Also in the event of a fire there may be insurance issues.
In their most recent 1997 Safety Notice, Ontario Hydro states:
"Aluminum wiring in residential installations will operate as safely as any other type of wiring if the proper materials are used and it is installed as per the manufacturer's instructions and the Ontario Hydro Electrical Safety Code."
Special care must be taken to ensure, for example, that connections are made to receptacles that are suitable for aluminum wiring. Further, where aluminum and copper wires are connected that proper paste/flux, and/or, the appropriate wire connectors, are used.
Doug, for a 100 amp sub panel you need #4 copper or #2 aluminum. You can use NMWU or Teck conductor for direct burial and make sure you take the bonding screw out of the neutral bar in the sub so it's not bonded to the can. And also make sure that all the ground wires from your circuits are on a separate ground bar. Use NOLOX compound if you use Aluminum wire or your connections will get corrosion.
thanks rob, i removed the bonding tab when i set the panel up to feed from a gennie [ground fault breaker on gennie ]. my plan is to put a 100 amp breaker in the house panel and feed to a 100 amp breaker in the sub panel to power circuits in the shop. i have a run of about 60 ft to go through the basement to the shop, all indoors. the aluminum is much cheaper than the copper. plan b would be to use awg 6 to a 60 amp breaker in the sub to power everything except the buzz box and use a 40 amp breaker in the main panel for the welder. i'll have to see what is more economical.
Doug, I think by the time you pay for #6 copper and #8 copper you'll find it way cheaper to go with the #2 aluminum Loomex. Also it would be less of PIA if you trip the welder breaker and have to go in the house to reset it. If you use Aluminum for the 60 feed the wire jumps to #4 and the welder to #6