Does electric shower require RCD?

[Spark123]

with a 100A main switch breaker, which will never see any action as, if the worst comes to the worst

That 100A isolator is only a switch disconnector with a maximum current rating of 100A, not a breaker or an MCB or the likes.

Well, today, I ran everything in the flat at full tilt and measured a maximum of 73A on the incomer (using a clamp meter). Nothing was getting remotely warm (except the kitchen and bathroom) and I'm sure even a few more amps could be pulled as the 60A fuse is a huge beasty. The Pyro, incidentally, is 10mm² (love this secret ASCII code!) which is good for +/- 90A, depending on which table you look at in the regs.

I still wouldn't advise running it over 60A for long, it will start to get warm. A 60A BS88 fuse has a fusing factor of around 1.45, for which it should disconnect iirc in 1hour.

So either I leave things as they are, buy a spare 60A and tell them to call me if it all goes dark and I'll come out for a small fee with my FB key & fuse, or I try to find a smaller main switch breaker (60A)...

Replacing the 100A switch disconnector with a double pole MCB, I'm not sure a 63A MCB will discriminate against a BS88 60A fuse.

 

[JohnD]

but i agree anything that your using wet and naked and is liable to be sprayed with water should be RCD protected.

Does that include the wife?

If yours is electrically operated.

 

[RF Lighting]

OK, so what do you do when you have to rewire and update (i.e. new appliances, electric shower) an ex-council tower block flat that's protected elsewhere by a 60A HBC fuse locked in a cupboard? OK, I got the FB key and removed said fuse to allow me to install a new CU, but that CU came, as most of them do, with a 100A main switch breaker, which will never see any action as, if the worst comes to the worst, the 60A will go first, leaving the poor tennant in the dark wondering what the f@#k happened and why there's nothing they can do to put things right at the CU.

Virtually all CUs come supplied with a 100A main switch.

This is not a circuit breaker, and will never 'trip' regardless of how overloaded it is.

Well, today, I ran everything in the flat at full tilt and measured a maximum of 73A on the incomer (using a clamp meter). Nothing was getting remotely warm (except the kitchen and bathroom) and I'm sure even a few more amps could be pulled as the 60A fuse is a huge beasty.

Physical size has no relevance to what current the fuse will operate at. If the fuse is rated at 60A then it will 'blow' if anything above this is pulled. (although it will need to be a sustained overload if only 73A)

The Pyro, incidentally, is 10mm² (love this secret ASCII code!) which is good for +/- 90A, depending on which table you look at in the regs.

You should only be looking at the correct table in the regs, which is table 4J1A, and rates 2H10 MICC at a maximum of 82A if installed to reference methods 12 & 13.
How is your cable run in?

So either I leave things as they are, buy a spare 60A and tell them to call me if it all goes dark and I'll come out for a small fee with my FB key & fuse, or I try to find a smaller main switch breaker (60A) which will, hopefully, trip first. Maybe better a bit of nuisance tripping than blowing the big guy. Actually, I doubt that would ever happen and I can just move on and forget it... but my advice is, folks, don't work on tower block flats. stick to good old houses with 100A incomers.

If you apply diversity then chances are there will be no problems, but if you are that worried then you could upgrade the submain cable and supply fuse.


My advice is folks, don't work on domestics. Stick to good old commercial and industrial jobs with >100A 3P incomers.

 

[Pensdown]

but i agree anything that your using wet and naked and is liable to be sprayed with water should be RCD protected.

Does that include the wife?

If yours is electrically operated.

....no but if she were I would I selected an RCD rather than an RCBO. I could tolerate her tripping out now and then on faults but tripping out on faults and overload.....

 

[The Jeep]

Time for my next lesson - how d'ya get those fancy highlighted quote boxes? Must've been off school that day...

Thanks for the replies - I didn't realise that the 100A switch wasn't also a breaker! Learn something new every day!

So the 60A Type 88 fuse is basically acting as the supplier's cut-out, normally found inside the house, but usually 100A and highly unlikely ever to blow. I agree, the 73A situation is unlikely to occur in normal use: I even had the kettle & toaster on, along with the washing machine at 90 degrees (ASCII code for that symbol anyone?), all the lights, the oven and the shower! And even if it did, it would only be for a short duration.

Upgrading the incomer and cut-out would not be an option here as the pyro is burried in the concrete floor for part of the way (no table for this Method (3?) in the regs, for some reason). The pyro is actually 3-core, but one core has been disconnected (the old off-peak supply), so I guess it counts as 2-core, single phase now, from the point of view of the tables.

I just hope folks don't go wild plugging bar-heaters into all the sockets...(but then, hopefully, the circuit MCB would trip first, but it all depends on what else is in use: I guess good old diversity will save the day).

Dunno about you guys, but my wife gets less wet when she's tripped out...

 

[JohnD]

Time for my next lesson - how d'ya get those fancy highlighted quote boxes? .

see if you can find the

button.

 

[The Jeep]

Time for my next lesson - how d'ya get those fancy highlighted quote boxes? .

see if you can find the

button.

You mean like this? Cheers John D!