I would think this would be something that could easily be Googled, but I've tried and can't find it.

We have a Trane XL-80 gas furnance and when we had an insulation guy checking out the furnace, he remarked that the furnace switch in our furnace closet should really be an SSU switch with a fuse in it. I forgot to ask him what amperage fuse to use. Anyone know?

  • Modern furnaces on suitable breakers don't need fused disconnects. That's old-school. What's your breaker and wiring situation? – isherwood Jan 7 '19 at 19:01
  • The guy's company does insulation but also installs furnaces. We showed him the furnace closet because we were asking him if it was okay that there was a gap in the ceiling of the closet leading into the attic. He said that everything looked proper except that he recommended the SSU switch. – Marc Abramowitz Jan 7 '19 at 19:01
  • Can you take photos of the informational label (s) on the furnace? It may be behind an access panel. – Harper - Reinstate Monica Jan 7 '19 at 19:01
  • 2
    I had that same furnace in my previous home. It was installed with a typical residential light switch in a box mounted to the chassis. NM-B ran through flex conduit from the ceiling. – isherwood Jan 7 '19 at 19:02
  • So the answer is that the question is invalid, and you should let furnace guys give you furnace advice. :) – isherwood Jan 7 '19 at 19:49

The switch is based on the load, but since the furnace is a dedicated circuit what size breaker is the unit on? I would guess a 15 amp but I haven't seen a gas furnace with anything larger than a 20 amp the switch must have a labeled on /off position but other than that a standard switch is fine.

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