British Gas heat pumps - some restrictions on their offering FYI

[markocosic]

1 hour ago, JamesPa said:

The thought of a UVC in a rental property gives me the screaming heebie jeebies

 

It also used to give the government the heebie jeebies until recent living memory. (dad was very happy to have one in the 80s once it became legal)

 

 

My understanding is that insurers don't like tanks in attics. Water damage is spendy and the claims histories for the types of "in need of some love, on average" property that still have vented cylinders are nasty.

 

Probably pales into insignificance vs the rental premium mind you!

 

 

Air to air for space heat in the flats, plus a towel rail.

 

Electric shower and a vented cylinder? How about a modulating tankless heater for the whole flat? (effectively an electric combi)

 

No Gas ticket. No G3. No stored water. No overflows/discharges.

 

If Sunamps weren't such a joke one can see why the landlord market might like those.

 

I'll link again to Qvantum.

 

https://www.qvantum.com/ISH23/GSHPM

 

It's a thermal store (bucket of hot water that you don't drink) with a plate heat exchanger for producing hot water on demand.

 

No Gas ticket. No G3. No stored water. No overflows/discharges.

 

You bring ambient temperature water (effectively a ground array; which could also be topped up using heat from outside air) to each apartment from a communal setup.

 

They have a heat pump for DHW, space heat, and space cool tucked in a kitchen cupboard etc. Plus a magic tank that does what Sunamp ought to do in terms of producing hot water on demand...

 

I think they're onto something.

[JamesPa]

50 minutes ago, markocosic said:

Don't blame the installer for wanting to include hot water. They're obligated to otherwise the job costs £5k more. And if they're gonna do hot water to get the grant - you automatically increase costs by £5k by not doing hot water - to then they think you're daft for not going all out on maximum performance and pleasure and resale value, but perhaps can't articulate this in the best way?

I'm not sure anyone is blaming installers for including dhw heating, its clear that the grant requires it.  The discussion is whether this has to be done by replacing the cylinder.

 

I reckon that most of the actual  install risk is in this not in the heat pump itself.  An installer has no idea what he will find under the floorboards (assuming he can get under the floorboards) when he tries to fit the UVC vent pipe with a continuous fall, new feeds if he insists on them and replumb bits of both the cold and hot water to suit.

 

So while fitting a heat pump is like fitting a boiler, fitting a heat pump plus UVC is a whole different ball game.

 

I can see why installers allow one week x 2 men, so do 1 per week.  The hp only job is much more straightforward and I would reckon that 2 per week is easily achievable.  Not necessarily less lucrative and an easier sell.  Obviously a bit of prequal is needed, but if the gas boiler gets the water to temperature then a hp running at 70 will do also, unless it has a really poor modulation ratio in which case the installer shouldn't be selling it anyway (or the house genuinely needs a 16kW heat pump which is rare).

Edited August 2, 2023 by JamesPa

[JamesPa]

33 minutes ago, markocosic said:

If Sunamps weren't such a joke one can see why the landlord market might like those.

 

I'll link again to Qvantum.

 

https://www.qvantum.com/ISH23/GSHPM

 

It's a thermal store (bucket of hot water that you don't drink) with a plate heat exchanger for producing hot water on demand.

Another reason to defer a dhw upgrade if you can.  There is the distinct possibility of some more intelligent technology in the next few years.  So if you have a perfectly functioning tank which is say 10 years old, why swap it out now for a UVC where a lot of internal space is taken up by a coil which you can't service and which introduces a load of G3 hassle, when something better (even if it's only a tank with an external PHE) is likely to come along before your perfectly functioning cylinder meets it's maker?  

 

PS a not such a joke sunamp would be attractive to me for my own house, it's not just landlords who might want one.  But as you say at present not up to par.

Edited August 2, 2023 by JamesPa

[Beelbeebub]

We have some flats using electric vented thermal stores.  Work really well.

 

That's said we had one brand of TS where a pin hole developed after about 7 years in the DHW coil.  The F&E tank kept filling up about 2lpm then overflowing.

 

Tenant called complaining of high elec consumption, cool showers and "dripping" noises 

 

At first I thought the ball cock had failed. But that was all fine.  Eventually traced to the only explanation (failed coil).

 

Swapped the whole thing out for another brand in a morning. Biggest balls ache was getting the things up 3 flights of stairs!

 

A HP driven one using high temps (65C flows) from a small capacity (sub 5kw) unit might make sense for small flats. The lower cop for DHW is still higher than direct electric. The smaller HP is then sized for more efficient running at the lower end of the scale (10C external say) where we spend most of the heating season. Only running flat out on a few days if the year, I wonder.if you could set it up so the electric immersion in the vented tank could contribute heat to the CH system?....

