Get rid of Gas - replace heating / DHW boiler, with what?

[tex360]

Hi

 

Long term lurker,  finally subscribed.

 

Hoping some of the experts could please give some advice,  I seem to be at a pause with an ambition to cut our households' CO2. Help!

 

Context: the house is a 1960's 4 bed detached (was 3 bed, expanded with a side extension 2012) and like so many houses of it's type is close to its neighbour, which is 1.4meter away. We own the gap between our house and their solid wall, closed off with a fence at one end. There's a gas central heating boiler downstairs that vents into the gap, and a separate hot water tank upstairs. 3kw of solar panels on the roof.  Last month about 70 KWh of that was diverted into hot water immersion so our summer gas usage is minimal. Obviously through winter that diversion won't happen.  Last years elec usage was 5000kwh and gas 15000kwh.   I have a new EPC, which is a C.

 

I had applied to be part of an OVO ASHP /Sunamp (or hot water store) trial, BUT their assessors said the the house wasn't suitable, with nowhere to put the external pump, as regs forbid within 1m of neighbour, nor at rear (not permitted under window) and couldn't be freestanding at the other side in side garden /next to the garage as the extension has a suspended concrete floor too far away from existing boiler location. Also they'd have to deal with the garage being in the way (solid floor) and run pipes around the outside of the house, then lift kitchen floor, etc etc etc etc. 

 

Please see exciting attachments with layout. 'B' = boiler location. 'No' = under window. The existing boiler 'B' is where we'd prefer inside components to be - if possible, as its where the existing plumbing is.   See the 1.4m gap between us and next house.

 

The objective is to a) make best use of the solar  b) get rid of gas entirely and its co2 c) ideally, take advantage of ASHP financial incentives. I had thought heat storage for DHW and an ASHP was viable. But is it!  This is where I'd like please to ask advice and sort out the facts!

 

Several questions.

 

1. is using ASHP to provide space heating and a water tank heat store, for DHW, viable?

 

2. if an ASHP is possible, where could you put it?

 

3. if in the gap is possible, which model/ thickness would fit that gap and pass 'regs' ? 

 

4. is a sunamp a cost /viable option to provide space heating (and possibly DHW?)

 

5. how would you do it!

 

cheers in advance for any thoughts or options. iain

Edited September 17, 2021 by tex360

[SteamyTea]

8 hours ago, tex360 said:

1. is using ASHP to provide space heating and a water tank heat store, for DHW, viable?

Yes

8 hours ago, tex360 said:

2. if an ASHP is possible, where could you put it?

Somewhere near the extention.  OVO wanted an easy install, a simple replacement job.  But you seem to have lots of space.

8 hours ago, tex360 said:

3. if in the gap is possible, which model/ thickness would fit that gap and pass 'regs' ? 

Do you mean the 1.4m gap?  If yes, then no.

8 hours ago, tex360 said:

4. is a sunamp a cost /viable option to provide space heating (and possibly DHW?)

No, forget the Sunamp.

8 hours ago, tex360 said:

5. how would you do it!

Self design and install with a decent plumber.

 

You need to do a decent heat loss analysis first.  If you have monthly bills, this will help a lot.

A kW (power) and a kWh (energy) are the same regardless of the way they are delivered.  Temperature is not energy.  And KWh, kwh, kw, Kw etc are not the correct units.  Always look out for this on any quotes, may seem minor, but it shows a standard of care.

 

The PV, when generating, and the ASHP when delivering will suck up any excess solar power, so timing becomes an issue, so run the ASHP between 10AM and 2 PM will help.  A half decent ASHP will give a CoP of 2.5 when heating water, so that is over twice as good as resistance heating.

 

Do that heat loss analysis first though.

[ProDave]

I would put the ASHP under the window where is says "no"  as long as your chosen ASHP model was no higher than the window sill outside.  That might mean careful choice of which ASHP to use.  I am not aware of any building regs that prohibit  an ASHP being under a window.  Ours is on the back of a garage but we do have a small, non opening window in the end of the living room that looks down onto it.  Obviously you might hear some noise from it yourself but in the summer when you want the windows open it will not be doing much.

