Dillsue

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

Isnt a large part of our energy woes the fact that Joe public neither understands or cares about the realities of energy generation or delivery?? Having to pay a bit more attention and understand the cost and effort of delivering power at peak times might help reduce peak demand??

Borehole=eureka! I'm currently battling with Hafren water over a 76% rise in water only supply over the last 5 years and 100% increase if I include the current bill. A borehole sounds a dream come true but I guess there's a fair wedge of an outlay.......and regulation?

Not sure about that. The DNO will know local grid demand and supply characteristics which the suppliers won't. I think its more likely the DNOs will be managing any grid balancing, maybe via suppliers, but it would be the DNOs calling the shots?? It's not just the total number of EVs that influence this, it's the number of EVs that support bi directional charging, and those where the owners have bought a bidirectional charger, and those where the owners have gone through G98/G99, theres more to it than just owning an EV. Whilst a growing number of EVs may support bidirectional charging I think it only going to be a (small?)proportion of owners that set themselves up for V2G, under the current framework. Maybe in a few decades once ICE cars have gone and there's greater public understanding and incentives to hook up your cars battery to the grid will things need managing differently

Aren't we in that situation now with home batteries that can be exported whenever the user chooses? Given that a V2H/G charger will either have a G98 cert or need G99 consent it's likely DNOs will be limiting or involved in what can be exported?? If thats to be a variable limit then I would guess it will be DNOs controlling chargers rather than suppliers???

Could be, I don't know the details of V2G and if it's entirely regulated externally or can be forced to export by the user??

The CHADEMO interface is very limited in Europe and I don't think any new cars are using it. I think any V2H/V2G development in Europe uses CCS. As I understand it any charger, home or commercial, is specifc to the interface. I think there's someone who's developed and CADEMO plug/interface that can draw on the cars battery but I think it's a Fred in a shed job and quite expensive??

Might be mistaken but I understood V2H and V2G were the same but V2H had export limitation set to zero??

Gen 1 and 2 leafs use CHADEMO for bidirectional charging and I don't think anyone is likely to develop any more V2X kit for CHADEMO in Europe. I've been fruitlessly looking for an ex trial V2X charger but those that come up are expensive and seem to be locked to the original trial?? I think there's hacks that involve altering the car but how reliable/safe/legit they are is anyone's guess....the US one I saw wouldn't cut it over here