OCP/Transfer sw.

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RUWired

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When is an OCPD required before a transfer sw on a service.Does the withstand rating need to be higher than the aic rating of the main after the switch.
Rick
 
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If the transfer switch is installed on service conductors it would need to be service rated (and would have a main built-in) or, if its not service rated, it would need service OCP protection ahead.
The withstand rating of the T.S. would need to meet the available AIC feeding the T.S.
 
Thanks Augie,I ran into a transfer sw fed without OCPD from an outdoor pad mount transformer today and thougt is was odd.I also have a similar setup to do, but the P.E. requested a service rated switch.I did'nt know the difference between the two.
Rick
 
There are service rated manual transfer switches that have no overcurrent device. In fact my transfer switch in my house is just such a beast. These have to be mounted adjacent to an overcurrent device if it is the service disconnect. So you could put it before the overcurrent device if the switch is service rated, or after if the overcurrent device is a breaker and you run a separate EGC.

Like others said, the AIC rating of the switch needs to be high enough for the installed transformer and conductors.
 
Has anyone ever used an auto transfer switch with a main breaker in it.I dont think theres enough room to actually put a breaker.I'm waiting for asco to reply with info on one they say is suppose to work with the 7000 series unit.
 
RUWired said:
Has anyone ever used an auto transfer switch with a main breaker in it.
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Plenty of times. The Generac/Guardian service-rated ATS's are examples.

The service disconnect must be either ahead of, or part of, the ATS. The service OCPD may be ahead of, part of, or after but adjacent to, the ATS.

In any case, the bonding, and origination of a separate EGC, must occur within the enclosure of the service disconnect.
 
LarryFine said:
The service disconnect must be either ahead of, or part of, the ATS. The service OCPD may be ahead of, part of, or after but adjacent to, the ATS.
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Thats what asco is saying, It needs to be in a seperate compartment prior to the ats.They don't make this with it built in.So then if a main needs to be installed prior to an ats, then i would'nt call it service rated.
Rick
 
RUWired said:
So then if a main needs to be installed prior to an ats, then i would'nt call it service rated.
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Or, to put it another way, it can't be considered service-rated.
 
chris kennedy said:
It sure does and an 800A switch also. I'll PM you a pic of the guts tomorrow.
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I would appresiate that.One of the problems with these ats were using is they have bypass isolation in them.Its like having two switches in one.
 
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