Power for heating controls. Double pole isolation needed?

[Colin Stamp]

Hi all,

The slowest re-wire in the history of the universe continues...

The next circuit in the firing line is the heating controls (bog standard Y-plan). My previous heating systems all got their power from a socket ring via an FCU with a 3A fuse, except the current one, which has a 13A plug-top! I'll be putting in a dedicated 3A MCB for the new circuit and I was wondering if I could dispense with the FCU.

The MCBs I'm using do say they're suitable for use as isolators, though they're only single pole of course. The boiler can have its own FCU if the instructions specifically ask for a 3A fuse.

So, would it be a big no-no to leave out the FCU? I'd put one in, but I'm having trouble thinking of a sensible place for it to go...

Cheers,

Colin.

[Dave Plowman (News)]

It's usual to have an accessible (and visible) isolator for service purposes. A boiler repair type might refuse to work on it without one.

[Dave Plowman (News)]

On my Viessmann system boiler, no such thing. All the connections needed are internal. So just needs a power feed. I made this a 13 amp plug and socket - even although it is on a dedicated radial.

[Heliotrope Smith]

Should be a 2 pole fused spur or unswitched socket with plug (fused 3 amp). As close as possible to boiler is prefered.

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[Dave Plowman (News)]

Just curious, but why does it matter if the socket is switched or unswitched?

[Andy Burns]

I suppose it it's unswitched you have to unplug it (isolating it fully) to work on it, if it's switched (likely only single pole) you could be tempted to just turn it off, and leave the neutral connected, and would be at the mercy of someone colour blind, or ignorant wiring it ...

[Heliotrope Smith]

Andy Burns wrote in news: [e-mail]:

Thanks. Yes that is the reason. Could be dangerouse working on appliance with neutral still connected.

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[Colin Stamp]

Hmmm, the boiler is right out on a limb, wiring-wise and it's not the only bit that might need servicing. If I have to put in an isolator, I'd much rather it went in the airing cupboard, some distance away but next to the pump, 3-way valve and wiring centre. It seems to make more sense, especially as the boiler will have its own isolator anyway. Or is it that heating engineers are trained to look next to the boiler for something to isolate the whole system?

Cheers,

Colin.

[Dave Liquorice]

Well some of us have slightly more complex systems...

is incomplete the top row is two RF room stats and two channel time switch. Next row down two wiring centers the slot is for the solar controller. Then four DP isolators for boiler/pump, stove controller, heating system and solar system. Immersion switch and unswitched socket with 3A fused plug to feed the lot (except immersion...). The stove controller is now bottom left corner.

Like wise, mine is like that so it's easy to connect to an extension lead and generator. Yes it has been used that way, in anger for 36 hours, and the system has only been in about eight months.

[Colin Stamp]

Mine seems to have been done like that so you can unplug the system to allow the kettle and toaster to both be used at the same time. You can then have a cold shower the following morning...

Cheers,

Colin.

[Heliotrope Smith]

Colin Stamp wrote in news: [e-mail]:

There may be ONLY ONE isolator for boiler and controls!!

It is a bloody nuisance to have to keep going up one or more flights of stairs to isolate the system when trying to find faults on the boiler. (But is not unknown).

Oh! My poor f***ing legs!!!!!!!!!!!!

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[ARWadsworth]

Have you got a reg for that one?

AFAIK there must only be ONE COMMON isolator but local isolation may be allowed.

[Colin Stamp]

That'd be a pain. I'd have thought clear labeling would have sorted out any confusion. Still, if I can't have a boiler isolator then fair enough. I'll just have to get a more hard-wearing stair carpet :o)

Cheers,

Colin.

[Colin Stamp]

It'd be nice if I could fit a boiler-only and an overall isolator. IMHO it would be a safer system. There'd be an isolator close by whether you were woking in the airing cupboard, or on the boiler in the kitchen. Less temptation to work live.

Cheers,

Colin.

[ARWadsworth]

IMHO you can do that. But Heliotrope is seldom wrong and he is always worth listening to.

If he is correct then there are a lot of incorrectly fitted boilers in council houses.