I am building a storage shed for a customer who just moved into his house last week. He had the electrician run a circuit from the maion panel to the outside corner of the house closest to the shed, and when I’m done they’re gonna lay conduit undferground and pull wire to a small sub-panel in the shed. He doesn’t have any hobbies, so the power is for general lights and receptacles. The shed is 16×20.
I was talking with him today, and he said the electrician had planned on putting 60A of 110 in the shed, and he mentioned that the cable at the corner of the house was “this big”, so I pulled off the cover plate out of curoisuty. Well, it’s actually 3 conductors plus ground, so I’m guessing he’s gonna get 220.
I didn’t see a number on the insulation, but it’s bigger than 12 ga, and stranded. The ground was obviously aluminum, and I saw the word ‘aluminum’ printed on the insulation.
Question: is that a problem? Should it be copper? The builder cut a few corners on the house, and they had a punch list several pages long, so I’m wondering if maybe they tried to get cheap on the electric service also.
“When asked if you can do something, tell’em “Why certainly I can”, then get busy and find a way to do it.” T. Roosevelt
Replies
Stranded alum service lines are common in my area; it was the solid branch wiring stuff that caused the big problems back in the 70's
Check that the Al connections are coated and the strands FILLED with gray nickel particle bearing grease. The grease prevents Al oxidation, the killer of Al wire connections. With the grease properely applied, OK.
No hobbies, 60A shed service?? Only got a 60A to my barn for a 250 A welder. Maybe the guy has no hobbies, but dabbles in indoor cultivation of certain "herb medicines"???
Stranded aluminum is common here for larger circuits, 40+ amps.
Alnox or other similar products will help prevent corrosion at the terminals / connections.
Note - pay attention to the connections made in the box at the "corner of the house" which you mentioned - connections can be made of aluminum to copper, but, special connectors are required - not just any old wire nut will do.
Jim
Never underestimate the value of a sharp pencil or good light.
If the electrician is competent, it'll be fine.
The deal on aluminum is that the material is cheaper than copper, but the cost of making connections to it is higher. Terminals need to be rated for aluminum, and it needs the gloppy anti-oxidation compound. So, it's only for big feeders that the savings on the material outweigh the labor to terminate it correctly.
-- J.S.
Aluminum is the standard material for conductors on services like that. Installed properly by an electrician it is as safe as copper. It is a fair amount less expensive. In industrial buildings it's used all the time.
I opened the main panel and looked at the connections. All the aluminum hots have the grey goop on the wire, and some of the neutrals have it on the bus bar, but not all.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Edited 12/9/2005 11:06 pm ET by FastEddie
Having the aluminum connections properly treated is, in many ways, more important then the hots. A bad connection on the hot side can leave electrons far from home and willing to kill to get back. If, possibly because the lights not on, someone assumes the power is off it is easy to get a nasty shock. A bad connection on a hot wire or neutral can cause a dangerous heat buildup but on the hot side often it just means a loss of power.There is also the question of neutrals maintaining the equal distribution of voltage. A failed neutral at the panel or at dividing point of a multi-wire branch circuit can have voltages running wild. Nothing like a good thing. A hot wire is what most people respect but it is the neutral that is the snake in the grass. Never assume it's the nice one.Another point is that anti-oxidants compounds are holy water. You can't make a bad connection good by dabbing on a little compound. As with most things under ideal conditions you can get by without it or just smearing a little on. To get the best results the aluminum conductor should be scrubbed free of contaminates and corrosion, the compound is then applied and scrubbed to break up the invisible aluminum oxide which instantly forms on exposure to air and then more compound is applied to get an even coat. This treated end is then installed on a aluminum rated terminal which is torqued to the manufacturers specification.IMHO, subject to individual preference, the best tool for removing oxides from aluminum conductors and scrubbing in the compound is a small stainless steel bristled brush. The small ones that look like a toothbrush and commonly used for welding works well. They go for something like $2.50 so they aren't going to tank the tool budget even if you buy two or three.