Part 7; Sequence Of Operation; Munchkin Temporary Fault Condition - Munchkin 399M Installing, Operating & Maintaining

Fig. 6-1
PART 7. SERVICING
A. SEQUENCE OF OPERATION
1. When power is first applied to the control, the control display will read the outlet tempera-
ture. The control will initially run through a self-diagnostic routine and then go into its oper-
ating mode. If there is no call for heat, the System will go into an idle state.
2. If the thermostat is calling for heat, the control will apply power to the circulator pump. If the
control determines the water temperature is below the programmed set point value minus
the switching differential, the control will initiate a heating cycle.
3. The control then performs selected system diagnostic checks. If all checks are successfully
passed, a pre-purge cycle is initiated (the blower will be on maximum speed).
4. When the pre-purge period is complete, power is applied to the spark ignitor for approxi-
mately 6 seconds. Approximately 2 seconds later, we verify flame. If a flame is not verified
during the trial-for-ignition, the gas valve is immediately closed and the control will return to
step. After three trials, if a flame is not verified, the control will go into a lockout mode. If a
flame is confirmed, the control enters the heating mode. The fire rate will be based on the
proprietary algorithm.
5. When water temperature reaches the temperature set point value plus 10 degrees F (or if the
thermostat call-for-heat is satisfied), the gas valve is closed and the control enters a post-
purge state (the blower will be on maximum speed). NOTE: If the thermostat is still calling
for heat, the circulator pump will continue to run until the thermostat call for heat is satis-
fied.
6. When the post-purge is complete, the control enters an idle state while continuing to moni-
tor temperature and the state of other system devices. If a call-for-heat is received, the con-
trol will automatically return to step 2 in sequence and repeat the entire operating cycle.
During the idle state and heat state, if the control detects an improper operating state from external
devices, such as the high-limit switch, the red light on the control will illuminate an error code will
appear in the display.
B. MUNCHKIN TEMPORARY FAULT CONDITION
A Temporary Fault Condition may occur in the installation of the Munchkin. This condition may lead
to a lock out condition of the controller, which will need to be manually reset through the S4/Reset
button. These temporary codes will help the installer correct the problem before going into a lock
out condition, which will require a manual reset. Example: A temporary fault-code of E15 indicates
that the Air Pressure Switch is open when the fan is in the pre-purge function, when it should be
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GAS SHUT OFF INLET VALVE
SOLENOID
VALVE
INLET PRESSURE TAP
START-UP PROCEDURES / SERVICING
OUTLET VALVE
SOLENOID
THROTTLE ADJUSTMENT
OFFSET ADJUSTMENT
MOUNTING
BRACKET
OUTLET PRESSURE TAP