A few electrical questions

[kiloran]

We had the British Gas serviceman round yesterday to do the yearly service for the gas CH boiler. My wife said they could not do the job because they could not isolate the electricity supply to the boiler.... new regulations, apparently, it has not been a problem in the past.

It seems we need an isolator by the consumer unit (under the stairs) or by the boiler (in the utility room).

I could probably fit something in the utility room. Any idea what sort of isolator would be needed to be compliant with the regs?

The consumer unit is an old-style fused unit, so I might get an electrician in to replace it with a modern unit and ensure appropriate isolation for the CH supply. What happens if the existing cables are not long enough for the new unit? Would this require a significant rewiring or can cables be extended? After it has been fitted, would this require access to sockets in all the rooms for testing? A simple swap would be great, but I don't want any unexpected complications right now.

--Alan

[Graham.]

the gas CH boiler. My wife said they could not do

boiler.... new regulations, apparently, it has not been a

boiler (in the utility room).

isolator would be needed to be compliant with the regs?

to replace it with a modern unit and ensure

are not long enough for the new unit? Would this

fitted, would this require access to sockets in all

unexpected complications right now.

Seems a bit drastic if the only reason for doing it is to provide boiler isolation.

[Owain]

A switched Fused Connection Unit like this

you go up a level you will see ones with neons and flex outlets)

But how is the boiler and associated equipment wired into the mains at the minute?

Cables can be extended, but this assumes they are suitable.

Yes, because the electrician needs to check the polarity and earth continuity at each socket.

Changing a fusebox can result in complications in the existing wiring coming to light. That is not necessarily a bad thing, of course.

Owain

[cynic]

Let me guess - they will send you a quote to do the work?

[A.Lee]

Easily done. Find where the electric goes into the boiler. Isolate properly, cut the cable in a suitable place, and fit a fused connector unit;

If you are not sure about where to put it, or how to do it, then get someone in who knows how to do it.

Alan.

[John]

A switched Fused Connection Unit like this

you go up a level you will see ones with neons and flex outlets)

But how is the boiler and associated equipment wired into the mains at the minute?

Cables can be extended, but this assumes they are suitable.

Yes, because the electrician needs to check the polarity and earth continuity at each socket.

Changing a fusebox can result in complications in the existing wiring coming to light. That is not necessarily a bad thing, of course.

Owain

Would fitting a socket and plug meet the isolation regulations? - or a spur box with a double pole switch?

[dom]

Fixed appliances must not use a plug socket. Use an FCU as others have said.

[george [dicegeorge]]

xxx I think that if an electrician fitted a new consumer unit he's have to test and verify that all the electrics are up to modern regs, and may have to rewire the whole house even if its perfectly safe! [g]

[Tim Streater]

Could you define a fixed appliance in this context. Seems to me obviously a boiler, cos you wouldn't be expecting to move that, but would it include e.g. fridge and washing machine? In my old house, when I had it remodelled (1995) the builder must have asked me where I intended to have the fridge because that ended up with a wall socket off an FCU (can't remember if the socket itself had a switch).

Where the washer/dryer went that also had two single sockets off FCUs. But it seems to me I could move a fridge elsewhere in the kitchen and run it off an ordinary socket, or plug a telly into an FCU'd socket.

[John Rumm]

An ordinary double pole switched fused flex outlet would do nicely. I am surprised you have not already got soemthing like that.

Seems rather excessive just to get a switch in boiler supply.

Cables can be extended if required.

Then don't change it now then.

One would test each circuit when reconnecting. So things like finding a broken ring would require further investigation to rectify before it can be reconnected. Same goes for any other unexpected faults. How old is the wiring in general? Do you have RCD protection on any/all circuits?

For more background on CU changes. have a read of:

[John Rumm]

That's not quite true and a little alarmist! ;-)

They will need to verify there are no faults in the circuits prior to reconnection, but that is not the same as bringing everything up to current standards. Generally you would bring your main equipotential bonding up to current standards if its not already. Everything else may be fine as it is if it passes basic tests like ring continuity, insulation resistance etc.

[js.b1]

Any fixed appliance may be isolated by an UNswitched socket (not a switched socket, by virtue of being unswitched it forces isolation by removal of the plug). Frankly I prefer an unswitched socket for isolation, nothing better than a few feet of air as insulation compared to knocking a switch with your elbow / plank / wood.

An exception is for heavy current devices, specifically a 3.3kW storage heater or 3.3kW immersion heater. That is because whilst a BS1363 plug is rated to 13A, in practice 10A is a better continuous rating. It is legitimate to use a plug n socket for an immersion, subject to zone restrictions, but it would be better to make it a 20A DP switch (CU protection) or if it must be a plug n socket use a 15A plug (shielded pin version available from RS) and 15A shuttered socket (MK, Crabtree etc).

So I too wonder how the OP has his boiler wired?!

[Lobster]

Indeed - and what about an oven: much more 'fixed' than a fridge or freezer? Most built-in ones come with a 13A plug already attached, apart from anything else, this indicates that it's OK to connect it to a standard ring main which AFAIK is specifically *not* the case when they are supplied *without* a plug.

David

[Tabby]

There's no requirement to bring existing installs up to the latet regs

One that keeps british gas engineers out. This is the perfect opportunity to get rid of them.

why?

So why replace the CU?

NT

[A.Lee]

I've fitted probably 15 built in and built under ovens in the last 2 years, and none of them came with a cable or flex of any sort. I have taken old ones out that have a flex and plug on them, but I always do away with the socket and put a fused connector in its place.

Most ovens will be near the limit for 13A plugs when they are fully on, so far better to get a good connection using 2.5mm cable, rather than the sometimes poor connections of a 13A plug.

Alan.

[Mike Harrison]

Why not?

[Man at B&Q]

Some, but I doubt it's most.

Hobs are a different kettle of fish.

MBQ

[Tabby]

Ovens arent on full load for long, so well within the abilities of a

13A plug/socket.

NT

[Owain]

An *unswitched* socket is acceptable. A switched one isn't, as some are only single-pole switched and someone might switch off but not pull out the plug.

A spur box with dp switch is what has been suggested.

Owain

[John Rumm]

Most single ovens have peak powers of 2.2kW or less IME. Many of these come with a plug fitted. The double oven or oven and grill combos however can have a higher power demand.

Diversity also plays a big part in reducing the effective load on domestic cooking appliances as well.