Another Al Wiring Question

Is Aluminum wiring for the service entrance wires okay? I believe only single strand aluminum branch wiring is a problem, but want to confirm.

Not a problem. I would bet that 95% of the homes I inspect are aluminum. Copper is a rarity.


Multi strand aluminum wiring is still to code if used for a dedicated 240 VAC appliance circuit.

Copper is the preferred feeder wire for manufactured homes.

Thanks for all of the answers.

So, if you found aluminum as feeder wire for a manufactured homes you would write it up as a defect?

Make sure aluminum SEC’s have anti-oxidant paste installed at the lugs. Some manufacturer’s use aluminum lugs, but the set screws are made out of steel. The paste helps prevent galvanic reaction between two dissimilar metals.

Stranded AL SEC’s are perfectly fine and expect to find them everywhere.

While a good practice, the use of anti-oxidant paste is not required by the NEC, unless called for by the wire manufacturer.

I agree, you shouldn’t be writing this up unless you know for sure that the specific lug manufacturer requires an anti-ox compound. To the best my knowledge most actually do not require it.

Aluminum is fine if sized properly. What could be a problem is the type of insulation on the wire. Where conductors enter the residence they should have a temperature rating of 90C. In other words the insulation marking should have an HH rating… THHN XHHW. The higher rating is for a better fire rating. Many older homes will not have this type of insulation, but newer construction should. There again electrical can be case sensitive according to the AHJ.

Mark what do you mean about a better fire rating and insulation type?

Wendy -

Aluminum stranded wire is probably the most common service entry wire in use in many areas. NO it would not be written /Just identified.

Not all insulation types are the same. Such as thermoplastics or rubber. The type of insulation or coating on the wire will give it a specific temp.(heat) rating. By having a higher temperature rating it would be less likely to melt down the insulation in high current situations, thus a better fire rating.
For instance, certain direct burial conductors(service lateral) could be used up to the meter. If enough was left over after making the connection to the meter, we would just use the same wire to go from the meter to the indoor panel. But now that the wire has entered the building it should have a higher insulation rating.
Not sure if this could ever be written up though as I am quite new to the home inspection world.

Direct burial cable used to feed a service are not for use inside the house.

I’m not understanding this concept. If the conductor is properly sized for it’s connected load why would the type of insulation make any difference?

I am wondering if they are confusing the differing insulation materials to have a higher ampacity over other types of insulation, like XHHN vs RHW.

Maybe Mark can explain. I can guess that he meant that a cable such as NM, which would have a 90 degree C conductors, but would be sized for ampacity at 60 degrees C would have a built in safety factor due to the cable operating well below it maximum insulation temperature value.

Correct. As of 2005 NEC. Before that, 6 feet were aloud inside. Type USE

Jim and Robert, I had to think about all this and why this was put in place. Thanks for keeping me honest. OK. I originally believed that the service entrance (meter to panel wire) was changed to 90c. wire to give that wire a better temp rating due to other ambient temps that may surround it, but also the fact that there is no over current protection for these conductors. A 200 amp main breaker protects the panel. If it trips, your service entrance can still be live. If a bad connection on the main breaker happens it could heat that wire considerably without tripping the main.
I’m pretty sure these and other situations have played a part in the change to 90c. But now that I have looked into it more, I have found out that USE type wire does not have a flame retardant covering. So it was no longer aloud inside, as it would probably add fuel to a fire.
OK, so if that is clear, what should I write on a report if ever I have to inspect one of the homes I wired before 2005.