Gemini™
In the case of the
7.2SEQUENCE OF OPERATION
Status (red and green) indicators located on the front of the control panel of this boiler are specifically de- signed to indicate the sequence of operations and the cause of common problems. Careful observation of indicators should provide a guide to most operational conditions and problems.
Refer also to the wiring diagrams in Section 8.
The sequence of operation for the
1.When the On/Off (main power) switch is turned on, a green indicator marked "Power" or the am- ber switch is illuminated. Power is applied through a series of normally closed limit switches, including water flow, gas pressure, and high tem- perature, and through the operating temperature control to the
2.The water flow limit switch is closed when there is adequate water flow through the boiler.
3.When adequate gas pressure is available, the low
4.If the temperature sensed by the
5.When heat is required, as indicated by outlet water temperature, power is applied to Terminal 6 of the programmer, which initiates the burner operating sequence, and to an indicator marked "Heat."
6.The programmer first energizes Terminal 4 which supplies power to the contactor for the blower mo-
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tor and the air flow switch, which initially shows low air flow with the "LowAir" indicator. This indicator will remain on until sufficient air flow is sensed.
7.A time delay of 10 seconds (standard) or 30 sec- onds (depending on insurance or local code re- quirements) occurs after the air proving switch closes and the programmer signals a continuation of the start sequence. During this time period the combustion chamber is
8.A
9.When a pilot flame is detected by the flame rod, a signal is sent to Terminal F in the programmer. Terminal 10 is
10.After the flame establishing period, Terminal 9 is energized, which opens the motorized main gas valve and the motorized gas valve to the fuel sup- ply in use and lights the "Main Gas" indicator. The boiler fires. After ten seconds, Terminal 8 is
An auxiliary panel prevents the motorized gas valves for natural gas and propane to be open at the same time.
A power failure during operation closes all motor- ized gas valves and shuts down the boiler. When power is restored the controller recycles to Step 1;