Noticed a duct/plenum in the basement (aprrox. 20’ away from furnace) that was too hot to touch. Never noticed before, of course I don’t usually touch them all either. I just happened to “lean” on this one to look at something else. Anyway, is this normal? What would cause temperature rise (heat exchanger problem?)? The thermostat was set at 80 to test furnace.
Thanks in advance.