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Servicing should only be performed by a Qualied Service Agent
CONTROL SEQUENCE (TYPICAL ALL MODELS)
TYPICAL SEQUENCE
1. When the control is powered it should display “waiting for connection” and “UIM v2.06”*. The
manufacturer and unit model will be next. The next display will include water temperature,
temperature setting and heater status.
* This number may change as software revisions are made.
2. The control performed selected system diagnostic checks immediately upon power up. This
includes confirming the proper state of the air/gas switches and ECO limit device and powered
anodes.
3. If the control determines that the actual water temperature inside the tank is below the programmed
temperature set-point less the differential, a call for heat is activated.
4. If all checks are successfully passed, the combustion blower is energized for the pre-purge cycle.
5. When the pre-purge cycle is complete, power is applied to the igniter element for the igniter warm-
up period.
6. At the conclusion of the igniter warm-up period, the gas valve will open, allowing gas to enter the
burner chamber.
7. The igniter will remain on for a short predetermined time period, then will be turned off.
8. The control will monitor the flame sense probe to confirm a flame is present. If a flame is not verified
within predetermined time period, the gas valve will immediately be closed, and the blower will
continue to run for approximately 30 seconds inter-purge. The control will try for ignition two more
times before lockout.
9. If a flame is confirmed, the control will enter the heating mode where it will continue heating the tank
water until the set point temperature plus differential is reached. At this point, the gas valve is closed
and the control enters the post-purge cycle.
10. The combustion blower will run for the duration of the post purge cycle to purge the system of all
combustion gases. When the post purge cycle is complete, the blower is de-energized and will
coast to a stop.
11. The control will now enter the idle state while
continuing to monitor the internal tank water
temperature and the state of other system
devices. If the temperature drops below the
set-point value less differential, the control will
automatically return to step 2 and repeat the
entire operating cycle.