Dillsue

Our calculated heat loss is 8.5kw at -2. We put in a 7kw LG Therma V and it's kept us warm all through this winter but it's worked very hard for the few days it's been freezing. I was wary of oversizing for the reasons JohnMo mentions and was wanting to install an 8.5kw Ecodan to exactly match our heat loss. The LG came up on ebay secondhand for a few hundred £ so went for that with a plan to run a fan heater or light the woodburner if the smaller LG unit couldn't cope. No fan heater or woodburner needed as the smaller LG has coped throughout and I'm very pleased with how things have worked out. We'll hopefully have benefitted from efficiency gains in running a smaller unit but the older Therma V doesn't calculate COP or energy produced so I'll never know for sure.

I've not looked at it and have no need to but good on you for doing it and making it available

If you go for 2 single phase HPs they can likely be wired on separate phases so you'll use 2/3 of your 3 phase supply;) Your spark will sort that out and hopefully balance the third phase with other house loads, as best he can. On the sizing of your heat pump, if its sized for -2 as ours is, it will rarely be running in those conditions. This winter we've had -2 for 1 night, zero for maybe another 4-6 nights and the rest above zero. With a single big unit, especially if it's oversized, you'll likely hit its modulation limit quite often and see short cycling so youll be paying higher bills for the life of the HP. I'd seriously think about getting an independant heat loss calc done from the likes of Heatgeek just to sense check the size of HP needed.

Our solaredge inverters run way beyond that at default settings:) Grid can be up to 253v so you'd need to legitimately run higher than that to export anything.

If you're paralleling the inverters and they are grid tied to the house AC, then you can connect multiple inverters, subject to the usual DNO restrictions. Unless there's some quirk of the inverter, they just autonomously pump power into your house/grid. We've got 2 PV inverters and soon to have a battery inverter all running in parallel with no control between them. Just watch out for voltage rise in the house if you're producing alot of power. The DNOs obligation is to limit the voltage at your service fuse to 253v. If you're trying to push alot of power into the grid through undersized cabling within the house, then you might find the house voltage rising significantly!!!

Solis confirmed you need a DC input from either or both the PV or the batteries....will have to get the batteries charged and assembled!

If you look on the ENA Connect Direct type test register there's a few grid compliant V2x chargers listed. Octopus and Indra have a few and one or 2 others but not many.....nothing from Sigenergy. If your car has V2L with 240vac outlets for camping/power tools, I beleive you can wire these to the generator inputs of Victron inverters fitted with genny inputs. Could get you up to 3kw out of the car??

Thanks for that. It adds more confusion as within the setup options you can configure the inverter to run without a battery!!! Did you have any PV input when the battery failed? I'm wondering if it needs a DC input from either PV or battery to power up??

Anyone know if a solis S5 EH1P 5K-L hybrid inverter needs to have active PV connected to start up? I want to test the comms to its export meter and don't have any PV or battery connected but the unit is dead with just the grid AC connected and the on/off switch in the On position. Anyone know if these units will power up with only the grid AC connected??

You'd need to ask the manufacturer

I think the building control specs I posted earlier are based on 25kg/m2. 10-11kg/m2 sounds quite light ??

Building control tables for C16 floor joists suggest 5x2" at 400mm centres will span 2.5m and 6x2" at 600mm centres will do similar. The 4x2" you've already got will likely carry several tons at the ends where they bear on the walls so bolting slightly deeper joists to the existing would likely be fine to prevent sag without bearing the new joists on the wall. If it were mine and the underside of the existing joists were pretty flat I'd glue and screw 2x1" to the underside of the existing joists to make a basic laminated joists. Another option would be to screw long strips of ply to the side of the existing joists.

So that would make it a G98 compliant unit

G98 has more onerous/specific requirents than those in the harmonised standards associated with the various EU/UK directives. As an example you can get a CE/UKAS marked inverter that meets all the requirements to legitimately be sold in the EU/UK but you can't connect that to the grid without complying with the countries grid connection standards, G98/G99 for the UK

For some maybe. Out of the box our solaredge ones are higher!!!!