EICR - Old Rewireable Fuse boards are these acceptable?

Whats that when its at home?  I  guessing some sort of heater controller ?

How’s that for a cracking bit of electrical engineering?


It wasn’t the one I was actually looking for ?

Another hazard is that some old Wylex board fuse bases had a small asbestos pad fitted in the centre of them for arc supression.

A CU in a nursing home in Scotland had a fire in a storeroom, about 10 years ago, many old people were killed in the fire, thought attributable to an open fuseboard which did not contain the molten metal which set fire to cardboard boxes. I have seen the results of molten metal sparking on the metal edges at fuses, probably caused simply by pushing in the fuses onto a faulty circuit. Be wary of fuses, especially where no cover is fitted and where the Public is concerned. When all else fails use bloody great nails.


Jaymack

If these Wylex CUs are from the 1980s I doubt they're the open backed wooden types - I'm pretty sure that Wylex switched to the moulded hard plastic types before then. (And the type of plastic that just charred a bit and went out when heated, unlike the later plastic DIN-rail type CUs that sometimes went up like the proverbial roman candle.)

   - Andy.

Fitting Wylex plug in M.C.B.s or G.E. Mini trip M.C.B.s offers better protection as it offers " "Close excess current protection, having a fusing factor of nearer 1.5 rather than 2)

Different rather than necessarily better I'd suggest. Fusing factor is but one of many parameters.


For instance fuses can sometimes be better than MCBs for faults on circuits with high Zs - e.g. Max Zs for BS 3036 15A for 5s disconnection time is 5.08Ω, while for a 16A B-type MCB it's just 2.73Ω - so blindly replacing a 15A BS 3036 with B16 MCB might extend operating time from under 5s to something exceeding 40s (if I'm reading Fig 3A4 correctly).


Certainly for overloads an MCB (or cartridge fuse) should be quicker - but if the cable has been correctly selected in the first place (taking Cf into account) does it matter?


   - Andy.

The open backed Wylex consumer units with a wooden frame had the paxolin back offered to fully enclose it to prevent fire spread. Fire could originate due to a bad joint inside the fuse box. The fuse boxes were o.k. if mounted on brick or a plastered wall, but it was feared that fire could spread if the fuse box was mounted on say wood or another combustible material. It also offered a better electrical insulation if the fuse box was mounted on a metal sheet. It was the Amendment 3 requirement of its day.


The B.S. 3036 fuse wire type carriers had a fusing factor of two, and offered "course excess current protection" The 5 Amp fuse wire was the most likely to blow when a filament lamp failed and shorted internally. The fuse wire being very thin ruptured virtually instantly in that case, and modest amounts of hot copper were produced in the bang, mostly enclosed within the fuse carrier assembly. I can not see any way that the products of a fuse wire rupturing could reach the insides of the fuse box and pose a risk.


I have come across old Wylex fuse boxes where the 15 Amp and 30 Amp fuse wire has never blown from installation in the 60s or 70s.


The biggest danger with rewirable fuses is that of somebody replacing the fuse wire with the wrong larger size of other bit of wire.


Fitting Wylex plug in M.C.B.s or G.E. Mini trip M.C.B.s offers better protection as it offers " "Close excess current protection, having a fusing factor of nearer 1.5 rather than 2)


Z.

If fitted with fuses and the cover is missing then C2 and needs replacing.

Or just find a replacement cover? (e.g. https://www.ebay.co.uk/itm/154416681465 ) - £15 when you just want the cover might seem steep but it's got to be attractive compared with the cost of a complete CU change.


  - Andy.