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RT-SVX063E-EN
reduced. If allowed to run backwards for an extended
period of time the motor windings can overheat and
cause the motor winding thermostats to open. This will
cause a “compressor trip” diagnostic and stop the
compressor
If a scroll compressor is rotating backwards, it will not
pump and a loud rattling sound can be observed.
Check the electrical phasing at the compressor terminal
box. If the phasing is correct, before condemning the
compressor, interchange any two leads to check the
internal motor phasing.
Variable Speed Manifolded with Fixed
Speed Compressors
Some models use an eFlex
™
variable speed
compressor manifolded with a fixed speed
compressor. It uses a patented manifold design that is
different from fixed speed tandems as follows:
1. The variable speed compressor is always first on
and located upstream in the suction line in position
1A;
2. A nozzle in the suction tee, directly upstream of the
manifold set, separates suction oil return to the
upstream variable speed compressor. It also
provides a sump pressure difference to move
excess oil from the variable speed to the fixed
speed compressor when both compressors are
running. The nozzle is specifically sized for this
variable speed manifold compressor combination
and must not be removed.
Suction restrictors are not used, and a smaller 3/8"
OD oil equalizer line is used to help maintain the
sump pressure differential.
Figure 93.
eFlex variable speed tandem
Fixed
speed
compressor
Variable
speed
compressor
Combined
suction
flow
Nozzle
Inflow
Precision Suction Restrictor
Tandem manifold compressors that have unequal
capacity sizes use a precision suction restrictor to
balance the oil levels in the compressors (see figure
below). This restrictor is placed in the smaller capacity
compressor. When replacing this compressor, it is
imperative that the proper restrictor is selected from
those provided with the replacement compressor.
When the compressors are restarted, verify that correct
oil levels are obtained with both compressors
operating.
Figure 94.
Precision suction restrictor
Compressor
Suction
Suction
Tube
Suction Restrictor
VFD Programming Parameters (Supply/
Condenser for Low Ambient Option)
Units shipped with variable frequency drives (VFD) are
preset and run tested at the factory. If a problem with a
VFD occurs, ensure that the programmed parameters
listed in
Table 70, p. 129
and
Table 71, p. 131
for
supply fan VFDs and
Table 72, p. 131
for condenser fan
VFDs (if low ambient option is installed), have been set
before replacing the drive.
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Verify parameter 1-23 is set to motor nameplate
frequency.
1. To check parameter 1-23 press the Main Menu
button twice (press the Back button if the main
menu does not display)
2. Scroll down to Load & Motor, press OK
3. Select 1-2, press OK
4. Press down until parameter 1-23 is displayed.
Parameter 1-23 can then be modified by pressing
OK and pressing the Up and Down buttons.
5. When the desired selection has been made, press
OK .
Should replacing the VFD become necessary, the
replacement is not configured with all of Trane's
operating parameters. The VFD must be programmed
before attempting to operate the unit.
To verify and/or program a VFD, use the following
steps:
1. At the unit, turn the 115 volt control circuit switch to
the Off position.
IIm
mp
po
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an
ntt:: HIGH VOLTAGE IS PRESENT AT TERMINAL
BLOCK OR OPTIONAL UNIT DISCONNECT
SWITCH.
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