Nickfromwales

The secondary loop is created by tee-ing off each hot water feed, just before it terminates at the outlet. Also, why on earth would you have a bath on the HRC? A few seconds of full flow from the highest flow rate outlet in the building will clear the dead leg in s few seconds max. As the bath is high volume / low frequency, I NEVER have the bath on HRC. Only will I ever put a shower on HRC, if it's literally the other side of the building and then I'll combine the basin and shower feeds to kill two birds with one stone. Rarely will someone be using a shower and a basin in the same room simultaneously.

Usually only in district heating systems, and never in domestic ( not that I've seen in over 25 years of heating and hot water installation ).

Fair comment. The system should be designed to cope with the dwellings requirements, not the designers personal preferences. Your choice. You'll not miss the other 3kW tbh, but I would go with the 18kW boiler if you intend selling at all? There's little difference in price, but those few bucks buys a lot of insurance.

Yup. The only thing missing is flow gauges so you can set the flow rates, but you can do that with a bit of maths ( length of loops vs % that you open each gate valve ) so all good. Nice Reliance TMV on that rig, so that will be plenty reliable for sure.

With 2 Willis heaters working on the above project the house would see 24oC without trying, and 26oC when we'd not babysat it closely enough and a bit of cheeky solar gain had been absorbed. The issue with "cranking up the heat" is the choice of emitter, and the thermal time constant of the dwelling. Most see 1oC temp swings over 24hrs, so there is no summer / winter, and no 'timed' heating event as such. A party would have to be anticipated and the house temp setting increased at least 12hrs prior to, to have any effect on the overall house temp ( if a passive raft is the emitter not radiators for eg ). Then you'll need to 'set back' prior to the party ending, so the house can re-acclimatise afterwards ( and not overheat you when the crowd of 100W heating elements leave after scoffing all the free food and sumping your best vino ). This is very much dependant on the fabric of the build and it's energy performance statistics of course.

I did a full heating install in a 300m2 build, with insulated raft, and it ran at 18.5oC with an outside air temp of -7 with a £35.77 3kW Willis heater. There were 2 installed, but one tripped out over the xmas away period and I discovered it upon my return to site. That was with 2x 200mm open vents through the roof to atmosphere ( where we were due to connect the MVHR unit later downstream ). As above, if the fabric & ventilation heat losses are managed you can heat with VERY little input, so the 15kW device will more than suffice. I would put the UVC on W-plan ( hot water priority ) so it can focus on heating OR hot water vs the 2 combined. You mention a "heat only" boiler, but I'd recommend a "system" boiler so you get the expansion, pump and pressure gauge etc all in one box. Heat only will require a lot of kit outside the boiler so is unnecessarily complicated IMO. Plenty around from £600 upwards, but the Worcester Bosch for a grand is a decent machine with a very low modulation. Intergas and Viessmann IIRC offering as low as 1 1/17th!!

Yup, a load of members have installed away from the MCS register eg self-install. You only need to be MCS to register the installation for the export guarantee scheme.......but; Same as @ProDave, who uses his diversion and strategic consumption to avoid export / promote self-consumption...... which means no mandatory need to register.

Not if you hand the crowds a series of print-out's of the PV production, with a brief of the savings in not importing all of the electricity needs Then it's irrefutable marketing power.

Most of the systems we install exceed our estimates, and the breakeven point is typically year 13.5, so probably year 14.5 when you include the second inverter being fitted when the original one snuffs it. A robust panel ( we're either LG or Solarwatt ) will still be producing a useful amount of output in year 30, so worst case is 10-15 years of "free" electricity after breaking even. The maths do work out for sure, and the real question should be; "how long will you be at the property" for to see this return If you're moving out in 10-15 years don't bother, or just fit a token array ( circa 2kWp ) to offset vampire / base loads and give a bit of kerb-appeal when marketing.

Cool. Tell him to use plenty of screws!!

Do you have the opportunity to pull the lot down? DIY is possible with suitable PPE. Messy, but a far better job than over-boarding. In for a penny

Simples. Get him to write a details scope of works and post it here before starting work. If they can’t be bothered, move onto the next fitter.

Gaps around the lining need the intumescent foam. Small gaps which you can’t foam can be sealed with intumescent acrylic sealant.

+1 to linings coming out. Who fitted them, and did they receive instructions to install to the required openings?

Fire doors Do NOT fail to install the intumescent foam.

If the room is empty, I would recommend pulling the lot down and starting over. Get a friend around, get suited up, and just beat the shit out of it until its all on the floor. A few rubble bags half-filled and sealed, then carried outside, and a couple of bottles of vino to celebrate thereafter. Would give some much needed therapy too .

https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DXQ5UbE-h2vg&psig=AOvVaw3VoqFsJGD6Hzd3SPG3JyiH&ust=1637361517939000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCLiA55X9ovQCFQAAAAAdAAAAABAD

The screws will need to be around 60-70mm long and be seen to be pulling into the surface of the bits of boards so you know they're not just spinning into thin air. If not, it is a waste of effort / time / cost.

Socket or coupler or even barrel.

Honest answer is I don't know how "safe" it would be to leave as-is, sorry. A temporary 'fix' would be to get a trade in who has a functioning brain, who could locate the joists and screw through these boards, through the original, and into the wooden joists, to get a mechanical fix. Then the risk of them falling would be mitigated.

Welsh joke, sorry!

https://www.screwfix.com/p/female-socket-x/77539?tc=FB3&ds_kid=92700055281954514&ds_rl=1249404&gclid=Cj0KCQiAkNiMBhCxARIsAIDDKNUekQc2LPr0XYZlnZpBllCNOCnMqaZTU1AD7MwI9JqB8oeKR1N3QtsaAgMIEALw_wcB&gclsrc=aw.ds ?

If it was, I'd have expected the moisture of the dab and the weight of the new bits of boards to have pulled the lot down already. If it is lath then it's deffo on borrowed time.

Removing this abomination will likely result in the original boards needing coming off. Prepare yourself for this to get worse before it gets better. Offer this chap a resolve. Tell him ( not ask ) that the only way you will let him finish this job will be for him to remove both the new "stuck" bits of PB and the original ceiling and for him to remove the spoil at his cost. Once at a clear ceiling, void of any ceiling boards whatsoever, employ a new person to board and skim ( plaster ) as required. Do you have some available funds to do so?