DIY. Installing sub-panel in detached garage to also run generator

[srogers]

I’m planning to run an electrical sub-panel to my detached garage (about 150’ away) and run it off my 200 amp home panel. I live out in the country in West Virginia and also want to be able to run my emergency generator in the garage when needed to send power back to the house. What size/type wire should I run under the ground and how deep should I dig the trench for this plan?

All help is appreciated!

Shane

 

[James]

You will need 2 cables, one from generator to main panel where an interlocked switch can be fitted and another from house to garage to power whatever is attached to the sub panel.

 

[srogers]

You will need 2 cables, one from generator to main panel where an interlocked switch can be fitted and another from house to garage to power whatever is attached to the sub panel.

Hi James, thanks for your input. So there’s no way (if the power goes out) to hook-up the generator to the sub-panel in the garage and run power back to the main electrical panel in the house? What size wire would you recommend?

 

[James]

You must have an interlocked switch that changes supply from grid to generator. If you put it on the sub panel, power can’t be back fed to the main panel as it will still be attached to the grid, even if the grid has failed.

 

[Megawatt]

I’m planning to run an electrical sub-panel to my detached garage (about 150’ away) and run it off my 200 amp home panel. I live out in the country in West Virginia and also want to be able to run my emergency generator in the garage when needed to send power back to the house. What size/type wire should I run under the ground and how deep should I dig the trench for this plan?

All help is appreciated!

Shane

First off what is the wattage of your generator? Second of all we can’t help without knowing this but the ditch needs to be 18 inches deep as long as you install conduit and 24 inches and then add 12 inches of dirt then install red tape in the ditch and then cover it up if you use direct burial cable. What is the amperage of the panel that you want to install? This all dictates the wire size. Sorry but need more information

 

[James]

thankyou @Megawatt , i had been avoiding the wire size issue as i am not sure about the requirements in the usa.
but i am pretty sure i am correct about the interlock between load, grid and generator needing to be a single device at the origin (in this occasion)
although, technically it would be possible to put a control system in that allowed gen set connection to sub panel with remotely interlocked switchgear, it would be in the magnitude of 10 to 100 times more expensive than running 2 cables and sorting it out at the main panel.

 

[Megawatt]

thankyou @Megawatt , i had been avoiding the wire size issue as i am not sure about the requirements in the usa.
but i am pretty sure i am correct about the interlock between load, grid and generator needing to be a single device at the origin (in this occasion)
although, technically it would be possible to put a control system in that allowed gen set connection to sub panel with remotely interlocked switchgear, it would be in the magnitude of 10 to 100 times more expensive than running 2 cables and sorting it out at the main panel.

Yes @James the OP will definitely need a transfer switch without a doubt. I have an indoor 50 amp automatic transfer switch at my home.

 

[srogers]

First off what is the wattage of your generator? Second of all we can’t help without knowing this but the ditch needs to be 18 inches deep as long as you install conduit and 24 inches and then add 12 inches of dirt then install red tape in the ditch and then cover it up if you use direct burial cable. What is the amperage of the panel that you want to install? This all dictates the wire size. Sorry but need more information

Hi Megawatt, thank you for your response. Generator is 7,500 watts and I can’t imagine needing for than a 50 amp panel for the garage.

 

[Megawatt]

Hi Megawatt, thank you for your response. Generator is 7,500 watts and I can’t imagine needing for than a 50 amp panel for the garage.

Honestly look at the double pole 4 wire receptacle on the generator because I think that it just has a 30 amp circuit. Anyway # 6 copper wire is good for 50 amps and I’m going to say I would use # 8 for 30 amps even though # 10 is also good for 30 amps but you don’t want a voltage drop. Good luck with your project and welcome to the forum