Bivalent ASHP and oil boiler

stuhse

You could get a sight glass for your oil tank which allows for more accurate observation of levels.  Simply order an oil fill up the moment you are below half full.   I'd be surprised if oil wont arrive in the time it takes to use 500litres.

By taking regular measurements of the oil level in the sight glass you can soon get used to the rate of use at different times of year and antiscipate placing your order slightly in advance if necessary.

We have a 1300l tank on our reasonably large and inefficient house...we have occassionally got caught out by forgetting to monitor the sight glass and trying to mesh deliveries with our village oil buying group.  I've thought about daisy chaining tanks, m very interested, what's the reason you've been told this is a bad idea ?

QrizB

FreeBear said:

QrizB said:

greenbee said:

For now, I just want to put a solution in place that will resolve the fuel insecurity of such a stupidly under-sized oil tank and potentially allow a switch-over at some unspecified point in the future (hence not necessarily wanting to replace a perfectly well-functioning boiler with a hybrid system).

If you don't mind being a bit Tom & Barbara, you can deal with fuel insecurity with a couple of these and one of these. And some hose.

For another £15, a 1000l IBC would be more effective. Unlikely to comply with current regulations for fuel storage though.

That's why I didn't suggest an IBC. The requirement for bunded tanks only applies to containers larger than 200 litres, IIRC. So storing in drums should be OK.

greenbee

Reed_Richards said:

greenbee said:

Solar is a no-brainer as we have a lot of very usable roof, and setting up EPS means not having to worry about working when the power goes out. We don’t use a huge amount of electricity, and will use less when the lighting is sorted out so we don’t have 23 inset LEDs on every time we go into the kitchen!

That low electricity usage is only for as long as you don't have an ASHP.  One of those will greatly increase your electricity usage and you will have to turn it off in the event of a power outage (or exclude it from your EPS) or it will quickly drain your battery storage capacity when it is active.

Don't you need dark glasses in the kitchen?   

Yep - so we're going to divide them into separate groups that turn on independently. There are another 12 in the open plan living area attached to it which we'll be doing the same thing with (although there we're also putting in a lighting circuit for table/floor lamps when we redecorate). The whole house has poor lighting design.

I know the electricity use will go up with ASHP, given it runs on electricity But we can more than supply our needs from what the roof will take. And obviously one of the advantages of a bivalent system would be that the EPS could power the oil boiler in an outage so we wouldn't be without heating... I suspect it'll take a while to work out the right options, but flexibility seems to be key. 

greenbee

stuhse said:

You could get a sight glass for your oil tank which allows for more accurate observation of levels.  Simply order an oil fill up the moment you are below half full.   I'd be surprised if oil wont arrive in the time it takes to use 500litres.

By taking regular measurements of the oil level in the sight glass you can soon get used to the rate of use at different times of year and antiscipate placing your order slightly in advance if necessary.

We have a 1300l tank on our reasonably large and inefficient house...we have occassionally got caught out by forgetting to monitor the sight glass and trying to mesh deliveries with our village oil buying group.  I've thought about daisy chaining tanks, m very interested, what's the reason you've been told this is a bad idea ?

Apparently you can't put a sight glass on a plastic bunded tank. So measuring stick is probably the answer. When we had a single skin tank the condensation level was the best option. If I was replacing the tank I'd probably go for metal - but I suspect that what is there is down to the space available. 

Keeping in sync with the village oil syndicate has proved impossible, partly down to the size of the tank - bear in mind the accuracy of the watchman, so it needs to be UNDER half full before you order for an 'on or before' date (sometimes it takes 24 hours, sometimes 2 weeks). With a 1000l tank that gives me somewhere between 500 and 400l remaining. And I don't want to get down below the feed pipe, so I'm not looking at having 500l to play with. Possibly 300l. And while I'm still working out how much we use on average, together with the impact of the odd cold snap (and heating that isn't properly controlled) it is really focusing our minds on how easy it would be to run out of oil here - particularly over the Christmas period when deliveries are non-existent or wildly expensive. 

I think the issue with linking tanks here is down to proximity to the fence. But it's something we'll revisit. 

lohr500

Although you would be paying more for a shorter lead time oil delivery, would that still not work out a lot less expensive than changing the boiler system, adding an ASHP or finding a way to fit a bigger tank?

Or even sign up to something like Boilerjuice's Connected service where they monitor the tank level remotely using a SIM enabled sensor. Again, I suspect you will pay a bit more than shopping around for each delivery but it passes the responsibility onto them to keep monitoring your tank and topping up as needed.

Or get something like this fitted to the tank outlet. I have a similar one on our tank and it is very accurate when compared to my measuring stick and known quantities of oil delivery. Take a reading when your tank is topped up and then wait until it has advanced by 500 litres, then reorder. I actually use ours every time to determine when to reorder. Far easier than messing round with a measuring stick and more accurate than relying on the LCD bar indications on our Apollo remote gauge  .

https://www.bes.co.uk/domestic-heating-oil-tally-meter-10mm-19438/?q=19438

Reed_Richards

greenbee said:

I know the electricity use will go up with ASHP, given it runs on electricity But we can more than supply our needs from what the roof will take. 

