Need Suggestions for Detached Garage Electrical

[Fried]

Hi

I would appreciate some suggestions for adding electrical services for a new detached garage. In addition, I have another future addition that might also play into this addition.

I’ve done a little reading on the subject, but have never done anything like this before other than installing ceiling fans and minor items of this nature. I’m probably capable of running wires to receptacles, switches, following code guidelines, but would not attempt any final connections, etc. that would have safety implications. I expect to find a licensed electrician to perform those or other tasks that are appropriate.

So what follows are a few alternatives (may or may not make sense – would not limit thinking to these!) that I conjured up after reading a little and some details on my existing house service panel and anticipated loads for the new detached garage/possible future addition.

• Double lugs at the existing house meter outlet: one set of feeders to my existing house service panel and another to a new service panel in the new detached garage. I understand that I would need to check to see if this is permissible or not with parish or power company regulations.
  
• Other means of splitting main service feeders to accomplish the above?
  
• Adding a sub-panel in my existing house off the main service panel and then supplying power to another sub-panel in the new detached garage (I don’t know if this is allowed or not; it would have an advantage to provide some spare circuit capability in the existing house. Likely would require upgrading the main breaker also? See details below).
  
• Adding a sub-panel in the new detached garage off the existing house main service panel. One concern here is available breaker locations in the existing service panel.

Detached Garage & Future Electrical Needs

Existing House

• ~3000 sqft
• Square D Q0 Main 200 amp Panel w/150amp main breaker
• 30 slots/with 10 twin capable slots
• All slots occupied, but there are 4 of the twin slots with just a single breaker
• Estimated existing load: Normal 110a (240V); Maximum 140a (240V)
• Electrical is underground (required by subdivision)

New Detached Garage Addition

• 60’ from existing House Main Panel
• Estimated load: Normal 10a (240V); Maximum 26a (240V)
• Circuits: 5 identified, probably a couple spares
• Presumably would want to run 240V to Garage (smaller cable?)

New Carport Addition/Existing Garage Close-in (future)

• Adjacent to House Main Panel, in-between house and detached garage
• Existing garage circuits probably adequate for closing in garage
• Estimated Incremental Carport load: Normal 2a (240V); Maximum 10a (240V)
• Carport Circuits: 2 identified (probably want to supply these from House Panel if possible). A couple spares would be nice, but not required.

[Snoonyb]

"Double lugs at the existing house meter outlet: one set of feeders to my existing house service panel and another to a new service panel in the new detached garage. I understand that I would need to check to see if this is permissible or not with parish or power company regulations.

Other means of splitting main service feeders to accomplish the above?"

This is normally accomplished through a gutter system, since most equipment may not support, as a UL approved method, and would require relocating your existing,

{"Adding a sub-panel in my existing house off the main service panel and then supplying power to another sub-panel in the new detached garage (I don’t know if this is allowed or not;"

"Adding a sub-panel in the new detached garage off the existing house main service panel. One concern here is available breaker locations in the existing service panel."}

it would have an advantage to provide some spare circuit capability in the existing house. Likely would require upgrading the main breaker also?

????????????

[HayZee518]

See if you can utilize the twin breaker spaces on two of the full size breakers 1" You will be providing a two pole 60 breaker which will feed two #6 hot cables along with two more #6's to a sub-panel in the garage. One of these 6's will be a neutral, the other an equipment ground. Feed these 6's in a 1 1/2" pvc run underground minimum burial 24 inches embedded in sand below and above. At sub-panel use a main lug panel with the addition of an aux ground bar. The equip ground cable from the main panel will go here. The neutral goes to the neutral bus WITHOUT the ground screw applied.

[Fried]

Thanks for the replies.

HayZee - Good idea. I actually thought about utilizing more twin slots, but didn't carry it very far. Now that you mention it, I see where I can probably free up 2 full size slots. Would it be reasonable to just try it with the existing 150 amp main breaker and upgrade to a 200a main breaker only if necessary? In reality, I would not be doing much in the garage (10a normal, 25a max) when seeing the maximum estimated house load case (110a normal, 140a max). Would this be expected to pass inspection?

Finally, any thoughts for another option to give me additional circuits on the exterior of the house or a subpanel inside in case I needed a few circuits for future carport, pool, or that new convection oven my wife wants? Thanks.

[HayZee518]

Only thing that comes to mind is a dedicated circuit for an outdoor gfci outlet. About the service amps - if the cable used is a 4/0-3 SEU there should be no problem upgrading the breaker to a 200 but if it is a 3/0-3 SEU forget it - won't have the ampere rating. Still........ use the #6 for a feeder and a two pole 60 to feed it. Always plan for at least 40% more than you actually need. For a 60 amp feed I wouldn't go much more than a panelbox with 20 sp breaker slots.