Cumberland VariFlame VF-16-ONG, Owner'S Manual

Page: 20 / 64

Chapter 3: System Overview
High Limit Switch (2)
WARNING
Never bypass the high limit switch. Bypassing the limit switch can cause the heater
to overheat.
The high limit switch is a “normally closed” thermostat switch that limits the outlet temperature of the
heater. If the outlet temperature of the heater ever reaches the temperature limit of the high limit switch,
the switch opens and the heater will go into lockout mode. A small manual reset button is located on the
back of the switch and must be pushed to reset the high limit switch anytime it is tripped. It is important to
investigate the source of the high temperature trip, as this is not normal. Typical sources of high limit
faults are a dirty blower wheel, restricted inlet, restricted outlet, and excess gas pressure.
Air Proving Switch (3)
The air proving switch is a “normally open” paddle switch that is used to sense when the blower wheel is
providing airflow. When enough airflow is being driven, the paddle of the limit switch will force the limit
switch to a closed state. If the switch is in a closed state when the blower is off, or the switch is in an open
state when the blower is on, the heater will go into lockout mode. Typical sources of air proving switch
faults are dirty blower wheel, restricted inlet, restricted outlet, and a dirty air proving switch.
Igniter (4)
The igniter is a hot surface heating element used to initiate combustion. The igniter runs off of 120VAC,
and has a short “pre-heat” period before the gas is turned on by the heater. When the igniter is operating
properly, it should glow red when power is supplied to it. Typical sources of igniter failure include improper
handling, improper maintenance, and shorting out to the burner.
Flame Probe (5)
The flame probe is a sensor that allows the burner control to sense when a flame is present. A flame will
create a small micro-current between the burner and the flame probe rod that is then sent to the control
board. Typical sources of flame probe failure are a bad ground or dirty flame probe.
Control Board (6)
The control board acts as the main control of the heater. The control board controls all of the heater com-
ponents and is responsible for making all safety related decisions. Any time the heater goes into “lockout”
mode, power to the control board must be cycled. Typical sources of control board failure include
improper power supply, shorted heater components, and improper maintenance.
Throttle Valve (7)
The throttle valve is a manually adjustable valve located between the main gas valve and the burner ori-
fice. The throttle valve is used to manually adjust the heater output. When the handle of the valve is paral-
lel with the pipe, the valve is in the “full open” position. A decal on the inside of the door shows the heater
output based on valve position, and should be referenced when making any adjustments.
Gas Valve (8)
The gas valve is used to turn on and off gas to the burner as well as control gas pressure. When powered,
the 24VAC solenoid located inside the valve, allows gas to flow. Typical sources of gas valve failure are
incorrect inlet gas pressure, dirty fuel, and improper maintenance.
20 PNEG-2091 VariFlame™ Heater