ProDave

I thought the pink stuff was what goes in the flush water. The stuff you pre dose the holding tank with comes in green or blue, green being the less bad one. But it is years since I have bought any as it lasts so long. If you don't have drainage, you could always did a deep pit in an out of the way bit of your site and just pour it in there. Years ago that used to be standard practice on remote caravan sites, they filled it in at the end of the year and dug a new pit for next year.

Definitely sounds like he has borrowed the neutral from a socket circuit which is most unusual.

Buy the cheapest small touring caravan you can. It will have a toilet, a sink with running water and a water heater. You will need to fetch water to keep filling it's tank, but it will be far cheaper than hiring a portaloo and will give them somewhere dry to have a break etc.

So the hall light is switched from 2 different locations in the hall and the landing light is switched from ONE location in the hall and one switch upstairs? The issue I am sure will be in that switch with all the wires and tape. I am certain you will find it is taking L from the downstairs light and sending the 2 "strappers" (the 2 alternate switched L's) upstairs on a t&e. and upstairs, the landing light is getting it's N somewhere from the upstairs light circuit. That is the normal borrowed neutral scenario. And the solution is usually to take an extra N from the downstairs lighting circuit up to the landing light. BUT the fly in the ointment is you say it is a SOCKET circuit that trips when you put the landing light bulb in. Can you confirm that is really the case? Anyway if you want to test this theory, disconnect the N from the landing light and insulate the removed cable, then connect a temporary cable from the landing light N to the downstairs light N at the consumer unit.

Where is this third switch and which light does it control? the two posted above that appear to be the switches for the landing light?

That depends how competent you feel. At least you can point the electrician where to look if you want to stump up his fee to do it. It usually means rewiring the offending light, sometimes needing a new cable pulled through between the upstairs and downstairs light switches. If you want to have a go, post some pictures of upstairs and downstairs light switches with the fronts unscrewed so we can see the wiring, and the landing light fitting with it's cover unscrewed so we can see the wiring in that.

Do you want to tackle fixing this landing light fault yourself?

He has done a neat enough job of that board. So you have a "borrowed neutral" on the landing light circuit. The usual thing is the landing light get's it's L from the downstairs light circuit and it's N from the upstairs light circuit. But a socket circuit tripping suggests the original electrician was a bit more "inventive" with where he borrowed the neutral from. In any event some investigation and wiring alterations for the landing light circuit is needed. This will have been a pre existing fault, the only issue here is the electrician should have found this as part of his testing before the CU change. I think I would tell him to issue the certificate for what he has done, and find a different electrician to fix the landing light fault, one that is not going to charge £90 per hour.

There are several off there. Are they all tripping? Are they tripping individually or do 2 trip when you turn one thing on? Try and get a picture square on, and one with the cover removed. As it appears to all be "lights" that are tripping, I put my money on borrowed neutral (neutrals between one circuit and another connected)

Our cat flap enters into the sun room, which is an unheated room outside of the sealed envelope of the house. It lets the cat in to a relatively warm and dry place and we let her into the house through what is a good pair of external well sealed Rationel doors. One feature of an air tight house, is you can open one window or door without getting much if any through draught. So in practice but a sealing strip around the door from your utility room to the rest of the house, and you might find the fat flap does not swing wildly in the wind.

You need a new electrician. Shame you did not question this here before you gave him the job. He s only responsible for making the new, or altered circuits compliant with current regulations. The simplest way would have been to fit rcbo's in the existing board if they can still be sourced (i.e not an obsolete make) So what has he done? Post a picture of the CU as it is now. I am guessing a split load board with 2 rcd's? What exactly is tripping? One or both of the rcd's or one of the mcb's? Once I know what you have I can advise more. As for £90 to fault find his own work, the second word in my reply to that would be "off" To test for earth leakage faults you need an insulation resistance tester. As you are not doing this professionally so are not interested in a calibration certificate you can usually find one for not much money on ebay. But it is also very likely your fault is not earth leakage but a borrowed neutral, very common on old lighting circuits.

T&e is fine if not exposed, i.e straight through the wall into the isolator. Flexible conduit is often a better option from the isolator to the ASHP rather than SWA.

Check with your local regs and BCO. Up here it is a minimum of 1200mm by 1200mm flat in front of the door. One (presumably) 900mm slab would not be enough,

From the link to the smart thermostat: Safety Independent mechanical safety mechanism So I expect the thermostat housing contains a relay and the normal mechanical over heat cut out, so it would still comply with G3. But not if you start butchering it to give it a separate supply source.

Yes that is what is required, but I have a feeling the Tesla switch in the OP is not configured like that and would require a certain amount of alteration if it were even possible.

I expect with that limited space by the time you have got the flat area in front of the door, there won't be room to get the ramp straight out. So more likely you will then have to have the ramp sideways, i.e. parallel to the front wall of the house. That would allow you to just have steps from the front of the flat area down to the drive as well, so convenient for everyone.

Keep us posted. It is sometimes difficulty to keep a clear head and diagnose exactly what is wrong.

You need to be clear in what way does the pump not work? Does it just not pump, with power applied? OR does it keep on tripping the RCD so power does not stay on long enough to see if it works or not? Quite likely insulation breakdown on the cable causing earth leakage and tripping the RCD. You need an insulation resistance tester to check that.

You are tackling this the wrong way. If it is excess solar that you are mainly using, then set the immersion thermostat as high as it will go. If you set it lower, then when your tank reaches say 45 it will turn off and your surplus PV will be wasted. So let it just heat as much as it can while the sun is out, and if tomorrow is cloudy and not much sun, you will have plenty in the tank for another day. I would also question if this will actually work for you? Most solar PV diverters supply a pulsed or power limited feed to the immersion heater to match the amount of surplus solar PV. I would expect this smart thermostat will be expecting a continuous power feed to it in order to operate, so I would not guarantee it will work when connected to the output of a solar PV diverter.

It can be very variable. My building warrant was delayed several weeks while we tried to find an acceptable drainage solution, only solved when SEPA finally said why not discharge to the burn. But then when we installed the treatment plant, BC were notified and did not want to inspect any part of that. All they were interested in was inspecting and pressure testing the drain pipe leading from the house to the TP.

You WILL need to check building regs before you go ahead. And sorry I am not up to speed with English regs, but in Scotland, a treatment plant must be 5 metres from a building, 5 metres from a boundary and 10 metres from a watercourse and you WILL need a building warrant to fit one. If your front garden is only 5 metres wide I don't see it being allowed there even if it would physically fit. but you talk about your field, so why not run the foul waste pipe under your garden, under your drive and into your field where you should have plenty of room to fit the treatment plant there? A sketch of your site layout would help. If the company is suggesting something that may not meet building regs then choose a different company.

You need to be sure it will fit in the front garden allowing for all legal distances to buildings, boundaries etc, and you have permission from the EA to discharge to the ditch.

That is the very last one I would want. You don't want to be the person replacing a jammed gearbox in that, and neither does anybody else. So I guess it's go it alone, BUT that relies on you having enough of your own land to do that, access to that land to get a digger in, and access to somewhere to discharge it to. If you need consent from your neighbours for any of that, then it is going to get difficult.

I would go for a new shared system but make sure it is a treatment plant, NOT a septic tank, and choose one that works with an air blower to agitate the contents, not the sort with rotating mechanical parts.

I read that as 7336 total maximum heat loss, which seems high to me but is in line with what the MCS estimate says. I found similar calculations in my SAP were 2 to 3 times over the actual real world heat loss.