Power Wire Sizing And Protection Device Equations - Trane IntelliPak Installation, Operation And Maintenance Manual

Installation
Table 27. Electrical service sizing data — crankcase
heaters (heating mode on 460/575 volt only) —
20-130 tons
Nominal Tons
(Air-cooled/
Evaporative condensing)
20-30/24-36
40-60/48-73
70-75/80-89
90-105
115-130
Table 28. Voltage utilization range
Unit Voltage Utilization Range
200/60/3
230/60/3
380/50/3
415/50/3
460/60/3
575/60/3
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 SAH_ (Cooling
Only) units, SXH_ (Extended Casing) units, SLH_ and SSH_
(Cooling withWet Heat) units, and SFH_ (Cooling with Gas
Heat) units Use Calculation #2 for SEH_ (Cooling with
electric Heat) units.
Load Definitions:
LOAD 1 = CURRENT OFTHE LARGEST MOTOR
(COMPRESSOR OR FAN MOTOR)
LOAD 2 = SUM OFTHE CURRENTS OF ALL REMAINING
MOTORS
LOAD 3 = CURRENT OF ELECTRIC HEATERS
LOAD 4 = ANY OTHER LOAD RATED AT 1 AMP OR MORE
CONTROL POWERTRANSFORMER FOR ALL MODES
20 - 40Ton Units, add 3 FL Amps
50 - 75Ton Units, add 6 FL Amps
90 - 130Ton Units, add 8 FL Amps
CRANKCASE HEATERS FOR HEATING MODE 460/575V
ONLY
20 - 30Ton Units, Add 1 Amp
40 - 60Ton Units, Add 2 Amps
70 - 75Ton Units, Add 3 Amps
62
(Add) FLA
1
2
3
3
4
Voltage
180-220
207-253
342-418
373-457
414-506
517-633
90 - 130Ton Units, Add 4 Amps
• Calculation #1 - SAH_, SXH_, SLH_, SSH_, and SFH_
Units.
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.
RDE = (1.5 x LOAD1) + LOAD2 + LOAD4
Select a fuse rating equal to the RDE value. If the RDE value
does not equal a standard fuse size as listed in NEC 240 -
6, select the next higher standard fuse rating.
Note: If the selected RDE is greater than the selected MOP
value, then select the RDE value to equal the MOP
value.
• Calculation #2 - Rooftop units with Electric Heat (SEH_
20 - 130Tons)
a. Single Source Power (380V, 415V, 460V, and 575V)
To arrive at the correct MCA, MOP , and RDE values for
these units, you must perform two sets of calculations.
First calculate the MCA, MOP , and RDE values as if the unit
was operating in the cooling mode (use the equations
given in Calculation #1 above).Then calculate the MCA,
MOP , and RDE values as if the unit was operating in the
heating mode as follows. (Keep in mind when determining
LOADS that the compressors do not operate while the unit
is in the heating mode).
For units using heaters less than 50 Kw: MCA = 1.25 x
(LOAD 1 + LOAD 2 + LOAD 4) + (1.25 x LOAD 3)
For units using heaters equal to or greater than 50 Kw:
MCA = 1.25 x (LOAD 1 + LOAD 2 + LOAD 4) + LOAD 3
The nameplate MCA value will be the larger of the cooling
mode MCA value or the heating mode MCA value
calculated above.
MOP = (2.25 x LOAD 1) + LOAD 2 + LOAD 3 + LOAD 4
The selected MOP value will be the larger of the cooling
mode MOP value or the heating mode MOP value
calculated above.
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.
RDE = (1.5 x LOAD 1) + LOAD 2 + LOAD 3 + LOAD 4
The selected RDE value will be the larger of the cooling
mode RDE value or the heating mode RDE value calculated
above.
RT-SVX36K-EN