Hi,
In my kitchen I have some unswitched sockets under the counter for the washing machine and dishwasher. These are switched above the counter by FCUs. Is there any reason that FCUs are used rather than 20A switches or is it just whatever they had to hand on the day? Just curious.
TIA
Fred wrote in news: snipped-for-privacy@4ax.com:
I have the same - built in 1988.
I must confess I have changed some FCUs to sockets so the one below the worktop is now a spur.
The FCUs are specifically designed to be used as part of a ring final circuit. It is unclear whether the modular 20A switches are rated in the same way. Certainly they seem to have much smaller terminals. This would suggest that 20A switches are suitable for a radial circuit with a 20A circuit breaker, but maybe not for a connection to a ring.
John
When I did a kitchen some years ago the advice from this group was that an unswitched socket under the counter was all you needed - no additional isolating switch. If the aim is to be able to isolate the unit for servicing, exchange, or in the event of a fault, then pulling out the plug should suffice. I assume this advice still stands.
Cheers
Dave R
20A switch would be fine. May have used FCUs so that a plain flex outlet could be used below instead of a socket. FCUs may have been cheaper, being more common.
They're fine if feeding a single socket with fused plug as the plugtop fuse provides overload protection to the 20A switch.
Are they spurs off the ring main, and are there more than one socket on each spur? If so, the FCUs are to protect the spur. If there's only one socket on each spur, I don't see the point of the FCUs.
What they had to hand. There is no requirement to fuse a single socket on a spur. If you had many, there would be.
The only function of the plug fuse is to protect the appliance cable.
I thought the requirement was that you should be able to turn off the power to the appliance without having to touch it? With the plug behind the appliance, that's not possible.
Yes, if you use that method, the plug should not be behind the appliance ! I like others have fitted a socket in the adjacent cabinet, and cut an opening so the socket can be passed through and plugged in. However, for the oven, I am fitting a fused cooker isolator, since this is hard wired and does not have a plug. I had enough sockets and things above the worktop without any more FCUs. If you are not careful you can have more sockets and switches than tiles.
Simon.
Doesn't it depend on whether the plugs & sockets are accessible without moving the appliance?
Only if the overload is downstream of the plug.
MBQ
That may be the primary reason - but it is inherent that the fuse will also protect the feeder cable from overloads (but not faults[1]) up until the first junction with other loads - so in this case, the switch suuply terminals if that is on the ring or before if it is a spur.
Either way, the design specification of the branch circuit the switch is controlling is 13A max so a switch capable of switching that current should be adequate.
[1] It could be argued that a fault downstream of the switch but before the plugtop fuse may provide sufficient energy to damage the contacts, I doubt whether a 20A switch is in much jeapody compared to a 32A switch.It's exactly what I am doing and I'm quite happy with the idea.
In which case it would be perfectly ok to have unlimited sockets on a spur. All the plug fuses would protect it. ;-)
Where do you get the '13 amp max'? The spur circuit must be capable of tripping the 32 amp protection in the CU in event of a fault.
In message , Adam Funk writes
Certainly a very important point if the appliance is going up in flames or sparking every where at the time :-)
Exactly, those problems make it hard to pull the machine out!
If the switch were close by I'd not go near that either. I'd turn off at the CU.
I don't get the presumed joke there??
13A max design current due to a single fused plugtop downstream. The switch can exceed its design current in normal use irrespective of the fact it is protected upstream by a 32A device.Tripping is another issue which will be unaffected by whether the switch is
20A or 32A. Either way, fault currents can get into 100's of amps for mS as I'm aware you know - the only debate is whether a 20A switch would be damaged by the I2t let through, and I would propose that it is highly unlikely unless it was closed onto a downstream fault - in which case that could cause damage to 32A switch's contacts too.
^^^^ cannot
Have something to add? Share your thoughts — no account required.
Ask the community — no account required