Manual

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7. LOW GAS PRESSURE SWITCH
The function of this switch is to de-energize the burner circuit if the gas pressure to the burner is
below its setting. Manual reset to energize.
Set: 2" W.C.
Test: Using test gauge in parallel with sensing tubing, adjust unit to high fire, decrease regulator
pressure at gauge below 2" W.C.
8. BURNER CONTROL MODULE
This module supervises the flame circuit and the energizing of the ignition/pilot and main gas
valves. A milli-volt circuit is used for flame detection and response.
Set: 1.25-5.0 Vdc signal on pilot flame.
Test: Fire unit, with manual shut-off valve decrease gas flow to burner until micro amp reading drops
and the relay causes the main gas valves to close. The safety circuit will cut out in 30 seconds.
9. ROOM OVERRIDE THERMOSTAT
The function of this thermostat is to cycle the unit to high fire if the room temperature requirement
is not being met. It overrides the ductstat on Maxitrol series 14 systems. It ships loose and
should be mounted in a location that has a representative temperature for the room.
Set: Desired room temperature.
10. ELECTRONIC MODULATING VALVE
The function of this control is to proportion the amount of gas to the burner to maintain the
desired discharge supply air temperature. This control uses an electric coil with a floating plunge
that will vary the force on a gas supply orifice supplying gas to the main burner. A 24V D.C.
signal positions the plunger inside the electric coil. At 0-5 volts it will be low fire; at 5-15 volts
modulation; and 15-24 volts at high fire.
Test: Check plunger for up and down motion by varying the voltage to the valve.
11. AMPLIFIER
This control converts 24 volts A.C. to 24 volt D.C. and varies the voltage to the modulating valve.
Test: Check input at transformer terminal for 24 volt A.C. -- check output at modulator terminals for 24
volt D.C. output while adjusting the temperature set point.
12. DISCHARGE AIR TEMPERATURE SENSOR
Discharge Control Units (Series 14):
The function of this sensor is to monitor discharge supply air temperature and with a temperature
sensitive element send a signal to the amplifier to make any necessary temperature adjustments.
Room Control Units (Series 44):
The function of this sensor is to monitor the discharge supply air temperature and with
temperature sensitive elements send a signal to the amplifier to maintain the maximum and
minimum discharge temperatures of the unit. It works together with the Room Selectrastat.