Used MCBs

I need a 50ampTP Square D QOE for a job, I have been quoted over £150 for a new one, I have a used one in my collection, I know its provenance, whaddya think folks?

crystal ball said:

I need a 50ampTP Square D QOE for a job, I have been quoted over £150 for a new one, I have a used one in my collection, I know its provenance, whaddya think folks?

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I won't bore/insult you with the 'official answer' but, pragmatically, I suppose that depends to some extent on the nature of the provenance about which you know! For example, was it commonly run at currents close to (or beyond!) its In, and do you have any idea/estimate of how many times it may have operated during its life to date as a result of over-current?

Kind Regards, John

It was for a building that I have maintained for over 20 years, if had tripped I would have been called out, it was feeding a DB that was mainly lighting and small power and has been stored in dry conditions in my office

crystal ball said:

I need a 50ampTP Square D QOE for a job, I have been quoted over £150 for a new one, I have a used one in my collection, I know its provenance, whaddya think folks?

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Perhaps you should discuss it with the client, some maybe ok with you using it, some not so.

I will be, its a not for profit outfit so trying to keep cost down, if there had been one in the DB not used I probably would have not thought twice about it

crystal ball said:

It was for a building that I have maintained for over 20 years, if had tripped I would have been called out, it was feeding a DB that was mainly lighting and small power and has been stored in dry conditions in my office

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Well, that sounds like as good a provenance as one could hope for - so (as has been said, provided the client is aware and agrees) it wouldn't seem to be an unreasonable course. I certainly know what I would do were it my own installation!

Let's face it, MCBs remain in-service for decades and, since we can't test them, we really never know whether they are still 'up to spec' - so moving one from one installation to another after a number of years' service is not materially different from 'leaving it in-service where it was'.

Kind Regards, John

Theres been so many types of them , would the new one even match the existing anyway.
If there was an old existing one fitted in the board, would many hesitate to connect a new circuit to that.
We do a lot of work on old Memshield 1 boards, new ones of them are also hundreds of pounds, old redundant ways are often reused, i would be more hesitant on reusing Rcbos though.

Yes the new one is a direct replacement, I will give the clients the option & if it fails in any way do a swap at cost + travel

crystal ball said:

Yes the new one is a direct replacement, I will give the clients the option & if it fails in any way do a swap at cost + travel

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Sounds reasonable to me.

Being pedantic, don't we allbhave boards/CUs full of "used" breakers ? They are all used once the circuit is powered up.

More or less my thoughts, really just testing opinion, quotes gone in and not heard back I think the cost will be too much even with a free MCB

SimonH2 said:

Being pedantic, don't we allbhave boards/CUs full of "used" breakers ? They are all used once the circuit is powered up.

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Exactly - as I said, putting into into service in a new board is really no different from leaving it in-service wherever it originally was installed (maybe for decades to come!).

Kind Regards, John

And when you move house, you are buying a CU (or 2, or 3, ...) of used breakers - with no idea how they might have been (ab)used by previous owners. I've never seen any suggestion that we should replace them all "because we don't know their history"

Personally I would reuse a MCB I had removed, but would not buy a used one. The reason I would not buy a used one is I was living on a caravan site during the building of Sizewell 'B' and the owner gave us a 5/6 amp supply. That was not enough for most people so they did all sorts to up there supply, clearly they had to do it live, there must be some very brave people living on caravan sites. The owner started to have problems with main DNO fuse rupturing so has to do something, so we fitted a 16A plug to a fan heater and went around the site, if the MCB did not trip we changed it, ended up with a box of LoadMaster MCB's in the main, there were some other makes all allowing more than needed to run a 2 kW fan heater. On inspection we found some 16 amp with 1 scratched off, and a load where the screw had been turned at the base, they were not put in the bin, god knows why, but these could in time be reused, there is no difference with fuses, I remember the bottle fuses in Algeria and we had a freezer which would not run without blowing a fuse, 16 amp was the limit in the holder, but rating it needed 20 amp, in desperation I opened a 20 amp fuse and 16 amp fuse and transferred the foil and sand as did not have a 20 amp carrier, I was very young at the time and rather worried about it, so told the normal camp electrician when he returned off leave, yes he said, I did the same.

So there is always a problem with second hand safety equipment be it a safety harness or a MCB, we don't know its history, but where history I known why not.