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PART 6. START-UP PROCEDURES
E. SEQUENCE OF OPERATION
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 at 80%).
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
temperature setpoint plus offset,
the gas valve closes and the
control enters a post-purge state
(the blower will be on at 80%). At
any time if an external thermostat
is being used and becomes
satisfied, the gas valve will be
closed immediately.
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.
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.
DANGER
PART 7. SERVICING
A. SERVICING THE EVO
1. Shut off the power supply to the
appliance (See Figure 1-4, Page 9).
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.
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.
B. PLACING THE EVO INTO NORMAL OPERATION