 

Maybe not the highest efficiency, but as long as it can hit 3.5ish that's ok, and a smaller external box and small tank.....

 

Hummm

[JamesPa]

3 minutes ago, Beelbeebub said:

I wonder.if you could set it up so the electric immersion in the vented tank could contribute heat to the CH system?....

Definitely possible in principle but might require an installer who can think out of the box and violates the requirement for a grant that the hp must provide 100pc of the heat load.  There are some out of the box thinking installers, but they are few and far between.

Edited August 2, 2023 by JamesPa

[markocosic]

22 minutes ago, Beelbeebub said:

A HP driven one using high temps (65C flows) from a small capacity (sub 5kw) unit might make sense for small flats. 

 

You're describing a Rotex HPSU.

 

Matey in Lithuanian countryside has an old one. Outdoor unit is tiny because it's a split rather than a monobloc. (done to avoid freezing and to make routing there primarily pipework a piece of push)

 

Indoor unit is a thermal store with ALL the valves and gubbins on top.

 

Daikin bought them out. They appear to have done nothing with that business/product line. Low volume to them. Too much mucking about with plumbers for the to respect it.

 

https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.daikin.ch/content/dam/document-library/installation-manuals/heat/air-to-water-heat-pump-low-temperature/hpsu-3xx-h/FA_HPSU_compact_4_0081414544_12_0615_web_GB_Installation%20Manuals_English.pdf&ved=2ahUKEwif0Mf64b6AAxUyS0EAHatMDm4QFnoECA4QAQ&usg=AOvVaw3onoP7Ujj8OQACfr5HaoZs

 

Bit crappy because coil type heat exchanger for DHW. Simple but poor performance. Also the outdoor unit is a long in the tooth R410a product with meh performance.

 

As a concept though, a split system with thermal storage rather than hot water storage has many plus points.

 

Samsung TDM style systems that add in a fan coil to deliver heating/cooling would be even nicer perhaps.

 

https://www.samsung.com/uk/business/climate/tdm-plus-specifications/

[HughF]

I was going to say the old systemate/boilermate thermal store wasn’t a bad thing for a flat….

 

I still think an f-gas heated sunamp is the way to go… hook it up to one of the ports on a multi-split, make it appear like an indoor head.

[TonyT]

9 hours ago, sharpener said:

 

I understand why even with weather comp S-plan is less than optimal because you then feed the CH at the HW flow temp. But Y-plan?

 

FWIW the HP would replace a 28 y/o oil boiler. We currently have its stat set to the min which is 65C. Weather comp not possible because this would result in acid condensate all the time. It has an economiser in the flue and this produces a small amount on startup, the condensate tray has been replaced twice as it is.

 

 

No, since the HP will increase the flow temp until it can get rid of the heat, the reheat time will be no worse than before. 6kW min o/p from an HP will still be twice as fast as the immersion heater. In any case it is not a consideration for us, the 210 l tank only needs heating once in 24h, atm entirely by PV.

 

 

No, the objections I have to replacing an OSO s/s tank in good working order are none of the above:

 

(i) massive disruption in order to dismantle and rebuild the airing cupboard, and lift carpets and flooring to run new pipework

or site new tank in utility room meaning there is no space for the thermal store I also want (which will fix the turn-down problem anyway as it will be a parallel sink for the heat)

(ii) cost thereof vs the small marginal savings given electricity is E7 night rate or free PV

(iii) waste of resources in scrapping off a tank prematurely

(iv) it is an unthinking brute force approach which totally lacks elegance in its design.

 

y plan isn’t hot water priority

 

its when the boiler can heat the cylinder at a very high temp  for good recovery times and then switch to heating mode  on a low temp  

[HughF]

Urghhh, Y plan….. the dreaded 3 port mid-position valve.

Edited August 3, 2023 by HughF

[HughF]

13 hours ago, JamesPa said:

 

Probably this is an excellent argument for heat pumps as opposed to boilers in rental properties.  Gas can explode, properly installed electrics are pretty much idiot proof.

I agree with you completely on this… and especially in flats. Kensa are doing some good work with communal boreholes, their shoebox w2w unit and a sunamp for dhw.

 

Lots of case studies on YouTube showing the tech.

[PeterW]

9 hours ago, TonyT said:

 

y plan isn’t hot water priority

 

its when the boiler can heat the cylinder at a very high temp  for good recovery times and then switch to heating mode  on a low temp  

How ..? Y-Plan doesn’t distinguish between heating mode on the boiler as in mid position it is supplying both heating and hot water simultaneously. W plan can do that, but only with an opentherm ready boiler or using a boiler that can control the diverted valve.

