Heat Pumps and Zones (or not?)

[Ivor Windybottom]

We're about to install a completely new central heating system - new pipework, radiators and one (big!) heat pump. It's a sprawling bungalow, so the rooms are fairly well isolated. Obviously there's no lagging between rooms, but they are all solid brick so have a reasonable amount of insulation.

We both work from home, in dedicated rooms. I'd like to have 3 zones, all zones would be independent, i.e. no zone would always be on. Weekdays would normally be Off>>Work>>Play>>Rest>>Off, with perhaps a two hour overlap for the transition between zones.

I understand that this would be fairly normal for a gas boiler, or even mandatory for a larger home. Is there any reason this can't or shouldn't be done with a heat pump?

I've seen "Heat Geek" on youtube saying they're often a bad idea with heat pumps (OR gas). I do get the arguments about flow temperature affecting efficiency, but I think our rooms are adequately isolated that this will be much less of a factor than stated in his video. The system is being designed for 42 degC flow, I'd be happy to set that as a maximum and see how it copes.

I do realise that electronic TRVs are available that can effectively zone room-by-room. I do get the point that they can modulate instead of being just on/off. But I still don't see a major fundamental difference between zoning and a load of TRVs being off. Also I'd rather avoid having a system that's dependent on a load of gadgets that may stop working (especially if cooking on a radiator pipe) and AA batteries that need regular changing and/or may leak (again due to suffering with heat).

I know that controllers for boilers are essentially on/off switches based on a timer and/or thermostat. I don't have experience of heat pump controls. If they are more complex, e.g. using modulated controls then can multiple units be used (one per zone) to avoid losing this functionality?

All opinions and disagreements very welcome!

 

[MNW67]

I know that controllers for boilers are essentially on/off switches based on a timer and/or thermostat. I don't have experience of heat pump controls. If they are more complex, e.g. using modulated controls then can multiple units be used (one per zone) to avoid losing this functionality?

Not sure what you are asking. Do you mean controls which can vary the flow temperature. Like OpenTherm and weather compensation.

Great video, thanks.

 

[BlueLoo]

The great carbon scam in effect.

Or why low temp heating systems might not be all they are cracked up to be because they are slow to react and need to be working 24/7 everywhere.

Zone everything anyway.
Every rad. Every room.

Better looking at it than for it.
You might find that your heat loss is low enough that hysteresis isn't a problem.

 

[MNW67]

Zone everything anyway.
Every rad. Every room.

I recall you've seen your consumption fall dramatically. What sort of temperatures do you have in the unused rooms and how far are they below the rooms that are in use? Also, roughly how much of the house is at each temperature.

 

[BlueLoo]

I recall you've seen your consumption fall dramatically. What sort of temperatures do you have in the unused rooms and how far are they below the rooms that are in use? Also, roughly how much of the house is at each temperature.

My hot temps are 21c.
I have rooms that are left off during the day (bedrooms and bathrooms) and they naturally fall to ~18c.
This is the same for the rooms left off overnight (downstairs) which drop to about ~18C.
Down time is about 10hrs.

Room Heat up time is rapid when called.
(Probably because this is individual, rather than full zone).

We have a set back temp of 10C on all rooms although it's never reached/used.

For the away mode, we have it a 5C.

The lounge is kept warm for 14 hrs a day. (8am to 10pm.) Thats the only full warm spot in the house.

We keep the hall, kitchen and dining room at a lower temp and heat it less.

Bedrooms are off all day and have a short boost during the weekday for rise and fall. All are set back to 18c during the night.

Individual room owners want their own setups. I have one who likes the room warm during the night, i have one who can't sleep if its anything above slightly freezing.

Outside the set times, rooms/users etc can (and do) use the boost.

Bathrooms are kept at a min of 18C so heating is on rarely. We have a short rise-fall boost as per the bedrooms .For baths and showers
The local boost (valve twist) is ace. Warm towels and a dry room afterwards.

 

[Johntheo5]

We both work from home, in dedicated rooms. I'd like to have 3 zones, all zones would be independent, i.e. no zone would always be on. Weekdays would normally be Off>>Work>>Play>>Rest>>Off, with perhaps a two hour overlap for the transition between zones.

I understand that this would be fairly normal for a gas boiler, or even mandatory for a larger home. Is there any reason this can't or shouldn't be done with a heat pump?

I've seen "Heat Geek" on youtube saying they're often a bad idea with heat pumps (OR gas). I do get the arguments about flow temperature affecting efficiency, but I think our rooms are adequately isolated that this will be much less of a factor than stated in his video. The system is being designed for 42 degC flow, I'd be happy to set that as a maximum and see how it copes.

