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FIG. 48 Transformer and Relay Locations
VARIABLE FREQUENCY DRIVE
FIG. 49 Internal Control Panel Location
A transformer and relay mounting panel is located above the front control panel, underneath the curved exterior front jacket panel. This panel contains a 100 VA transformer to drop 120 VAC to 24 VAC for internal control operation, an optional electronic low water
FIG. 50 Variable Frequency Drive
This appliance uses a variable frequency drive (VFD) to control operation of the combustion air blower motor. The variable frequency drive is supplied with 120 VAC power. The blower motor operates on 230 VAC 3 phase power. This three phase voltage is generated by the variable frequency drive and supplied directly to the blower motor. The variable frequency drive receives a signal from the Excel 10 controller based on water temperature to vary the frequency of the voltage supplied to the blower motor from 15 Hz up to 60 Hz. This varies the output of the combustion air
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