Trane BCHE Installation, Operation And Maintenance Manual page 143

these overload conditions. If the motors cannot achieve
rpm close to the target for a specific period of time, the unit
will disable electric heat and fan-status indicators.
MCA/MOP and Power Draw
ECM motors have variable output but are shipped at
specific settings to deliver proper performance and
reliability. The power draw indicated in the catalog indicates
the power consumed when applied properly (as shipped
and with the nominal ESP applied). However, the
nameplate of the unit indicates the maximum input draw of
the motor, as the motor settings can be changed to draw
more power.
Electric Heat Relays
For quiet operation, the units employ power relays instead
of definite purpose contactors for electric heat actuation.
The coils of multiple relays are hooked in parallel to
simulate a multi-pole contactor, as shown in the following
figure. Two sets of three relays are used to perform the
function of a two 3 pole contactors.
Troubleshooting Other Unit Functions
In some cases, the normal or abnormal operation of the
ECM may interact with other components in the system.
BCX-SVX002A-EN
Diagnostics and Troubleshooting
Generally, verification of the engine and adapter boards'
wiring and configuration should be checked if there are
unexplained abnormalities in other areas of the unit:
• Valve operation
• Electric heat operation
• Changeover sensor operation
• Damper operation
• Condensate overflow switch
A high degree of protection is provided on electric heat
units. If electric heat fails to actuate, it may be because of
one of the following events:
• Fans are failing to meet target speed. If a second motor
is not present, all settings for speeds for Motor 2 should
be set to 0000.
• Hot water may be available in the changeover coil.
• Target speeds for motors may be set too high:
– The F F P P R R V V parameter may be set incorrectly.
– The A A i i P P U U parameter may be set incorrectly.
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