34000 Autry Street, Livonia, MI 48150 | 800.968.5530 | Fax 734.419.0209 | www.hamiltonengineering.com | LIT91127US REV 5/2018
Page 40
SERVICING
E. SEQUENCE OF OPERATION
DANGER
Water temperature over 125ºF can cause severe burns
instantly, or death from scalds. Children, the disabled,
and the elderly are at highest risk of being scalded.
See instruction manual before setting temperature at
water heater. Feel water before bathing or showering!
Temperature limiting valves are available.
1.
When power is first applied to the control, the control display will read the temperature Setpoint.
The control will initially run through a self-diagnostic routine and then go into its operating 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 module will determine if the water temperature
is below the programmed set point value minus the switching differential. It will then 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 4.5 seconds.
Approximately 1/2 second later, flame is verified. If a flame is not verified during the trial-for-
ignition, the gas valve is immediately closed and the control will return to Step 3. After four 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 firing rate will be based on the control’s proprietary algorithm.
5.
When water temperature reaches the temperature set point value, the burner will be at
minimum firing rate. If, when firing at minimum rate, it reaches 3°F over temperature setpoint,
the gas valve closes and the control enters a post-purge state (the blower will be on maximum
speed). At any time if an external thermostat is being used and becomes satisfied, the gas valve
will be closed immediately and display will read “0”.
6.
When the post-purge is complete, the control enters an idle state while continuing to monitor
temperature and the state of other system devices. If a call-for-heat is received, the control will
automatically return to Step 2 in sequence and repeat the entire operating cycle.
7.
Built in freeze protection: all models will automatically turn the pump on if the heat exchanger
reaches 41°F and the burner if it reaches 37°F, it will turn off at 50°F.
Note: power must be left on for this protection to function.
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 control will illuminate an error code in the display.
PART 7. SERVICING
A. SERVICING THE EVO
1.
Shut off the power supply to the appliance (See Figure 1-4, Page 11).
2.
Remove the front cover security screw(s).
3.
Undo the two latches at the bottom of the cover (if applicable).
4.
Remove the cover.
B. PLACING THE EVO INTO NORMAL OPERATION
1.
Replace the front cover in the normal position.
2.
Close the latches on the bottom of the cabinet (if applicable).
3.
Replace the security screw(s).
4.
Turn on the power supply to the appliance.