Dillsue

Collecting parts at the moment. Once it warms up will swap/fit new radiators and then get the heat pump fitted. We're having a hybrid system with WBS and LPG boiler as backups so aiming to have a slightly undersized HP with the WBS topping the heat up on the very few freezing days we have.

My experience with Cool Energy is they massively oversized our heat pump suggesting a 16kw pump for a 6.5kw heat loss. When I gave them the detailed heat loss calcs for comment, they never replied. There's a recent thread on here where they offered a 10kw pump for a 3kw heat loss. It's likely that sort of oversizing and attendendant high running costs are leading to the bad publicity you're reading.

I think the dilemma is whether you can put self installed which Roger wants to do

It's a G98 notification so export is already happening and an "installer" has already done the work. In theory the only legitimate answers are Building Control or a part P spark but some DNOs do accept self installed;)

The industry(power distribution) is all for best practice and asking for installers details/qualifications sort of drives that but reality is your DNO ain't really interested in what goes on the other side of their cutout/fuse. Thats BC's/part P's domain. For a G98 the system is live so the testing/certification horse has already bolted. For G99 you could be submitting months in advance and not know who your installer will be so quite legit to put N/A or N/K.

It was the cool energy quote at 10kw that I commented on. I had a similar daft quote from them

Possibly less than 75m2 with the loft.

Would need at least a 300mm slab over 75m2 to gobble up 57 ton so not your average build

I'm guessing a HP heating 57 tons of concrete isn't gonna be found in your typical British home??

The heat geek Web site suggests a range of 40-65 w/m2 for a renovated house with CWI and DG so your 9kw loss is based on their worse case. Using 40 w/m2 gives you a 6kw heat loss. If you allow half that figure for your new build extension then you're up to 9kw so a 12kw heat pump should be more than adequate and likely oversized. The more I read about heat pumps the more I beleive they should be undersized rather than oversized for max year round efficiency. If there's concern about being cold for the few days of the year it's freezing then keep a £20 fan heater handy

I was commenting on yorkieselfbuilds 3kw loss and 10kw pump

So you've got a house with a max heat demand of 3kw and they're suggesting a HP with a minimum output of 4.89kw. That pump is likely gonna be short cycling for its whole life, cost you alot to run and pack up sooner than it should.

Nope. They're likely greatful that you've bothered to tell them.

I don't know what UKPN ask for but the ENA G98 notification that they should be using doesn't ask for the cutout size. Maybe check you're using the correct forms?? The ENA forms are all available on line and it's likely G98 form B you should be using For the export limitation that should be built into a G98 compliant inverter. Are you using an SE3680H inverter or smaller??

With G98 it's notification within 30 days after commissioning, so after switching on.

That's exactly where we ended up with an MCS cert but the DNO having no record of the install. If SE have confirmed the inverter is G98 compliant then steam on with the notification.

G98 is a notification not an application. How do you know the G83 wasn't registered? Our DNO had no record of our G83 install but admitted that it doesn't necessarily mean they didn't receive it!! If your inverter is an older one that is G83 compliant but not G98, you might run into problems submitting generation a G98??

The FIT rules changed a few years ago and aren't necessarily a blocker to batteries. Physical constraints may but not FIT

Have CE done their MCS design to size your heat pump at 10.5kw? Did you or anyone else check their sizing?

Shame things haven't worked for you as it's so frustrating to have conflict. As in all walks of life, money talks so don't pay anything else until they've completed or you agree otherwise. For extra costs get a breakdown from them to understand what they are claiming for then go back to their quote/tender and see what they allowed for. If it says estimate or there's a quantified bill of materials then they may well be justified in claiming for extras but you need their breakdown of extras to understand the claim. In terms of delays you need to work out the realistic costs of the delays to work out of its worth getting into a fight with them. If you've got other work going on, fighting with 1 contractor over what may realistically be a few hundred pounds might not be worth the aggro. Remembering that you want them to honour any warranty and set the system up properly- having a fight over a few hundred pound might jeopardise aftersales

If your neighbours install solar in the future and everyone's systems start tripping on sunny days, who do you think is going to get shutdown when the DNO investigates? It's everyone's grid so why not stick to the rules and keep it working for everyone's benefit- you'd likely be a bit miffed if a neighbours unauthorised system kept causing yours to trip. In terms of enforcement, look up the National Terms of Connection which you signed up to with your electricity supplier.

Never looked at air tightness measuring but do you not need calibrated pressure/flow meters?

I'm just looking at factoring in ventilation losses and am struggling to understand suggested air changes! Seems a figure of 0.5 ACH is reasonable for a reasonably well sealed house. If I use this figure it puts the heat loss up by about 50% which is having a massive impact on radiator sizes needed to run at 35 degrees. If half the air in the house is replaced every hour that's 4 complete changes of air in the 8 hours were in bed. We don't have the heating on overnight as the house holds its heat fairly well. Seems implausible that the house is getting 4 changes of potentially freezing outside air overnight or it would be freezing next morning, which it isnt. Only explanation I can see is theres enough thermal capacitance in the fabric that can reheat multiple changes of air?? Is 0.5 ACH actually what happens or is that a figure the B Regs want you to aim for??

I don't know about Tigo or any others but SolarEdge has full monitoring of each optimiser/panel so you can see individual panel production. I think you can set alerts on their monitoring platform to let you know if any stop producing

I think panels are very reliable but if you do get a faulty one how do you know which one is faulty without monitored optimisers? Remember that panel shading can be bird s**t, algae growth, passing clouds, neighbours trees growing, future telephone pole etc etc. Optimisers allow easy expansion using panels of differing wattage. They also allow panels on the same string to face differing directions without reducing collective production. If you're using SolarEdge optimisers, batches come up on ebay at a fraction of retail price so don't have to be painfully expensive