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FIG. 48 Transformer and Relay Locations
VARIABLE FREQUENCY DRIVE
FIG. 49 Internal Control Panel Location
FIG. 50 Variable Frequency Drive
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 cut-off, a high limit alarm re lay, an alarm relay, an ignition
relay, gas valve relay, pump relay, louver relay and VFD power
relay.
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