Any reason why I couldn’t use a 13kw Mercedes car battery as a powerwall?
Then buy 6 x 230w panels, used from a solar farm.
Add in a 2kw inverter, i guess ypu want overcapacity for longevity, heat, safety etc. I can source this on ebay for close to £1k.

Before you spend any money find a sparky who will wire all that up for you.

The inverter(is your 2kw inverter grid tied) and panels are no issue but plenty people have fallen fowl of trying to make a car battery into a house battery and failed to find a working BMS. To bring the voltage from car DC to house. – typically house is 48v

Insurance issues

And lastly . Cars are typically LnMC (Volatile and need heat controlled )

House are generally life4po – much more stable and temp tolerant….

So it can be done – but unless your doing it your self finding someone to put their name to it and for your insurance to remain valid might be tricky

molgrips

Are you saying December’s bill was more than Nov? When did the cold snap start?

First full week of December IIRC. To be precise for me it was 2pm on Friday 9th Dec while driving to West Kirby as I thought “Oh that’s a bit cold” so put the heated seats on for the first time since last Feb & then @ 2:30pm it started to snow.

Before you spend any money find a sparky who will wire all that up for you.

The inverter(is your 2kw inverter grid tied) and panels are no issue but plenty people have fallen fowl of trying to make a car battery into a house battery and failed to find a working BMS. To bring the voltage from car DC to house. – typically house is 48v

Insurance issues

And lastly . Cars are typically LnMC (Volatile and need heat controlled )

House are generally life4po – much more stable and temp tolerant….

So it can be done – but unless your doing it your self finding someone to put their name to it and for your insurance to remain valid might be tricky

I’d also run any plans past your dno too first, they can get a bit funny if you fry one of their employees with your cobbled together system.

Ah ha! Just had my latest bill from shell appear. Oddly they’ve allowed me to reduce my DD again, weird as I put it to the minimum allowed only a few days ago. Makes little difference currently as it was already below the government energy bills support scheme payments so my DD is effectively zero currently.

Insurance issues

Our house insurance didn’t ask anything about whether we had a Solar system or not, so I assume they don’t care….

I’ve had the battery installed outside, so if it did ever burst into flames it would just scorch the brickwork up the side of the house rather than burn the house down….

Although I do wonder if anyone steals these things, it’s basically £5k bolted to the back of the house…

Our house insurance didn’t ask anything about whether we had a Solar system or not, so I assume they don’t care….

Did your installer install a battery meant for a car ?

Yes you raise a good point about DNO. When you go to apply and look for the certification for your battery and if it’s type approved I suspect you’ll not be getting approved.

Although I do wonder if anyone steals these things, it’s basically £5k bolted to the back of the house…

Yes mine went in the attic because the risk of theft is real.

Did your installer install a battery meant for a car ?

Pretty sure that’s not a specific exclusion in the house policy…

That’s fine *footflaps said* might not apply if your lashed up battery causes a fire……

Without a DNO g99 certificate issued by your batteries manufacturer (mercedes?) You won’t be getting DNO approval so it’s academic really.

The main problem would be the inverter, a stand alone inverter just generates a crude sign wave at roughly 50 Hz and roughly 230v, a domestic solar inverter is syncing with the mains, tracking the tiny fluctuations in voltage as appliances switch on and off and adjusting it’s output accordingly (inc disconnecting if the DNO supply fails).

The BMS is also managing battery health eg on dark winter days ours randomly charges and discharges the batteries to various levels, which I assume is to keep them in good condition.

You won’t be getting DNO approval so it’s academic really.

That doesn’t actually stop you installing it!

Be amazed if there aren’t loads of systems where the paper work was never completed. Not seen any for ours actually – do you get a copy?

Be amazed if there aren’t loads of systems where the paper work was never completed. Not seen any for ours actually – do you get a copy?

I assume you don’t plan on exporting.

As for just not telling them – well if that’s how your moral compass points – that’s on you. Doesn’t make it any less of an obstacle to fitting your system legitimately.(!)

Nothing (physically)stopping you bypassing the meter while your at it!10 minute job including finding the tools.

