Converting from oil boiler to heatpumps (Air-air and air-water)

[Rodders53]

You need to improve insulation and draught-proofing as much as is allowed by the building's listed status: consult with any Listed / Conservation Officers as to what's possible to do. That will reduce the heating input needs.

You are currently eating through 45-60MWh per annum in Kerosene? 123-164 kWh/day on average!! Likely to be 3-4x that some days in winter (if not more) and just a few kWh in summer (to top up the HW tank)? That's going to need a bigger than average ashp I suspect and may even require a 3-phase electric supply, ptentially?

NB You ideally don't want (emergency cold backup) immersion heaters in any of the units (nor crankcase 'vampire load' heaters) in the heat pumps - even with stored battery supply. It'll quickly deplete stored energy in colder / darker times when you are using the most energy for heating anyway.

Oil is currently, May 23, under 6p/kWh where I live. Don't forget the true cost of your solar generation should include a capital depreciation (renewal/repairs) and the same for battery storage lifetime. Just like a replacement oil tank at £3k for 10 years life = a £300 pa standing charge: around 3p/kWh for my 1000 litre-ish pa consumption.

CAN you fit air-air or air-water ASHPs to this listed building?? I'd have thought the Planners / Listed Buildings'd not like the look too much?
Mind, if solar panels have been allowed then anything might be OK visually

My a-a pumps will go into defrost mode (but close vents/stop fan on internal units when doing so). They do a defrost when we stop the heating sometimes as you can hear the unit running on after the 'off' is pressed. Minus 12 C: I don't think we've been that cold here so haven't had any problems like you describe so far.

Check out other forums (Moneysaving expert and self build ones where there are threads on ASHPs, designs etc.,.) as well as here.

 

[crappy]

No, only the certified test figures. What's the refrigerant in your annex unit, who is the manufacturer?

See link above to Panasonic unit.

Its a air to air unit? so what have the rads got to do with it?.

Yes, this is the one in the annex and I want to put the same unit(s) into the house for air. My pondering is, do I use them or water? If there was one which could reliably give me 80c like my dead Dinosaur boiler, perfect.
Even if I did use air, what about bathrooms and smaller spaces. Still need those warmed.

You ideally don't want (emergency cold backup) immersion heaters in any of the units (nor crankcase 'vampire load' heaters) in the heat pumps - even with stored battery supply. It'll quickly deplete stored energy in colder / darker times when you are using the most energy for heating anyway.

Yes, I had thought of that. It might be too eager to keep it defrosted and hence kill my battery capacity.

CAN you fit air-air or air-water ASHPs to this listed building?? I'd have thought the Planners / Listed Buildings'd not like the look too much?
Mind, if solar panels have been allowed then anything might be OK visually

Yes. The units will be tucked away back of rural house you cannot see, next to where the oil boiler is. So long as I don't mess with the main beams, I'm OK. The pv is on a not-visible-from-anywhere garage.

 

[Rodders53]

You're best spending on insulation and making the place less leaky of the heated air before anything else. (It should be the cheapest way and more environmentally friendly than burning excessive amounts of even renewable energy)?

80C radiators are surely a dangerous burn risk!

Hybrid heat pump/oil burner devices e.g. https://www.grantuk.com/products/hybrids/ may be something to investigate?

 

[Johntheo5]

Thermodynaically not a bad idea as you can get the room temperature up fast in the morning and then change over but who is going to ever run the HP if the Cost of running the boiler is less, at present energy costs you would require a unattainable HP COP??

 

[crappy]

Hybrid heat pump/oil burner devices e.g. https://www.grantuk.com/products/hybrids/ may be something to investigate?

Very in. Will take a look.

You're best spending on insulation and making the place less leaky

Unable to do any more. External barn is shiplap, internal all exposed 200 year old oak beems. Windows already fairly new double glazed.

My only option is more fire hence my wanting to find the cheapest way.

I'm jealous of a friend in Ireland, new build house, could heat with a box of matches...

run the HP if the Cost of running the boiler is less, at present energy costs y

Could you run those calcs past me again? Not sure how it works out cheaper than 7.5p/kwh (considering I've already invested in pv and battery)

 

[crappy]

Currently oil is, Inc vat, 55.88. Come down a lot.

