ECN Forum Forums Code Related Discussion NEC & other Code issues Transfer switches

When installing a transfer switch ahead of a main breaker panel,should you bring all available grounding electrode conductors to the transfer switch (listed as suitable for use as service equipment, therefore considered first point of disconect?)and bond right there, then use SER from the transfer switch to the panel? Or is SEU o.k to use from the transfer switch to the panel,considering the panel is usally only a foot or two away??

Does the transferswitch have a disconnecting means or overcurrent protective device built in?

I believe the actual transfer switch is the disconnect. It is labeled as suitable for use as service equipment. It does not contain overcurrent protection though.

[This message has been edited by cthusky (edited 02-12-2002).]

Cthusky
I’ll try to keep this as short as possible. First look at Service-Equipment in the definitions then section 230.91(NEC 2002) allows the service disconnect to be located immediately adjacent to the overcurrent device (main breaker). Both the transfer switch and the distribution panel are considered service-equipment. 250.24(C) specifies that the grounding electrode conductor be connected to the service-equipment, that could be either the transfer switch or the distribution panel adjacent to the transfer switch, both are consider service-equipment. Either place you land the grounding electrode conductor, only three conductors between the transfer switch and the dist panel is all that is required between the two panels using the Edison three-wire system.

Thanks for the reply,I thought though you needed to use SER because of 250-24(a)(5). Since the transfer switch is the bonding point/disconnecting means, using a three wire to the panel from there would mean a "load side connection" of the grounded and grounding conductors.Yes/no