when did they stop selling these 3phase 32A switch fuses?

According to this the brand was consolidated with MEM in 1998

So if it was still using the 'Bill' name then it puts it at least 24 years old.

The photo is not very detailed to see much of the state, or to get an idea of the environment. For exampe, if damp/corrosive it might look as seen in 20-ish years, but if fair environment then it could be 50 years old, etc.

In terms of "life remaining" I would want some detailed photos showing the inside and underside to see if risk of SWA gland area rusting through, also to operate it and verify the action is good, and to get an idea of the state of the contacts when open in case it has been closed a few times on to a fault, etc.

That is a Bill Masterlink switch-fuse and as above Eaton ceased the Bill brand in 1998. The fact it has the plastic red logo logo and not a sticker probably puts it in the 80s early 90s and I doubt it is much earlier if it is rated at 32A and not 30A.

When you ask about "life remaining" then there are two situations I see:

• First is an untouched installation where the question is simply of safe continuation, and as above I would inspect it, operate it and verify nothing looked wrong. In that case of nothing troubling I would leave it.
• Second is where it is part of some installation that is being renovated and/or change of use. In this case the fact it is probably 80s era would make me change it so then next couple of decades are reasonably sure.

I was watching some 70s music channel tonight and it occurred to me the children press-ganged in to some late 70s videos are probably grandparents now! Tempus fugit...

Some facts:

1. Between main db and rusty switch fuse is 4 core old colours 6mm2 swa run underground with 50A type B single phase mcb marked up for my client's business. Only yellow and black live conductors used. Red and blue taped off.

2. My clients business uses a reasonable steady power of 10kW single phase fed from the BILL switch fuse by new colours 16 or 25mm2 SWA connected to yellow phase to provide 230V supply.

3. Business has been operated for several years until recently when smoke started to come from the rusty box containing the rusty switch fuse.

4. Supplier of electricity claims my client has overloaded the supply and it is all his fault and liability to replace.

5. My client relied on site electrician - but not the current one - to arrange a single phase supply for his business.

6. My client has never touched contents of rusty box and does not use the switch on the switch fuse.

7. Previously I believe the 6mm2 was used to provide 3 phase 4 wire for the business on site before my client. There is a way in the db with a 3phase 32A type B cb marked up for the previous business use.

For your delectation:

If that is a 32A unit, picture a bit blurred then someone has fitted a 63A fuse to a 32A carrier. I suspect the combination of this, poor connections (the yellow crimp through the neutral is now black) and excessive current has resulted in what has happened.

What rating of single-phase supply was asked for in the first place? If greater than 32A the previous sparks cheated, if 32A or less then he still cheated but in a different way. The burnout at the switch looks like a regular loose terminal or corroded switch contact. Overload or no overload, that would eventually have burned out. In any case I wouldn't trust a standard yellow crimp at 32A especially with half the strands of an oversize conductor.

IMO not worth arguing too much about, as it looks like a simple fix. Leave the B50 in place but parallel the conductors of the 6.0. Assuming it serves no function, put an adaptable box in place of the switchfuse and connect through with proper crimps.

As Lucian says, it might not be worth the effort to argue if it is not going to be a full commercial-rate replacement of the TPN fused-switch that might come to ~£500-ish.

Paralleling up the existing 4C SWA is a good idea as it then meets the 50A MCB rating for overload. If local isolation is needed then a cheap rotary switch would do. This sort of thing is not hugely more expensive than an adaptable box and would also allow the cables to be joined without any crimps just using 2 of the 3 poles (though a ferrule to keep the two paralleled cables together is always a nice touch):

The workmanship is pretty poor on that as well, as the newer cable's gland is not properly attached (maybe bend radius too optimistic as well).

Also a bit odd to be using 4C for that when only 1 phase is in use!

I have forwarded this post and your responses to my client. All very helpful. I have asked him whether he actually asked for so many kVA, or whether he was ever told the maximum kVA. Also if he has increased the load since the first site electrician connected him up.

This has already been repaired. They are just arguing over liability and in the end a compromise.

He actually has four 3kW machines but can only ever use three of them. He sought my advice a few years ago and I had a look and said he should ask for the original 3 phase 32A supply to be reinstated by the site and he should remove the single phase consumer unit and fit a three phase one. At the same time the rusty box and its contents should be swapped for new and accompanied by a signed of certificate with the test results and allowable kVA. The site refused. We do not know if it was at this stage the conversion to single phase off the 50A cb was done and the 32A hrc fuse was swapped for a 63A one.

The underground 6mm2 at single phase is good for 53A and at 3 phase something like 44A IIRC. Run is only 5m.

I thought it proper to say thank you to everyone who contributed to this thread. Between my client (my brother-in-law) and me we have crafted a carefully worded reply to the site which represents the history as well as we can know it and promotes a business-like compromise on liability for the cost of restoration.

PS: In my earlier life we had rigid change management procedures which included keeping tabs on power/current consumption and associated cable/fuse/mcb/mccb ratings and settings. Happy days.

PS2: We used to do monthly IR camera surveys looking for overheating and caught a few combined busbar tap-off switch fuses needing some love and attention before they failed completely which would have caused 'questions to be answered' by me to my masters.

PS3: I have often thought sites including homes should have at least an 'electrical record book'. Maybe some do?