Furnace is a Rheem Classic Series Super Quiet 80. Installed in 2003. Furnace kicks in and fires up, blower seems to work fine, but the furnace kicks off before it reaches the temperature set by LUX PSP511 thermostat.
Any idea why furnace turns on, stays on for maybe 5 - 10 minutes and shuts off before reaching the temperature set by thermostat. 90 day filter installed 30 days ago.
Appreciate any help I can get.