Phase Rotation

[YoungBart]

Does it need to be correct?, Because we recently whent to a job and stuck on one of the consumer units was a sign saying 'Phase Rotation Incorrect'. As I'm still an apprentice I don't know about the test, and No one I asked has ever done one, So Does it not matter that it is wrong? Or is the test just used as a guide?
Thanks
James

 

[stef]

Well, on an idustrial scale it is more often so: some new machines were installed, all motors run in the wrong dierection, one simply changes the phase rotation on the distribution panel and puts a sticker on it. This simply means that the designed phase sequence brown black grey has been changet to i.e. brown grey black.


Correctly the three phase sequence is clock wise L1, L2 and L3 as generated and so follows a new istallation as well. But how long is a new installation new? On an industrial site it is just a recommendation, not a must. ( yet )

 

[edexlab]

This is relevant to a job I'm currently doing ,I'm fitting >20 kw PV on a Chicken shed and the phase rotation is incorrect , I haven't checked at the mains position yet and the install is on a submain which also hasn't been checked continuity wise to confirm this.

Part of the trouble is the maintenance staff there will bodge anything to get it working ,I reckon I'll be filling out at least one A4 page for the comments on existing installation on the certificate, and I get the feeling they won't like me pointing out any incompetence

Now if I insist on changing it back then I've then got to go around the whole site checking that all the 3 phase fans and motors are rotating the right way this could mean around a weeks work the client/main contractor won't want to pay for

The Inverter I'm installing probably won't be affected by the phase rotation being incorrect (afaik but I'm going to check to be sure) it does have a fan but this is single phase and there are no other motors involved
so its a bit of a sticky issue obviously if it has to be done then I'll do it but is it that big an issue if the existing installation is left as is and we record the facts on the certificate and display them on the CU as I can see a lack of cooperation from the client (I'm a subcontractor on this job)

Ps Young Bart
This test is usually done via continuity test and then with a phase rotation meter which shows that the 3 lines are present and whether the rotation is clockwise or anticlockwise which as stef points out has a bearing on the rotation direction of a 3 phase motor

 

[JD6400]

Hi Edexlab , if you do go down the route of kicking up a stink ( sorry i could not help it , as it is a chicken farm ! ).
You best bear in mind that if it will take a week to check , they will almost definitely tell you to do one !
As by the time you have finished you will have starved most of the flock to death , and if they have any feed elevators with back stops in them , if put in to reverse it will most likely rip the head off it .
Some times it is just best to let sleeping dogs lye , if you know what i mean !

 

[somersetsparks]

We found an installation with 'incorrect phase rotation' labels plastered over one of the busbar chambers and evry piece of equipment it fed! (Which was lots!), the problem all stemmed back to the main panel, when it was manufactured, the phase labels were stuck on back to front (red blue yellow) and the sparks that installed dutifully connected it that way!

 

[Plonker 3]

We found an installation with 'incorrect phase rotation' labels plastered over one of the busbar chambers and evry piece of equipment it fed! (Which was lots!), the problem all stemmed back to the main panel, when it was manufactured, the phase labels were stuck on back to front (red blue yellow) and the sparks that installed dutifully connected it that way!

Nothing wrong with following manufacturers instructions.

 

[JD6400]

I have just spent the last few days with the commissioning engineers on one of the larger grain driers / stores we have had this year , and it would appear that the new 400amp head that has just been brought in especially for this project is in reverse !
I will take one of our meters that are capable of telling rotation back there next week when we go to clear site and move the cherry picker to the next store , but i am buggered if i am going to change all the kit back now , if it is the wrong rotation as i suspect it is !

 

[edexlab]

Hi Edexlab , if you do go down the route of kicking up a stink ( sorry i could not help it , as it is a chicken farm ! ).
You best bear in mind that if it will take a week to check , they will almost definitely tell you to do one !
As by the time you have finished you will have starved most of the flock to death , and if they have any feed elevators with back stops in them , if put in to reverse it will most likely rip the head off it .
Some times it is just best to let sleeping dogs lye , if you know what i mean !

Yup this is what I'm concerned about
However with the aspect of switching things off it would definitely have to be of a very short duration as I'm told it only takes a few hours of high temperatures within the shed for them to start smothering themselves and then dying ,which is the main concern, I'm pretty sure that this bloke would'nt hesitate to forward the bill to me, that is if I made it off site alive as he's a bit of an animal himself!

 

[edexlab]

Also I was told by an NICEIC inspector that there is an area around liverpool where every supply has the wrong rotation due to the DNO transformer being wired wrong and he said it's been like this for years.

 

[Rotax100uk]

we had this the other day with refrigeration plant, comp started up and didnt sound very good, shut down swap phase over and away it goes

 

[YoungBart]

Thanks for the replies guys, I wasn't too sure wether It was a major problem or not. And it seems that others have had similar problems.

 

[Risteard]

Also I was told by an NICEIC inspector that there is an area around liverpool where every supply has the wrong rotation due to the DNO transformer being wired wrong and he said it's been like this for years.

Belfast is reversed too.

 

[Darkwood]

The only real concern is that everything in the installation follows the same connection plan thus you dont have some submains going one way while other are opposite, i have in the past corrected rotation from the ISU to the main isolator but with a varied range of machines from Russian lathes to Japanese grinders all of which run different rotations to each other their is just no winning on some jobs but to take each machine as it comes.