 

If you used 15000 kWh of gas, expect the ASHP to use at least 5000kWh of electricity.  i.e. your electricity usage will double.  How will a doubling of your electricity bill compare to your present electricity and gas bills?

 

You do NOT want a "thermal store"  you want an unvented hot water cylinder and because the hot water is usually not quite so hot from an ASHP you need it bigger than your present one so probably 300 litres.

 

Now what size heat pump?  you really need a proper heat loss analysis but very roughly my 5kW ASHP uses about 1600 kWh of electricity each year,  yours is going to use about 5000kWh each year so a very rough guess is you will need something about 15kW.  That might be the problem that a 15kW unit is too tall to fit under the window without being seen from inside?

 

And the last question, how is the heat delivered?  I will guess standard radiators.  Those will all need to be changed for larger ones as again the water flowing through them will not be as hot as from the gas boiler.

 

[tex360]

Hi!

 

I'm sorry for not replying earlier, the notification I thought I had set - didnt

 

thank you for your comments - I shall gather some info and will reply in next days. I believe the heat loss was calculated, I'll search. Yes I expect a number of the radiators will need to be changed.   I had expected the elec usage to increase quite a lot. I am sure we throw a lot of heat straight out of the window, literally - warm downstairs, but everyone wants it cool upstairs and the upstairs windows seem open an awful lot of the time in winter. We will probably add some kind of air recircuation upstairs - off topic now but when we lived in canada the house had just that and no opening windows  for 6 months of the year, so we need fix that here.  We are fully aware of behavoural changes we will need to make.

  

 

thanks again! 

 

 

[ProDave]

Don't have heating upstairs of you don't like it hot (we have no heating upstairs)

[tex360]

Hi again

 

I looked up the 'technical report' from Ovo's assessors, here's the only page with any reference to numbers. Sorry this is all I presently have to indicate the losses.

 

 

Here's our per-month kWh actuals for elec and gas, for 2020 / 2021 to date: Oct to March is about 12000 of the years' gas, ETA actually 19000 in 2020, perhaps 16000kwh in '21.

 

 

 

Usage	Elec kWh	Gas kWh
Jan 2020	496	2581
Feb 2020	501	2388
Mar 2020	447	2304
Apr 2020	414	2304
May 2020	363	993
Jun 2020	360	716
Jul 2020	340	472
Aug 2020	1441	409
Sep 2020	540	779
Oct 2020	642	1581
Nov 2020	695	2227
Dec 2020	696	2227
2020 total	6935	18981
Jan 2021	770	2736
Feb 2021	751	3000
Mar 2021	439	654
Apr 2021	654	256
May 2021	256	380
Jun 2021	380	503
Jul 2021	503	438
Aug 2021	438	500
Sep 2021	331	244
Oct 2021	not yet	not yet
Nov 2021	not yet	not yet
Dec 2021	not yet	not yet
2021 total	4522	8711
	(to date)	(to date)

 

so I need to:

 

a. Confirm the losses and sizing for the ASHP.  I need find someone to measure this properly and do the sizing for the pump and radiators. Thanks for your comments re kWH not being the proper measures of heat loss/needs. 

 

b. Find a pump of correct size that fits, and consider other locations (under the window etc). The side passage is inappropriate (why though? noise? Closeness regs? or is planning permission needed?  I dont care much about a slightly lowered cop if thats the reason)

 

Two more thoughts have occurred to me in the last week -

 

1. See to the right of the house, there's a window and a door at the back fo the garage? there's radiators inside the extension and in that garage. Do monobloc-type ASHP's mean there only connection to the house is via the central heating circuit itself, all the pumps and diverters are in the external unit and it could go there/ attach to the central heating pipework (possibly)?

