Coping With Hazard of Different Wiring

QUESTION: We bought our home in 1985, and plan to add several new electrical circuits and install new light fixtures and ceiling fans into already existing circuits. The problem is that all circuits, switches, light fixtures, receptacles and appliance connections were wired with aluminum wiring components.

We know we must replace failed switches and receptacles with ones that are approved for use with aluminum wiring, but we don’t know what to do about installing new copper-wired fixtures in existing circuits. A friend warned us that connecting copper to aluminum wiring could create a fire hazard. Is this true?

ANSWER: Aluminum wiring is a potential fire hazard. Between 1965 and 1973 about 1.5 million homes were wired with aluminum, which at the time was approved by the National Electrical Code. Later it was found that dangerous overheating in 15- and 20-amp circuits, at some connections between aluminum wires and outlets, switches, fixtures and appliances resulted in fires.

Correcting the problem does not require rewiring the house. You can replace switches and outlet receptacles that are unmarked or marked AL-CU, with devices that are marked CO-ALR.

Or, you can use existing switches and outlets provided you attached short copper pigtails to the ends of the aluminum wires and to the devices (aluminum-to-aluminum splices are an exception). It’s also necessary to connect light fixtures and appliances with copper pigtails.

Because of the potential for a fire, it is important that copper wire pigtails be attached to aluminum wires with specially designed connectors (wire-nuts can be used, however, at copper-to-copper connections, such as light fixtures).

The Consumer Product Safety Commission recommends using a compression-type crimp connector with heat-shrink insulation. These are called Copalum Compression Connectors. They, and the crimping tool used to install them, are made by AMP Inc., Copalum Program, MS 140-13 P.O. Box 360B, Harrisburg, Pa. 17105.

Furnace Blows Dust When It’s Turned On

Q: Several years ago, we had a furnace installed and started getting a great amount of dust every time it was on. When we had it checked out we discovered that a return air duct had been laid over the dirt floor in the crawl space with no cap, and all the dust was being brought into the house. Other than taking the ducts down to remove the dirt, is there anything we can do?

A: All warm-air furnace systems must have a filter in the return duct to trap dirt and dust in the airstream. The filter prevents airborne particles from getting into the air.

There could be several ways the airstream that enters the room picks up the particles. The filter may be dirty, it may not be the correct size or it may not have been installed properly so particles slip past it. Or, you may not even have a filter.

If none of the above causes the problem, you should consider installing an electrostatic filter in the return duct. These filters are effective in removing dust and dirt from the air.

We’ve assumed you’ve replaced the missing end cap on the return duct, but you should also seal the joints between the sections with duct tape. Also, a portion of the return duct in the crawl space should be insulated.