Old buried conduit ground test

[wch]

What is the best procedure for verifying continuity of old buried
steel conduit for continued use as the equipment grounding conductor?
Say this is (2) 3.5" C. rigid or intermediate steel, 40 yrs. old, 200' long.
What's the prognosis for reuse of two sets of 4- #500 MCM Cu, 3.5" C.?

 

[chris kennedy]

Plenty of room for a 1/0 EGC in both 3?'s. Not in the budget?

 

[wch]

Apparently alum was used, not Cu. (say 4-700 mcm Al);
then if RMC, 40% = 4.004 in2. That's not even enough
for the 4.404 in2 of the 4-700's. I'll have to verify if
the C. is 4" instead of 3.5". How easily would the EGC be
installed? Apparently, the cost is up for grabs.
A 1/0 Cu EGC increases it to 4.6263 in2, < 5.153 in2 for 4" RMC.

 

[chris kennedy]

Sorry, your fist post stated 500cu. Now I gather your leaving the existing conductors in the conduit and just want to verify the conduit as the EGC, or will you be re-pulling this?

 

[wch]

Reply to Chris Kennedy

Reply to Chris Kennedy

I regret the delay.
We prefer a new EGC wire, since exist raceway is 40 yrs old.
It appears that a Cu EGC will be better than alum EGC, also better for
installation--pulling flexibility and x-area. Any problem if insulated Cu EGC is combined with Al feeder phases & neutral? The exist neutral may be a downsize from the phase size...we don't have the raceway description (size or matl). except the 4-wire feeder is aluminum. What is the probability that
raceway continuity for EGC is still good?