Trane CSRA025FAF0, Installation Operation & Maintenance

Page: 41 / 83

CSRA-SVX02A-EN 41
Installation
Table 3 — Customer Connection Wire Range
Power Wire Sizing and Protection Device Equations
To correctly size the main power wiring for the unit, use the appropriate
calculation(s) listed below. Read the load definitions that follow and use
Calculation #1 for determining the MCA (Minimum Circuit Ampacity), MOP
(Maximum Over current Protection), and RDE (Recommended Dual Element
fuse size) for each unit. Use Calculation #2 to determine the DSS
(Disconnect Switch Size) for each unit.
Load Definitions: LOAD 1 = CURRENT OF THE LARGEST MOTOR
(COMPRESSOR OR FAN MOTOR)
LOAD 2 = SUM OF THE CURRENTS OF ALL
REMAINING MOTORS
LOAD 4 = CONTROL POWER TRANSFORMER
= AND ANY OTHER LOAD RATED AT 1
AMP OR MORE
Calculation #1
(MCA, MOP, and RDE)
MCA = (1.25 x LOAD 1) + LOAD 2 + LOAD 4
MOP = (2.25 x LOAD 1) + LOAD 2 + LOAD 4
Select a fuse rating equal to the MOP value. If the MOP value does not equal
a standard fuse size as listed in NEC 240-6, select the next lower standard
fuse rating.
Note: If selected MOP is less than the MCA, then select the lowest standard
maximum fuse size which is equal to or larger than the MCA, provided the
selected fuse size does not exceed 800 amps.