What size copper wire?

[Junkman]

I have a 200 amp automatic transfer switch that I am going to install in place of the existing 200 amp manual transfer switch for my genset. The instructions in the automatic transfer switch say that it should be wired with copper wire. Presently, there is aluminum wire going from a disconnect switch in to the manual transfer switch, and then it goes out that box with a 90 degree sweep downward to another 90 degree sweep, under the concrete floor. Then it comes out of the floor with a 90 degree sweep into another disconnect switch. The reason for this is that I added onto the garage, and moved the original service to the new garage. Every time it went underground, and back up, the inspector wanted a circuit breaker disconnect. How difficult will it be to pull the original aluminum wire through the two 90 degree sweeps, and replace it with copper? Since all this change made the original circuit breaker box a sub panel, there is also a #4 copper ground wire in the PVC conduit. The conduit is a 2 1/2" run that is about 30 feet with the 2 90 degree sweeps. I intend to leave the #4 copper wire in the pipe, and just pull the 3 new copper conductors, if this is possible. The wire from the disconnect on the back of the meter to the new transfer switch is very short, so that one shouldn't present a problem. Thanks

 

[shamrock12]

For 200 amps at this short run, you would use 3/0 gauge copper. They will be stiffer and more difficult to bend but it should not be a big issue pulling through 2-1/2" PVC with a couple 90 degree sweeps.

Personally, I think whoever wrote the instruction manual has no clue what he is doing. There is really no good reason why you would need to use copper conductors instead of aluminum. I would check the lugs inside the automatic transfer switch and see if they are rated for aluminum too. You may see something like Cu-Al which mean either copper or aluminum conductors can be used.

 

[Mustang51js]

Is this a residential building or a shop garage. You can use 2/0 copper if it's residential but I believe you need 3/0 if commercial. Also is everything set up for 200 amp allready,because if the aluminum wire reaches to new lugs in transfer switch then I would just use what you have. More than likely it just recommends copper but prob has aluminum lugs in it anyway. What brand transfer switch, I install a lot of generac generators so I know them fairly well.

 

[shamrock12]

Is this a residential building or a shop garage. You can use 2/0 copper if it's residential but I believe you need 3/0 if commercial. Also is everything set up for 200 amp allready,because if the aluminum wire reaches to new lugs in transfer switch then I would just use what you have. More than likely it just recommends copper but prob has aluminum lugs in it anyway. What brand transfer switch, I install a lot of generac generators so I know them fairly well.

I normally would have selected 2/0 copper myself but instead of risking another lengthy debate with some of those hard-core code police here on this forum, I am just going to play it safe. Since this will be downsteam of the main breaker disconnect, he would have to adhere to the 75 degree column as most breakers are rated for up to 75 degrees C. Yeah, it probably won't make much of a difference but gotta keep those guys happy, right?

 

[Junkman]

It is a residential building, and the transfer switch was made by Asco. I would need to check which series if that makes a difference.

 

[rockwithjason]

If the instructions specify copper then you must use copper or you will violate the code, the ul listing and any warranty.

 

[Norcal]

As long as it's a residence, 2/0 copper is fine.

 

[Speedy Petey]

I find it hard to believe that the instructions say to ONLY use CU wire. That would be absurd since many/most places use AL for service entrance.

I also would say 2/0CU. The assumption that this is residential was a safe one, although now we know it for certain. The fact that this is down stream of a disconnect does not change this.

 

[Norcal]

It meets code so there is no reason not to use 2/0 unless money is burning a hole in your pocket.