SceneryDriver
Senior Member
- Location
- NJ
- Occupation
- Electrical and Automation Designer
In a few weeks, I'm going to be installing an 18KW whole-house NG-fired generator and associated transfer switch. I'm a little rusty on residential service details; in Entertainment, we just run everything (L, N, and G) full size, but obviously that's not the case with a resi service. I want to make sure I get the grounding/bonding correct as well.
What's existing:
200A 120/240 underground service comes up into a meter pedestal on the side of the house. Service conductors come out the back of the meter pedestal, through the rim joist in 2" PVC conduit, and drop directly into the top of a 200A CH panel in the basement. Ground is a Ufer original to the '83 house build (lots of rock below the topsoil make ground rods a nightmare), with a #4 bare copper conductor coming out of the slab under the panel. Water ground runs to the nearest copper pipe with insulated #4 (compliant when the service was upgraded ~20 years ago).
What I'm planning:
Service conductors from the meter to the ATS:
Mount the Milbank 200A transfer switch to the right of the existing panel. Replace the existing PVC drop into the panel with a section of either 2" Greenfield with (2) 2/O copper phase conductors, (1) 1/O copper neutral conductor, and (1) #4 copper ground conductor. That short run of Greenfield will let me get into the transfer switch. Plumbing and other obstacles prevent me from considering EMT for the relocation. I could also use a piece of 2/O - 1/O - #4 copper MC cable as well, if I can source a ~10ft piece reasonably. Grounding bushings with lay-in lugs on each end.
ATS to panel:
Transfer switch has a 200A main utility breaker; from the ATS output to the lugs of the existing panel, a short run of 2" EMT with (2) 2/O copper phase conductors, (1) 1/O copper neutral conductor, and (1) #4 copper ground conductor. Grounding bushings with lay-in lugs on each end.
Grounding:
Relocate and extend (with irreversible splice) the #4 feed from the Ufer to the ATS and make the N-G bond there; I will remove the bonding screw in the existing panel, and rearrange the neutrals and grounds since it's now a subpanel. Run new #4 back to location where water line enters the house (well water with copper pipe underground).
Generator to ATS:
1-1/2" EMT for power, from ATS to generator location; final few feet outdoors in LFNC.
Generator has a 100A breaker; pipe will contain (2) #3 copper phase conductors, (1) #4 copper neutral conductor, (1) #4 ground conductor, (2) #12 copper conductors to power the battery charger/oil pan heater/ battery heater from the ATS.
There will be a separate 1/2" EMT run from the ATS to the generator location for a LV COM's cable; the generator and ATS communicate over 18-2 twisted pair.
At the generator:
I'm considering running the #12 conductors through a 30A air conditioner -style disconnect, to allow power to be removed from the generator for service. Do I need a 120V GFCI "service" outlet within 6' of the generator? There's an existing outlet about 20' away.
Thoughts?
Thanks,
SceneryDriver
What's existing:
200A 120/240 underground service comes up into a meter pedestal on the side of the house. Service conductors come out the back of the meter pedestal, through the rim joist in 2" PVC conduit, and drop directly into the top of a 200A CH panel in the basement. Ground is a Ufer original to the '83 house build (lots of rock below the topsoil make ground rods a nightmare), with a #4 bare copper conductor coming out of the slab under the panel. Water ground runs to the nearest copper pipe with insulated #4 (compliant when the service was upgraded ~20 years ago).
What I'm planning:
Service conductors from the meter to the ATS:
Mount the Milbank 200A transfer switch to the right of the existing panel. Replace the existing PVC drop into the panel with a section of either 2" Greenfield with (2) 2/O copper phase conductors, (1) 1/O copper neutral conductor, and (1) #4 copper ground conductor. That short run of Greenfield will let me get into the transfer switch. Plumbing and other obstacles prevent me from considering EMT for the relocation. I could also use a piece of 2/O - 1/O - #4 copper MC cable as well, if I can source a ~10ft piece reasonably. Grounding bushings with lay-in lugs on each end.
ATS to panel:
Transfer switch has a 200A main utility breaker; from the ATS output to the lugs of the existing panel, a short run of 2" EMT with (2) 2/O copper phase conductors, (1) 1/O copper neutral conductor, and (1) #4 copper ground conductor. Grounding bushings with lay-in lugs on each end.
Grounding:
Relocate and extend (with irreversible splice) the #4 feed from the Ufer to the ATS and make the N-G bond there; I will remove the bonding screw in the existing panel, and rearrange the neutrals and grounds since it's now a subpanel. Run new #4 back to location where water line enters the house (well water with copper pipe underground).
Generator to ATS:
1-1/2" EMT for power, from ATS to generator location; final few feet outdoors in LFNC.
Generator has a 100A breaker; pipe will contain (2) #3 copper phase conductors, (1) #4 copper neutral conductor, (1) #4 ground conductor, (2) #12 copper conductors to power the battery charger/oil pan heater/ battery heater from the ATS.
There will be a separate 1/2" EMT run from the ATS to the generator location for a LV COM's cable; the generator and ATS communicate over 18-2 twisted pair.
At the generator:
I'm considering running the #12 conductors through a 30A air conditioner -style disconnect, to allow power to be removed from the generator for service. Do I need a 120V GFCI "service" outlet within 6' of the generator? There's an existing outlet about 20' away.
Thoughts?
Thanks,
SceneryDriver
