Ask Me Help Desk - Generator Transfer Switch Install

I live in south Florida and have a typical home built in 2005 with a 200A service which is fed through the bacck of the meter housing into the breaker box inside the garage. Or I should say, was fed that way. Last year I decided to put in a transfer switch so I could properly hook up my generator outside to the whole house without putting in one of those cheesy transfer switch breaker boxes from Home Depot. I bought a Cutler Hammer 200A double position disconnect switch and mounted it outside next to the meter. I put a 2" conduit between the two. I ran 3 Aluminum 4/0 conductors from the meter thru the conduit to the transfer switch and I ran 3 more Aluminum 4/0 conductors back thru the 2" conduit from the transfer switch to the meter housing and back into the pass through nipple that goes in to the breaker box.

Is this against any code? I have 6 4/0 Aluminum conductors in the same conduit with power flowing in different directions. They were extremely tight getting them in the conduit but the whole setup has performed flawlessly for 2 years. Now I am considering going to a 320A service and am wondering if I am in compliance with the code before I have the power company poking around hy home.

I have more questions but let's start with this one first.

Thanks.
Larry

Your conduit is a bit undersized, but how long is it? If it's a close nipple it's probably not an issue, but for any length of run, 3" would be required. Perhaps some of the other electricians will chime in on this one.

Two very serious violations,:

1) You did not properly size the feeder conductors. 250 Kcmil "Aluminum" conductors are rated for 200 Amps. Not 4/0. 4/0 "Copper" conductors are rated for 200 Amps.

2) Without knowing the Cable Type and the Conduit type I am making a "SWAG" response.

I am doing this calculation using THHN/THWN type cable and "Rigid Metal Conduit".

Please refer to Annex "C" of the NEC 2008 code, table "C8" using THHN/THWN insulated conductors. According to this table, a trade size 2 conduit is only listed to hold four 4/0 conductors. Not Six. But you have Aluminum, not Copper conductors.

The correct size for six 250 Kcmil conductors would be a Trade Size 3. That conduit can hold up to seven 250 Kcmil conductors. See Annex "C", Table "C8", RMC conduit.

3) Did you derate the conductor load? For 4 to 6 current carrying conductors in a single conduit, you must multiply the amperage (200 A ?) by a factor of 80% or .8. See Table 310.15 (B)(2)(a).

So if your conductors are carrying 200 Amps, you multiply 200 by .8 = 160 Amps. Any load higher than 160 amps would risk melting the insulation on the conductors and exposing bare conductors, because of the heat build-up in the conduit.

If the conduit is a nipple, 24" or less, you do not have to derate the conductors.

As you noted, the 6 #4/0 Al did not fit well in the 2 " conduit. Assuming this is a steel rigid conduit or PVC Sch 40, only 4- #4/0 XHHW are allowed.

Most if not all aluminum conductors use XHHW.

Don't worry about someone seeing this, just make the necessary corrections when you do change the service. Until then, thou, this is a violation. Working fine since installed is irrelevant, you do not know if any damage was done to the insulation. This is why there are standards and codes.

Changing to a 320 Amp service will be a good time to change this conduit.

By the way, #4/0 Aluminum XHHW is allowed for a residential service entrance conductor, per NEC Table 310.15 (B) (6). So the #4/0 Al XHHW is fine.

Another violation is having the service entrance conductors go from the meter directly to the transfer switch with no circuit breaker protecting the transfer switch.

When using the conduit fill tables in Annex C of the NEC, any of the tables that are for "Compact Conductors" will be for aluminum conductors.

Thanks for the responses.

To answer some of your questions...

The conduit is a single 90 deg elbow going from bottom right knockout hole in the meter pan to the side of the gigantic switch. Total length in conduit is less than 18".

It was a real bear to get those conductors through that elbow but that was the largest elbow my Home Depot had on hand.

I thought 4/0 was good as I simply looked in the meter to see what was coming in and matched it. In fact, FPL has two 4/0 and one 2/0 for neutral. I bettered them by going all 4/0.

As for the disconnect between the meter and switch, this baffles me and doesn't make any sense. What is the reasoning behind this?

I was thinking of running another conduit straight out the top of the switch and into my soffit, over and back down into the top of my load center. That will fix any conduit issues.

