Heat Pumps and Zones (or not?)

[MINAMI]

I dont know the U values. the ground floor is pretty much a big open plan living of 80m2 with 3 main "zones": Kitchen and living room + hallway + guess room. First floor has 4 bedrooms with 2 bathrooms. Loft has 250mm insulation.

 

[MINAMI]

I reckon you can over-analyse. Despite my engineering design background I didn't bugger about with maths at all, I used HeatPunk (free!), you just draw your house, tell it what each wall is composed of then it helps you to find the right radiator sizes. You can then play games with flow temperature vs radiator size.

I've ended up with a design that's tolerable from an aesthetic angle that will theoretically heat the place adequately at a flow temperature of 42 degC.

I'm going to keep quiet about all this homework when I start talking to plumbers soon. I don't want to be the nightmare smartarse customer, but I will quietly compare their design with mine. Unless they come up with something better of course.

I'm just going to install the thing and see what happens. The zone valves will be installed but all manually locked open. Then I can start manually closing them and see what happens. I'm also bench-testing timer/thermostats for each of the zones in parallel. Hopefully I'll arrive at a point where I have a good plumbing system and controls I'm happy will do the job, then I just need to wire them in.

I promise to post my findings!

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?

 

[robinbanks]

I dont know the U values

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

Loft has 250mm insulation.

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!

 

[drives]

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.

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.

 

[robinbanks]

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!

 

[drives]

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!

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.

 

[SimonH2]

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.

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" !

 

[drives]

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.