RT-SVX34C-EN 35
Installation Electrical
Electrical Wire Sizing and Protection Device Equations
To correctly size the main power wiring based on MCA (Minimum Circuit Ampacity), use the
appropriate equation listed below. Read the definitions that follow and then use Calculation #1 for
determining MCA (Minimum Circuit Ampacity), MOP (Maximum Over current Protection), and RDE
(Recommended Dual Element fuse size) for TC (Cooling Only) units and YC (Cooling with Gas Heat)
units. Use Calculation #2 for TE (Cooling with Electric Heat) units.
Load Definitions:
LOAD 1 = CURRENT OF THE LARGEST MOTOR ( Compressor or Fan Motor)
LOAD 2 = SUM OF THE CURRENTS OF ALL REMAINING MOTORS
LOAD 3 = FLA (Full Load Amps) OF THE ELECTRIC HEATER Ta bl e 11, p . 35
LOAD 4 = ANY OTHER LOAD RATED AT 1 AMP OR MORE
CRANKCASE HEATERS FOR HEATING MODE ONLY - 208/230 VOLT
- 27.5 - 35 Ton Units, Add 1 Amp
- 40 - 50 Ton Units, Add 2 Amps
460/575 VOLT
- 27.5 - 35 Tons Units, Add 1 Amp
- 40 - 50 Ton Units, Add 1 Amp
Calculation #1 - TC*, YC*-27.5 to 50 Ton Units
MCA = (1.25 x Load 1) + Load 2 + Load 4
MOP = (2.25 x Load 1) + Load 2 + Load 4 (See Note 1)
RDE = (1.5 x Load 1) + Load 2 + Load 4 (See Note 2)
Calculation # 2 - TE*-27.5 to 50 Ton Units
A. Single Source Power (all voltages)
To calculate the correct MCA (Minimum Circuit Ampacity), MOP (Maximum Over current
Protection), and RDE (Recommended Dual Element fuse size), two (2) sets of calculations must be
performed;
Table 11. Electrical Service Sizing Data — Electric Heat Module (Electric Heat Only)
Models: TED/TEH 330—600 Electric Heat FLA
KW Heater
Nominal
Unit Size
(Tons)
Nominal
Unit
Voltage
36 54 72 90 108
FLA FLA FLA FLA FLA
27½-35
208 74.9 112.4 — — —
230 86.6 129.9 — — —
460 43.3 65.0 86.6 108.3 —
575 — 52.0 69.3 86.6 —
40- 50
208 — 112.4 — — —
230 — 129.9 — — —
460 — 65.0 86.6 108.3 129.9
575 — 52.0 69.3 86.6 103.9
Note:
1. All FLA in this table are based on heater operating at 208, 240, 480, and 600 volts.
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