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During the sequence of testing on a 3 Phase DB, would the main switch be off on all tests (live and dead) except for ZS and RCD test where it would be switched on.

Thanks.
 
Ideally yes the board would be off for the dead tests whether three phase or single but if you are doing a periodic this isn't very often practical. To be honest I have been doing periodics for 30 odd years and am so used to working on live boards and switch panels I never even consider isolating them even if I can. But in an ideal situation yes you should isolate for dead tests.
 
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Yes, main switch off while earth disconnected for Ze (3 tests, each phase to earth). Reconnect earth. Then 3 x PEFC, 3 x PSCC (Double largest reading).
Main switch remains off for all continuity and IR tests.
Obviously main switch on for Zs and RCD tests.
 
I assume this is a classroom situation.
 
During Phase Sequence/Rotation test on a 3 Phase DB -

Do you test with main switch on or off.

If tested from Incoming side with switch off it would test Supply side.

If tested with main switch on would it test the supply side and the whole installation ?
 
During Phase Sequence/Rotation test on a 3 Phase DB -

Do you test with main switch on or off.

If tested from Incoming side with switch off it would test Supply side.

If tested with main switch on would it test the supply side and the whole installation ?
Not quite. What you are mainly bothered about is the overall rotation remaining consistent for the whole installation. So you would test at the incomer and check it's clockwise.
Then on any 3ph circuit you want to ensure that it is still clockwise at point of connection to load, so usually the isolator.
Though not great practise it doesn't hugely matter if two phases are swapped at the MCB, and two are swapped again at the isolator as both 'mistakes' cancel each other out and the rotation remains the same.
 
Having the 3-phase rotation right is very important for many applications as motors going the wrong way is bad news. Especially if its a sewage plant...

One reason I don't like labelled black line conductors instead of the 3-phase colours is the greater chance of a mix-up in phase order along the way. Certainly you should be confirming rotation both are the supply point and then at the isolators, etc, for any 3-phase loads.

Never assume that because one item is working OK the rotation is correct as some things like 3-phase UPS and some VFD (e.g. used in newer air-con, etc) don't care as they simply rectify the incoming power and chop it up for end use as needed.
 
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