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ROBERTSHAW 7222WDER SEQUENCE OF OPERATION
When initially energized, the 7222WDER control will perform a self-diagnostic check and the red LED will momentarily flash 3-4 times.
On a call for heat, a check is made by the control to ensure that the air pressure switch on the blower is in the open position (if closed
the sequence pauses and the blower is not energized). With the air pressure switch proven open, the control energizes the blower
(Terminal 7). With the blower energized the control checks to ensure that the air pressure switch closes. At this point the air pressure
switch must close or the blower will run continuously. As the high limit switch on the blower is wired in series with the air pressure
switch, both switches must be closed (energizing Terminal 5) or the blower will run continuously. With proven airflow and the high limit
switch closed, a flame safety check is undertaken to ensure that a flame is not present prior to ignition. Providing a flame signal is not
detected, the hot surface igniter is energized and a warm up period of approximately 17 seconds is initiated. Following the igniter
warm up period, the control allows gas flow to the burner initiating a 4-second trial for ignition period. The control will normally estab-
lish a flame and maintain the flame until the call for heat is satisfied. If a flame cannot be established, is extinguished, or the flame
signal drops below 0.7 microamps, the control will stop the flow of gas to the burner. The blower continues to be energized and a 30-
second interpurge is undertaken. The control will attempt for ignition again. If the control cannot establish ignition after three attempts,
it will lock-out. The red LED will flash continuously indicating a lock-out condition occurred. Unplugging the 120VAC-power supply to
the water heater then restoring power will reset the control.
ROBERTSHAW 7222WDER TROUBLE SHOOTING GUIDE
Blower will not start
1. No Power to unit
2. Thermostat setting too low
3. Defective air pressure switch (must be
open at start-up before blower is ener-
gized)
4. Defective blower
5. Disconnected or loose wire
6. Control locked-out
1. Plug in power cord, check fuses/supply
voltage
2. Increase thermostat temperature setting
3. Replace air pressure switch
4. Replace blower
5. Repair/reconnect wires
6. Reset – determine cause of lock-out
Blower runs continuously
1. Air pressure switch not closing due to
insufficient draft - check for:
a) vent piping blocked
b) piping length too long
c) frozen vent termination
d) clogged/dirty blower
2. Disconnected, torn or blocked pressure
sensing tubing from air pressure switch to
blower housing
3. Air pressure switch not closing due to
defective switch
4. High limit switch open due to excessive
vent temperature or defective switch.
1. Determine cause of insufficient draft.
Check draft with manometer at pressure
switch (refer to Table VI for minimum
acceptable draft settings)
a) remove blockage
b) reduce vent length/increase vent
size
c) clear termination of snow/ice
d) clean blower wheel
2. Reconnect or replace pressure sensing
tubing
3. Replace defective pressure switch
4. Determine cause of overheating check
for: overfiring, insufficient air supply, high
ambient air temperature (once activated
high limit must be replaced)
Hot surface igniter
not glowing following
warm-up period
1. 120VAC polarity reversed at 120VAC out-
let receptacle
2. Defective hot surface igniter
3. Defective Control
1. Reverse polarity at 120VAC outlet recep-
tacle
2. Replace igniter (Check for 120 VAC sup-
ply to igniter across I1 & I2)
3. Replace control
Control locked-out
*Continuously flashing
red LED (Resettable
lock-out condition)
1. No gas supply
2. Gas control in off position
3. Insufficient gas supply
4. Incorrect manifold gas pressure
5. Incorrect gas type
6. Defective igniter/loose or disconnected
wire
7. Improperly positioned, dirty, or defective
flame rod/loose or disconnected wire
8. Main burner orifice clogged
9. Blocked water heater flue
10. Defective control
1. Check /turn on gas supply
2. Turn control to On position
3. Ensure correct supply pressure for gas
type (Nat Gas 7.0” w.c.) (Propane 11.0”
w.c)
4. Check/adjust for correct manifold gas
pressure (Nat Gas 3.5” w.c.) (Propane
10.0” w.c)
5. Ensure correct gas type for water heater
model
6. Replace defective igniter/reconnect wiring
7. Reposition, clean, or replace defective
flame rod/reconnect wiring
8. Remove obstruction
9 Remove blockage/clean flue
10. Replace Control
Control locked-out
*Solid red LED
1. Internal control fault
2. ECO failure – excessive water tempera-
ture
3. Excessive humidity/damp environment
1. Replace control
2. Replace control
3. Allow control to dry
Symptom Possible Cause(s) Corrective Action