Where to mount switch for hand wash unit (in the UK) ?

My garage has a small room attached with a sink. I'd like to fit a hand wash unit above the sink, so I can get hot water. The one I have is similar to this:

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but is 7.2 kW.

I consider myself competent to fit the water heater (I have an electrical engineering degree, I'm a member of the IEE and a chartered engineer). However, I'm not sure of the IEE regulations on this, in particular where a switch must be placed.

The house has a 3-phase supply, one of which goes to the garage. This is fused at 80A in the house, and goes to an 8-way consumer unit in the garage. Hence there is plenty of power in the garage for this.

I have fitted a 40 A RCBO, with a trip current of 30 mA. (The load current is 32 A @ 230 V, so I thought a 40 A breaker was probably optimal).

Obviously I need to run a cable from the consumer unit to hand wash unit. For this I have 6 mm^2 twin and earth.

But I have two questions:

1) Is it normal (or advisable) to put a switch close to the hand wash unit, so it can be isolated without going to the consumer unit? Given the heater will be on its own RCBO I could switch it off at the consumer unit, without affecting anything else. It's only about 10 m away from the consumer unit, but there is a door between the consumer unit and the sink.

2) It if is usual to put a switch near the hand wash unit, where should it be - height, distance from sink etc. Should it be so high up, that it can't be reached from the floor without standing on something?

In some ways, I think it might be safer (and cheaper) to have no switch near the handwash unit at all, but I suspect there should be one.

Can anyone tell me what the latest IEE regulations say on this?

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That's OK providing it's not running in thermal insulation, and not grouped with lots of other cables running at or near their max capacity.

A switch near enough to the heater to be under the direct control of someone working on the heater is required (another room wouldn't count). If the switch is too far away or in another room, it would need to be of a type which can be locked in the off position by the electrician's own padlock.

I would suggest using a pull-cord 40A electric shower switch. Although a pull cord switch is not structly required in this location, it's not unreasonable to think it might well be used by people with wet hands, having just washed them, so it would be a good idea here. Get a good quality one (such as MK) for this high current load, not just the cheapest one in the store. A pull-cord shower switch must have a mechanical on/off indication (and it might also have a neon light, but that's not required).

I suggest you mount it so the cord can be reached from the basin, but it doesn't hang down in the way directly over the basin or heater.

That's why I suggest using a pull-cord shower switch, which will be fixed to the ceiling.

17th Edition regs will apply.
Reply to
Andrew Gabriel

That is not a problem.

That is the sort of help I needed. The consumer unit (MK Sentry) can't be padlocked, so I need a switch. (At least I don't think it can be padlocked. I can't say I noticed, but it might be possible to do it).

Good idea. The unit has its own 'switch', which is controlled by the flow of water. i.e. turn water on, and the heater runs. But clearly that is useless for servicing. I don't believe there is any other switch on it, but I'm not 100% sure. (It is in the garage and I can't be bothered to go and look).

I'll get one of them.

I was aware of that, but I don't have a copy of the regs, and don't want to buy a copy just to find this out where to mount a switch. But your idea of a shower type switch seems good.


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I think most (all?) MK MCB's can actually be locked off. You will see two tiny holes either side of the dolly, and they take a locking bracket. Can also be used to lock the MCB's on (that doesn't stop them from tripping, but does stop them from being switched back on again after having tripped).

However, the local pull-cord switch is a much better solution, and I would also suggest you switch off there when you've finished working in the garage for the day.

One other thing -- you tug quite hard on the cord of those high current switches -- make it's screwed into a joist and not just plasterboard.

IEE also do something called the "On-Site Guide". That is a very good summary of the parts of the regs applicable to a house. Make sure you buy the one which goes with the 17th Edition (still lots of older ones in the shops).

When modifying an installation like this, you should also check things like the installation's earth bonding are up to current regs. You don't need to bring the whole installation up to 17th edition regs, but the parts relevant to the safety of your new work should be.

Reply to
Andrew Gabriel

Thanks for that. I'll check for interest sake, but from a practical point at home, I'm not going to padlock them. I'll just fit the pull switch.

Cheers. Useful to know. I can easily arrange that. All I need now is the weather to get a bit warmer. I don't fancy fitting this in this weather

- I'll wait until the weather warms up and I don't need it!

There is one there are the minute, but it is only 2 or 3 kW, and just not enough to be very useful when the outside temperature is low.


PS, I will probably see you in a few days. There is someone of your name giving a talk at LOSUG on ZFS, which I assume is probably you.

Dave (using a Sun Blade 2000 with ZFS file systems)

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Yes, that's me!

See you.

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Andrew Gabriel

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