miller furnace
#4
The heat anticipator is a small electric adjustable heater element that is wired in series with the "W" circuit (white thermostat wire) that controls the gas valve or electric sequencer of the funace. It is adustable to allow it's output to be set for proper anticipation. The anticipator is mounted near the t-stat sensing element. It's job is to provide heat to the sensing element (only during a call for heat) so that the thermostat "thinks" it is slightly warmer in the room than it is. This is needed because of the residual heat that the furnace will put into the space after the flames are extinguished. (Fan runs until exchanger cools down.) Not enough extra heat (anticipation) on the sensing element & the funrace will "overshoot" the set point making it too hot. Likewise, too much antipication, & furnace may short cycle & then come back on very soon because once anticipator is de-energized room is still below setpoint. Several short cycles may eventually get temp. up enough to satsify t-stat. Since the anticipator is wired in series with the fuel control, if it burns in two (opens) the furnace cannot come on. If you jump red & white at the thermostat & furnace fires up, stat or ant. are bad. T- stat must be replaced. If jumping these two leads doesn't fire furnace, problem is elsewhere. NEVER allow control wires goig to gas valve touch or anticipator will overheat & burnout. Hope this helps