Dillsue

You've already got a "petrol pump", you just want a bigger/second one

Is this additional supply for a commercial/hobby workshop?? When we wanted consent to export more PV our transformer was upgraded for free as the old transformer was deemed undersized for a modern house. Your DNO may well see a difference in a domestic supply and what they class as a commercial supply. If you tell them you want to have a heatpump for the house and an EV charger you might find they'll upgrade the supply to the house FOC. You can then run a supply to the workshop from the bolstered house supply. You'll likely have enough spare capacity to run the house on a heat pump:)

That depends on how you value the cost of keeping your gas/oil boiler. If you do nothing then the cost of continuing to burn fossil fuels needs to include your share of the following current and future expenditure- Government spending on mitigating climate change Electric and water companies spending on mitigating climate change Uninsured property damage due to withdrawal of insurance for weather induced damage Increased food costs due to drought/flooding Limited payments to poorer countries to help deal with climate change Potential unlimited payments to countries impacted by climate change following the ICJs legal opinion on industrialised countries being sued by those impacted by climate change.

You said to fit a gas boiler as there were no downside risks to doing that. I said there's potentially massive risks if you've got kids. In reply to your "Eh?"- If we continue down the road of burning fossil fuels it will be our kids that have to deal with the fallout of us kicking the can down the road. In the same way that the current generation is having to suffer the cost of dealing with our parents limited action. All expert opinion I see suggests that the longer we leave dealing with climate change the more expensive it's gonna be, which our kids/grandkids will cop for.

When you consider the cost of heating with oil/gas are you including the current and future cost that we'll all have to pay to deal with a worsening climate crisis due to continued burning of fossil fuels?

You probably need to forget the power of the boiler you've got already as historically massively oversized boilers cost peanuts and ensured householders were toasty hot without the need to do any design work. Our heat loss is around 4.5kw but we have a 25kw lpg boiler as that was the smallest size available when it went in 20+ years ago.

My brother has just bought a new build from a "reputable" Shropshire Home builder. On the entrance to the builders compound there's a large board reminding the various trades of how some of their basic tasks should be done to ensure quality. That suggests to me that the builder knows they have issues The builder wouldn't let my brother snag the place before completion so it was done once they'd moved in. Months later after a complaint to the directors the long list of snags is getting progressed. Two of the more memorable snags were a 1.5mm step in a kitchen work surface joint and cable insulation nicked so the live incomer was exposed in the consumer unit. I think lots of people are happy in their houses because they don't know how things should be done or our standards have dropped low enough that poor workmanship is the norm.

There are potentially massive risks if you've got kids

If you want to lessen the risk then use a heatgeek outfit. You may or may not find a good HP install outfit but that's likely a bigger risk of things not being right than using a heatgeek outfit. If you want to research and understand more about heat pumps then get your boiler repaired, do your research and get the HP installed next spring

At 35deg C+ you'll know they are on but they won't feel toasty hot like a typical boiler fed rad. Do the calcs. Your heat geek calcs should give you loss per room so you know the output you need. Use the manufacturers figures to give you the adjusted output you need at low temps and you can then pick your rad/rads. Any rad without a convector is going to be less efficient than the same rad with a convector but you won't know what you need without doing the calcs

You are right that BTUs are BTUs and watts are watts. No matter what the style it's the output that matters, but..... The output of the rads needed as the flow temperature drops increases quite considerably. Manufacturers supply correction factors for their rads at lower flow temps so once you have the loss for a room you can size the rad for your planned flow temp. I'm designing at 35deg C and have just finished installing the last of the replacement/additional rads and there's some big uns gone in!! Unless a room has a very low heat loss the fancy tall rads without any convectors will likely give a very low output at HP low temps. Do the calcs and see for yourself.

?? It's their £7.5k isn't it?? So long as you've given the installer any docs/info they need surely you getting involved with Ofgem is going to muddy the waters??

Absolutely. Alway do correspondence from the outset in writing and that's not necessarily pen on paper.... text, WhatsApp, email are all written records that you can go back to weeks/months/years later. The moment there's any hint of issues arising, make sure you've backed them up!

