Phase Rolling vs Phase swaping

[mbrooke]

Brain freeze- can rolling phases result in reverse spinning or will it go unnoticed? Think ABC gets connected BCA or CAB

 

[Jraef]

Rolling does not change rotation.

 

[mbrooke]

Rolling does not change rotation.

Thanks!

Question- can this have any effect on a large building (just curious)?

 

[electrofelon]

FYI I have never heard the term "phase rolling" it must be a regional jargon thing. I remember this thread from a while back someone asked what "bumping phases" meant and I think most hadn't heard that term either.

 

[drcampbell]

It might be used to equalize single-phase loads across a three-phase service.

 

[LarryFine]

I can see it mattering only on high-leg systems.

 

[zbang]

Actually, I've done this a few times with temp setups; with spider boxes and the like, it always seems like C has the lightest load, then B, so I'll roll the phases from one area forward (ABC-> BCA) and from another area back (ABC-> CAB) to get a better balance. Seems to work (in my environments, mostly single-phase loads).

 

[mbrooke]

FYI I have never heard the term "phase rolling" it must be a regional jargon thing. I remember this thread from a while back someone asked what "bumping phases" meant and I think most hadn't heard that term either.

Its done on distribution circuits. Picture lots and lots of high legs, where one can is always more loaded then the other one or two. By rotating each bank down line you get a nice balance.

 

[ptonsparky]

Secondary only here.

Rolling the phases for motors on a high leg system can reduce the current imbalance. Measure, roll. Repeat, repeat, then use the combination with least imbalance. A problem that follows the roll points to downstream issues.

 

[StarCat]

On about getting my mind around this one. Suppose you had a 240V 3 PH high leg service on a commercial property with a bunch of heavily loaded Air Conditioning units, and noticed that there was quite a good voltage imbalance seen at the line side of all the RTU disconnects. Could phase rolling be used in this instance and where would you implement it? We are assuming that the way the panel loads were configured, was unbalanced by possibly more single phase loads than what the space originally had.

 

[kwired]

Its done on distribution circuits. Picture lots and lots of high legs, where one can is always more loaded then the other one or two. By rotating each bank down line you get a nice balance.

If you rotate all of them, you just rotated the imbalance.

You should be alternating which line single phase services connect to also, and when an unbalance condition seems to be persistent you change a select few to balance things out. Those high leg delta services need to have "rolling" of primary or swap the non high leg secondary conductors if your balancing act will change rotation.

 

[drcampbell]

Presumably, it would be implemented by the utility "rolling" the primary connections to the transformers, to reduce a voltage and/or current imbalance in the primary-voltage distribution phases.

 

[StarCat]

This clarifies things.
Thanks