Lochinvar 000 through 2, 1 warranty Low Air Pressure Switch, Excel, Blower, Transition, Burner

blower from 25% up to 100% of capacity corresponding to the same variation in burner input. The output from the Excel 10 to the variable frequency drive ensures that combustion air and gas are always supplied in the proper ratio for clean combustion. The variable frequency drive is driven to 100% during the pre-purge portion of the start-up sequence. The variable frequency drive is then provided a signal to operate at 50% for initial burner ignition. After main burner ignition is established, the Excel 10 will use the variable frequency drive to vary the blower speed based on desired water temperature set point, the variation in actual water temperature from the desired set point and the various operating characteristics programmed into the control’s software.

When removing the variable frequency drive from the appliance, disconnect the power wires to the combustion air blower at the terminals on the variable frequency drive. DO NOT disconnect the power wires at the blower motor. Note the marking of the wires for proper reinstallation of the three phase power wires to the VFD. Both the wires and the VFD terminals are marked for proper location of wire terminals. Incorrect installation of the wires may reverse rotation of the blower motor resulting in major operational problems.

CAUTION￿

The voltage output from the variable frequency drive to the combustion air blower is 230 volt 3 phase. Avoid contact with high voltage wiring.

A differential air pressure switch is used to prove operation of the combustion air blower. The pressure switch sensing points are installed across the point of pressure drop as the air moves into the inlet of the burner. This switch measures the same pressure drop points similar to those used by the ratio gas valve to adjust manifold gas pressure. Correct differential pressure across the sensing points of the pressure switch proves operation of the combustion air blower to the Excel 10 control. The Command Display will exhibit a Status Alarm of LowAirPress and the appliance will shut down operation when the differential pressure switch detects a sustained low air condition.

HIGH GAS PRESSURE SWITCH LOW GAS PRESSURE SWITCH (Optional)

High and/or low gas pressure switches are available as an option on this appliance. The high gas pressure switch is used to monitor the maximum gas supply pressure supplied to the gas train. If gas pressure exceeds the maximum setting of the pressure switch, the appliance will shut down and a gas pressure fault will be indicated in the Command Display. The low gas pressure switch is to monitor the minimum gas supply pressure supplied to the gas train. If gas pressure falls below the minimum setting of the pressure switch, the appliance will shut down and a gas pressure fault will be indicated on the Command Display. GasPressFail will be shown on the Display for either a high or low gas pressure problem.

LOW AIR PRESSURE SWITCH

PRESSURE SWITCH
BLOWER	~
	~
TRANSITION
	~
	~
BURNER

FIG. 51 Low Air Pressure Switch

EXCEL 10

FIG. 52 Excel 10 Control Module

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