20
50ZH
Typical wiring schematic (cont)
Electric Heater Wiring
C
W1
W1
TO
UNIT POWER
WIRING
BLK
YEL
BRN (COMMON)
VIO (STEP 2)
WHT ( STEP 1)
CONTACTOR 2
YEL
BRN
YEL
CONTACTOR 1
YEL
YEL
BRN
YEL
YEL
FUSE BLOCK
L2
L1
YEL
YEL
BLK
BLK
F3
F4
F1
F2
EL 1
EL 2
EL 3
BLK
BLK
BLK
AUTO-LIMIT
452=5v
457=7v
455=2v
LEGEND
FLA — Full Load Amps
LRA — Locked Rotor Amps
MCA — Minimum Circuit Amps
MOCP — Maximum Overcurrent Protection
RLA
—
Rated
Load Amps
NOTES:
1. In compliance with NEC (National Electrical Code) requirements
for multimotor and combination load equipment (refer to NEC
Articles 430 and 440), the overcurrent protective device for the
unit shall be Power Supply fuse. The CGA (Canadian Gas
Association) units may be fuse or circuit breaker.
2. Minimum wire size is based on 60 C copper wire. If other than
60 C wire is used, or if length exceeds wire length in table,
determine size from NEC.
3. Unbalanced 3-Phase Supply Voltage
Never operate a motor where a phase imbalance in supply volt-
age is greater than 2%.
Use the following formula to determine
the percentage of voltage imbalance.
% Voltage imbalance
max voltage deviation from average voltage
= 100 x
average voltage
EXAMPLE: Supply voltage is 460-3-60.
AB = 452 v
BC = 464 v
AC = 455 v
452 + 464 + 455
Average Voltage =
3
1371
=
3
= 457
Determine maximum deviation from average voltage.
(AB) 457
(BC) 464
(AC) 457
Maximum deviation is 7 v.
Determine percent of voltage imbalance.
7
% Voltage Imbalance = 100 x
457
= 1.53%
This amount of phase imbalance is satisfactory as it is below the
maximum allowable 2%.
IMPORTANT: If the supply voltage phase imbalance is
more than 2%, contact your local electric utility company
immediately.
®
*Heater capacity (KW) based on heater voltage of 208v, 240v, & 480v.
If power distribution voltage to unit varies from rated heater voltage,
heater KW will vary accordingly.
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