25' Tap

[hillbilly]

I recently saw a tap from a 200A 240V main to a 30A 2 pole enclosed breaker. The tap was 25' long.
The wireman had used 6/3NMB with #10 ground to make this tap. The 25' tap rule states that the tap conductors must be rated at least 1/3 the ampacity of the main. In my opinion, for this installation to be correct 2 things must be assumed. First is that the NMB amperage
is selected from the 90C column and second is that the grounding conductor is not required to be sized for 1/3 the main amperage. The installation was neat, the cable was protected and the installation had been inspected. It seems to me that the tap rule was violated. Seeing this led me to re-study the tap rules and I'm still not clear. I've always installed 25' taps in conduit with all conductors (grounding included) rated atleast 1/3 the amperage of the main.
Any Opinions?
thanks
steve

 

[iwire]

Re: 25' Tap

Steve I agree that the NM is not rated for the 66.6 amps that is one third of 200.

I also I agree the EGC is to small from the 200 OCP to the 30 amp breaker enclosure but not for the same reasons.

The EGC is not sized to one third of the main it is still selected by table 250.122 but it never has to be larger than the tap conductors themselves

The EGC has to be sized to the rating of overcurrent device in circuit ahead of equipment, conduit, etc.

The 200 main requires a 6 AWG copper EGC be used between the two enclosures.

Bob

[ July 17, 2004, 05:13 PM: Message edited by: iwire ]