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CTV-PRB004-EN
Electrical System—Design Guidelines
There are three functions that electrical engineers must address when designing electrical systems
that include chiller motors and the associated starters:
1.
Means of disconnect
2. Means for short circuit interruption
3. Making sure that the starter enclosure has an adequate short-circuit current rating for the
available fault current (low voltage) or properly sized fuses (medium voltage)
Disconnect Means
Low-voltage disconnect
Low-voltage starters from Trane do not have a disconnect means as standard. The standard line
power connection is a terminal block (i.e., main lug only) connection. An optional non-fused
disconnect switch, in a molded case as shown in
Figure 40
, can be installed. These non-fused
disconnect switches typically have locking provisions to allow the switch to be locked open; often
with up to three different padlocks.
A non-fused disconnect switch is used when servicing the chiller to protect someone from personal
injury, and it can also be used as a load-break switch in an emergency. Since the disconnect switch
is a non-fused device, current limiting protection must be installed upstream of the chiller by
others.
Figure 39. Electrical rating label locations
AFC—available fault current
Three-phase line power
SCCR—starter short-circuit
AIC—circuit breaker
ampere-interrupting rating
Starter door
current rating
Figure 40. Non-fused disconnect
CTV-PRB004.book Page 52 Sunday, December 18, 2011 6:39 PM