Be amazed if there aren’t loads of systems where the paper work was never completed. Not seen any for ours actually – do you get a copy?

Yes, you can’t get an export MPAN without it.

December bill was £240 – ouch – but Nov was an estimate so I can say that Nov + Dec was £400. I thought I was doing quite well 🙁

Plumbing has become a hobby. I now think I want some bigger rads, ours are all pretty small.

I have been watching a little more what I am doing with heating but not to the level of detail that Molgrips has 🙂  I nevr used to bother at all – just put inon when cold

I have turned circulating water temp down ( modern combi boiler, old microbore plumbing and rads without fins) and turned the thermostat dow ( 18 not 20) and looking at a thermometer

Observations
It seems to take much longer for the flat to heat up so to get the same temperature rise so the heating needs to be on longer.  I am far from convinced turning the circulating water temp down to 60 has actually saved any gas to get the same temp rise in the flat

I feel really cold when the flat is at 16C even with thick socks on and two fleeces.

Its offices below my flat and post covid they are not in as much – I am obviously getting less heat rising up thru the building

I am far too lazy to actually monitor use properly!  i have an inefficient gas fire that heats one room – I really need to check out if that uses more or less gas than using the central heating

I need to get some thermostatic radiator valves!

Molgripos – there are calculations you can do for rad sizes – that must be right up your street!  IME rad sizes are usually over specced not under.  I’d be surprised if you need bigger.  Bigger rads to compensate for lower circulating temps would be a false saving would it not?  Total energy usuage would be similar?

It seems to take much longer for the flat to heat up so to get the same temperature rise so the heating needs to be on longer. I am far from convinced turning the circulating water temp down to 60 has actually saved any gas to get the same temp rise in the flat

It will. Let’s assume for now your boiler is 100% efficient. It will burn to heat up the water in your radiator system, then switch off when that water is up to temperature. The water will then keep circulating, the rads will be warm heating up the house, and the water will get cooler until the boiler comes back on again. If the set flow temperature is lower, then the water will heat up to that temp quicker but the rooms will get warmer more slowly. But it will even out, because all the heat generated by this hypothetical boiler ends up in the house one way or the other.

Now, your boiler isn’t 100% efficient – there are two things that affect this. The main one is the condensing, so the warmer your return temp the less efficient it is. The other is short-cycling, turning off and on less than say 3 mins each time. The reason for lowering your flow temp is that it also lowers the return temp. If you run it hot, more of the heat from the gas will be escaping through the flue. If your flow temperature is 60C then the return might be say 50C, which is alright. But if your flow is at 50C then the return might be 41C which is much better. You will gain 3-4% efficiency or something.

Your boiler will vary its heat output, so that when you turn it down it will try to turn itself down to maintain a constant temperature in the flow water. The problem is that most boilers don’t go down low enough to match the heat output from the radiators, especially in a small property. If you turn the flow temperature down the radiators output less heat, which means the boiler needs to put less heat into the system. If it can burn low enough to match that heat and keep a constant flow temperature then fine; but if not it will have to turn itself off and on. If it’s turning off and on every 3 minutes or so, it loses a tiny bit of efficiency, but if it’s off and on every 30s it loses quite a bit, like 5% or so IIRC. So if your boiler is very powerful it will heat up the water too quickly and have to switch off again.

The other factor is that if your boiler can turn itself down really low (someone here has one that goes down to 1.5kW) then it will also gain efficiency by having a really big heat exchanger relative to the size of the flame.

The problem with running low temperatures though is the heat output from the radiators might not be enough, so in cold weather you may have to turn it up and take the hit on efficiency. Lower temperatures work better with bigger radiators – or smaller better insulated rooms, or both.

TL;DR the hotter your flow the more heat is leaving your house via the flue, end of. Go as low as you can to get the house to heat up. You may have to run it longer, but that doesn’t matter.

Bigger rads to compensate for lower circulating temps would be a false saving would it not?

No. The bigger the rad, the more heat can be dumped into the room at a lower temperature. So the cooler the return temps, and the more efficiently the boiler works.

