Manual Transfer Switch

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stickboy1375

Senior Member
Location
Litchfield, CT
As long as my transfer switch (contains no fuses or breakers) is rated as Suitable for Use as Service Equipment, then I can use the main breaker in the panel as my overcurrent protection as long as its adjacent thereto?
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
I did 6 installs like this for a single customer at different locations. Each service was a 400 amp K7 meter can, then the manual transfer switch, then a 400 amp MB panel. We used a SUSE rated switch made by Ronk as they are well made and attractively priced. My experience tells me that some AHJ's at first glace say this is not compliant and may need some convincing.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
What the heck is a K7 meter can???

It's a 3 phase, 4 wire, 320/400 amp, w/bypass direct meter socket. The POCO where these jobs were done gave up CT metering a long time ago unless the load is solidly above 600 amp. I know that may be foreign to many, as I know many utilities only use direct meters up to 200 amp.
 
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resistance

Senior Member
Location
WA
It's a 3 phase, 4 wire, 320/400 amp, w/bypass direct meter socket. The POCO where these jobs were done gave up CT metering a long time ago unless the load is solidly above 600 amp. I know that may be foreign to many, as I know many utilities only use direct meters up to 200 amp.
How does K7 fit into what it is? Depending, A CT is not required for services up to 320A continuos (residential). And not required for commercial 3PH up to 200 amps continuos. Again, it depends.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
How does K7 fit into what it is? Depending, A CT is not required for services up to 320A continuos (residential). And not required for commercial 3PH up to 200 amps continuos. Again, it depends.

K7 is just how they were locally known. I think the 7 refers to 7 jaw, don't know about the K. I didn't mean to turn this into a discussion about metering, but as for allowed meter types and sizes that's the utility's call, not the NEC. I've worked in many areas that the POCO CT meters anything over 200 amp. Don't know why, but its their call.
 

meternerd

Senior Member
Location
Athol, ID
Occupation
retired water & electric utility electrician, meter/relay tech
K vs. S....

K vs. S....

A "K" base meter is a bolt in 400A type (Form 16K). An equivalent S base meter is a Form 16S socket base meter and is rated at 320A (80% of 400A). 7 refers to the number of terminals. Most utilities have gone away from 400A K base meters and use Class 320 S base meters. It's more of a safety issue to most utilities, because a socket base meter is safer when removing or installing when energized.

Didn't mean to go off on a tangent, but it's a good topic. Definitely NOT an NEC thing, though.
 
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augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
A possible fly in the ointment might be the low AIC rating of non-fuse switches, but as long as you AIC is less than 10k you should be o.k.
 

peter d

Senior Member
Location
New England
If you use your transfer switch as the service disconnect, you have to separate grounding and grounded conductors in the panel next to the transfer switch, and make your sole N-G connection there.
 
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