Flash Codes; Resets; Heat Anticipator Setpoints; Gas Valve And Controls - York DW-15 Installation Manual

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 26. 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.
The auto reset rollout switch must reset before
NOTE:
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
52
limit has not functioned correctly. Replace the pri-
mary limit.
TABLE 24: LIMIT CONTROL SETTING
Capacity, MBH
Units
(Tons)
Input
15, 17.5, 20 & 25 300
15, 17.5, 20 & 25 400
I G N . C O N T R O L # 1
R O L L O U T S W .
S E N S O R # 1
G V 2
G A S
V A L V E
I G N I T O R # 2
B U R N E R C O M P A R T M E N T
FIGURE 24 - GAS VALVE AND CONTROLS

FLASH CODES

The UCB will initiate a flash code associated with
errors within the system. Refer to UNIT CONTROL
BOARD FLASH CODES Table 27.

RESETS

Remove the call for heating by lowering the thermostat
setting lower than the conditioned space temperature.
This resets any flash codes.

HEAT ANTICIPATOR SETPOINTS

It is important that the anticipator setpoint be correct.
Too high of a setting will result in longer heat cycles
and a greater temperature swing in the conditioned
space. Reducing the value below the correct setpoint
will give shorter "ON" cycles and may result in the low-
ering of the temperature within the conditioned space.
284816-BIM-B-0707
Limit Control
Opens, ºF
Output
240 195
320 195
I G N . C O N T R O L # 2
G V 1
G A S
V A L V E
I G N I T O R # 1
S E N S O R # 2
Unitary Products Group