together nicely.

I'm going to leave the heat pump's own controller looking after the hot water. So I just need four simple on/off heating controllers, each wired to a zone valve and all the zone valve microswitches wired in parallel to give the heat pump the on signal.