I do realise that electronic TRVs are available that can effectively zone room-by-room. I do get the point that they can modulate instead of being just on/off. But I still don't see a major fundamental difference between zoning and a load of TRVs being off. Also I'd rather avoid having a system that's dependent on a load of gadgets that may stop working (especially if cooking on a radiator pipe) and AA batteries that need regular changing and/or may leak (again due to suffering with heat).

I know that controllers for boilers are essentially on/off switches based on a timer and/or thermostat. I don't have experience of heat pump controls. If they are more complex, e.g. using modulated controls then can multiple units be used (one per zone) to avoid losing this functionality?

All opinions and disagreements very welcome!

Is it too messy to install UFH in the bungalow?, UFH would suit as you both work from home and require a constant temperature for long periods.
When specking the rads ensure that they are adequately sized as a rad with flow&return temperatures of 42C/37C will emit < 30% of a T50 rad, a potential oversizing factor of X3.
How is your HW being heated?.

 

[Mister Banks]

I recall you've seen your consumption fall dramatically. What sort of temperatures do you have in the unused rooms and how far are they below the rooms that are in use? Also, roughly how much of the house is at each temperature.

Zoning each room individually isn’t always a good idea. I have a Wiser system and the iTRV’s are not very accurate at measuring actual room temperature, they read to low at the lower end and too high at the upper end. If you can afford a Wiser room stat in every room then it would work much better but the cost would be pretty big.

 

[Ivor Windybottom]

Thanks for the replies. I'll address some of the points raised...

We're not green evangelists. Mains gas doesn't exist here, it's borderline whether a heat pump costs more or less than gas but when gas doesn't exist then it's a no-brainer these days, as the only alternatives are oil, gas via a tanker/truck, electric heat or solid fuels. All of which are more expensive to install and/or run and all have major additional issues.

I'm happy with big radiators. I've done the analysis and can get comfortable temperatures with tall double radiators and a 42 degC flow temperature, in reality it will be even lower once running.

The floors are solid concrete, with no insulation. I know that underfloor heating is available as a 25mm mat, but I'm not convinced that it would be economical to run due to the lack of insulation. Also doubt it would deliver adequate heat into the air. Also we have wooden parquet floors that would all need to be destroyed or covered. Also would like carpets in the living room and bedrooms. Also want a reasonable response rate, don't want to leave it simmering away all day and night.

Hot water will probably have to be a cylinder. I don't like them but they're normally the reality of heat pumps. I already have an instant electric water heater feeding a distant shower room and it's excellent but it takes 40A when running. I doubt any electrician would install a second one in addition to a heat pump and everything else, as we have a single phase 100A supply and the DNO want about £15k to upgrade it. Also will have solar installed at the same time so heating the water when the sun comes out may make sense anyway, effectively storing cheap energy.

The question, which may have got lost, is... Is there a fundamental issue with zoning with a heat pump? I don't want to zone as finely as individual rooms, I would like to divide the house into 3 zones and have them all on at different independent times. The heat pump may be supplying none, 1, 2 or all 3 zones at any point in time. In addition, effectively the hot water cylinder would be a fourth zone.

Also whether it would be possible to use multiple heat pump thermostat/timers? I understand that these can modulate instead of just being on/off. It would be good if a number of them could work together. E.g. if zone 1 wants 30 degrees and zone 2 wants 40 degrees at the same time then the heat pump provides 40, the higher of the two. Whereas 3rd party controllers would just say on or off, and the heat pump would run at a fixed or perhaps weather dependent temperature.

I'd like to have everything mains powered and hard-wired. Don't want to keep replacing or recharging a bucketful of AA batteries to keep the system working.

I have little knowledge and zero experience of heat pumps. If they work differently to this then I'd be glad to be put right.

 

[Mister Banks]

Thanks for the replies. I'll address some of the points raised...

We're not green evangelists. Mains gas doesn't exist here, it's borderline whether a heat pump costs more or less than gas but when gas doesn't exist then it's a no-brainer these days, as the only alternatives are oil, gas via a tanker/truck, electric heat or solid fuels. All of which are more expensive to install and/or run and all have major additional issues.

I'm happy with big radiators. I've done the analysis and can get comfortable temperatures with tall double radiators and a 42 degC flow temperature, in reality it will be even lower once running.

The floors are solid concrete, with no insulation. I know that underfloor heating is available as a 25mm mat, but I'm not convinced that it would be economical to run due to the lack of insulation. Also doubt it would deliver adequate heat into the air. Also we have wooden parquet floors that would all need to be destroyed or covered. Also would like carpets in the living room and bedrooms. Also want a reasonable response rate, don't want to leave it simmering away all day and night.

Hot water will probably have to be a cylinder. I don't like them but they're normally the reality of heat pumps. I already have an instant electric water heater feeding a distant shower room and it's excellent but it takes 40A when running. I doubt any electrician would install a second one in addition to a heat pump and everything else, as we have a single phase 100A supply and the DNO want about £15k to upgrade it. Also will have solar installed at the same time so heating the water when the sun comes out may make sense anyway, effectively storing cheap energy.

