transfer switch

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M

mcelweec@gmail.com

CMAC1
Location
NYC
Occupation
Electrician
on a project the engineer/contracting company erred in ordering the ATS equipment(you may have read my previous thread).Basically what I have is two generators with iso neutrals,EM tie switchgear with bolted neutrals and 4 pole ATSs.One of the solutions that came up,was to provide an isolated neutral in the transfer switches and abandon the neutral poles.They have contacted the ATS manufacturer,he believes this can work but is not sure if this would be code compliant.Basically the question is can a 4 pole transfer switch be used as a three pole?.
 
mcelweec@gmail.com said:
on a project the engineer/contracting company erred in ordering the ATS equipment(you may have read my previous thread).Basically what I have is two generators with iso neutrals,EM tie switchgear with bolted neutrals and 4 pole ATSs.One of the solutions that came up,was to provide an isolated neutral in the transfer switches and abandon the neutral poles.They have contacted the ATS manufacturer,he believes this can work but is not sure if this would be code compliant.Basically the question is can a 4 pole transfer switch be used as a three pole?.[/quote]



I do not see why not.
Click to expand...
 
Why not? We have a job that is all 3 wire and the engineer spec'd 4 pole ATS's. Which is better than another job where they sepc'd 4 poles and the EC installed 3 poles. Talk about an expensive punch list item, 8 ATS' 100-1200 amp in size. The EC went bankrupt and we were hired to furnish and install the ATS's
 
it actually sucks,this and other costly errors/omissions by the engineer is hurting my relationship with the company and also hurting my bottom-line.
 
MC,

You should be paid thru change orders if there are violations that the engineer missed. Don't short change yourself, why should you pay for his mistakes.
 
JWCELECTRIC said:
MC,

You should be paid thru change orders if there are violations that the engineer missed. Don't short change yourself, why should you pay for his mistakes.
Click to expand...

That would be my question also. How is it supposed to be your fault for someone else's mistakes? Unless your company supplied the engineering and equipment specifications.
 
I'm not following the problem.
What is an iso neutral?
If the generators are SDS or non-SDS's, you can still use a 4 pole switch. It is the other way around that would be a problem, if the ATS was 3 pole, then the generators must be non-SDS's (no N-G bond).
If need be, I see no problem using a 4 pole switch as a 3 pole switch.
In large sizes, I often use a 3 pole CB for single phase feeders and leave the unused poles marked and empty.
 
ron said:
I'm not following the problem.
What is an iso neutral?
If the generators are SDS or non-SDS's, you can still use a 4 pole switch. It is the other way around that would be a problem, if the ATS was 3 pole, then the generators must be non-SDS's (no N-G bond).
If need be, I see no problem using a 4 pole switch as a 3 pole switch.
In large sizes, I often use a 3 pole CB for single phase feeders and leave the unused poles marked and empty.
Click to expand...

You modify the ATS controls for single phase operation or special order a control panel?
 
I have not used a 3 pole ATS as 1 or 2 pole, because of the possible control confusion.
On occasion, I need a 125A 1 or 2 pole breaker. Since availability is difficult, I allow a 2 or 3 pole circuit breaker to be used.
 
brian john said:
Why not? We have a job that is all 3 wire and the engineer spec'd 4 pole ATS's. Which is better than another job where they sepc'd 4 poles and the EC installed 3 poles. Talk about an expensive punch list item, 8 ATS' 100-1200 amp in size. The EC went bankrupt and we were hired to furnish and install the ATS's
Click to expand...

I've seen this sort of thing a couple of times - the engineer specs an oversized 4 pole ATS for no apparent reason other than "future." Maybe it's cause they charge a percent fee and a 4 pole transfer switch racks up material costs a bit :D
 
ron said:
I'm not following the problem.
What is an iso neutral?
If the generators are SDS or non-SDS's, you can still use a 4 pole switch. It is the other way around that would be a problem, if the ATS was 3 pole, then the generators must be non-SDS's (no N-G bond).
If need be, I see no problem using a 4 pole switch as a 3 pole switch.
In large sizes, I often use a 3 pole CB for single phase feeders and leave the unused poles marked and empty.
Click to expand...


Ron the problem is both generators are feeding parallel switch gear that has a solid neutral. "If" he used the fourth pole, the gensets would be SDS's and the equipment grounds would be parallel to the neutral conductors. The OP wants to keep the gensets non SDS's so he's asking if it;s ok not to use the terminals identified for the neutral conductors in the ats's. The op will have to install an isolated bar or float the splices in the ATS's.

Rick
 
Rick,
I beleive switching the neutral at the transfer switch gives you the choice of having SDS sources or not. It doesn't require you to bond the n-g at the gens, it just gives you the choice.
 
ron said:
Rick,
I beleive switching the neutral at the transfer switch gives you the choice of having SDS sources or not. It doesn't require you to bond the n-g at the gens, it just gives you the choice.
Click to expand...

Ron if you choose not to bond the gensets and you are using the switched neutral, the fault path would not be able to trip the genset breaker. It is also required to bond at the first OCPD.

Rick
 
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