I find that hard to believe if you are calculating your needs with the ASHP.  And there is a terrible mismatch between when solar panels generate plentiful electricity and when you need that electricity for heating.  Would you care to share your calculations on this?

I have a heat pump and a 6.5 kWh battery which I fully charged overnight from the mains, finishing at 07:00.  2 hours 40 minutes later the battery state of charge is down to 38%.  It's 7 degrees outside.  The vast majority of that 4 kWh used will have been consumed by my heat pump.  There is 100% cloud cover but even if it was completely sunny I don't expect that my panels (4.8 kWp) could feed my heat pump for more than 2 or 3 hours over the middle of the day in December.  

QrizB

Looking at this from a different angle, if the main concern is one of running out of oil during a cold snap, you could fit a back-up direct electric heater to your system.

Something like this would be much cheaper to fit than a heat pump, and (assuming that you rarely need to use it) would let you keep your current oil system ?

https://www.plumbnation.co.uk/trianco-aztec-classic-tri-12kw-electric-flow-boiler-169-9208

12kW might not be enough as a permanent heat source, but it would certainly stop you freezing if you ran out of oil.

matt_drummer

Reed_Richards said:

greenbee said:

I know the electricity use will go up with ASHP, given it runs on electricity But we can more than supply our needs from what the roof will take. 

I find that hard to believe if you are calculating your needs with the ASHP.  And there is a terrible mismatch between when solar panels generate plentiful electricity and when you need that electricity for heating.  Would you care to share your calculations on this?

I have a heat pump and a 6.5 kWh battery which I fully charged overnight from the mains, finishing at 07:00.  2 hours 40 minutes later the battery state of charge is down to 38%.  It's 7 degrees outside.  The vast majority of that 4 kWh used will have been consumed by my heat pump.  There is 100% cloud cover but even if it was completely sunny I don't expect that my panels (4.8 kWp) could feed my heat pump for more than 2 or 3 hours over the middle of the day in December.  

I am soon going to be writing a small book on here about my heat pump experience.

So I thought it might be helpful to explain how this works, think of it as a prelude!

@Reed_Richards, you just don't get it do you?

In the spring and summer I was generating 80kWh a day of electricity at times but I don't use that.

I got paid for exporting more than 70kWh a day at times as I just don't use that much electricity in the sunny months.

That money is now buying the electricity to run my heat pump when it is not sunny enough to generate the electricity required to run the heat pump.

What I have done is banked my solar generation when I had too much so that I could use it when I need it.

Why is this so difficult for you to understand?

In the same way that you feel the need to point out flaws in other people I think you need to start thinking outside your own setup, you may be happy with it, but that doesn't mean it's the best in the world and can't be bettered.

There is no reason why, if @greenbee has enough roof space to generate significant amounts of export in the sunnier months that they can't bank those exports just as I do and use the income to pay for running the heat pump when it isn't sunny enough.

Why would you advise @greenbee that solar panels won't work in powering a heat pump when clearly they do, I am doing it, just because you don't, won't or can't do it doesn't mean the rest of us can't! 

Anybody with enough roof space and sufficient funds to buy the solar panels could do what I have done. You don't need a huge mansion to do it, my house is 98m2 with a 40m2 garage, I have about 80m2 of roof space that is filled as much as I can with solar panels, maybe 60% of the roof area.

I generate more than I consume in a year by quite some margin and so even though my export payments are less than the import cost the net result is I get paid more for exports than I need to pay for imports.

On an annual basis my solar panels pay for all of my electricity use with some money left over as an income. 

There's no magic in this.

Why keep telling people that it is not possible?

@greenbee could do exactly the same as me.

greenbee

Thanks for all the ideas - Yes, I do realise that I won't necessarily always generate enough electricity to power the heatpump, but as @matt_drummer says, this can be offset by export savings that will pay for either electricity or oil.

I had a long discussion about it with the friend I mentioned previously who does a lot of retrofitting of all types of heating systems into buildings as part of restoration/conversion projects. Ultimately I'm looking for resilience and future proofing while not doing a full replacement in one go. I simply can't deal with having all the floors up replacing pipework at the same time while trying to work amongst the noise, dust and chaos. However, being a bit more prepared for when the oil boiler does pack up and need replacing is worth planning for - and if we're putting in solar and EPS then the heatpump in a bivalent system looks like it makes sense on the back of an envelope calculation. 

Obviously we also need to get a better handle on our oil consumption so we can plan more effectively, but TBH I don't know anyone in the real world who doesn't struggle with this from time to time (unless they're signed up for telemetery and regular top-ups which then restricts you to a single supplier). Apparently it's tradition for certain friends to run out of oil just before Christmas 🙃

Reed_Richards

matt_drummer said:

What I have done is banked my solar generation when I had too much so that I could use it when I need it.

Why is this so difficult for you to understand?

Glad to see you back, @matt_drummer .

 It's not too difficult to understand, although you are absolutely correct, it is outside my own experience.  I think what you sometimes forget is that your solar panel system is much larger than the average one.  I am limited to exporting 3.68 kWh per hour and the maximum I can generate is 4.8 kW.  So there is no way I could ever come close to exporting 70 kWh per day as you do.  It's really great what you have, but usual.  Hopefully @greenbee has the roof area and DNO permission to set up, and get the full benefit from, a large solar array like yours.