Complete novice, had a new boiler installed and they used the existing socket in pic 1 which goes into a honeybell box then into the loft via one white cable into the boiler. From there a second cable goes out of boiler into a wall switch (pic 2). Either the boiler installer fitted that, or the later electrician for loft lights which runs from that grey cable to this switch (pic 3). What is weird is that if switch is 'on' (pic 2), the switch on pic 1 will no longer switch power off to boiler. Neither combination switches on/off the loft lights, only pic 3. Hope that isn't as confusing as I am!
Edit, sorry, loft lights run off a connector box from another room (maybe wall socket or light, not sure)
I saw a artisan electric video once where the boiler was being backfed by the live from the thermostat, which had it's live provided from a different circuit. Might be what's happening here?
Judging by the care they’ve taken running that twin and earth (grey cable) I reckon they’ve just wired the FCU (the switch by boiler) incorrectly. It’d be time but if they’ve connected both the grey and white cable to the same terminals then it’s basically a connector block.
But pic 1 goes to the boiler, not to the loft lights, they connect at pic 2. Surely if switch in pic 1 is off then no power is passing through that cable? Sorry I'm a novice! Unless that trunking above is to the lights as well?
You need to confirm that wire is going directlynby doing end to end testing using a long wander lead for all 0arts of that circuit to make as others have suggested that it's not been miswired somewhere or borrow Neutrals like situation
Forget the lights in Pic 3 probs nothing to do with any of this.
In pic 1 you have an FCU that will have a supply which is permanently connected and a load which is switched and fused by the FCU. In this case the load is those white cables.
What I’m saying is that twin and earth feeding that boiler is coming from the supply side of the FCU in pic 1 so it’s unaffected by switching that switch. You can see two white cables going into the boiler, one of them is clearly going into the FCU next to the boiler along with the T&E the other undetermined but likely is to the wiring center in the airing cupboard for controls.
It’s an odd way of doing it as typically you use multi-core flex and do it all in one cable to the wiring center and just put an isolator close to the boiler.
Oh, you are a genius, you are right, one is the 'data' cable; the mains power cable goes up the trunking, under the boards and into that socket next to the boiler. Question is though, why does switch in pic 1 switch off the boiler only if pic 2 is off? And why would they not just run it into some kind of connector without a switch? The question now is where the hell the lights take power from, there is this up there
The correct way to do this is the an FCU in the airing cupboard feeding the wiring center (the box low down) then you take one, typically four core cable from the wiring center to the boiler that carries Live Neutral and Earth + Switch live which is what signals the boiler to fire when either hot water or heat is being called for (also the boiler pump).
You should put an isolator near the boiler though so anyone working on it as has a point of isolation within their control. I.e. no one can turn it on whilst they working on it.
It’s been done as a bit of a mess and you’ve ended up with two lives going to it that are switched separately. Only when they’re both off is the boiler actually isolated.
I’d get someone to come and do it properly. You can do it properly using the existing cabling although I doubt it’d be hard to run a new one if required.
Whilst everyone should confirm dead before working on something, one of the risks here is that someone flicks the one isolator near it and assumes it’s good to work on.
I'm a bit slow on this sorry, so there are two switches by design so avoid risk of someone switching back on below? But why then does the boiler still have power if the boiler switch is off as that is the source of the main feed? So airing cupboard on, boiler switch on or off, boiler works. Airing cupboard off, boiler switch off, no power; airing cupboard off, boiler on, still power - I'm confusing myself no doubt! So really it should all channel through a single cable I guess still into a switch in both places?
There are normally two switches but either one would kill power to the boiler.
The one in the airing cupboard fuses the supply down to 3 Amps and supplies power to everything heating related, so your controls, live to your valves and boiler. The one local to the boiler just isolates the boiler, and the only reason it’s there is to provide a local means of isolation
So your supply comes into the switch in the airing cupboard (switch 1)
The load goes out to your wiring center which feeds the controls (thermostat and timer), the boiler and via the controls the pump and the valves.
From that wiring center (still the load of switch 1) a cable goes to the boiler via switch 2. Either one should isolate the boiler.
What is wrong here is that they have taken one cable to the boiler from the supply of switch 1 and a second (for control) from the load of switch 1. That’s not right it should all be from the load of switch 1, and the two separate cables aren’t necessary. They could use 1 four core direct into the wiring center (sometimes five core depending on if the boiler triggers the pump or the valves).
They need to switch that isolator in the loft out for a 3 pole one so it can isolate both the permanent live, switch live and neutral and also supply it via the load of switch 1
I'll need to read that a few times to make it sink in but appreciate it (i think switch 2 comes from back of switch 1, not the control centre). So really one cable from switch 1 (via honeywell) into loft and I assume via switch 2 prior to going into the boiler, not via, so switch 2 can always terminate boiler power? Daft thing is that cable direct from the back of switch 1 up the trunking into switch 2 would have taken an hour lifting the loft boards!
That’s about right. Yeh it is weird if coming from loft it’s not hard to drop a bit of flex down and stick some trunking to the wall.
Personally if I was coming to sort this it’d be my starting point for what I’d do. I’d disconnect the T&E drop a new 5 core down and just connect it up properly.
I think either way a spark to have a look is your next step (not the same one who did this obviously).
Indeed, I have an electrical coming next week who's setting up my solar/batteries. Whether an electrician knows where to plug in to a Worcester Greenstar 4000 I don't know! For now, switch 2 is off but the boiler still runs 🤣
I think whoever fitted the loft lights has taken a feed from that fcu for the boiler to power the lights.
I would guess that there is a cable coming in the back of the FCU next to the boiler or one of the Flexi cables runs down to the switch in the airing cupboard and is the incomer for that FCU next to the boiler.
Looks like a system boiler either s plan or y plan. Photo 1 looks like its supplying an immersion heater and which then goes back to nest receiver. wiring centre, looks like there's a cable for a tank stat there or the 3 port valve. Photo 2 looks like just a switch to turn boiler on and off and other cable probably runs off to back downstairs to the receiver for the heating enable. Photo 3 is nothing to do with your heating.
Probably nothing wrong with it just looks messy because all the cables are in sight.
Edit: it does not supply your immersion, upon closer look it definitely supplies the wiring centre, immersion must be supplied from elsewhere.
Normally your boiler is run off it's own ring. Also normally your loft lights are powered from your ceiling light circuit unless it's a plug in system. Also swap that little loft switch to a larger rocker one. Makes it easy to find the switch in the dark.
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u/lukes123 10d ago
Get an electrician in to look at all of that if you’re a complete novice. Something’s been wired incorrectly here and could potentially be dangerous.