The manufacturer of a piece of mobile equipment that our company is inspecting has installed a 25 KW generator as the primary source of power for the equipment. They have also installed a double throw safety switch as a means for connecting to a permanent power source. They have installed the line and load wiring between the generator control panel and the double throw switch in the same conduit. Is this acceptable?
Generator Wiring
- Thread starter clarkm
- Start date
- Status
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Generator Wiring
Maybe. Assuming it was done under a permit and inspected, then:
Does the generator have a bonding jumper between the neutral and the frame?
Does the generator have overcurrent protection?
Is the transfer switch ahead of or behind the service?
What is the overcurrent protection to the transfer switch.
The main concern is the generator configured as a separately derived system or not.
Maybe. Assuming it was done under a permit and inspected, then:
Does the generator have a bonding jumper between the neutral and the frame?
Does the generator have overcurrent protection?
Is the transfer switch ahead of or behind the service?
What is the overcurrent protection to the transfer switch.
The main concern is the generator configured as a separately derived system or not.
Re: Generator Wiring
I believe there is a bonding jumper on the neutral but I would have to verify this.
The generator does have overcurrent protection.
The transfer switch would be considered behind the service I would think. The generator is normally the primary source of power. The generator feeds its control panel. The output of the generator panel then goes to one side of the transfer switch. The transfer switch then feeds a circuit breaker panel. The conduit for the load side of the control panel to the transfer switch also contains the return wiring that feeds the circuit breaker panel. Thus if you are on land power the wiring feeding the circuit panel would still be routed through the generator control panel.
I am not sure about the seperate derived system, I will have to check this out.
There is overcurrent protection in the generator control panel.
I believe there is a bonding jumper on the neutral but I would have to verify this.
The generator does have overcurrent protection.
The transfer switch would be considered behind the service I would think. The generator is normally the primary source of power. The generator feeds its control panel. The output of the generator panel then goes to one side of the transfer switch. The transfer switch then feeds a circuit breaker panel. The conduit for the load side of the control panel to the transfer switch also contains the return wiring that feeds the circuit breaker panel. Thus if you are on land power the wiring feeding the circuit panel would still be routed through the generator control panel.
I am not sure about the seperate derived system, I will have to check this out.
There is overcurrent protection in the generator control panel.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Generator Wiring
Is this a 120/240 V single phase system?
The generator is the normal source, IE almost always running?
You are connected via the transfer switch to some source of commerical power?
Is this a 120/240 V single phase system?
The generator is the normal source, IE almost always running?
You are connected via the transfer switch to some source of commerical power?
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Generator Wiring
The generator supply is a feeder, it would require OCP at its line side. The generator panel would be protected from OC from the generator and from the service OCPD.
There would be no neutral to case bond in the generator, a main bonding jumper would be in the service, with a grounding electrode system there.
This is assuming the service and its connection to the utility neutral is always made. If not it would seem to me that the generator becomes a "utility" source and is a seperatly derived system.
The generator supply is a feeder, it would require OCP at its line side. The generator panel would be protected from OC from the generator and from the service OCPD.
There would be no neutral to case bond in the generator, a main bonding jumper would be in the service, with a grounding electrode system there.
This is assuming the service and its connection to the utility neutral is always made. If not it would seem to me that the generator becomes a "utility" source and is a seperatly derived system.
brian john
Senior Member
- Location
- Kilmarnock, Va
- Occupation
- Retired after 52 years in the trade.
Re: Generator Wiring
Tom:
One item of note is the "manufacture" depending if the total package is listed would effect any answers. Repeating Tom's post I believe
If the generator is connected to a utility source through the MTS (manual transfer switch) then you need to verify the bonding jumper at the gen set and if the MTS has a pole to open the neutral. single phase 120/240 2 pole switch then the bonding jumper is lifted, single phase 120/240
with a 3 pole switch then the bond remains in place.
If the service is not connected the bond jumper remains in place.
The genset needs OCP and you need OCP from the utility feed
Tom:
One item of note is the "manufacture" depending if the total package is listed would effect any answers. Repeating Tom's post I believe
If the generator is connected to a utility source through the MTS (manual transfer switch) then you need to verify the bonding jumper at the gen set and if the MTS has a pole to open the neutral. single phase 120/240 2 pole switch then the bonding jumper is lifted, single phase 120/240
with a 3 pole switch then the bond remains in place.
If the service is not connected the bond jumper remains in place.
The genset needs OCP and you need OCP from the utility feed
Re: Generator Wiring
I guess my original question has been lost. Is it legal under these circumstances for the line and load conductors, assuming they have OCP in both directions, legal to be in the same conduit between the MTS and the Generator control panel. The load conductors from the MTS pass through the generator control panel enroute to the distribution panel whether the MTS is connected to the generator or a commercial power source.
I also overlooked a portion of the first part when Tom Baker said assuming it was done under a permit and inspected. I can not assume this as the unit was manufactured in Canada and we were not supplied any paperwork stating that it was inspected.
I guess my original question has been lost. Is it legal under these circumstances for the line and load conductors, assuming they have OCP in both directions, legal to be in the same conduit between the MTS and the Generator control panel. The load conductors from the MTS pass through the generator control panel enroute to the distribution panel whether the MTS is connected to the generator or a commercial power source.
I also overlooked a portion of the first part when Tom Baker said assuming it was done under a permit and inspected. I can not assume this as the unit was manufactured in Canada and we were not supplied any paperwork stating that it was inspected.
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