 

2. Simplification.  Maybe I shouldn't worry about the DHW via ASHP.  I read somewhere to heat 100L of water from 10 to  60 degrees requires about 6kWh. If that is correct(?) could I just heat DHW from octopus cheap night rates using a newer cylinder.. if its really only 200l / 2 x 6kwh x 5p, (c. 60p per day in winter) would that be a decent compromise in your view?  ie DHW - excess solar in summer,  elec only in winter off a cheap rate.. and ASHP for space heating only?  The tank could stay upstairs a mixergy or some other solution just for DHW.

 

Thanks again for your responses!. Really appreciated. And very clear in your rejection of sunamp etc.

 

iain

 

 

 

 

 

 

[tex360]

5 hours ago, ProDave said:

Don't have heating upstairs of you don't like it hot (we have no heating upstairs)

 

I agree 100%! I'd like the ground floor heated and keep the doors closed! let convection take care of the upstairs... we are in Uk, its not cold !

 

 

 

[SteamyTea]

11 hours ago, tex360 said:

could I just heat DHW from octopus cheap night rates using a newer cylinder.

Those cheap deals will be pulled from the marketplace.

Heat your water from a heat pump, you know it makes sense.

11 hours ago, tex360 said:

Here's our per-month kWh actuals for elec and gas, for 2020 / 2021 to date: Oct to March is about 12000 of the years' gas, ETA actually 19000 in 2020, perhaps 16000kwh in '21

Here is a quick and dirty chart

[tex360]

thanks for the graph btw,  what ratio extra elec for 1000kwh has heat did you assume please. 3000kwh seems to equate to c. 1100 elec kwh from your experience?

 

thats an approx elec cost range of 500kwh (c £100 per month) to 1100kwh (c £220 pm) over the months we use space heating.

 

I still cant see a way to heat the DHW from an ASHP, if I CANNOT fit it in the alley. And I still dont have a definitive reason why not ( is that location banned by actual law? or do I need apply for planning permission?)

 

OK, locating an ASAHP under the rear window may be possible if we lift the floor and route the ASHP output to where the current gas boiler is, and heat the radiators and DHW cylinder that way. But locating the ASHP to the right side of the house - a far better location - where I also have a couple radiators - would surely still be OK for heating only. 

 

Maybe my next step on this journey is to abandon ASHP for now  - until the models available inc thinner units! - and focus on cutting gas usage.

 

 

[SteamyTea]

6 minutes ago, tex360 said:

until the models available inc thinner units

Probably not going to happen, it is very mature technology.

7 minutes ago, tex360 said:

and focus on cutting gas usage

You should be doing that anyway, but think of it as energy usage, rather than gas usage.

[tex360]

Ok, ta.   Anyone please able to answer my other questions please?   TIA!

Edited October 4, 2021 by tex360

[billt]

I would speculate that there won't be enough free space around the heat pump. They need some distance from adjacent surfaces, usually 500mm+ from the sides and at least 1m from the cold air outlet. If you reduce these distances the efficiency will be severely compromised.

[Ferdinand]

1 - Congratulations on getting an old house to a 78C. That is about half as much heating required as an E or an F, and is a good figure.

2 - How airtight is it? That could make quite a difference to your heat load as the commonplace is that 25% of heat is lost through air leakage. That may be a good route to reduce gas heating usage. Consider an air tightness test, and a hunt for draughts (see Smoke Pencils)?

3 - We have a heat model ss available on the forum. I strongly recommend that you consider doing your own to further build understanding.

4 - Don't neglect to think about controlled ventilation. Do you have trickle vents? If so, consider alternative strategies.

5 - How is your house humidity-wise?

6 - Can you use those single inlet single box heatpumps that just do one area to cover any gaps?

7 - As you say, don't neglect marginal gains - which is the agenda about LED lightbulbs, lo carbon appliances, low current standbys, washing lines and so on. Suspect you are on quite a lot of that. One option which some have found effective has been a Quooker type hot water setup vs a too-often used kettle. Personally I would consider it, but my insulated kettle is still going strong.

