Is there an easy fix,, Electrical prob..

That sounds like an RCD then, is it possible the lighting fault started when the RCD was fitted, not when the central heating was fitted? Are all circuits in the house going through the RCD, or just some of them?

When people have been referring to 'borrowed neutrals' they mean that e.g. as in your case the live for the landing light is taken from one circuit, but the neutral for it is taken from a nearby circuit that is more convenient, but nevertheless the wrong one - an RCD can "see" this as a fault.

As others have hinted, I don't think you have the knowledge to fix the problem, but at least you are in a better position to explain to an electrician that "the RCD trips when the landing light is used" rather than "the tripper trips".

If do you feel you need to fix it yourself rather than get someone in, it's not impossible to learn, but suggest you read through archives here for safe working, RCDs, two-way switching, borrowed neutrals, and old house wiring, take photos of everything before you touch it and ask again regarding what you intend to do ...

Or rather, this /may/ be the cause of your fault ... too little info to tell.

no :)

I dont

NT

Ok,,

So,, two lighting circuits,, with the positive feed from the downstairs circuit.

With a borrowed neutral from another circuit,, Every thing is hunky dory-until i swtch the upstait hall light on and the rcg takes a hissy fit because he aint connected to that circuit as well...

The Rcd is supposed to be connected to the downstairs lights and bathroom fan alone,,

Surely, the borrowed negative being used, will be borrowed from the upstairs light circuit.

Where will an electrician have picked up the wrong negative,, fusebox or in the loft,,

What if the two lighting circuits were made common,,?

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It is beginning to sound like a borrowed negative is the probable fault..

As yet, One does not know where it has been borrowed from..

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Its the same old fuse box,, with two new wires leading down to rcd.

....

single RCD, either for whole house or a newish circuit

sounds like 1950s twisted pair cotton covered rubber. A pic could clarify

'30mA' means an RCD

possible

we're a way from knowing yet

a clear pic of fusebox area could help

almost certainly. Need to sort out some basic facts first.

NT

Clearly we've no idea if thats the situation or not

What if you stop tripping and help us get some real facts.

NT

Then you solve the problem.

Before we go too much further, could you tell us if our consumer unit is a split load one:

or if recently fitted, then it might be one of:

I don't think it's either John. The OP says that just the bathroom fan and downstairs lights are on it - so I think it is a standalone unit

Well,, was just working on that for meow,,

here are the units,,

an eight fuse version of this

Old Wylex fuse box.. ///

With a fused RCD spur for the downstairs bathroom fan and lights.

same as this one..

Power Breaker H92WP-C White RCD Fused Spur unit,

When I switch the upstairs hall light on, the breaker trips which puts the downstair lights off and the fan in bathroom...

This only happens when there is a bulb in the holder,,

Certainly, there could be some old wiring that needs replacing as in old style braided dropper wires,or maybe the plumber damaged some wiring,,

I favour the borrowed negative theory at this time. So far, ive had a wee look in the light switches for clues, downstairs double switch live feed jumped over from downstairs hall light

Ive not located negative connection yet..

I suspect, probably from the upstairs light circuit..

.. Im considering this Proposed action,

temporarily disconnect negative from upstairs light circuit at the fuse box.

Switch the light on and see what happens.. Obviously,, I would not expect the light to come on, but if the tripper did not go off..

Would that not indicate that the borrowed negative had been identified'' ?

I lost my meter along with my home..

trying to live without my meter..

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A white RCD fused spur has been fitted to serve the bathroom fan and light,,

Very much like this

On Sunday, November 16, 2014 6:43:47 PM UTC, nuther didint post link,,

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To reach the ceiling rose and replace the old fittings and wires, would require a plank over the staircase onto a pair of steps, with no parachute..! it certainly needs doing, but it might not fix the problem..

The jobs I used to do,,

Some off my stuff

here

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ok I think I can see a plausible mechanism...

There was previously two lighting circuits each with its own fuse, and no RCD.

When the shower fan etc was installed it needed RCD protection, and since it was to be powered form the downstairs lighting circuit (as is common with fans that need triggering from the lighswitch), they had to install a RCD spur, and connect the whole lighting circuit to it. So far so good, it means the fan and the downstairs lights are now all RCD protected.

However, the downstairs lighting circuit also feeds a lamp upstairs, and alas the neutral connected to the same lamp returns directly to the fuse box without going through the RCD. So the moment the light turns on (and there is a bulb in there). the live connection to it comes via the downstairs circuit and hence the RCD, and the neutral was probably connected to the upstairs lighting circuit that is not connected via the RCD. Hence the RCD sees and imbalance. and does what it is designed to do and trips.

It won't be visible at the switch - that normally only has live and switched live. However if there is only one live in (and the jumper wire is a big clue) then it suggests the live from one circuit only is being connected to both switches.

Correct.

Indeed.

Multimeters can be had for under a tenner.

O what fun,,

Mike..

Quite possible. Also possible the RCD actually feeds the fusebox and the 1950s wiring is kaput. We're not going to know until the OP gives us the requested info.

NT

If it is a borrowed neutral problem (from a 2nd lighting circuit), putting both lighting ccts onto the RCDed feed would solve it. If its not a 5/6/10A circuit you'd also need a fuse for it.

NT