 

BG and others like Y-Plan as retrofit as it’s cheap and only needs the one valve and no pipe work changes. It’s a compromise especially if fitting a heat pump

[Beelbeebub]

10 hours ago, markocosic said:

You're describing a Rotex HPSU.

 

Matey in Lithuanian countryside has an old one. Outdoor unit is tiny because it's a split rather than a monobloc. (done to avoid freezing and to make routing there primarily pipework a piece of push)

 

Indoor unit is a thermal store with ALL the valves and gubbins on top.

Neat idea. 

 

I like the everything up top idea. I also like the fact the outdoor unit can be small from a planning (and just finding a space for it) pov.

 

The only negative is the need for fiddling with the refrigerant. Plumbers can't do it and people with F-gas don't want to do plumbing (in general).

 

Technically r290 isn't F-Gas and releasing it isn't a global warming or ozone issue.

 

Plumbers are used to working with (and qualified for) flammable gases, though it should probably be a small seperate add on qualification.

[markocosic]

45 minutes ago, Beelbeebub said:

The only negative is the need for fiddling with the refrigerant. Plumbers can't do it and people with F-gas don't want to do plumbing (in general).

 

This is a major issue in the UK at the minute. Not just the ticket (£1000 and a Mickey Mouse course) but the experience generally (flaring pipes / brazing pipes).

 

I think it'll disappear as more folks ask for domestic AC though. And it'll be plumbers who upskill to fit these rather than air conditioning folks who do domestic plumbing.

 

Europe is more relaxed about this stuff. In the DIY sheds €600 minisplits; €150 vac pump/flare tool/gauge set kits; off you go.

 

When it's limited charge R290 the FGas requirement disappears and it's just the plumbers being scaredycats as the barrier.

[markocosic]

51 minutes ago, Beelbeebub said:

and just finding a space for it

 

They don't seem to do hot water cylinder cupboards on the continent.

 

It's either a wall hung tank in the bathroom, wall hung tank on the balcony, or standalone tank in basement.

 

So this thing just sits against a wall in a room. Demolish the cylinder cupboard and sit it against a wall type thing.

 

It would be ideal if it were 56*56*1800 say, so it could be a kitchen unit easily. That wouldn't work with their fat blown foam/plastic body tank though.

 

For houses you could, if so inclined, build a plastic tank with everything up top, ready to shove the space heat and hot water pipes through the old boiler flue hole...

 

Doesn't get *that* cold here and if space isn't quite such the constraint.one can afford insulation.

[DanDee]

55 minutes ago, Beelbeebub said:

Neat idea. 

 

I like the everything up top idea. I also like the fact the outdoor unit can be small from a planning (and just finding a space for it) pov.

 

The only negative is the need for fiddling with the refrigerant. Plumbers can't do it and people with F-gas don't want to do plumbing (in general).

 

Technically r290 isn't F-Gas and releasing it isn't a global warming or ozone issue.

 

Plumbers are used to working with (and qualified for) flammable gases, though it should probably be a small seperate add on qualification.

Whilst in the UK you can buy Mitsu only as monoblock , in the Netherlands they sell only split systems.

[HughF]

Plenty of opportunity to lie when ordering f-gas stuff from the online suppliers over here. And from what I can make out, it's actually non-enforceable against DIY installers.

 

As Marco says, the course is 5 days and a grand, and never expires. I expect most plumbers to upskill at some point. I'm not a plumber but I'm probably going to do it later this year.

 

Edited August 3, 2023 by HughF

[TonyT]

10 hours ago, PeterW said:

How ..? Y-Plan doesn’t distinguish between heating mode on the boiler as in mid position it is supplying both heating and hot water simultaneously. W plan can do that, but only with an opentherm ready boiler or using a boiler that can control the diverted valve.

 

BG and others like Y-Plan as retrofit as it’s cheap and only needs the one valve and no pipe work changes. It’s a compromise especially if fitting a heat pump

 

I was thinking about opentherm.

this article explains it better.

 

 

 

https://theintergasshop.co.uk/content/189-why-hot-water-priority-is-the-reason-s-and-y-plan-should-be-banned

 

 

 

 

[JohnMo]

33 minutes ago, TonyT said:

 

I was thinking about opentherm.

this article explains it better.

 

 

 

https://theintergasshop.co.uk/content/189-why-hot-water-priority-is-the-reason-s-and-y-plan-should-be-banned

 

 

 

 

Have you pointed to the correct link, that's about priory hot water, instead of S and Y which I also think should be banned.

 

Opentherm is a different subject again. 

 

W plan is just really a 3 way diverter, instead of mid point valve - X plan gives you two distinct flow temps. One can be weather compensated normally.

