Old consumer units and electric shower

[richwilliamson]

Morning all

I've recently moved into the first house I've owned, built in about 1975, and am discovering the joys of ownership vs renting.

The house had an electric shower fitted when we moved in. While I was using it the other day the isolation switch went bang - inside the wires were all charred. Did a bit of investigating of the electrics for the first time.

The shower is wired to its own separate consumer unit, specifically a Memera one. It takes cartridge fuse, and the cartridge is stamped 30A. This didn't quite ring true for our shower which is 9.5kW and sure enough it wasn't a fuse inside, but a length of what I'm hoping at least was fuse wire, which had obviously blown.

This is a picture of the 3 consumer units which make up the system:

http://farm3.static.flickr.com/2414/2177176263_464134578f_o.jpg

And this is a picture of the unit the shower is wired to, and one of the cartridge which goes into it:

http://farm3.static.flickr.com/2365/2177968012_4eec5b8903_o.jpg
http://farm3.static.flickr.com/2246/2177968364_ef554d296f_o.jpg

The angle blocks some of the wiring (sorry!) but you can just about see the Memera shower CU also connects to this other Wylex one:

http://farm3.static.flickr.com/2075/2177968086_eac65e5025_o.jpg

The other 3-way CU is for the lights and sockets.

Two questions then really:

a) with apologies for my ignorance, what's the Wylex CU that the Memera one is connected to actually for?

b) is there any way of salvaging what's already there for the shower? I'm guessing not as 45A fuses don't seem to exist for Memera stuff, even if it wasn't stamped 30A - god knows what the wire was in there before! If not, do I need to replace it with something like this?

http://www.screwfix.com/prods/69659...nits/Volex-Shower-Unit-63A-30mA-RCD-1x50A-MCB

And if so, is doing that one of those notifiable things I read so much about on here?

If you need any more info please ask...

Any other useful advice also welcome... cheers!

 

[Adam_151]

The house had an electric shower fitted when we moved in. While I was using it the other day the isolation switch went bang - inside the wires were all charred. Did a bit of investigating of the electrics for the first time.

Chances are there was a loose connection and this caused heating and this let to a run-away situation where the heat degrades the connection further, which in turn gets hotter, and this continues until

A) someone switches it off
B) the connection falls apart totally and opens the circuit
C) the switch melts into a fault situation it goes bang and the fuse opens
D) The whole lot catches fire, and you don't have a switch to worry about anymore... or a bathroom at all for that matter..

The shower is wired to its own separate consumer unit, specifically a Memera one. It takes cartridge fuse, and the cartridge is stamped 30A. This didn't quite ring true for our shower which is 9.5kW and sure enough it wasn't a fuse inside, but a length of what I'm hoping at least was fuse wire, which had obviously blown.

Sounds like its actually a re-wireable fuse then (unless someone bodged fusewire into a cartridge fuse holder!), the term cartridge refers not to the the nature of the way the carrier fits into the board, but to the cylindrical cartridge fuses to BS1361 that are sometimes used

a) with apologies for my ignorance, what's the Wylex CU that the Memera one is connected to actually for?

No idea, its your installation not mine , try turning it off and see stops working!, whatever it is, it appears to have been looped off the supply to the MEM switchfuse

b) is there any way of salvaging what's already there for the shower? I'm guessing not as 45A fuses don't seem to exist for Memera stuff, even if it wasn't stamped 30A - god knows what the wire was in there before! If not, do I need to replace it with something like this?

I'm guessing you probably need a cabling upgrade, it would appear this was a 30A circuit that someone came along and stuck a 9500kw shower in the end, without too much thought (9500/240 = 39.6A)

No idea whether that switchfuse can take a 45A carrier, johnd which his enclypeadic knowledge of the MEM pproduct range might , but really you perhaps ought to upgrade it to something that gives your shower RCD protection

http://www.screwfix.com/prods/69659...nits/Volex-Shower-Unit-63A-30mA-RCD-1x50A-MCB

Volex is not considered as one of the better makes of kit, and if it were me I'd fit a board with at least a couple of ways and get rid of that looped off wylex switchfuse and extend that 20A circuit to it as well (would need to work out what it was though), to do an even nicer job of it all, it would have even more ways and would replace the main CU as well

And if so, is doing that one of those notifiable things I read so much about on here?

