SE Rated vs. Non SE Rated Transfer Switches

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What is the correct definition of a SE Rated automatic transfer switch vs. a non SE rated automatic transfer switch? Hope this makes it to Tom Baker... he was quoted in a discussion on this matter with my business partner.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
OP, welcome to the forum! :)

That means the transfer switch is "service entrance" rated, and can act as the main disconnect, which is the first thing the conductors from the meter must hit.

A non-SE rated transfer switch must be preceded by a service-rated main disconnect.
 
Larry... Thanks for the input. It is my understanding that all transfer switches that carry the "Service Entrance" rating must have a overcurrent / disconnecting means built in... there in lay definition of "Service"

Nick
 

iwire

Moderator
Staff member
Location
Massachusetts
The listing requires that an transfer switch suitable for use as service equipment will have an externally operable means to disconnect both sources, it may, or may not contain over-current protection.

This info can be found in the UL general directory. (White Book)
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
The typical SE T/S has a main service breaker and a switch or breaker for the generator input; both are ahead of the T/S mechanism itself.
 

tom baker

First Chief Moderator
Staff member
The term UL uses is "Suitable for use as service equipment" - meaning it has an externally accessible means to independantly disconnect each source intended to be a service. And they may be marked Normal Source only (only means to disconnect normal source).
The UL listing information is very long and detailed - catagory WPTZ- I recommend you go to the UL Web site and look it up.
 

chris kennedy

Senior Member
Location
Miami Fla.
Occupation
60 yr old tool twisting electrician
If it comes with a factory means to establish a main bonding jumper, it is suitable for use as service equipment.
 

CBomonti

Member
additional question, same subject

additional question, same subject

Similar question, same subject:

From the ASCO site:

...The ASCO Series 185SE Residential Service Entrance Power Transfer Switch combines the series 185 automatic transfer switch with circuit breaker disconnect device for the normal source. An additional circuit breaker for the emergency source in optional. In addition, main jumper is provided to connect both the neutral and ground conductors in accordance with NEC requirements for service entrance equipment. For use on Optional Standby Systems as defined by NFPA 70: National Electrical Code (NEC)...

I have a single building installation with a "Optional Standby" generator (not an "emergency" generator).
The Normal power is from a utl xfmr (480v, 3ph, 3w).
The generator is (480v, 3ph, 3w) and has a main ckt bkr.
I intend to intall a service rated 3ph, 3w, ATS. This ATS will have a ckt bkr on the normal power connection to meet NEC service entrance req'mts.

Two questions;
1. Per code, do I need to add the "optional" ckt bkr for the standby power connection to the ATS?

2. The load is a 480v, 3ph, 3w system. I am installing 3 phase conductors and a ground conductor from each source to the ATS, no neutral conductor. The ground will be connected/bonded to the "grounded" neutral at each source. Is that correct? (I am being told by others I have to run the neutral from the xfmr to the ATS and ground it there, not sure about the generator side).

Thanks for your help
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
CB, welcome to the forum! :)

1. Not if the generator's breaker is adequate protection for its conductors, and qualifies as the stand-by disconnect.

2. Unlike neutrals, the various EGC's can be continuously interconnected. The service electrodes will land in the T/S.

a. A grounded conductor should be part of the service supply, and bonded at the T/S as well, but need go no farther.
 
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