Voltage Imbalance - Trane CCRC Series Installation, Operation And Maintenance Manual

I I n n s s t t a a l l l l a a t t i i o o n n — — E E l l e e c c t t r r i i c c a a l l
cause control components to malfunction and shorten
the life of relay contacts and condenser fan motors.

Voltage Imbalance

Excessive voltage imbalance between phases in a
three-phase system can cause motors to overheat and
eventually fail. Maximum allowable imbalance is 2%.
Voltage imbalance is defined as 100 times the
maximum deviation of the three voltages (three
phases) subtracted from the average (without regard to
sign) divided by the average voltage.
E E x x a a m m p p l l e e
• L1 measured = 221 V
• L2 measured = 230 V
• L3 measured = 227 V
Table 5. CCRC/CIRC Condenser Electrical Data
Tons
20, 29, 32
35, 40
50, 60
Note: All motors for CCRC/CIRC units are rated at 1 hp (0.7457 kW).
20
Voltage
# Fans
200 4
460 4
575 4
200 6
460 6
575 6
200 8
460 8
575 8
221 + 230 + 227
3
N N o o t t e e : : L1 = 221 volts is the maximum deviation of the 3
voltages from the average of the 3 voltages.
Therefore, the imbalance percentage is:
100 (226 - 221)
226
The 2.2 % imbalance that exists in the example above
exceeds the maximum allowable imbalance between
phases.
FLA (ea.) LRA (ea.)
4.1 20.7
1.8 9
1.4 7.2
4.1 20.7
1.8 9
1.4 7.2
4.1 20.7
1.8 9
1.4 7.2
= 2.2%
= 2.2%
MCA
17.4
7.7
5.9
25.6
11.2
8.8
33.8
14.8
11.5
CXRC-SVX01J-EN
MCB
20
15
15
30
15
15
40
15
15