The question, which may have got lost, is... Is there a fundamental issue with zoning with a heat pump? I don't want to zone as finely as individual rooms, I would like to divide the house into 3 zones and have them all on at different independent times. The heat pump may be supplying none, 1, 2 or all 3 zones at any point in time. In addition, effectively the hot water cylinder would be a fourth zone.

Also whether it would be possible to use multiple heat pump thermostat/timers? I understand that these can modulate instead of just being on/off. It would be good if a number of them could work together. E.g. if zone 1 wants 30 degrees and zone 2 wants 40 degrees at the same time then the heat pump provides 40, the higher of the two. Whereas 3rd party controllers would just say on or off, and the heat pump would run at a fixed or perhaps weather dependent temperature.

I'd like to have everything mains powered and hard-wired. Don't want to keep replacing or recharging a bucketful of AA batteries to keep the system working.

I have little knowledge and zero experience of heat pumps. If they work differently to this then I'd be glad to be put right.

There are a few interesting YouTube channels that have a lot of useful info, Heat Geeks for the theory and then Urban Plumbers and John Tisbury for installation examples.

 

[Ivor Windybottom]

Have seen lots from them all. Haven't seen anyone zoning with a heat pump though.

 

[MNW67]

Also whether it would be possible to use multiple heat pump thermostat/timers? I understand that these can modulate instead of just being on/off. It would be good if a number of them could work together. E.g. if zone 1 wants 30 degrees and zone 2 wants 40 degrees at the same time then the heat pump provides 40, the higher of the two. Whereas 3rd party controllers would just say on or off, and the heat pump would run at a fixed or perhaps weather dependent temperature.

I can't answer your main question as to whether zoning will be a good idea. As regards the controls, it is my understanding that ASHPs are very much dependent on using the outside temperature (i.e. weather compensation), rather than room temperature, as the primary way of controlling flow temperature. Working my way through how Worcester Bosch do things, it seems that zones are possible (except they call them heating circuits). A maximum of 4. It looks like you might even be able to set different flow temperatures for each zone by using mixing valves. The highest of these flow temperatures would seem to be set by the weather compensation curve. However, it appears you can also have a small degree of "room influence" by designating one room (only) as a reference room and using the temperature in that room to alter the flow temperature set by the weather compensation. I can post links if you think you might find them useful. Anyway, that is the way one manufacturer does things.

If you don't get answers here, there may be other forums which specialise more.

 

[Johntheo5]

Have seen lots from them all. Haven't seen anyone zoning with a heat pump though.

This may be worth a read.

Weather compensation and heat pumps - What installers need to know

Heating wizard Jez Climas shares his thoughts and knowledge on how to run heat pumps efficiently in relation to weather compensation: What is weather

www.installeronline.co.uk

here are some heat pump weather compensation curve(s) from this link.

 

[Ivor Windybottom]

Right, thanks for all the info that's really useful. We're looking at Daikin, have emailed them and will report any help they give, although I suspect their answer will be to speak to one of their plumbers. I was hoping to know the right answer in advance as a test of the plumber's capability and also to know it's being done in the best way.

I was imagining that the heat pump would look at the difference between current room temp and desired and set its flow temperature accordingly. If it's just outside temp then it already knows this itself and the internal controllers just tell it to switch on or off so not as complicated as I thought.

So it sounds like I could buy any 3rd party 3 or 4-zone timer/thermostat or just buy 3 or 4 single ones. Each one would control its own zone valve then I guess the feedback switches would be interconnected and wired to the heat pump. So if anything wants heat then the heat pump gets the signal to switch on.

There won't be a "master" zone, any one of them could be the only one that's on.

 

[Johntheo5]

Nothing to do with zoning but one vital item I rarely if ever see discussed is defrosting and how its controlled, some just have a simple timed defrost cycle, others measure the dP across the evaporator to determine the cycle times, there are probably other methods as well.

 

[Mister Banks]

Right, thanks for all the info that's really useful. We're looking at Daikin, have emailed them and will report any help they give, although I suspect their answer will be to speak to one of their plumbers. I was hoping to know the right answer in advance as a test of the plumber's capability and also to know it's being done in the best way.

I was imagining that the heat pump would look at the difference between current room temp and desired and set its flow temperature accordingly. If it's just outside temp then it already knows this itself and the internal controllers just tell it to switch on or off so not as complicated as I thought.

So it sounds like I could buy any 3rd party 3 or 4-zone timer/thermostat or just buy 3 or 4 single ones. Each one would control its own zone valve then I guess the feedback switches would be interconnected and wired to the heat pump. So if anything wants heat then the heat pump gets the signal to switch on.

There won't be a "master" zone, any one of them could be the only one that's on.

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