Add aluminum wiring in a house with copper

Question

This is more of a practical question than an NEC one. I've dealt with aluminum wiring in a prior home and know how much of a pain it is to use CO/AL bridges and Noalox to meet code.

In my case I need to run a long 100 ft 240V 30A circuit. 10AWG CU is crazy expensive compared to a couple years ago. 8AWG AL is reasonable, about the price of 10AWG before the price hikes. In a home with all-copper wiring built in the 2000's, would you recommend adding a circuit with AL? One of my concerns is if/when I sell the house, the inspector may raise a flag on the AL circuit. Any other concerns I should be thinking about?

Another option is to use UF cable which hasn't spiked in price. It sounds unbelievable, but check the big box stores and you'll be surprised. I've read that UF cable is hard to work with due to conductors being rigidly encased.

Answer 1

Yes, that sounds like a fine idea.

My only suggestion is to upsize another step to #6 alumimum. This will place you more definitely in the "heavy feeder" category (which as Ecnerwal discusses, has never been a problem), quell buyer complaint, while also giving you wider selection and availability of wire. By and large it won't affect your ability to attach to connectors, and if you do need to pigtail to copper, ILSCO's "Mac Block Connector" is an affordable Polaris class connector that takes up to #6.

Do check the connectors to make sure they are AL rated. Most sockets are; some appliances are not glares at Tesla.

Setting torques correctly is a Code requirement for any lug or terminal that specifies a torque - even the little stuff. The importance of this was known, but in the 2000s it was discovered that electricians are really bad at setting torques (one test booth taken to trade shows did tests on couples and found the electrician wasn't any more accurate than their spouse.) All this research centered on copper wire, but it jibes with aluminum - electricians always set torques on heavy feeder, but never set torques on receptacles and switches during the making of the 70s aluminum wire crisis.

Finding an affordable torque screwdriver is a pain. I like "beam type" torque wrenches, because they never need calibration. For around $25 most home stores sell a 1/4" beam-type torque wrench that goes to 100 inch-pounds.

Answer 2

Virtually all 30A devices will be supplied with terminals compatible with aluminum.

Large feeder wire was never the problem with aluminum wiring. 10 & 12 Ga Aluminum wire on copper/brass terminals not designed for it was the problem.

Aluminum is fine, safe, and sane for the application. Install it correctly, of course, inclusive of noalox paste or equivalent and correctly torquing the connections - but you're now supposed to correctly torque the connections regardless of wire type or size, as that became a recognized issue.

Answer 3

As long as the ends (breaker and receptacle) are both marked for Aluminum use, technically everything will be fine.

However, some jurisdictions may place their own limitations on use of aluminum wire. For example, in Montgomery County, MD:

17.02.01.11

Section 310.15(B) Tables. Delete the first sentence and substitute with the following: The minimum size of conductors must be as shown in Table 310.15(B)(16) through Table 310.15(B)(19), as modified by Table 310.15(B)(l) through (B)(7), except that the minimum size of aluminum and copper-clad aluminum conductors must be No. 2. The use of aluminum conductors is limited to service entrance and feeder applications only.

which effectively means you can't use aluminum in this application, at least not without some extra equipment so that it isn't a simple branch circuit.

Answer 4

Give AFC or MC cable a try, it currently is about the same price as as the aluminum and it should comply with your code requirements.