Heat Pumps and Zones (or not?)
- Thread starter Ivor Windybottom
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Hey @Ivor Windybottom , do you go with this setup in the end. How is your experience with this set up. Do you have a chance to test out what you said here?
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Honestly, you're setting yourself up for a fail. Heat pumps are not drop in replacements for boilers; in a poorly insulated, draughty house you will be cold, or spend a fortune on electricity and become one of those people who moans about how crap HPs are.
HPs are amazing, in the right property, but you'd be better off keeping the existing heating system and spending the money you're going to spend on an HP, on making your property right for an HP. Well insulated and draught proofed your gas bill will drop anyway
It's mediocre, I'm afraid; wouldn't even pass current regs for a new build.. You can make the loft the last thing you turn your attention to by all means but I'd recommend an upgrade if going for a low grade heat source like a heat pump. Assess insulation and draught detailing everywhere else, thermal imaging camera, especially at night in winter with the heating on (inside and out) - see where your losses are
Don't let me put you off getting an HP right now, if you're determined to do it that way.. just be aware it'll be an expensive game of catchup to have to buy an HP and then improve the property so it runs efficiently. If you have the cash to do it all at once, crack on!
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Appreciating there will be a limit to what a particular building fabric can sustain in terms of lower flow temps and comfortable IAT if a house is particularly poorly insulated and draughty, but I think that the majority of properties would be suitable for ASHPs, if the emitters/heat losses are correctly assessed and emitters upgraded as required. Anything under 50oC max flow temp wise with a more modern unit is likely going to match a gas boiler for efficiency, therefore it becomes much of a muchness I feel, if you want to replace a gas boiler with an ASHP, or look at fabric upgrades first (some of which may be cost and/or disruption prohibitive). Any central heating system is going to cost more, if a property is slightly less well insulated, and ASHPs are no different or perhaps no worse. Granted it can be very expensive and unforgiving if a poor install is carried out.
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You think the majority of UK properties are suitable for an ASHP as a direct, drop-in replacement for a boiler, so long as the rads are upsized?
OK.. Might just have to agree to disagree on that one!
OK.. Might just have to agree to disagree on that one!
Why would they not be, unless you needed such massive radiators that it becomes unfeasible? If the emitters are upgraded to match heat losses at sensible flow temps I don’t see why it would be a problem. Pipework diameter might be the only other consideration potentially.
Our house is very average. Probably worse than average to be honest. ASHP works fine though.
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Let me translate that ...
So a drop-in replacement, you just might need to upgrade one or two items - such as rads and pipework, otherwise known as "the entire system" !
Could be extensive, if for some reason your main flow and return pipework is undersized, or perhaps all your radiators are the smallest size possible and your gas boiler runs constantly at 60 to keep your house warm in winter. Probably not the case though. We only needed 4 or 5 rads changing (we have 17 in total).
Just sharing our experience and perhaps the point is that they can work perfectly well in houses not built to passivhaus standards.
Glad it is working well. What heat pump/controls did you go for?
I’m running ours on pure weather compensation now. No room influence/thermostats and single zone. Works very effectively.
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Vaillant Arotherm plus R290 10kw Heat pump with 250 litre Vaillant uniSTOR heat pump unvented cylinder. Heating / DHW Expansion Vessel, Diverter Valve, Isolation
Valves ,Y Strainer, Flexible Connection, Magnetic Filter, sensoCOMFORT, VR92, Heat Pump Interface, Wiring Centre -VR 71, Outdoor Temperature Sensor.
These are our system for ASHP. We have UFH for the whole house as well with addition 10cm insulation for ground floor, and 7.5cm insulation for the first floor. We dont have cavity wall insulation yet, but put extra 10cm insulation for the loft
Valves ,Y Strainer, Flexible Connection, Magnetic Filter, sensoCOMFORT, VR92, Heat Pump Interface, Wiring Centre -VR 71, Outdoor Temperature Sensor.
These are our system for ASHP. We have UFH for the whole house as well with addition 10cm insulation for ground floor, and 7.5cm insulation for the first floor. We dont have cavity wall insulation yet, but put extra 10cm insulation for the loft
Sounds good, and simple set up. Minimal zoning and no buffer tank.
