A
HE, DE & RE MANUAL
IOM-26
21 of 33
Oct 12 R4
9.
Set thermostat or
controller to the “OFF” position and turn unit control switch “ON”.
10.
Check the amperage draw of each motor and compressor. Refer to unit or motor rating plate for full
load amps. At the unit, check and record the voltage while it is running. For 3 phase power the
phase to phase voltage imbalance should be less than 2%. A 2% voltage imbalance can cause up
to a 10% current imbalance that will overheat motor windings.
To calculate voltage imbalance (NEMA method) refer to the following example:
Phase to phase voltage readings:
235V 236V 230V
The average Voltage between legs is 233.7V
(235+236+230)/3
Highest voltage deviation from average is:
233.7V
– 230V = 3.7V
Voltage imbalance percentage = Highest deviation divided by average X 100
3.7 / 233.7 x 100 = 1.6% This imbalance is less than 2% and therefore is OK
If voltage imbalance is greater than two percent (2%), turn off main disconnect and contact
the installing electrical contractor to have the voltage condition corrected.
11.
Enable heating and/or cooling; refer to unit function for correct sequence and operation.
12.
Confirm field wiring voltage drop is less than 10% when equipment is operating.
13.
For the unit to operate properly a system air balance must be performed to ensure correct air flow.
Failure to do so can damage the equipment and/or building and can be a cause of poor indoor air
quality.
14.
Some units are equipped with an adjustable coil air bypass. This must be field adjusted during the
system air balance to ensure proper air flow across the coil. Adjust the bypass to achieve coil
pressure drop as stated on the submittal and/or the unit function sheet.
15.
Set all controls to the settings indicated on the wiring diagram.
16.
Re-install all access panels.
17.
Remove any packing material or debris and dispose appropriately.
