NO EGC at 12' site lighting poles

[AZsparky]

Hi all:
We have a site lighting replacement project, 23 replacement fixtures on 12' poles which go directly into the ground. But, the current fixtures and feeder conduits have no EGC. The junction boxes feeding the lighting have no EGC either. The current RMC conduits are almost 50 years old and not usable for trying to pull an EGC. What do you think is the best course of action to make this installation safe?

 

[kwired]

Hi all:
We have a site lighting replacement project, 23 replacement fixtures on 12' poles which go directly into the ground. But, the current fixtures and feeder conduits have no EGC. The junction boxes feeding the lighting have no EGC either. The current RMC conduits are almost 50 years old and not usable for trying to pull an EGC. What do you think is the best course of action to make this installation safe?

RMC is permitted to be used as an EGC, what condition is the RMC in?

 

[iwire]

Dig a trench and replace the circuit.

Other than that there are no code compliant options unless you trust the RMCs

 

[AZsparky]

Thanks guys...I will test voltage using the RMC as the ground as I change each fixture (Cheapy RAB YLS70). I'll bet the results are not good...I'm told the replacement of the conduits and wire is not a budgetary option for this old townhouse style community. But, I bet it might be when breakers start tripping from dead shorts....This project has been electrically "maintained" by many various handymen and electricians for 50 years. Photocell redundancy here has totally run amok. As the original RAB HPS fixtures failed, they eventually bypassed the ballasts and installed incandescent or CFL spiral lamps in them. **shakes head**

Thanks again for the feedback. Bob...

 

[Ponchik]

If there is a ground fault and the breaker trips that shows that the RMC is still able to carry fault current. So no need to install EGC.

If the RMC is damaged you will still measure voltage across the hot and conduit, it just may not be in good enough shape to carry ground fault.

 

[kwired]

Measuring voltage to that RMC and its ability to carry fault current are not the same thing.

You likely can measure full voltage from hot conductor to sticking other meter lead in the dirt. But try to connect a load from hot conductor to the dirt and it will not be able to carry enough current to operate the load. Same can go for the RMC if it is severely deteriorated.

I'm not sure just how to test this in a manner that will not get all kinds of remarks about how unsafe the testing method may be.

Maybe try seeing if it will carry a 12 VDC load - simple car battery and a 12 volt lamp with the RMC used as one conductor of the circuit as a starting point. If it will not carry that it definitely is not in good enough condition to depend on for an EGC for a 120+VAC circuit.

 

[petersonra]

There are EGC testing instruments available.

I think that it is likely that the UG RMC is still an adequate EGC. If by whatever means you determine it is not adequate, then you will need to replace it.

My observation would be that if the RMC is no longer adequate as an EGC, it likely means it is no longer adequate as a conduit either.

 

[kwired]

There are EGC testing instruments available.

I think that it is likely that the UG RMC is still an adequate EGC. If by whatever means you determine it is not adequate, then you will need to replace it.

My observation would be that if the RMC is no longer adequate as an EGC, it likely means it is no longer adequate as a conduit either.

All true.

Unless you have some unusual corrosive conditons, your RMC is likely adequate.

If you ever uncover buried RMC you often will find the most corroded part is the first few inches below grade level. Deeper portions receive less oxygen and therefore are not as prone to oxidation. Type of soil and contents of that soil do have some impact.

 

[G._S._Ohm]

A 12v car battery with a heavy load (like several headlamp bulbs in parallel) will pass several amps through the conduit, and you measure the voltage drop along the length with leads that do not touch the leads that pass the current. This is what Kelvin clips do.

Depending on your DVM you can measure milliohms or micro-ohms of resistance and knowing the cross-section you can figure what equivalent AWG conductor and termination resistance you are dealing with.

Conduit cross-section in sq. inches should be (Pi/4) ([OD^2] - [ID^2])