If they said in their quote they would handle the grant application but they've not provided OFGEM with information and the application has lapsed then that's entirely down to them. I'd politely explain this to them and politely suggest they get their finger out. I wouldn't worry about any small print saying they can reclaim the grant sum from you as that would likely only be enforceable if the failure of the grant application was outside the installers control, which it doesn't appear to be. You seem to be in a good place, other than things not going smoothly!

If the company said they would handle it then leave them to it and definitely don't pay them in lieu of the grant. Just be conscious that if you get arsey with them it may impact any warranty work so keep things amicable, as best you can!

As I understand it you can self install a system but the design and commissioning needs to be done by an MCS registered outfit. That's how the MCS umbrella scheme that we looked at worked.

If you want an accurate sense check on heat loss calcs borrow enough electric fan heaters to match the calculated loss, spread them round the house and heat the house with them for 24/48 hours during a cold snap. If you log the external and internal temps hourly you'll be able to see if the heaters can keep the house up to temp. Our calculated loss at -2 was 4.6kw and 4.1kw of fan heaters kept the house just below design temp when it was 0/-1 outside. Gave me a good degree of confidence that the 4.6kw calculated figure was good to work with.

Thanks for all the info and comments. We'll suck it and see with existing coil for the next winter and fit a pumped PHE next year if we hit problems.

We have a relatively new open vented DHW cylinder with indirect coils for solar thermal, WBS and LPG boiler. Were adding a 7kw Therma V ASHP and retaining the cylinder as its a waste to swap it out and there's no BUS/MCS involved. I'm going to try the HP using the existing boiler coil at .44m2 with a back up plan of adding a PHEX if the small coil doesn't work or becomes costly. We're currently on Octopus Go so can run the DHW overnight in the cheap period so even with a poor COP it's unlikely going to break the bank, but I would like thing to be as efficient as possible so..... The cylinder is 2 metres tall and I've got space to the side to fit a PHEX and tap into the CW feed at the bottom and HW outlet at the top with predominantly vertical pipework. What I'm pondering is if the circulation through the PHEX/DHW would work with gravity convection alone without its own circulation pump?? Anyone done it or know if its possible/impossible??

Here's solaredges take on bypass diodes https://knowledge-center.solaredge.com/sites/kc/files/se_technical_bypass_diode_effect_in_shading.pdf

There was a long thread on here a while ago on net metering and I think it was eventually shown that the net metering only works if youre exporting at exactly the same time as you're importing. If there's 1kw load on L1 and at the same time 1kw of export on L2 then no import or export gets recorded. If there's 1kw of load on L1 and no export on L2 then the meter starts recording the import. If the L1 import stops and 5 mins later 1kw of export starts on L2 it doesn't cancel the import already recorded on L1 Be nice if it offset total export against total import but that old thread suggested it doesn't. There'd be a massive scramble for 3 phase connections if it worked that way!

Got the tee shirt for the winter outage, with young kids at the time, and never been without a genny since. If you've got a working non electric heating system now, don't replace it but add a HP to it and use the existing system as a backup to the HP. Existing system will likely run off a small genny which will keep the heating, lights and telly going. Heat pumps are complex technology and it's you'll do well to get a quick fix if something fails so having a backup for power cuts and HP failure is a nice place to be, for me anyway:)

So even working with manufactures guidelines doesn't guarantee flawless operation. Interesting observation

Our therma v needs a minimum area around it of 2100mm x 1300mm for operation and that includes 700mm at the front for maintenace access. 700mm might be OK for a Korean midget to work on it but I used at least a meter to wire it. That would give an area of 2100mm x 1600mm before shrubs/fence/screen. That's quite a chunk of space in a small garden. It's a fact that some people find them intrusive in small gardens as our HP came from a plumber that had removed it and refitted a gas boiler for the very reason the new house owner didn't want it in their garden!!

In your shoes I'd have no problem putting it on the roof as it's just like the 1000s of AC units on all manner of buildings. My only reservation would be having it bearing on the roof below with the risk of vibration being transmitted through the roof. As you suggested I think I would hang it off the wall or or on a pair beams spanning the roof and supported by the wall either end. At the distance it is from the neighbours, I don't think I'd even mention it to them