Putting a switch in between sort of sux.

My issue now is going to be that my transfer switch, rated for 200A, is going to be undersized when I go to 320A service. So I will have to split off essential items, basically leaving it the way it is now and the additional 100A service I am putting on the other end of the house to feed A/C #2 and the pool will not be able to be on the generator. For practical reasons, that will be just fine. Its not worth changing to a 400A transfer switch at this time just to hafe those items running after a storm.

I would appreciate an answer on the switch between the transfer switch and the meter though.

Thanks,
Larry

One quick question:

Is the transfer switch listed for the application? Is it break before make? Does it have an Off position?

Generator Transfer Switch

Quote:

Originally Posted by modelav8r

It was a real bear to get those conductors thru that elbow but that was the largest elbow my Home Depot had on hand.

2" was WAY too small for what you did. I am surprised you got them in without damaging them.
HD and Lowe's are not the only places to buy electrical supplies. There are electrical supply houses in any city.

Quote:

Originally Posted by modelav8r

I thought 4/0 was good as I simply looked in the meter to see what was coming in and matched it. In fact, FPL has two 4/0 and one 2/0 for neutral. I bettered them by going all 4/0.

As TK stated, 2/0CU or 4/0AL are standard for a 200A residential service entrance.

Quote:

Originally Posted by modelav8r

As for the disconnect between the meter and switch, this baffles me and doesn't make any sense. What is the reasoning behind this?

The only time this is accepted is if the transfer switch is "service rated". If not you need a service disconnect before it. The reasoning is that you have rather large UNFUSED conductors in this enclosure.

Quote:

Originally Posted by modelav8r

I was thinking of running another conduit straight out the top of the switch and into my soffit, over and back down into the top of my load center. That will fix any conduit issues.

It will. The fact that you will be quite long going into the house (more than 5-6') will be offset by the fact that you will now have a switch outside.
Don't forget, you need FOUR conductors after a main disconnect. The panel then becomes in a sense a sub-panel.

Quote:

Originally Posted by modelav8r

My issue now is gonna be that my transfer switch, rated for 200A, is going to be undersized when I go to 320A service. So I will have to split off essential items, basically leaving it the way it is now and the additional 100A service I am putting on the other end of the house to feed A/C #2 and the pool will not be able to be on the generator. For practical reasons, that will be just fine. Its not worth changing to a 400A transfer switch at this time just to hafe those items running after a storm.

Typical for a 320A service is two 200A panels. It is also quite common to do exactly what you describe. Essential items in one 200A panel fed through a 200A transfer swtich, and everything else in the other 200A panel.
320A meter pans can have dual lugs installed so you can run two runs on the load side, one to each panel.

Contrary to what some think, it is NOT necessary to have everything in the house working during a power outage/emergency.

Thanks again everyone.

The transfer switch is break before make. It is ON-OFF-ON.
So, do I still need a disconnect between the meter and transfer switch?

If I reroute the service entrance wires from the transfer switch as stated, it will be more like 10-12 ft of wires. Now do I have to run the new wires I am speaking of in conduit all the way into the load center or can I ditch the conduit after I get through the soffit and run right into the top of the load center through an anti-chafe type of fitting?

Another thing is that I wanted to put the 2nd panel in the other end of the house but I am wondering if it is prudent and costworthy to do so. Would I need another disconnect outside between the meter and the 2nd load center? You seemed to indicate that I would due to the distance away. Especially if I decide to ditch the 100A load center and go with a 200A one, I am looking at running four 4/0 or bigger wires about 70 or 80 ft. I think it might be better at this point to just put it next to the 1st 200A load center so I could feed it with another 10 ft of 4/0 rather than 80 ft.

I believe this might eliminate the need for a secondary disconnect.

You also said I need 4 conductors after the disconnect but the switch only switches two conductors and the neutrals are tied together off to the side inside the box. Those same three just run inside to the load center. Ground is made from the strap from neutral I believe. The only place I have a ground rod or wire is going into the meter pan and it stops there.

I didn't wire it that way, I simply took the three wires in my meter pan to the transfer switch and 3 more wires from the switch back to the load center.
Anything wrong with that?

Larry