Element
Operation and Maintenance
L-OMM-0003_A
• 10/8/2021 Technical Support • (800) 526-0288 • Mon-Fri, 8 am - 5 pm EST Page
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b.
The Electronic Low Water Cut-Off control is a self-contained electronic device which
senses the presence of water at the top of the storage tank. When the presence of water
is confirmed, the contacts close on the ELWCO and is sensed by PIM control.
c.
The High Temperature Limit is combined in a common probe body with the upper tank
sensor. The PIM will compare the high limit thermistor temperature with the upper tank
thermistor temperature. If the two temperatures are not the same, a sensor failure will
result.
d.
When the High Temperature Limit operation has been verified by comparison, the limit
temperature will then be confirmed to be under the maximum allowable temperature.
e.
Terminals P1-P2 are closed to activate any connected remote devices.
f.
The circuit between Terminals C1-C2 is closed by any connected remote proving
switches, enabling the water heater to continue the sequence of operation.
Call For Heat
- If the operating control senses that the temperature at the upper tank sensor is
below the water heater setpoint and the previous control interlocks and safeties are satisfied,
the following sequence will begin:
a. Terminals P1-P2 are closed to activate any connected remote devices.
b. The circuit between Terminals C1-C2 is closed by any connected remote proving
switches, enabling the water heater to continue the sequence of operation.
c. The High Gas Pressure and Low Gas Pressure Switch (if equipped) are energized and
their monitored pressures are proved. The individual safety circuits will close when
satisfied and be sensed by the PIM control.
d. When the burner blower is energized and operation is verified to close within 60 seconds
to prove flow.
e. The ignition pre-purge delay takes place.
f. The voltage level of the 24 VAC supply input is confirmed to be above 18.0 VAC.
g. The Ignition cycle begins.
h.
Heat-Up
- Following the pre-purge delay, the hot surface igniter will be energized:
i. The flame control will send 120V to the hot surface igniter for approximately 20 seconds.
j. The HSI Element proving current is verified.
k. The heat-up delay takes place to allow the hot surface element to reach ignition
temperature.
Ignition
- When dwell time is completed a 4-second Trial for Ignition (TFI) period is initiated:
a. Gas Safety Valves are energized.
b. The hot surface element is de-energized during the last second of the TFI period.
c. During TFI the flame safeguard control will monitor the flame using flame rectification
through the hot surface igniter.
d. If the flame control senses the presence of flame before the end of the TFI period, the
igniter will be de-energized and the flame control will continue to monitor the flame,
through the igniter, until the operating thermostat ends the call for heat condition.
Heating
a. The flame status, airflow switch, LWCO switch, water pressure switch and other safety
switches are continually monitored for proper state.
