I need to install a 175 foot underground feed between a generator and a building and need help with finding the wire. My research indicates I can use either a copper 2-2-2-4 thhn or aluminum 00-00-00-1 thhn in a grey schedule 40 conduit. Is my research correct? What is the precise desingation (and perhaps a source) for this wire?

Need to know the capability of your generator,
30 Amps, 200 Amps.
You can use smaller conductors with Copper, and is more Expensive.
Ever Planning on Future Upgrade?
At least use large enough conduit, I would run an extra 3/4" for control/data of Generator

Be sure to be at least compliant with NEC. If not code compliant, insurance will be useless. Aluminum wire is notorious for coming loose through thermal expansion and contraction per degree temperature change. It's still in use because it's light weight, and cheap... Good luck...

Excuse me, left out 125 amp 120/240 single phase

Are you saying the generator puts out 125 amps?? I seriously doubt that. That is a 30kW genny.

Be sure to be at least compliant with NEC. If not code compliant, insurance will be useless. Completely untrue.


Aluminum wire is notorious for coming loose through thermal expansion and contraction per degree temperature change. This is only an issue if the conductors were not terminated correctly in the first place.

Completely untrue.

This is only an issue if the conductors were not terminated correctly in the first place.

My experience disagrees. If the NEC isn't useful what's the need for it, or the expense of enforcing it?

37 years of experience with air transportable radar and comm equipment reveals that even correctly terminated aluminum wire must be periodically inspected and tested for tightness to insure dependability.

My experience disagrees. If the NEC isn't useful what's the need for it, or the expense of enforcing it?
My disagreement was with the fact that your insurance is "useless". I have it from the source that this is completely untrue.





37 years of experience with air transportable radar and comm equipment reveals that even correctly terminated aluminum wire must be periodically inspected and tested for tightness to insure dependability.Well that certainly is commendable experience with regard to building wiring. Not sure how it relates though.
My less than 37 years experience with building and construction wiring disagrees.

If this were true then why is this not required by code? Or why are AL conductors still allowed by code?

Money. Labor costs have made preventive and predictive maintenance unpopular. We are now in a "use it until it fails, then replace it" mode of thinking. "Fix it before it breaks" has fallen out of favor due to costs. Connections should be periodically inspected and cleaned of corrosion, then tightened with a torque-measuring tool appropriate to the application.

Additionally, insurance companies enjoy collecting premiums, and dislike paying claims. Any excuse available to deny a claim, will be utilized by the claims adjuster... give them a pebble, they will drop a boulder on you...

Connections should be periodically inspected and cleaned of corrosion, then tightened with a torque-measuring tool appropriate to the application.
In a perfect world yes, in the real world, not so much.

Again, aluminum terminated properly will be fine for years. I have seen just as many copper connections fail because of improper terminations.

Additionally, insurance companies enjoy collecting premiums, and dislike paying claims. Any excuse available to deny a claim, will be utilized by the claims adjuster...give them a pebble, they will drop a boulder on you...Agreed, but they cannot legally deny a claim because something was not done "to code".
They would have to find some other loop hole.

excuse me, left out 125 amp 120/240 single phaseBlingster, what is the kW output of this generator?

The policy doubtlessly contains a clause related to electrical installation or modification which hasn't been certified by a licensed electrical inspector, whose seal should be visible on the switch box... In case of building damage by fire, that's what is looked for. My observations about aluminum wire are based on the annual maintenance requirements of my customers, and my direct observations while performing those tasks. "Shoot" a series of connections of any size, with an infra-red thermometer. When carrying a similar load, one will find a loose, or corroded terminal will be hotter... this is wasted power, money and increases corrosion. The PM is done to avoid burning fuel, just to heat the connection.

The policy doubtlessly contains a clause related to electrical installation or modification which hasn't been certified by a licensed electrical inspector, whose seal should be visible on the switch box...In case of building damage by fire, that's what is looked for. Again, and finally, I have been told by insurance adjusters and agents this is simply not true.

Are you saying the generator puts out 125 amps???? I seriously doubt that. That is a 30kW genny.

Actually, I'm using a 60kw (250 amps) generator and sending 30kw (125 amps) in each of two directions, one 40' and the other 175' - of course, I would prefer copper, but the cost may force me to use aluminum - any thought on how to determine and find a proper wire set for the 175 foot run?

Gee, that must be why you should always get a permit and then have the work inspected by the AHJ.

Work that has been inspected and approved by the AHJ is covered by insurance. The risk you run if the work has not been inspected and the insurance company determines that the cause of the fire came from work that may not have been approved opens a door for them to deny the claim.

Point 2: You cannot use THHN wire or cable. You must use THWN-2 or another type cable that is listed for "Wet" conditions. Even though you are using conduit, it is still considered as a wet area.

Finally, care has to be given to the size of wire used. With a run of 175 feet, there will be wire sizing concerns because of voltage drop considerations.

Completely untrue.

This is only an issue if the conductors were not terminated correctly in the first place.


I agree!

actually, i'm using a 60kw (250 amps) generator and sending 30kw (125 amps) in each of two directions, one 40' and the other 175' - of course, i would prefer copper, but the cost may force me to use aluminum - any thought on how to determine and find a proper wire set for the 175 foot run?I'd really like to know how you are splitting the output in half. 30kW one way and 30kW the other. I sure am curious.

I'm sorry, at the risk of sounding like a jerk, and an assault of the red boxes, I have to say:
If you are installing a 60kW generator you should damn well know what you are doing ahead of time!
This is not a toy, nor is it a DIY project. This is a serious expensive undertaking.
PLEASE, call in a pro.