4 pole ATS

[ActionDave]

It shows the improper choice of a transfer switch that doesn't switch the neutral.

It would be a lot easier to remove the bond at the generator than put in a new transfer switch.

 

[RD35]

I find that most transfer switch installations in our area are done incorrectly when it comes to bonding. Folks (DIY'ers...and some professionals) will install a breaker interlock and a generator feed breaker in their panel. Or, they will install a 2-pole, double throw switch. In either case, they will run a 4-wire generator feeder circuit to an L14-30 inlet where they use an extension cord to plug the transfer switch or house panel into their little 7000W portable generator. The problem lies in the fact that the generator is bonded internally. So power flows parallel through the grounded and grounding conductors of this 4-wire circuit. Funny thing is that the local inspectors and AHJ seem to be fine with it. I have considered not connecting the grounding conductor at one end or the other in order to force a fault current to travel through the neutral wire to the generator in this case. It sounds wrong to do this, but it would prevent the parallel flow problem. A 3-wire SO cord with Black, Red, White conductor colors would be even better. Any thoughts?

 

[kwired]

I find that most transfer switch installations in our area are done incorrectly when it comes to bonding. Folks (DIY'ers...and some professionals) will install a breaker interlock and a generator feed breaker in their panel. Or, they will install a 2-pole, double throw switch. In either case, they will run a 4-wire generator feeder circuit to an L14-30 inlet where they use an extension cord to plug the transfer switch or house panel into their little 7000W portable generator. The problem lies in the fact that the generator is bonded internally. So power flows parallel through the grounded and grounding conductors of this 4-wire circuit. Funny thing is that the local inspectors and AHJ seem to be fine with it. I have considered not connecting the grounding conductor at one end or the other in order to force a fault current to travel through the neutral wire to the generator in this case. It sounds wrong to do this, but it would prevent the parallel flow problem. A 3-wire SO cord with Black, Red, White conductor colors would be even better. Any thoughts?

Not all those small generators have the neutral bonded. You can set it up for what you have, then owner buys a new generator sometime down the road that is not the same, they still can plug that L14-30 cordset they already have into it though so nothing gets changed.

I believe NEC has made some changes and now requires some labeling, but will be read and not understood by many owners, if the L14-30 is still there they will just plug in what they have and not understand what that labeling actually means.

If the transfer switch is part of service equipment or is adjacent to service equipment, which seems to be fairly common in dwelling applications, the potential consequences are lessened anyway, IMO.

 

[ActionDave]

I find that most transfer switch installations in our area are done incorrectly when it comes to bonding. Folks (DIY'ers...and some professionals) will install a breaker interlock and a generator feed breaker in their panel. Or, they will install a 2-pole, double throw switch. In either case, they will run a 4-wire generator feeder circuit to an L14-30 inlet where they use an extension cord to plug the transfer switch or house panel into their little 7000W portable generator. The problem lies in the fact that the generator is bonded internally. So power flows parallel through the grounded and grounding conductors of this 4-wire circuit. Funny thing is that the local inspectors and AHJ seem to be fine with it. I have considered not connecting the grounding conductor at one end or the other in order to force a fault current to travel through the neutral wire to the generator in this case. It sounds wrong to do this, but it would prevent the parallel flow problem. A 3-wire SO cord with Black, Red, White conductor colors would be even better. Any thoughts?

It is almost always a rubber cord between the inlet and the generator so other than the idea that some current on the green wire it's not such a huge big deal.