York ZF 180 Series Installation Manual page 46

1061903-XIM-A-0713
• Proper wiring between the room thermostat and the
UCB, and
• Loose wiring from the room thermostat to the UCB
7. If 24 volts is present at the room thermostat but not at the
UCB, check for proper wiring between the thermostat and
the UCB, i.e. that the thermostat G terminal is connected to
the G terminal of the UCB, and for loose wiring.
8. If the thermostat and UCB are properly wired, replace the
UCB.
9. If the blower motor runs with the fan switch in the "ON"
position but does not run shortly after the furnace has
ignited when the fan switch is in the "AUTO" position,
check the room thermostat for contact between R and G
during "W1" calls.
On calls for heating, the supply air blower operates but the draft
motor does not (the room thermostat fan switch is in the
"AUTO" position).
1. The draft motor has inherent protection. If the motor shell is
hot to the touch, wait for the internal overload to reset.
2. If the motor shell is cold with the room thermostat calling
for heat, check for line voltage at the motor's Mate-N-Lok
connector attached to the evaporator partition. If line
voltage is present, replace the draft motor.
3. If line voltage is not present, check for line voltage at the
heat relay (RW1) contacts in the main control box and
check to see if the (RW1) is pulled in.
4. If the (RW1) relay is pulled in, check for a loose line voltage
connection.
5. If the (RW1) relay is not pulled in, check for 24 volts at the
(RW1) coil. If 24 volts is present, replace the (RW1) relay. If
24 volts is not present, check for a loose 24 volt connection
back to the relay board and check the connections from the
room thermostat to the relay board. If all connections are
correct, replace the relay board.
The draft motor runs but the furnace does not light and the
sparker does not spark.
1. The ignition control (IC1, IC2) may be locked out due to
either a flame roll out or 100% shut off. These safety features
are described above. If lock-out has occurred, 24V must be
removed from the ignition controls. This is done at the unit or
by resetting the room thermostat. After resetting 24V, check
for proper furnace operation. If lock-out continues to occur,
locate the source of the problem and correct.
2. Check all 24 volt connections from the relay board to and in
the gas heat section. Check low voltage connections to the
(ETD) located in the control box.
3. If the furnace is hot, it may be out on an over-temperature
condition, wait for limit reset.
4. If the furnace is cold, check for 24 volts at wire 241
attached to the electrical time delay (ETD) located in the
main control box. If 24 volts is not found, replace the ETD.
5. 24 volts is found at wire 241, remove the wires attached to the
(TDR) and with a VOM, check for continuity across contacts 1
and 2. If none is found, the (TDR) is open and must be
replaced. If there is continuity, re-attach the wires.With the
draft motor running, check for 24 volts at terminal 4 of (RW1-
2) and (RW2-1). If 24 volts is not present, the centrifugal
46
switch (CS) has not closed or has gone bad. Check the line
voltage to the unit - if it is correct, replace the draft motor. If
line voltage is low, call the power company.
6. Check for 24V at terminal 2 of (RW1-2 and RW2-1). If 24V
is not present, check for 24V at (RW1 and RW2) relay
coils. If these relays are pulled in, then check for a loose
connection at terminal 2 and terminal 4 of each relay. If no
problem is found, then replace (RW1 and/or RW2) as
required.
7. If 24 volts is present at the ignitor controls, check all control
wiring at the ignitor controls and the high tension wire to
the ignitors. Check that the ground wires from the ignitor
controls, the gas valves and pilot burners are all intact and
making good electrical connection. Check to make sure
that the ceramic insulator on the pilot ignitors or sensors is
not broken or cracked, if all are intact, replace the ignition
control IC1 or IC2.
The draft motor runs and the ignitor sparks at the pilot burner
but the pilot does not ignite and a gas odor is not detected at
the draft motor outlet.
1. Check to make sure gas is being supplied to the unit. Make
sure that the gas pressure to the unit is within the proper
limits as described in the "POST START CHECK LIST"
page 40 and that the pilot adjust screw is allowing some
flow of gas as described in "PILOT CHECKOUT" page 41.
2. Check all wiring between the ignitor control and the gas
valve. Check to make sure the ground connections are
intact.
3. If the wiring is intact, check for 24 volts across terminals
"PV" and "COMMON" on the ignitor control. If 24 volts is
not present, replace the ignitor control.
4. If 24 volts is present, remove the pilot burner and remove
the pilot orifice from the pilot burner. The orifice is removed
in the direction opposite the flow of gas. Inspect the orifice
for obstruction. If it is clear, replace the main gas valve.
The ignitor sparks at the pilot burner but the pilot does not ignite
and a gas odor is detected at the draft motor outlet.
1. Adjust the pilot adjust screw on the gas valve as described
in "PILOT CHECKOUT" page 41.
2. Check the supply pressure as described in "POST START
CHECK LIST" page 40. Make adjustments as necessary.
3. Check the pilot orifice for obstruction as described in
paragraph above. Clean as needed but the problem should
not be the gas valve.
The pilot burner ignites but the ignitor continues to spark and
the main burners do not ignite.
1. Make the same checks and adjustment as described in
"PILOT CHECKOUT" page 41.
2. Check the supply pressure as described in "POST START
CHECK LIST" page 40. Make adjustments as necessary.
3. Make sure that the pilot burner is not bent or damaged.
4. Make sure that the ground connections at the pilot burner,
gas valve and ignitor control are intact. Check the high
tension wire for good electrical connection. If all are intact,
replace the ignitor module.
Johnson Controls Unitary Products