Incompatible wire and connector causes furnace fire

As the weather grows colder, homeowners may be looking at upgrading their furnace to get ready for winter.  When installing a new furnace, safety officers at Technical Safety BC suggest that homeowners be attentive to manufacturers’ specifications on the types of wire to be used. In most cases, manufacturers will specify only copper wires to be used. 

Aluminum wire is only to be connected to devices specifically approved for aluminum connections, by devices specifically approved for aluminum terminations.  In a recent incident at a BC home, the wire nuts used were rated “copper only” and the incompatibility with the aluminum termination resulted in a fire. The main overcurrent protection was a 15 amp single pole breaker, installed in a 100A combination panel.

The home was originally wired with aluminum wire and a new, high efficiency furnace, installed approximately four years ago, was fed with aluminum wire and terminated with “copper only” wire nuts. This connection oxidized over time leading to a break down in the connection, causing excessive heat.  This connection was eventually hot enough to melt the insulation off of the conductor, causing arcing and the subsequent fire. 

Fortunately, the owners were home at the time were able to quickly extinguish the fire and nobody was hurt in this incident.

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