ELECTRICAL QUESTION

[Dave Hembree]

We are adding a large addition (2200 sq ft) to our existing 2400 sq ft home. I will be adding a 200 AMP panel in the new addition that feeds from the exisitng panel (will likely need to upgrade main service too). My question is the best way to connect the new panel to the old panel. The run will be around 100 feet and likely need to be a pretty large cable. With copper prices through the roof - one electrician has recommened using aluminum for the 100 ft run (we will use copper 12/2 for all runs from the new panel of course). I remember hearing that aluminum wiring is bad - is aluminum wiring just a bad idea for the circuits - but OK for the long run from panel to panel.

Or should I just suck it up and use copper for the 100 ft run??

[Rudy]

Thats right, its fine for a heavy run to the new panel. He'll use proper AL connectors of course and no one will be the wiser

Its your $$

[Bill]

It is common to use aluminum wiring for the main feed. If it is installed properly, anti-oxidation goop applied to connections, and connections torqued per panel manufacturer's specifications, it should be fine.

These connections are usually done "right" since they are so important.

It is numerous house switch/outlet aluminum wiring connections done wrong and in a hurry which have problems in future years.

I have aluminum main wiring going to a subpanel I have, but everything else is copper.

[Steve Barker LT]

It has something to do with COST. and the fact that al will liberate heat in free air much better.

[Dave Hembree]

Thanks for all the answers - one question since the last 2 posts have mentioned using Aluminum for overhead wire service - my aluminum wire will be in a cramped attic, inside a 6" PVC pipe I installed under about

15" of loose fill insulation. I will also have coax, telephone, and CAT6E wiring in that 6" tube. Will this cause any problems with heat, interference with other cables, etc?? I don't know how hot that aluminum wire will get - and I am hoping that 6" PVC is only about half full of wires when I get done (electric, coax, cable, CAT6E?!

[tim]

"Rudy" wrote in news:lwsbh.24$ [e-mail]:

Amusing story about copper vs alum. I put myself through college working for the maint. dept. One job we were doing was new service entrance and breaker panels for a 50yr old building. All the raceways and boxes were sized properly for the COPPER wiring planned for the service entrance (think it was 4/0 - at least was on edge of break where next size wire meant bigger raceways etc.) Purchasing agent went looking through his catalog and noticed that next size larger AL would carry same current at one half price so that is what he ordered. It was verrry interesting working with those guys trying to fit the oversized AL into the raceways and into the cable clamps that were one size too small!

[Matt Whiting]

The raceways and/or conduit wasn't sized properly then to begin with. A properly sized conduit or raceway isn't that close to being full to start with. Fill factors are almost always 50% or less. If one size larger wire caused a problem, then the initial design was faulty and did not meet code.

Then again, this has an urban legend feel to it...

Matt

[Matt Whiting]

I don't have a copy handy here at home, but I'm about 99% sure that the NEC does not allow high voltage and low voltage wires to be in the same conduit. This could cause a very dangerous situation if a rodent gets in there and chews the insulation such that a low voltage wire gets in contact with a hot supply line.

Matt

[Steve Barker LT]

You definitely do not want your data and phone lines running parallel with high current. You'll get interference at best and at worse, you may get some induced current. Run a separate metallic (grounded) tube for the data if it has to run close to this feeder.

[Erik Dillenkofer]

The National Electrical Code won't allow low voltage (CATV, phone, and network) in the same conduit as the power.

[Deputy Dumbya Dawg]

One can NEVER mix power and signal conductors in a conduit. That being said, you do not need conduit for any of these wires in this job. Just nail the AC service cable to the ceiling joists every two joists and dress your holes properly and put the other wires in the conduit if you must. Every time the distance between conductors doubles the strength of possible inductive/magnetic coupling decreases 6dB. Starting with the thickness of the insulations and doubling that thickness 32 times will give you 30 DB of isolation. That is a couple of inches at most. If the wires touch in one spot it is not the same as if the wires run parallel for the distance of the run.

There is no increased danger to humans from a 220 service entrance wire over any other 220 wire used in your house. Potential electrocution current is a function of your body resistance and the voltage, these two parameters limit the potential for current flow in your body, not the conductor size and the generator capacity.

Properly sized conductors should not get hot, maybe a little warm to the touch if you are drawing current near the ampacity of the conductor but never hot.

peace dawg

[tim]

Matt Whiting wrote in news:dULbh.1104$ [e-mail]:

It wasn't the full part, it was the bend radius where the conduit came into the raceway and left the raceway to enter the main disconnect.