Transfer Switch

Status
Not open for further replies.
L

lauraj

Senior Member
Location
Portland, Oregon
I've made a challenge to my class to come up with a reason for why someone would choose to design a 4-pole vs. a 3-pole transfer switch, so I also need to come up with a good answer, which I don't really have yet either. I've read some of the past posts regarding this, but I am still a little unsure it. One of the reasons for going seperately derived was in the case of ground fault protection on the service. I wanted to clarify this, because if everything is wired correctly, I don't see why you would have use a 4-pole transfer switch. Is there something I'm missing here?

Any other reasons for using the 4-pole?

Thanks,

Laura J
 
I always spec out 4-pole when the service has a ground fault relay incorporated (2 or more Ground fault relays) and/or more than 1 ATS involved in the line. I believe it is done to prevent nuisance tripping of the ground fault relay. I read an article from EC&M (electrical construction and maintenance magazine) approx 2 years ago on this. you can search their website for old articles. Hope it helps
 
The way I see it, ground-fault issues aside, if the generator has, or can have, the neutral isolated from the equipment ground, it's simpler to go with the non-SDS setup.
 
lauraj said:
Larry, are there generators out there where it is not possible to separate neutral and ground?
Click to expand...
Small camping generators are famous for this, but that's single phase. Since you're talking 3 or 4 pole, I'm assuming you're talking 3 phase only.
 
Status
Not open for further replies.
Top