A Different Wire Gauge Question

[Diggin It]

Is 2AWG copper, 19 strand THHN equivalent to 2/0 copper 7 strand RHH/RHW for a 100A Service Entrance?

For a three conductor service entrance, can the feeds wires be mixed; two of them 2/0 RHH/RHW and the third one 2AWG THHN? All will be in either rigid conduit or sealtight.

Reason for asking: I have 2/0 RHH/RHW already installed and a couple of short pieces left over, but I'm not sure I have enough. I picked up a piece of 2AWG THHN at the blue box store store for 50 cents a foot instead of their normal $1.82/ft.

If it isn't compatible or just ill-advised, I can use this for a ground wire and get some 2/0 at another supplier.

 

[LouNY]

#2 is considerably small (lighter) gauge wire then #2/0;
if this link works it is a chart of NEC service entrance wires and ampacity,
View attachment nec ampacities.pdf

 

[3Ts]

#2 and 2/0 are not equivalent.
The answer to your question somewhat depends on distance, but you should be able to do it. Don't forget to include a ground wire, so you'll have 4 wires in your conduit. I assume you are running wires from the main panel to a sub panel, but service entrance implies from the power line to the main panel.

 

[Diggin It]

I have 2/0 from the meter base to a 100A Service Disconnect, then to the main breaker panel. That has been inspected and approved. I'm adding an Automatic Transfer Switch between the Service Disconnect and Main Breaker Panel. Total distance will less than 15 feet, probably less than 10 feet. Ground is already in place, but outside the conduit.

Meter Base >> Service Disconnect (SD) >> ATS >> Breaker Panel (BP)

The short piece of THHN would either be between the SD and ATS or between the ATS and BP. The decider will be how much length I need in each segment which I won't know until I get the ATS and see the internal connections. I might only need one line in one segment and I might be able to use the THHN for the Neutral so the two hots are 2/0. All speculation and preparation for now.

 

[workinonit]

That entire run needs to be sized the same. So 2/0 for L1 and L2. 2 trade sizes lower for the neutral(#2 should be fine) and 2 more trade sizes(#4 or #6) for the ground. The generator to the ATS needs to be sized for the rated current of the generator.