Types of Ring Main Fuse

[Matt King]

In my fuse box I have mostly got "typical catridge fuses" as shown in "Changing a fuse on the consumer unit" How To under Electrics on this website.

However, one has been replaced by a newer looking fuse, a grey cuboid box that has a yellow On/Off rocker switch in it. On this newer fuse there seems to be no way replace the fuse wire/fuse itself - you can't open it up.

Unless it's faulty, do this type of fuse ever blow?
If so can they be reset?
Do I need to go to a builders merchant to buy replacements - Wickes and Maplin's websites don't seem to have them?

Many thanks!

 

[Matt King]

Is it a Low Voltage European Miniature Circuit Breaker as described in Wikipedia?

These either self reset - after how long?
Or are manually reset - by turning switch to off? For how long?

Do they have to be removed from the Fuse Box/disconnected from the mains to be reset?

Cheers,
Matt.

 

[JohnD]

Yes, it is an MCB.

As we aren't American we don't call it "European"

More than likely you have a Wylex Standard fusebox in cream or Brown. There were about 20 million of these installed in the UK and they are still made, though there are now better and more modern ones available. Or it might be a metalclad one in grey (less common)

Wylex make plug-in MCBs to almost the same size and fit as the plug-in fuses, including brass prongs on the back like a fuseholder. However you never need to pull them out, you just flick the switch to reset. They do not reset themselves. They don't generally go wrong

The yellow colour you mention suggests it is a 20Amp one. Common colours are White for 5 or 6Amp (used for lighting circuits); red for 30 or 32Amp mostly for socket rings, sometimes for cookers; blue or 15 or 16Amp, almost always used for Immersion heaters. As well as the colours you should see the rating printed on the front - B6, B32 etc.

If you have a Wylex standard, the fusebox itself might have a main switch rated at 60Amps (which is considered a bit low these days) or it may be a 100Amp one. It depends on age and number of fuseways. There may be a moulded rating or a stuck-on label.

Replacement MCBs are readily available for Wylex, in case you should want to replace your old fuseholders, but the replaceable cartridge fuseholders are perfectly acceptable.



If you ever want to buy some new ones, they are available (provided they are Wylex as described) from Electrical merchants or discount mail order companies, including Screwfix. However, remember that there were millions installed, and many have been taken out and replaced by more modern consumer units; and they don't generally go wrong, so you can usually buy sets of second-hand ones on Fleabay for a couple of pounds each. You have to get the plastic shields that go behind them as the size is probably not quite the same as your old fuseholders; and you MUST turn off the main switch when removing or fitting any fuse, MCB or plastic shield.

 

[Matt King]

Perfect John, thanks.

I'm 99% sure I've got a Wylex board with Cartridge Fuses and one Mini Circuit Breaker. The house was built in the 1930's and I haven't replaced the board that was here at least 18 years ago.

 

[ban-all-sheds]

Might be an idea to have an electrician do an inspection of the entire electrics, given its possible age.

 

[JohnD]

Here you are:

If yours is a Brown one it is probably between 30 and 50 years old and overdue for replacement.

If it is cream and has a 100Amp switch it is a bit out of date but no reason why it should not continue in use until you need a rewire or upgrade for some other reason. (edited: though as Ban says, it might be rather old and have other defects).


Note however that (although there is a conversion WRX kit available) the boards do not include RCD protection, so for sockets likely to be used with equipment outdoors you must; and for electric showers you should, provide RCD protection either with an additional RCD on the circuit; or an RCD socket (or at the very least an RCD adaptor). Unless you have a 100Amp main switch your board is not suitable for an electric shower.

 

[Adam_151]

I've got a Wylex board with Cartridge Fuses and one Mini Circuit Breaker.

When people say cartridge fuses on here, sometimes they don't actually mean cartridge fuses:

Cartridge fuse:

And they go in a carrier like this for a wylex standard board:

Strangely enough when someone says cartridge fuse, they quite often don't have a cartridge fuse, but a re-wireable fuse, heres one for a wylex standard board:

And you put fusewire in them

 

[JohnD]

Strangely enough when someone says cartridge fuse, they quite often don't have a cartridge fuse, but a re-wireable fuse

Well! I didn't know that! What a pain in the elbow!