Hello all,

I'm looking for assistance with wiring practices in particular the way items like contactors and circuit breakers are wired.

I have a couple of guys who insist there is nothing wrong with wiring in the bottom of contactors. For example, the three phases go in L1,L2,L3 and come out T1,T2,T3 of the first contactor but then are looped into the second contactor using T1,T2,T3 and then out on L1,L2,L3!!

Same goes for similar devices; circuit breakers etc....

To me this goes against common wiring practice but I am looking for peoples thoughts on this. More importantly, are there any standards detailing this?

I feel the 'L' prefix is there for a reason - to denote the live side of the device. It is also, I believe, convention to wire from the top to the bottom.

Thought please? Why shouldn't or should this be done

Thanks

I'm not sure there's a widespread convention - e.g. in a conventional CU the main switch is supplied from the top, but MCBs from the bottom. MCBs in type-B 3-phase boards seem to go either way around (seemingly depending on manufacturer).

Many devices that you might think could be orientation sensitive (e.g. RCCBs) seem to be documented as working either way around.

That said, I don't recall a T prefix on the devices I've used (terminals tend to be numbered 1,2,3,4, etc), so we might be talking at cross purposes...

- Andy.

I think that most devices will work either way around but I would have said from a practical point of view there was an accepted way to wire.

The devices I am talking about are contactors which have the 'T' connections. Even circuit breakers have 135 and 246 terminals and it has been known for these to be wired differently.

I thought there were some standards which detailed this kind of thing but I unable to find anything hence the question.....

I don't see a problem if it's done consistently in each panel though it's generally bad practice to position circuit breakers with opposite orientations inside a panel i.e. all the switches should move the same way for off and on.

We have some Schneider switchgear where the lowest outgoing breakers are bottom fed while all the others above are top fed for space reasons; no problem from the manufacturer's assembly standards side but we didn't like it because the inconsistency could cause a safety hazard if you isolate and then forget which busbar end is live.

Regards, Tim

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Everyone loves a fireman - but hates the fire inspector.

I have to agree with you - I have seen a lot of 3-phase panels when I used to be involved with that sort of work and the L1, L2, & L3 were always the incoming side and the 'T's' the outgoing. Multiple contractors are usually looped from the top in the L1-L3's to the next. Just good practice if nothing else so there's no confusion when isolating a fuse etc.

Tony