Sub panel feeders for generator

Status
Not open for further replies.

triplex15

Member
Location
Virginia
Is it allowed to feed a detached garage sub panel and a seperate sub panel for the emergency generator circuits in the same conduit. I have a 2" conduit for the detached garage sub panel (125amp) using 2/0 AL and they want a few circuits in garage controlled off of an emergency generator and I was going to add a small 50amp sub panel for emergency circuits using #8 CU. I need to know if this is acceptable. Thanks
 

RUWired

Senior Member
Location
Pa.
If your supply voltage is 120/240 single phase to the sub panels, and your 125amp sub panel is calculated load is 120 amps or less the 2/0 al will be ok but the # 8 awg cu. will need to be upsized to 6 awg cu.
 

kacper

Member
Location
Islamorada
You will have resize your wiring base on derating factor.
Please look table:
Table 310.15(B)(2)(a) Adjustment Factors for More Than
Three Current-Carrying Conductors in a Raceway or Cable
If the conduit is run on the exterior wall or roof you also need to take a look
at table: Table 310.15(B)(2)(c) Ambient Temperature Adjustment for
Conduits Exposed to Sunlight On or Above Rooftops

As far generator itself make sure that the ampacity of the coductors is min. 115% of the nameplate current rating. Code section:445.13 Ampacity of Conductors.
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
445.13 applies to the conductors to the 1st overcurrent device. This is normally at the generator.
 

triplex15

Member
Location
Virginia
I will have a generator panel in the garage of the dwelling unit and I need to get a few circuits in the detached garage on with generator if they lose power. That is the reason I will have 2 sub panels in the detached garage.
 

benaround

Senior Member
Location
Arizona
Is it allowed to feed a detached garage sub panel and a seperate sub panel for the emergency generator circuits in the same conduit. I have a 2" conduit for the detached garage sub panel (125amp) using 2/0 AL and they want a few circuits in garage controlled off of an emergency generator and I was going to add a small 50amp sub panel for emergency circuits using #8 CU. I need to know if this is acceptable. Thanks

As far as the two sub-panels, yes it is ok , 225.30(A)(4). As far as the rest of it goes,

there could be questions.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
I've often wondered whether there was a compliant way to use the same conductors to feed to an outbuilding with normal power and back when on a generator using the same conductors. Doubtful.
 

wwhitney

Senior Member
Location
Berkeley, CA
Occupation
Retired
You will have resize your wiring base on derating factor.
Please look table:
Table 310.15(B)(2)(a) Adjustment Factors for More Than
Three Current-Carrying Conductors in a Raceway or Cable
If the feeder conductors and the optional standby conductors will never be energized at the same time, then they could occupy the same raceway without requiring derating?

Cheers, Wayne
 

RUWired

Senior Member
Location
Pa.
I've often wondered whether there was a compliant way to use the same conductors to feed to an outbuilding with normal power and back when on a generator using the same conductors. Doubtful.
BasicaLLY A TRANSFER SWITCH.
 
Last edited:

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
BasicaLLY A TRANSFER SWITCH.
More like two of them, one at each end. With a main interlock at the main panel. I think it's more trouble than it's worth to even investigate.

I have a 3/4" PVC conduit between my shed and my house. I can runa separate genny feeder in it if I want, and get an interlock for my CH panel.


So, never mind. :cool:
 

st1976

Member
Location
CT
A variation on this theme

A variation on this theme

How about this variation... 120/240v 1 phase residential

I want to put my generator at the detached garage instead of next to the house. It will be quieter and the house and the generator will be closer to the LP tank.

Can I run the sensing/charging circuit and the feed back to the house in the same conduit as long as I derate for more than 3 current carrying conductors?

Can I add a circuit for lights in the garage in the same conduit as well?

Of course the low voltage circuit to the transfer switch will be in a separate conduit.

-st1976
 
Status
Not open for further replies.
Top