If you had say an electric boiler that simply put energy into the water then yes, you’d be correct. But because this is a gas boiler the efficiency of the gas flame/water heat exchanger is a factor; and because it’s a condensing boiler the efficiency is affected by the return temp. If I have bigger rads with water flowing in at the same rate, the water will be cooler as it exits the radiator as it’s been in there longer shedding heat. And cooler return temps = more efficiency.

Fair enough

Might take a long time to pay back the cost of the new rads tho

Might take a long time to pay back the cost of the new rads tho

If you’re paying £2k a year for gas, then a 4% increase in efficiency would save £80/year. A 600 x 900 type 22 rad is at least £75.
Chances are you’re changing to a bigger radiator than this, so even if you swapped the radiator FOC (fairly doubtful) you’re probably not going to save enough to pay for 1 radiator/year.

Might take a long time to pay back the cost of the new rads tho

Yes it might, but we’d have a much warmer living room during that period. I think it’s a single panel 60×90 so yeah the replacements are about £75 which could get ma double panel 60×120 I think and 3x the heat output.

£75 which could get ma double panel 60×120

As I said 60 x 90 Type 22 is £75 at Screwfix… that’s the cheapest one that size.

Why would it be warmer? Surely it would get to the same temp but potentially save you up to 4% off your gas bill.
(plus would you not need to swap all your rads to larger ones before turning the flow temp down otherwise the rooms with smaller rads would be colder. Serious Q)

Surely it would get to the same temp

Yes, but there’d be two or three times as much area to transfer heat from. And yes you are right some of my rads would still be small but not all the rooms have the same heat requirements. It’s a 3 storey house, the downstairs is cold for whatever reason – maybe the front and back door, maybe the existence of the integral garage, on top of the fact that the heat simply rises. The downstairs rads are also last in the circuit so they lose more heat from longer pipe runs; the upstairs rads are the same temp as the boiler output and the downstairs ones a fair few degrees lower. The kitchen rad was already a big one, the hallway one we made big many years ago. The next coolest room is the living room – it’s big and has two tiny rads in it. The bedrooms also have small rads but they are upstairs so warmer anyway; they are smaller, and the rads get hotter anyway. I could put the ones from living room into the landings, on which the current rads are even smaller, but there might not be enough space.

Yes, but there’d be two or three times as much area to transfer heat from.

…. but it’s still the same temperature, it would just heat up quicker! (?)

Re the other information: I’m sure your own property has its own quirks (and it sounds it) but I thought you were advocating everybody change their rads for bigger ones (if ‘normal’ size). I was querying whether you needed to do them all at the same time – it seems you probably do – which is pretty spendy for a potential saving of £80/year.

Combined bill from 27th September to 5th January was £360.00.Thank Boris I got £200.00 of the bill.Come April and the end of the support scheme, I will have to make serious savings.The tories will pay for this at the next election.

but it’s still the same temperature, it would just heat up quicker!

The heat loss from the room is proportional to the temperature in it. The warmer you make the room the more power (energy * time) flows out of it, so the more power you need to put in. Therefore smaller rads might be ok to keep the room at 15C but if I want it at 20C I’ll either need hotter rads (bad) or larger rads. The larger rads will heat up to 45C but put three times as much energy into the room, so they can heat 3x the volume of air to 45C.

Re the other information: I’m sure your own property has its own quirks (and it sounds it) but I thought you were advocating everybody change their rads for bigger ones (if ‘normal’ size). I was querying whether you needed to do them all at the same time – it seems you probably do – which is pretty spendy for a potential saving of £80/year.

Yeah you’re right. Basically, the cooler you make your flow temps, the bigger your rads need to be to heat the same rooms. Wether or not it’s worth changing rads is up to you – I think that in my case I think that one room is under-specced so they can be changed. I can do this myself easily, so I might. I doubt it’ll pay for itself but hey ho. If I were going for the cheapest option I’d just nudge the boiler temp up a bit, lose a few % efficiency until it warms up again.

it would just heat up quicker!

It has to add heat faster than it’s being lost, that’s the key point. Too-small or too-cold rads won’t just heat the room up slower, they won’t heat it up at all because they won’t outstrip the heat loss.