 

[Rodders53]

Not sure how it works out cheaper than 7.5p/kwh (considering I've already invested in pv and battery)

Currently oil is, Inc vat, 55.88. Come down a lot.

Oil is in round numbers a little over 6p/kWh of heat into the radiators for as long as you have it in the oil tank... or tanks.

On average you use around 140kWh per day. You can store only 27 kWh in the battery -- say 100kWh of heat from a heat pump with a generous COP of 4 {newer ones might get close in warmer times} (but then all the rest of your leccy during the non-off peak is full price (whatever that is for you?).

So you can't HP heat the home 24/7from your stored cheap electric. Yes that 100kWh is as cheap as chips - about 2p per kWh of heat (ignoring the cost of the battery storage, and how many cycles you can get before needing to replace them). {Again in practice you won't get that COP of 4 all the time, nor will you want to regularly discharge the battery bank to that level. Perhaps 20 kWh per day / charge is more realistic?.}

Winter you'll be nearer wanting 480 kWh heat input a day. So that's a continuous 20kWh in every single hour of the day? A mahoosive heat pump or two or? Certainly in the very cold the COP will drop, maybe even as low as to 1 and then oil could be cheaper. This is sort of where the hybrid systems may have something to offer you?

Any newer oil burner would want to be condensing so not run at such high temperatures (e.g. 50 C return) and thus radiator upgrades may be essential in any case.

{NB You actually need someone in to do much more precise numbers wrt the heat input/losses of the rooms and building overall so as to get the correct design(s) of potential heating systems, radiator upgrades, underfloor insulation and/or slab storage of the heat input?.}

Perhaps you may need to build rooms within the walls of this barn structure that can be insulated better?

 

[crappy]

Very interesting - thanks.

Insulation / rooms in rooms - cannot do at all. Really is no option here
Roof / I have no ceiling. I have vaulted roof everywhere and explosed oak beams. Not entirely sure what insurlation I have up there but will not be able to improve it.

Calcs -
Where do you get 140KWh from for heat demand? Is that average for a UK home?

The part I really cannot wrap my head around is the unit in the annex. I cannot off-hand find the measurements for it but every online calc said he needed a 4.2KW unit. I bought a 5KW job. It does the job bloody well and only ticks over and sips juice.

Today I even had the door and window open for fresh air and the heater running

Yes, today was an idea day for COP so slightly skewed.
This thing, once settled, is sipping around 0.2KWh.


I'm really not understanding where your power demand is coming from. 20KWh every hour?

 

[Rodders53]

You are currently eating through 45-60MWh per annum in Kerosene? 123-164 kWh/day on average!!

Calculated from your own oil consumption figures:

I "top up" oil 3 times a year and always 1500-2000L

3 x 1500 litres is 4,500 litres x 10 (kwh/litre) = 45,000 kwh = 45 MWh divide by 365 days = 123 kWh per day.
140 kWh is just a number in-between the 4,500 litre and 6,000 litre you gave.

Of course if you meant you use 1500 to 2000 litres a year... then rework the numbers a bit (divide by 3) i.e.
41 to 54 kWh/day on average.
But you still won't have enough cheap stored electricity in the colder days of winter where that heat requirement will be much higher and with a poorer COP from any heat pump.

 

[Johntheo5]

Very interesting - thanks.

Insulation / rooms in rooms - cannot do at all. Really is no option here
Roof / I have no ceiling. I have vaulted roof everywhere and explosed oak beams. Not entirely sure what insurlation I have up there but will not be able to improve it.

Calcs -
Where do you get 140KWh from for heat demand? Is that average for a UK home?

The part I really cannot wrap my head around is the unit in the annex. I cannot off-hand find the measurements for it but every online calc said he needed a 4.2KW unit. I bought a 5KW job. It does the job bloody well and only ticks over and sips juice.
View attachment 304251

Today I even had the door and window open for fresh air and the heater running

Yes, today was an idea day for COP so slightly skewed.
This thing, once settled, is sipping around 0.2KWh.


I'm really not understanding where your power demand is coming from. 20KWh every hour?

Of course sipping 0.2kw looks impressive, you really have to know the HP output, not easy with a air/ air unit.