Unbalanced 3-Phase Supply Voltage
Voltage unbalance occurs when the voltages of all phases of a
Perform the following steps to determine the percentage of voltage imbalance:
Grounding
WARNING:
The unit cabinet must have an uninterrupted or unbrokenelectricalgroundtominimizepersonal injury if an electrical fault should occur. Do not use gas piping as an electrical ground!
This unit must be electrically grounded in accordance with local codes or, in the absence of local codes, with the National Electrical Code (ANSI/NFPA 70) or the CSA C22.1 Electrical Code. Use the grounding lug provided in
1. M e a s u r e t h e l i n e voltages of your
Example:
AB = 451V
BC = 460V
AC = 453V
the control box for grounding the unit.
STARTUP AND ADJUSTMENTS Pre-Start Check List
Prior to
√ Verify the unit is level and condensate can drain. Check |
condensate drain line(s) for proper slope and trap. |
√ Verify the air handler is mounted securely. |
√ Verify the surrounding area and top of the unit is free |
from obstructions and debris. |
2. Determine the average voltage in the power supply.
In this example, the measured line voltages were 451, 460, and 453.The average would be 454 volts (451 + 460 + 453 = 1,364 / 3 = 454).
3. Determine the maximum deviation:
Example:
From the values given in step 1, the BC voltage (460V) is the greatest difference in value from the average:
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| 460 - 454 = 6 |
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| 454 - 451 = 3 |
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| 454 - 453 = 1 |
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4. Determine | percent | of |
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voltage imbalance | by |
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using the | results from |
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steps 2 & 3 in the following | 100 x | = 1.32% | |||||||
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454 | |||||||||
equation. |
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max voltage deviation
from average voltage
% Voltage Imbalance = 100 x
average voltage
The amount of phase imbalance (1.32%) is satisfactory since the amount is lower than the maximum allowable 2%. Please contact your local electric utility company if your voltage imbalance is more than 2%.
√ Check all ductwork connections. Make sure the duct |
work is adequetly sealed to prevent air leakage. |
√ Check all coil connections for leaks. |
√ Verify that the line voltage power leads are securely |
connected and the unit is properly grounded. |
√ Verify that the low voltage wires are securely connected |
to the correct leads on the low voltage terminal strip. |
Make sure the thermostat is wired correctly. |
√ Verify the blower rotates properly.Check the blower belt |
between the pulleys for proper tension and alignment. |
√ Verify the power supply branch circuit overcurrent |
protection is sized properly. |
√ Verify all fi lters are in place and all equipment access/ |
control panels are in place |
Motor Sheave Adjustment
The motor sheave consists of an outer, moveable pulley face and an inner stationary face. To adjust the motor sheave,
1.Relieve the belt pressure by loosening motor mount bolts and the belt tensioning bolts on the motor mount.
2.Move the blower fan belt out of the way (if necessary) and loosen the set screw in the outer sheave face.
3.Rotate the face in increments of one half or full turns only. NOTE: This maintains the set screw position precisely over the fl ats on the pulley hub. Rotating the sheave clockwise (when viewed from the lead end of motor - opposit end of shaft) will make the blower run slower which decreases airfl ow. Rotating the sheave counter clockwise (as viewed from lead end) will cause the blower to speed up.
4.Tighten the setscrews after the desired adjustment has been made and verify the moveable face is properly secured.
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