General > General Technical Chat
Post a picture of your Fuse Box
Whales:
Maybe it's an explosion containment thing?
Ed.Kloonk:
--- Quote from: Whales on October 10, 2022, 03:44:53 am ---Maybe it's an explosion containment thing?
--- End quote ---
One thing that has happened since the single pole RCDs showed up is the ones with rating >16 amps can get hot. And of course there's no provision for air flow, rather they get cascaded. Multiple light dimmers on the same light switch bank, this happens to. It says in the manual not to do it but the info gets chucked with rest of the packaging.
themadhippy:
--- Quote ---Any reason why is outlawed?
--- End quote ---
not outlawed,just against the current regs that are not statutory.As for why?well were british and like to be different old chap,plus plastic boards melt and burn when a loose connection in the fuse board causes it to catch fire.
tom66:
--- Quote from: Black Phoenix on October 10, 2022, 12:40:06 am ---
--- Quote from: IanJ on October 09, 2022, 01:42:42 pm ---Shed fusebox at bottom of garden via buried armoured cable (see it coming up from bottom left). This is a plastic fusebox which I believe is outlawed here in UK now.
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Any reason why is outlawed? I ask that because plastic consumer units are used in the rest of the EU without any problems. Same in China, Japan, Germany, etc.
Although in most Instalations in the UK I follow its always a metal box that it's used.
Because of the grounding of the armored cables?
--- End quote ---
Just in case of an overheating conductor or loose connection, it adds fuel to the fire. Metal CU's keep any such overheating contained for longer, possibly long enough for the MCB/RCBO to trip and isolate the fault.
They aren't too expensive, though presumably cost more than plastic - I got a 7-way one (excl breakers) for £30 for the recent install for the EVSE.
Gyro:
Yes, basically fire. Too many house fires caused by loose and overheated connections that are not contained by the plastic enclosure. Metal enclosures have been mandatory for new installations since the UK 17th ed wiring regs. There are restrictions on fire exit paths through the top and rear of the enclosure, fire retardant gromets and glands, fire retardent caulk sealing etc.* Many (most?) older UK homes have the mains feed coming in under the stairs, so have the consumer unit in the same place - directly under a wooden primary escape route! There are many videos on the subject. High drain items like high kW electric showers and EV chargers only make the problem worse.
Personally I think 'cage clamp' terminals are the primary culprit, particularly on the incomming supply tails into the consumer unit. Even when tightened to the correct torque, the thick 25mm2 stranded tails will easly work loose under movement and thermal cycling. If people don't use the appropriate torque settins and torque screwdrivers, the problem is even worse. I think these are a definite step backwards compared to the old twin screw terminations, where the screws bear directly on the conductors and have 100% redundancy.
When we had our smart meter fitted a few years back, I purchased a Wylex double pole isolator switch (cage clamp) ready to ask the installer to fit in line between the Meter and consumer unit (to allow safe future replacement / maintenance). The installer took one look at it, went out to his van and returned with a double screw terminated isolator. He said there were too many problems with the tails loosening or even falling out with the cage clamp types. With a pair of screws tightened down hard on the cable in a constrained diameter terminal, there's no way that the cable will work its way out past the depressions over time.
I have similar concerns about the new-fangled 'Wiska' type maintenance free junction boxes, where the solid core wire is simply pushed under the sharp edge of a leaf spring (or lever action). Put a cable tie through the tags on the plastic box and stuff it under the floor and it becomes maintenance free. Has nobody else seen problems caused by push-in terminations inside flourescent light fittings. Maybe the metalurgy has improved, but let's see if the springs relax and start causing fires in 20-30 years time. They are effectively point contact connections.
P.S. * I meant to comment on this on tom66's second CU in reply #44. That PE wire coming out of the top of the second CU really ought to have a flame retardent gromet (or at least a bit of intumescent caulk around it). The hole is too big to pass regs. Seeing some of the other installs drove it clean out of my head. :D
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