Properly monitoring the electricity for refrigeration equipment helps assure long life of the equipment.
This is especially true for three phase units.
Three phase power can severely damage motors when a single phase condition occurs.
What do I mean by single phase?
Single phasing occurs when one of the three wires drops its voltage.
Without full voltage from all three legs, three phase motors will not start, will not run correctly, and become very hot to the touch.
Damage to motor windings can be severe and cause motor failure.
What could cause a single phase situation?
Starting with the obvious, the power company could drop a phase.
Many times the high voltage transformer blows a fuse or a power wire goes down.
When this happens, it affects the entire building. All the three phase electricity for refrigeration is bad.
(See real-world-refrigeraion.com for a real world example!)
Blown fuses in the equipment or equipment disconnect, will single phase the motors.
Also check the contacts on the contactor or starter. If they are damaged or worn, they can drop a leg of power.
Loose connections or burnt wires can single phase a motor. Inspect the connections. Look for wires with signs of overheating.
What do I recommend for protection?
Install a phase monitor!
A phase monitor does what the name says, it monitors all three phases.
If one or more lines drop out, it kills the control circuit stopping the refrigeration equipment.
Phase monitors are becoming more and more effective.
They can be adjusted for sensitivity and different voltages.
The also have time delay features to keep the equipment from short cycling if the power flickers on and off.
Another common feature is line side monitoring and load side monitoring.
What do I mean?
They monitor the top of a starter and the bottom of a starter. In other words the power across the individual contacts.
If one of the contacts is bad, the difference between the top and bottom voltage stops the unit.
Most monitors have a least one set of normally open and normally closed contacts.
The normally open contacts open the control circuit. The normally closed contacts can be used to activate an alarm.
Phase monitors are vital when using three phase equipment!
Keeping tabs on the electricity for refrigeration equipment helps insure reliable and trouble free operation over many years.
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