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What Transfer Switch Ahead of Span Panel?

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Tradesmanx

Member
Location
Sammamish, WA
My customer has a smart SPAN panel capable of load shedding. He also has a 24,000-watt portable generator and needs a transfer switch. SPAN says the transfer switch must go ahead of the SPAN service panel. I don't want to add a backed-up loads panel, because that would require taking circuits out of the SPAN smart panel defeating its purpose. Now, if the transfer switch goes ahead of the SPAN panel, then I'm pretty sure it will have to be service rated as it will sit between the utility meter and the SPAN panel. If this is the case, will I have to separate out the grounds and neutrals in the SPAN panel? If so, it will mean I'll have to research whether the SPAN panel still works with the grounds and neutrals separated out. Additionally, I'm seeing conflicting posts on whether a circuit breaker is required in the transfer switch. One post indicates a breaker in the transfer switch is not required as long as it is installed within 15 feet of the service panel (in this case SPAN) and suggests that since there is a breaker in the original service panel, a breaker is not needed in the transfer switch. If this is true, what about the portable generator side. I'm assuming the generator has a built-in fuse. If true, it would mean there are already fuses after each side of the transfer switch. I'm not sure I can trust the post about the 15' thing and no breaker required in the transfer switch. So, to recap... 1) Do I have to separate out the grounds and neutrals in a panel after a service rated transfer switch with no main breaker or fuse, 2) Can I use a transfer switch with no breaker or fuse in this situation, and 3) which brand specific 200A transfer switch would you suggest?
 

Tradesmanx

Member
Location
Sammamish, WA
So, it's basically standard to separate out the grounds and neutrals of a service panel downstream from a transfer switch. I'm hearing the code has tightened up and now a breaker in the transfer switch ahead of the service panel is required. Is this true?
 

marmathsen

Senior Member
Location
Seattle, Washington ...ish
Occupation
Electrical Contractor
NEC 2023 250.24(C) Main Bonding Jumper.

For a grounded system, an unspliced main bonding jumper shall be used to connect the equipment grounding conductor(s) and the service-disconnect enclosure to the grounded conductor within the enclosure for each service disconnect in accordance with 250.28.

I would consider the transfer switch a disconnect. What code cycle are you on? The Span panels are pretty new, is there also an emergency service disconnect outside per 230.85?

Rob G - Seattle
 
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