Sunlife Enterprises SUNLINE DM180 - Manual (Page 41)

356214-XIM-A-0108
Johnson Controls Unitary Products 41
If the temperature limit opens three times within one
hour, it will lock-on the indoor blower motor and a flash
code is initiated (See Table 24).
GAS VALVE
The UCB continuously monitors the GV. Any time the
UCB senses voltage at the GV without a call for heat
for a continuous five-minute period, the UCB will lock-
on the indoor blower and a flash code is initiated
(Table 24). When voltage is no longer sensed at the
GV, the UCB will de-energize the indoor blower follow-
ing the elapse of the fan off delay for heating.
If voltage has been sensed at the GV for at least 15
seconds during the fan on delay for heating and GV
voltage or "W1" is lost, the indoor blower is forced on
for the length of the fan off delay for heating.
SAFETY CONTROLS
The unit control board monitors the temperature limit
switch and the gas valve of gas furnace units.
The control circuit includes the following safety con-
trols:
1. Limit Control (LS).
This control is located inside the heat exchanger
compartment and is set to open at the temperature
indicated in the Limit Control Setting Table 21. It
resets automatically. The limit switch operates
when a high temperature condition, caused by
inadequate supply air flow occurs, thus shutting
down the ignition control and closing the main gas
valves and energizing the blower.
2. Centrifugal Switch (CS).
If the draft motor should fail, the centrifugal switch
attached to the shaft of the motor prevents the igni-
tion controls and gas valves from being energized.
3. Redundant Gas Valve.
There are two separate gas valves in the furnace.
Each valve contains a main and a redundant valve.
The redundant valves are located upstream of the
main gas valves. Should either or both of the main
gas valves fail in the open position the redundant
valves serve as back-ups and shut off the flow of
gas.
4. Flame Sensor Rod / 100% Ignition Control Lock-
Out.
The flame rods and controls are located per Proper
Flame Adjustment Figure 22. If an ignition control
fails to detect a signal from the flame sensor indi-
cating the pilot flame is properly ignited, then the
main gas valve will not open. It will continue to try
and ignite the pilot for a maximum of 85 seconds,
then if the pilot flame is not detected, the ignition
control will lock out furnace operation until 24V
power is removed from the module either at the
unit or by resetting the room thermostat.
5. Rollout Switch.
This switch is located above the main burners in
the control compartment, which in the event of a
sustained main burner rollout shuts off and locks
out both ignition controls closing both gas valves.
The ignition controls lock out furnace operation
until 24V power is removed from the controls either
at the unit or by resetting the room thermostat.
NOTE: The auto reset rollout switch must reset before
allowing furnace operation.
6. Auxiliary limit switch (AUX) -
This control is located inside the heat exchanger
compartment and is set to open at 190°F. It is a
manual reset switch. If AUX trips, then the primary
limit has not functioned correctly. Replace the pri-
mary limit.
TABLE 21: LIMIT CONTROL SETTING
Units
(Tons)
Capacity, MBH
Limit Control
Opens, ºF
Input Output
15, 20 & 25 300 240 195
15, 20 & 25 350 280 195