I seldom see AL conduit spec or discussed in this forum. Conduit is allowed to be used as an EGC.
However due to the iron in GRC or EMT or equal
the the magnetic field arising from the fault current increases the impedance of the conduit
thus limiting the lenght of the run. However the AL is not effected in the same way since it has no iron. The length of the run can be much greater and still provide a good EGC. Under what conditions other than in concrete or underground would AL conduit not be used? This subject is covered very well in the Soares Book on Grounding.
However due to the iron in GRC or EMT or equal
the the magnetic field arising from the fault current increases the impedance of the conduit
thus limiting the lenght of the run. However the AL is not effected in the same way since it has no iron. The length of the run can be much greater and still provide a good EGC. Under what conditions other than in concrete or underground would AL conduit not be used? This subject is covered very well in the Soares Book on Grounding.