I'd be interested to know whether anyone employing extensive microzoning within their property can evidence any savings from doing it. I tried it- zoning rooms that we didn't use much with smart TRVs and closing doors one winter. Keeping upstairs warm at night and large set backs for downstairs rooms. It saved me nothing, and cost a lot of time and hassle keeping doors closed. The boiler would also cycle a lot more due to restricted flow rates. We've removed most TRVs now apart from bedrooms but even then they rarely shut off. Flow rates are generally between 20 and 25l per min.
I appreciate there is one school of thought with respect to zoning being a modern approach but there are many (including myself now based on our experience) who would say the opposite applies. Microzoning within domestic properties is outdated thinking and the key is to keep and maintain warmth within the entire building fabric. Then...trickle the heat in. The concept of employing buffer tanks to try and make microzoning work with a heat pump seems nonsensical to me. A key part of efficiency is maintaining flow rates and volume within the system. Why would you waste energy effectively heating a buffer tank. Again considered by a fair few as a bit of a red flag if an installer wants to put a buffer tank in and a lot of complaints from people with poorly performing systems have a buffer tank in their system. I would actually say our ASHP was a drop in replacement for the boiler, more or less particularly if you already have a pressurised unvented system. Radiator upgrades were generally easy and didn't even need any pipework adjustments as there's normally enough wriggle room in the pipework to simply take a K1 off and put a P+ or K2 in it's place.
I'd also be interested to know what other family members think of having to close doors all the time and there being numerous cold spaces within the house to maintain the zoning approach.
I do think there's a bit of an obsession with keeping heat pumps running continuously and actually the cheapest way of running one, is for it to be turned off. In October for example I'll use a home assistant automation to turn it off when the indoor temp reaches a certain level. Between Mid Nov and Feb/March though ours is running pretty much all of the time, albeit it will cycle roughly once an hour in slightly milder weather.
The flip side of microzoning is ... comfort.
Our house has variable heat load in several rooms.
Downstairs, the main room is hard to heat with door open as the heat buggers off upstairs - but it has to stay open.much of the time so the menagerie can come and go. But close the door and it gets toasty quite quickly.
Then the main living room (which is upstairs) can be cold (lots of windows, high vaulted ceiling), or can be very hot (large south and west facing windows), and can.get heat from downstairs ... or not.
Then you get rooms like the kitchen which can need heating - or be too hot with heat from cooking and the tumble dryer.
Seroiusly, it would be impossible to get anything resembling comfort without individual room controls - which I'm working towards (all the main rooms have it so far). Without it, we'd have rooms too hot and/or too cold, and most likely both at the same time - which we did have when we bought the house.
And if you aren't comfortable then.you waste energy. If it's too hot you are wasting energy. If it's too cold you'll waste energy when SWMBO whacks the controls up to max.
Our house has variable heat load in several rooms.
Downstairs, the main room is hard to heat with door open as the heat buggers off upstairs - but it has to stay open.much of the time so the menagerie can come and go. But close the door and it gets toasty quite quickly.
Then the main living room (which is upstairs) can be cold (lots of windows, high vaulted ceiling), or can be very hot (large south and west facing windows), and can.get heat from downstairs ... or not.
Then you get rooms like the kitchen which can need heating - or be too hot with heat from cooking and the tumble dryer.
Seroiusly, it would be impossible to get anything resembling comfort without individual room controls - which I'm working towards (all the main rooms have it so far). Without it, we'd have rooms too hot and/or too cold, and most likely both at the same time - which we did have when we bought the house.
And if you aren't comfortable then.you waste energy. If it's too hot you are wasting energy. If it's too cold you'll waste energy when SWMBO whacks the controls up to max.
I meant moreso those who are using drastic setbacks to unused rooms, but in any case radiator balancing can result in even temperatures across different rooms as of course the emitters aren't going to be precisely sized for the heat loss of the individual rooms.
I think you'd be surprised if you removed all your microzoning controls, TRVs or whatever you have and just ran weather comp- just how stable you could get the IAT of all rooms. I can bore you with some graphs from our house which has a lot of the same challenges you describe but in summary rather than feeling last century I realise now how primitive our space heating setup was with set flow temps.
As for inadequate flow rates, boilers need bypass valves. Most good ASHP installs will be an open loop. Maintaining flow rate is just a necessity of anything employing a heat exchanger and I thought more down to physics rather than poor product design.
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