Of course, turning the flow temp up by 10C doesn’t increase the return temp by 10C, because more heat is being emitted by the rads at a higher temp… I’m now back at 60C in this cold weather with return temps up to 52C.

I dunno, I think I’m going to buy motorised rad valves, stick sensors all over everything and create my own smart heating system….

Afternoon. Me here with the 2022 boiler.

I’ve not gone so far as to measure return temps, but the flow is still 47° on mine. I didn’t get the weather compensation fitted so I would have to do it manually and I can’t be bothered. I can get away with this because I have relatively large radiators and a pretty good thermal envelope.

The boiler will modulate as required automatically to achieve 47° flow, down to as low as 1.5kw it often just trundles along like this and makes the contrast with the full bore burn for HW quite noticeable.

In the minus 5 mornings, the house DOES take longer to warm up, but I’ve set the heating up to start earlier to compensate. It’s still a touch chilly, but thats not really a bad thing since it stops lazy teenagers be late for the college bus, and stops lazy adults from just flopping about inefficiently before work…

Does your boiler have an internal pump?

Yes. System boiler. Chosen because its fully integrated with the electronics that decide the burn rate so it all works together. Also covered by the same warranty unlike a stand alone.

That’s what I’d like. Probably a grand and a half’s worth though eh?

My living room temp is at 11.4c at the moment.

Hands and feet are very cold.

Somehow I noticed, central heating working fine, my flat does not retain heat for longer period than before. Damn, my bill will go up again this month.

C.1300.

2700 for a new stainless cylinder, boiler, ancillaries, install and conversion to an unvented system – I took a risk on leakage risks that went my way.

The advantage with the system boiler is you get all new integrated flow control paraphanalia as part of the install instead have having old diverter valves and pumps lying about to crap themselves down the line, plus it all works better as part of the integrated design.

I think you building structure is the root of your problems chewkw. Are you not able to add insulation?

At 11.4° I suspect you’re below dewpoint. Wet walls will get even colder and you are in a downward spiral.

I think you building structure is the root of your problems chewkw. Are you not able to add insulation?

At 11.4° I suspect you’re below dewpoint. Wet walls will get even colder and you are in a downward spiral.

No, it is rented property with the neighbour not around most of the time so not much heating on.

Arrgghhh … yes, feels like downward spiral now. Now I need to heat longer. Where are my neighbour when I need them to heat up the place. arrghhh …

Move or speak to your landlord.

I have the same issue with my downstairs neighbour, I think he works on the rigs, when he is away for 3 weeks my house (1st and 2nd floor “double-upper” as they say in Scotland) is noticeably colder!

I just had a new boiler installed with all the fancy NEST stuff, you really have to keep an eye, it decided the house was too cold at 0200 last night and cranked it up to 20 degrees. My tech support will be over this weekend to help me set it up usefully.

The advantage with the system boiler is you get all new integrated flow control paraphanalia as part of the install instead have having old diverter valves and pumps lying about to crap themselves down the line, plus it all works better as part of the integrated design.

That doesn’t actually sound like an advantage as they’ll all need replacing long before the tank itself does. We must get through a new pump every 5-6 years and the odd motorised valve maybe every 8 years.

Not putting the heating on – how’s it going…?

Badly!! Got home from another week working in Glasgow and living room was 11 degrees…heating on 😂 35 minutes later, and we’ve achieved 14.5. I may have to turn it off again 🤔🤣

Talk to the landlord.
And say what? The government have given me £400 towards my heating, but i spent it all on sticky buns and penny chews. So I’ve no money for heating, and the moisture in the air from showers, breathing and cooking is condensing on the coldest wall of each room.

So tell me please mr landlord, what are you going to do about it?

I can tell you pretty much what the landlord will say. Turn. The. Heating. On.

That doesn’t actually sound like an advantage as they’ll all need replacing long before the tank itself does

It does to me. They’re all in the boiler as service items and thus covered by a 10 year warranty on the new install.

If I had relied on the old stuff in the house that was 12 years old, I would have less efficiency, less reliability and less protection if it failed.