Edited August 3, 2023 by JohnMo

[TonyT]

In my head I’m talking about x plan 2 temps one for heating one for recharging cylinder?

[Beelbeebub]

19 minutes ago, JohnMo said:

Have you pointed to the correct link, that's about priory hot water, instead of S and Y which I also think should be banned.

 

Opentherm is a different subject again. 

 

W plan is just really a 3 way diverter, instead of mid point valve - X plan gives you two distinct flow temps. One can be weather compensated normally.

Can you post a system diagram of "X plan"?

 

As far as I can tell there really isn't any actual difference between S,Y,W or X

 

In essence all of them take the pumped flow through the heat generator and direct it between the cylinder and central heating zone(s)

 

S uses 2port valves on a T (or manifold)

Y uses a 3 port valve with a mid-position actuator

W uses a 3 port valve with a 2 position actuator.

 

The major difference between them seems.to be in the wiring of the various valves to each other to "hard wire" the logic 

 

But from a plumbing perspective there is very little difference, an S or Y plan could be made to function exactly like a W plan by controling the valves with a microcontroller rather than thermostats and timers closing circuits.

 

The only problem might be if you have a very complex system. My parents have a horrendous system where multiple zones are actuated by the thermostat closing a contact that motors a 2port zone valve, then a microswitch in the actuator closes a circuit that power the pump (as far as I can tell directly) and commands the boiler to fire. It's a nightmare to trouble shoot with wires going every which way and multiple points of failure.

[JohnMo]

Here is a snippet out of my Atag gas boiler manual. This is X plan. 3 way wired back to the boiler, the boiler then knows what temp it fires at. ASHP are the same configuration X plan.

[JohnMo]

16 minutes ago, Beelbeebub said:

The only problem might be if you have a very complex system. My parents have a horrendous system where multiple zones are actuated by the thermostat closing a contact that motors a 2port zone valve, then a microswitch in the actuator closes a circuit that power the pump (as far as I can tell directly) and commands the boiler to fire. It's a nightmare to trouble shoot with wires going every which way and multiple points of failure.

And would imagine if the efficiency was worked out it would be hideous, lots of small zones; boiler short cycling here we come. Running weather compensation you would remove most or all the zones and have single point control thermostat and with radiators have it set to weather compensation with the addition of load compensation to compensate for a slight miss match of heat load and demand.

[Beelbeebub]

21 minutes ago, JohnMo said:

Here is a snippet out of my Atag gas boiler manual. This is X plan. 3 way wired back to the boiler, the boiler then knows what temp it fires at. ASHP are the same configuration X plan.

So basically using some actual logic (probably microprocessor based) to provide 2 "setpoints" or modes for the boiler to control it's temperature to.

 

As i said, the old way of doing things was just dumb hardwiring of dumb components together that had developed over the decades as more.functions were added and had to be backwards compatible.

 

Yeah, that crap should be ditched. All you need is a 3 port or (possibly more flexible) 2 X 2port valves (s plan) winter directly to the controler and the system works out what flow temp it should be outputting and which valves should be open or closed.

 

Question: unless you have really low thermal mass in your house, do you ever need to have your heating and hot water demands satisfied at the same time? You just stop heating for a bit and supply the DHW at a higher temp, then drop back to heating again? 

[Beelbeebub]

26 minutes ago, JohnMo said:

And would imagine if the efficiency was worked out it would be hideous, lots of small zones; boiler short cycling here we come. Running weather compensation you would remove most or all the zones and have single point control thermostat and with radiators have it set to weather compensation with the addition of load compensation to compensate for a slight miss match of heat load and demand.

It's actually not terrible. It uses a thermal store as a buffer with the UFH taken from the middle. Short cycling isn't much if an issue 'cos although there are loads of zones, the house is stupidly big so they are plenty big anyway. 

 

That said it would work much better with a WC heatpump. The flow temps are sub 40C for keeping the place warm and it would get me out of having to deal with the wiring - just leave everything open, maybe a few rooms on the south side with high temp cutouts

 

Bigger problem is it uses these horrible rubber pipes that are going brittle, several loops have failed already (20 years old) and are going to have to be replaced. I'm praying none of the ones in the slabs go....

 

[JohnMo]

7 minutes ago, Beelbeebub said:

thermal store

Thermal store isn't any to do with any of the plans above, nice and simple for the boiler, just heat the cylinder, it doesn't care about anything other than the cylinder. But no use for the heat pump, as you need a second cylinder for DHW.

 

1 hour ago, Beelbeebub said:

and commands the boiler to fire

Do the individual zones call the boiler for heat, they should just call for a pump to start, to draw hot water from the store. The store thermostat does the calling for heat, independent of the heating system.