Harman® • PF-120 Owner’s Manual_R3 • 2014 -___ • 10/14
25
3-90-08120c
The
Low Draft Pressure Switch
is a differential pressure switch
that monitors the negative pressure (Draft) in the firebox. If the
draft becomes too low for proper combustion, the switch opens,
cutting power to the feed motor and the igniter circuits. This switch
is connected into the AC (high voltage) wiring.
The
Control Board/ESP
combination is responsible for all high
limit safety control. There are 2 high limits, one normal operation
high limit and one backup high limit. The control has an automatic
diagnostic circuit that continuously monitors the ESP and Room
Sensor for faults. If a fault should occur, the control sends a status
alert and at the same time the unit goes down to minimum feed/
minimum burn as a safety condition.
Low Draft Pressure Switch
Feed Motor
Combustion Motor
B. Motor and Component Location
PF-120 Pellet Furnace Safety Devices
Igniter
Circuit Breaker Box
UPS Connection
NOTE: UPS connection only for
power failure shut down
ESP
