Replacing Oil with Ground Source Heat Pump

lovehols

Hello

We have a purchase going through on a 2 bed bungalow. It is rural and currently uses oil central heating, and as I understand was installed c2010 Worcester Bosch boiler, serviced etc. There is also a wood burner, although not connected to a back boiler.

We are forward thinking, and know we will be extending (subject to planning permissions and ideas from architect) with a view to a second storey. Needless to say the current boiler would be insufficient due to extending the size etc so we would need to replace or look at renewable energy.

There is a big garden area although the garden is adjacent to a canal, exactly how much space is needed for a GSHP? Would the closeness to the canal have any impact on efficiency?

I've read that GSHP are not always enough to heat hot water and heating and they can become less efficient heating so my question is for people with GSHP what is your secondary source to heat hot water?

We would like to retain a wood burner/multifuel stove in the house, but could this contribute to heat/water heating?

I've it the EPC details of the current property into the https://renewable-heat-calculator.service.gov.uk/Default.aspx website and the indication is that with GSHP there is a grant of £2100 a year (though the figures may change a little as I'm estimating it will be next year when the building starts)!

I'm just doing some early research, but any general thoughts or advice would be great - in non technical terms!

matelodave

The "grant" isn't really a grant it's called the Renewable Heat Incentive (RHI) and is worked out on the basis of how much heat you generate, minus the amount of energy you put in.
It is worked out from an EPC (after you've had all the work done and had a new EPC) or you can have an energy meter fitted which measures it and you'd get a variable RHI depending on how much heat you generated.

You'd need to get a full survey and calculations done to give you a better idea of what you might get. AFAIR you need a minium EPC rating of D so you may need to improve your insulation etc first which could reduce your heat requirement and thus lower your RHI payment

I've got an Air Souce Heat Pump and get around £700 a year. We get enough hot water & heating for all our needs so there's no reason why a GSHP should be any worse providing it was sized and designed correctly - others with more experience of a GSHP can comment.
I guess it would depend on the size, type, area and depth of the underground collectors.

Hopefully others will come along with lots more info, but if you are serious then get as much info as you can to understand how it works, what pitfalls there are and how the system should be operated. You'll then be able to evalutae designs to see if they cover all aspects of your system

Heatpumps are different to other types of heating systems and so the whole system has to be designed correctly by someone who knows what they are doing - get at least three quotes and make sure that they cover everything.

I produced a detailed specification of my requirements which made it easier to compare quotes from different suppliers They all had the same parameters to work to and I could judge how well they matched them even though the implementation may have been different.

Ectophile

You've probably got a standard wood burning stove at the moment. But you can get ones with back boilers fitted, to do the hot water.

Not surprisingly they take longer to heat up than a normal stove, but should be able to produce a useful amount of hot water.

You'd need to get an expert in to make sure it's all sized correctly.

lovehols

Thank you everyone. I need to do some more research. The more I read the more I'm worried about the hot water element and the water not getting hot enough. From someone who has a steamy hot bath every night it sounds like having heat and hot water at the same time is when it is less efficient.

That said, I'm not keen on just replacing the oil and would rather have something with more predictable cost than the variable oil coats.

matelodave

I wouldn't say that electricity was more predictable unless you assume that it will increase in price every year.

If you want hot steamy baths then it will cost you to have them - a heatpump is designed to run at fairly low temperatures so to get hot steamy baths then you'll need to use an immersion heater to acheive the higher temperature.

Most systems will allow you to have what ever temperature you want just that you dont get the benefit of the heatpump when you want it above 50 degrees or so as the immersion heater has to take over to raise the temperature above that.

You might find that having it on an E7 contract might be beneficial if you want to heat your hot water overnight, but be a bit wary as the heatpump could be running most of the day so you'd need to do yur sums to see if E7 would be benefical.

We have our temperature set to 45 degrees, which is more than hot enough for our needs - we shower, dont have a bath. The temperature is boosted to 60 once a week to sterilise the tank against legionella so the immersion element kicks in at 50-55 degrees to get it to 60.

lovesgshp

Size of current property in Square Mtrs?
Rads Or underfloor heating?
Refurbished size, plus as above question.
Hot water would be no problem with a correctly sized tank, so how many people will be using it?

lovehols

lovesgshp wrote: »

Size of current property in Square Mtrs?
Rads Or underfloor heating?
Refurbished size, plus as above question.
Hot water would be no problem with a correctly sized tank, so how many people will be using it?

Thanks, I'll try and answer as best I can.

- Current size just under 75 Square Metres - one level, bungalow.
- Will be looking to do away with rads in favour of underfloor heating all through.
- Refurbished size estimate double, 170 square metres at least including an upstairs
- Just two of us, but will be doing Airbnb for one room so on some occasions 4-5 people. To give you an idea we are currently in a bungalow on a condensing A rated system and with a cylinder and when I've had a bath and OH wants one the hot water runs out and we have to put the immersion heater on for some quicker hot water as it takes ages to heat up!

lovesgshp

OK, thanks.
170 sq mtrs finished size, you may get away with a 11kw output pump, but probably14Kw.
Ground loops approx 2x100 mtr excavations, with 2 feeds in each.
Hot water: I would think a 300 ltr tank, with the pump prioritized to hot water production and set at 50C.

lovesgshp

Some more thoughts:
If you are going to be highly insulated, then probably the 11kw unit will be enough.
A 300ltr hot water tank also should suffice for your needs. If not, a 500ltr unit. I have a number of installs working here in Italy on 300ltr units with no hot water problems.

matelodave

Our bungalow is around 140sq.m and we've got an 11kw airsource heatpump feeding underfloor heating and a 200litre hot tank.

It has cavity wall insulation of sorts - looks like rockwool/fibre glass but installed when the place was built in 1986.

There's 300mm plus insulation in the loft and 1999 uPVC double glazed windows and we managed to push the EPC up from a G to a D when we refurbed it nearly eight years ago.

It then started to get into the realms of diminishing returns, costing far more than it would save.

I reckon we've probably just about broken even with the lowish energy bills (just under £800, last year) considering that we are at home all day and the heating runs virtually continuously at this time of the year. It doesn't get turned off, just turned down a bit overnight otherwise it takes ages to reheat the place - two days if you turn it off. (something we discovered just after we'd got it and went away for a couple of weeks).
If we do shut it down for holidays etc then it's timed to come back on the day before we return so there's enough time to get the house up to temperature.

We've had about £2000 in RHI payments since they started and there's still around £3000 to come