8 - Do you have space for more solar?

9 - Are you paying attention to water usage?

10 - Do you have a number for actual Annual Energy use per sqm of floor area? That is quite a useful comparator.

 

Ferdinand

 

 

[IanR]

Do you really need the original patio (?) doors? now you have new French doors in the extension?

 

How about, change these to a normal window and fit the ASHP below, then run the pipes around the outside to the existing boiler location. Fix them to the wall and insulate very well.

 

ASHP could be "end on" if that helps, as long as your neighbour does not have a window opening on the flank of their property.

 

 

If you want to keep the original patio (?) doors, then fit the ASHP under the next window along, as previously suggested by others, and still route the pipes around the outside (under the steps up to the patio doors), just insulate even better due to longer route, or go for a split ASHP with thinner bore pipes that are easier to insulate to a higher degree.

 

16 hours ago, tex360 said:

And I still dont have a definitive reason why not ( is that location banned by actual law? or do I need apply for planning permission?)

ASHP under PD must meet MSC requirements. Minimum distance of any part of the ASHP must be at least 1m from your boundary. With the need for 300mm air gap from a wall to the back of an ASHP, you'll never fit one in a the 1.4m gap. ASHPs are not going to get any thinner, it's a mature technology, just relatively new to the UK.

 

 

[tex360]

IanR - very creative. thank you, will consider.

 

And good info re the pipes and split considerations, and re the MSC requirements. I will research.

 

thank you!

 

[tex360]

BillT and Ferdinand - thank you also - I shall investigate and will reply soon. I'll follow that calculation link. thanks v much!

 

Windows open upstairs is something i need clamp down on... yes we have trickle vents in certain windows.. the double glazed patio doors are 30 yrs old and theres a single glazed door on the kitchen. You are right, we need consider those. I've told the mrs she can pay the elec and gas bill from now on, I suspect this will focus things:)

 

NB the EPC says: "The primary energy use for this property per year is 148 kilowatt hours per square metre (kWh/m2)." is that what you wanted?

 

ta

Edited October 4, 2021 by tex360

[joth]

Does the neighbour have any windows or doors in that opposing wall 1.4m away? If not, you may have a chance to put the external unit there via a planning application.

You'd ideally want to wall mount it, so you still have use of the ally, and have it expelling air down the direction of the ally (toward front or rear of the house, depending on prevailing wind direction) rather than towards the neighbour's wall. Alternatively a split system that moves air vertically might work (and be smaller and lighter to wall mount)

If the neighbour is really onboard with the project you could offer to allow clearance and an easement so they can externally insulate their wall there. (Or even install their own wall mount ashp there too in future). It would slightly encroach into your plot but would give them extra sound insulation as well as energy savings. But planning applications never go the way of mutual benefit so not sure why I'm even suggesting it. 

[tex360]

joth, thanks for this thought. we both have a tiny window 'overlooking' the alley. its closed off one end, so no passage needed. good thought, thank you v much.. if anyone has any make / model names that might fit such arrangement (i dont thin a split with the pumps in the house will be accepted by other half btw) please do share so I can investigate. thx again

Edited October 5, 2021 by tex360

[TW9]

I was accepted on the OVO trial that you applied for. The install is happening this week and it's organised chaos. The photo is the back of the garage complete with 4 Sunamp heat batteries, a Damien Hirst masterpiece in copper piping and enough wiring and control boxes for mission control.

[SteamyTea]

4 minutes ago, TW9 said:

accepted on the OVO trial

How much are they going to charge you for off peak power.

Be interesting as the prices have risen.

[TW9]

I don't know yet. I'm on a tariff that's the same price all the time at the moment but have yet to talk to OVO about running the system.

[SteamyTea]

2 minutes ago, TW9 said:

I'm on a tariff that's the same price all the time at the moment but have yet to talk to OVO about running the system.

Will be interesting to see what they have on offer.