It came to light when the incomer was examined to see if the company earth could be used, ie convert TT to TN. The earth connection (which is only use d to earth the incomer box) appears to consist of 1-1.5 square mm of copper twisted round the cable with the cable's earthed sheath not accessible. So it's inadequate for TN use. And of course TNC-S is not an option on a dual pole fused supply.
NT
I like the instruction 'use asbestos tube when re-wiring'.
Sounds to me like a complete renewal here is in order. Its probably knackered after all those years anyway, but I bet its replacement won't last anywhere near as long! Brian
Perhaps a museum might like it if it can be removed intact. Brian
not knackered at all. It survived decades powering an all electric system of storage heaters & immersion heater without complaint. I can only conclude it was well made and conservatively specced.
NT
Hopefully, one of the fuse carriers has been swapped out for a solid metal link:
What size are the tails from the main cutout? They look like modern PVC tails of at least 16mm^2 - which would suggest the cutout has at least been opened some time in more recent history.
I would check with the distributor whether an upgrade to a modern 60 or
100A feed is available, and chances are you would get TN-C-S anyway.(that label ought to go in the wiki somewhere - perhaps the dating electrics article)
It's Amendment 3 compliant isn't it???
Instructions of how the DNO would change it are here
Obviously this is not something even you should do yourself.
If it is DP fused the DNO should replace it quite quickly.
Owain
I could look but would it be a good idea?
electrical use has certainly not been constrained to anything like 30A. Ove n, microwave, kettle & washing machine may be on at once. At least space & water heating are no longer electric, they used to be. It seems Isco were m odest about their product's capabilities.
I believe it got those tails in 82
yes - though I've not got any date for it yet, I presume 1930s. Searching t he patent numbers got nowhere.
I presume 'SP only' means single phase, but it couldn't be used for 3 phase , I guess it means don't use it on 2 phase at that voltage, which would put 1kV between the poles.
NT
I believe it is. But not compliant with 1955 regs.
DP fusing is easy to rectify, and it seems to be in sound condition. But I think they should replace it on the grounds that it is overloaded.
NT
Opening the cover is probably low risk, but I would be very cautions pulling a fuse carrier on something that old (and of that design)
as the label says, fusing current 57A... Combine that with the short term load nature of many kitchen loads and you are likely to get away with it even if its still fused at 30A.
Yup, SP only is single phase.
There are not enough "ways" for 3ph use.
IME cutouts for three phase use tend to be either a 3ph head end designed for the purpose, or three separate single phase ones.
There would be no practical purpose in taking two phases through something like that, since without the third phase you would need a neutral - so you would need three poles even for that.
that's what I thought
the good news is the rest of it has proven capable well beyond its spec.
2 phase distribution was common in the 1930s.NT
Examined by whom?
A 30A rated incomer would not really be considered adequate for a 5 bedroom property these days unless there are just lighting and ring main circuits connected to it.
30A is not sufficient for most modern electric cookers or showers
The incomer may be rated to suit, so that might also need to be replaced.
Hard to work out what you mean.
NT
inquisitive fingers opening it without a tool, running a TT earthed 5 bed h ouse. Is that satisfactory?
rth could be used, ie convert TT to TN. The earth connection (which is only used to earth the incomer box) appears to consist of 1-1.5 square mm of co pper twisted round the cable with the cable's earthed sheath not accessible . So it's inadequate for TN use. And of course TNC-S is not an option on a dual pole fused supply.
Nope, can't remember.
NT
If the fuse unit is rated at 30 amps, then the incoming cable was probably sized to suit and may well need to be replaced if a higher capacity supply is needed.
Oh, good point. It looks capable of 100s, but the DNO will figure it out.
NT
Well have a think about it, was it the milkman or the postman?
If it really is DP fused then call your supplier and have it swapped ASAP
p inquisitive fingers opening it without a tool, running a TT earthed 5 bed house. Is that satisfactory?
earth could be used, ie convert TT to TN. The earth connection (which is on ly used to earth the incomer box) appears to consist of 1-1.5 square mm of copper twisted round the cable with the cable's earthed sheath not accessib le. So it's inadequate for TN use. And of course TNC-S is not an option on a dual pole fused supply.
The plan is to ask them to look at it once the other work is done, hopefull y to replace it. I'm a bit hesitant to pull the fuseholders out to see if i t's still DP fused.
NT
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