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KAH Operation & Maintenance Guide
Page: 32 of 88
7. When connecting heaters with more than one stage,
wire stage No. 1 so that it is the first stage on and the
last stage off.
8. The heater must be wired so that it cannot operate
unless air is flowing over it. This can be accomplished
by using a built-in airflow switch and a remote
interlock. See the accompanying wiring diagram
for the method used with this heater and provide
appropriate interlock wiring as illustrated. This
diagram will be located inside of the electric heater
control panel.
9. If not supplied as part of this heater, install a line
disconnect switch or main circuit breaker in accordance
with the National Electrical Code. Depending upon
the heater’s location and accessibility, a built-in
disconnect switch may meet this requirement.
10. All electrical connections in the heater, including
both field and factory made connections, should be
checked for tightness before operating the heater.
In addition, after a short period of operation, all
connections should again be checked for tightness.
11. If heater is wired to a heating / cooling thermostat,
use a thermostat with isolating circuits to prevent
possible interconnection of Class 2 outputs.
12. If the heating elements are divided into several
sections with resistance wire between two or
more sections, maximum KW per sq. ft. should be
calculated as follows:
SECTION 2 - START-UP & OPERATION (CONTINUED)
Electrical Installation
1. Follow the wiring diagram on the inside of the terminal
box.
2. Supply connections must be made with copper wiring
rated for 75° C minimum.
3. If supply connections are for 250 volts or greater, all
wiring must be insulated for 600 volts.
4. When making line connections to heater element
terminals FOR FINNED TUBULAR HEATERS
ONLY, apply a 1/4” wrench to flat section of terminal
immediately below threads. Otherwise damage to
terminal may result.
5. Supply conductors for heaters rated less than 50
KW, must be sized at 125% of rated load. On heaters
rated 50 KW and more, the supply conductors may
be sized at 100% of rated load, if indicated on the
wiring diagram. The line current for either a single or
three phase load is calculated as follows:
1-Phase Line Current = (KW x 1000) / Voltage
3-Phase Line Current = (KW x 1000) / (Voltage x 1.73)
6. The following table shows the maximum current for
75 °C copper wire with not more than 3 conductors
in a raceway. It is based on the National Electrical
Code Table 310-16. The amperages shown are for
125% and 100% wire sizing. If there are more than
3 conductors in a raceway, derate these amperages
per Table 310-15(b)(2)(a).
Heater Nameplate KW
Number of
Heated Sections
Area of One
Heated Section
x
√
AMPS
Wire
Size
Awg /
MCM
AMPS
Wire
Size
Awg /
MCM
AMPS
Wire
Size
Awg /
MCM
125% 100%
125% 100%
125% 100%
12
14
80
100
3
184
203
4/0
16
12
92
115
2
204
255
250
24
10
104
130
1
228
285
300
40
8
120
150
0
248
310
350
52
65
6
140
175
2/0
268
335
400
68
85
4
160
200
3/0
304
380
500