Oh, absolutely! , and no offence to you, but I'd suggest that this might be a little out of your competance, and you'd be better getting someone in...

 

[richwilliamson]

Cheers for your reply - it was actually a cartridge fuse holder which someone had wrapped fuse wire round. Worrying indeed.

And sorry - I forgot that bit, I've tried turning off the Wylex unit and absolutely nothing happens anywhere which is why I thought it might be something to do with the shower!

And don't worry there's no way I'd try and do something like this myself! You're quite right, definitely out of my depth. Just wondering what would be involved. Replacing the whole lot might be the best option. Ta for the advice on the Volex stuff though!

 

[Adam_151]

Cheers for your reply - it was actually a cartridge fuse holder which someone had wrapped fuse wire round. Worrying indeed.

Indeed, someone must have found out that a BS1361 cartridge fuse eventually fails and decided to bodge it, fusewire at the best of times is a much cruder form of protection, and an overload that will operate a 30A BS1361 will not necessarily do the same to a 30A BS3036... but please tell me that this dangerous moron didn't wrap it round in such a way that there were multiple strands linking across the carrier

And sorry - I forgot that bit, I've tried turning off the Wylex unit and absolutely nothing happens anywhere which is why I thought it might be something to do with the shower!

Perhaps you have overlooked something? Immersion heater? kitchen applicance? outbuilding? extra socket in a corner? heated floor? CH controls? loft socket?

It could be for somehting that is now removed... have you tried to see how far you can follow the cable?

And don't worry there's no way I'd try and do something like this myself! You're quite right, definitely out of my depth. Just wondering what would be involved. Replacing the whole lot might be the best option. Ta for the advice on the Volex stuff though!

Indeed, the niceest option would be a complete CU upgrade, and with it being a 1975 property, then unless mr. bodger has done other stuff with the electrics, then there shouldn't be too many issues, bonding will most likely need an upgrade (but that'd have to be done whether it was a new CU or just a new shower circuit), and it perhaps might be a good idea to split the kitchen sockets off onto their own ring final circuit due to the demands of todays cooking applicances, but you should be free from problems such as vulcanised india rubber insulation on cables, and no earth in lighting circuits, I'm not saying it'll necessality be a trouble free thing, but the odds are in your favor over say a house 15 years odler![/quote]

 

[richwilliamson]

but please tell me that this dangerous moron didn't wrap it round in such a way that there were multiple strands linking across the carrier

Fortunately (well, relatively speaking!) no, just the one.

It could be for somehting that is now removed... have you tried to see how far you can follow the cable?

I'll keep searching for the mystery item operated by that, can't follow the cable very far though unfortunately.

I'll start the search for an electrician then to sort this mess out! If I could only find the former owners...!

Cheers for the advice.

 

[JohnD]

No I don't recognise the MEM switchfuse. It looks relatively recent, though, in grey plastic, and it is quite a large size. I'm a bit surprised there's no legend by the switch. Maybe there is something inside. There were popular MEM 15A and 30A metalclads around in 1975, smaller than that, and the current 60A one is also smaller. It seems to be fed from the Wylex though, possibly off the main switch (maybe the supply side terminals ) which is not sensible or satisfactory.

I am also surprised to see a Brown Wylex. The ivory ones were around by then. The cabling looks neat, perhaps someone was saving money on switchgear. I have a feeling there is a Henley and perhaps a main switch on the other side of the wall - there should be.

A nice new Memera with a few RCBOs will replace all the old CUs and make a lovely job of it

p.s. that mouse entrance could do with filling up