Incorrect Polarity

[dodge26]

My point is if you were running a new supply to an existing board, and the new supply is coming from the adjacent board. At what point would you check the polarity. As I see it, you wouldn't check the polarity when disconnecting the old supply only when you have ran the new supply?????

 

[MDJ]

. At what point would you check the polarity.

Before energising if machines or any 3 phase kit was on the board.

 

[spark 68]

Of course you would (or should), at least check rotation, at least at DB level as well as at the point of use, both before and after.

The regs say phase sequence should be maintained throughout the installation, but in the real word we know this is not always possible in installations that may well have been added to and altered over the years, or may have been connected differently from the beginning.

This is not always possible to easily correct, most times additional equipment being wired to suit the existing.
Where necessary "phasing out" should also be done where more than one supply is present, or likely to be connected.

 

[dodge26]

Before energising if machines or any 3 phase kit was on the board.

So post install we have verified phase rotation at DB and isolators. Would you have done anything different.

 

[spark 68]

So post install we have verified phase rotation at DB and isolators. Would you have done anything different.

Little good it will do after the horse has bolted so to speak, and damage has already been caused, it should be checked before as well as after.

 

[Knobhead]

On that not Sintra I had a supply upgrade to a building which meant a new DNO cable into building from street and because the cable layers had put the cable the wrong way around they couldn't connect the phases in the correct order and fit them in the joint ..... The guys who connect it are different from the idiots that lay it ...too many departments lack of communication!

How much cable jointing have you done?

There’s no option but go with the lay of the cable especially in a breach joint. Phase colours mean nothing, you sort it out at the termination.

The first plants I worked on had 433V forward and reverse along with 550V (always reversed).

The 11KV had been reversed since 1925

 

[Darkwood]

How much cable jointing have you done?

There’s no option but go with the lay of the cable especially in a breach joint. Phase colours mean nothing, you sort it out at the termination.

The first plants I worked on had 433V forward and reverse along with 550V (always reversed).

The 11KV had been reversed since 1925

Yep not exactly my field i have to admit- Tony but just going by what the guy fitting and terminating the consumer end said ... he just said that there was no reason for it to be reversed on the connection in this case i can see its not always an option regarding the responses but with said case he just said it was a breakdown in communication and they have several different departments from the estimation to final connection and its common for stupid mistakes to occur.

 

[Sintra]

Can anyone give us some regs on the following.

We recently re-wired a supply to an existing DB. The DB was supplying some 3 Phase condensor units. The new supply needed to come from the adjacent Generator backed board. Turns out the 2 separate supplies into the building 1 had reverse polarity the other was ok. Therefore we inadvetently re-wired the new supply with correct polarity, however the units were relative to the incorrect polarity :93::93:. Which caused a shed load off damage to PCB's/diodes.

The original AC fit out was 10+ years ago:waving:, so there is a bit of finger pointing
:13:

We know this should be labelled accordingly, can anyone come up with reg's or literature on it?

Why did you not investigate further prior to the work starting?

The issue was the original supply to the board was reversed at source Red/Blue/Yellow (colours at the board were correct), so us removing the supply and re-supplying from an alternative board which had the correct phasing of Red/Yellow/Blue, which on completion we tested and the phase rotation was correct.

It was actually incorrect for the equipment it was supplying.

My point is if you were running a new supply to an existing board, and the new supply is coming from the adjacent board. At what point would you check the polarity. As I see it, you wouldn't check the polarity when disconnecting the old supply only when you have ran the new supply?????

If you could clearly see reversed phase rotation on the existing supply to the board then further checks would be needed.

So post install we have verified phase rotation at DB and isolators. Would you have done anything different.

Seems to me you are trying to justify doing the job without the proper thought and testing being given to it.

 

[Knobhead]

Yep not exactly my field i have to admit- Tony but just going by what the guy fitting and terminating the consumer end said ... he just said that there was no reason for it to be reversed on the connection in this case i can see its not always an option regarding the responses but with said case he just said it was a breakdown in communication and they have several different departments from the estimation to final connection and its common for stupid mistakes to occur.

It only makes a difference on feeders that can be paralleled.

As for rotation, I’ve no sympathy for the OP. It doesn’t take long to phase out. For a new drive you take the coupling or belts off the motor and run it light for direction. It’s not rocket science!

By convention if the phase rotation is correct, connecting the motor RYB to 123 should give clockwise rotation looking at the shaft. Wouldn’t put money on it though

 

[shanky887614]

It only makes a difference on feeders that can be paralleled.

As for rotation, I’ve no sympathy for the OP. It doesn’t take long to phase out. For a new drive you take the coupling or belts off the motor and run it light for direction. It’s not rocket science!

By convention if the phase rotation is correct, connecting the motor RYB to 123 should give clockwise rotation looking at the shaft. Wouldn’t put money on it though

I don't know how accurate they are but can't you use a phase tester before disconnecting old supply.

That way you can sought it at the board because it shows which way it will spin etc