4
FIGURE 8: JUMPER BAR SHOWN INSTALLED ON
CIRCUIT BREAKERS.
Note: Circuit breakers installed in this device are the
short-circuit protection of internal wiring and to serve as
a service disconnect. Circuit breakers installed within
this device DO NOT provide over current protection of
the supply wiring.
SEQUENCE OF OPERATION
All heaters have a built-in delay feature to delay the
heater from coming on before the air handler is operating.
There is no delay-off feature. As soon as the thermostat
is satised, the heater de-energizes and the air handler
will continue running for approximately 1 minute. An air
pressure switch is in series with the fan interlock relay for
added protection and safety. The heater is designed for
a softer start so that there is a short time delay between
stages.
CAPACITY AT LOWER VOLTAGES
The elements are rated at 240 Volts and should not be
used at higher voltages. Lower voltages are acceptable.
However, heaters are resistive loads so capacity is
reduced by the square of the voltage ratio.
kW (output) = kW (rated) x (V/240)
2
Therefore, multiply the rated capacity by the factor
shown in Table 3 to determine the actual output of the
heater at other voltages.
TABLE 3: HEATER CAPACITY FACTOR
AT OTHER VOLTAGES
Voltage Factor
240 1.00
230 0.92
220 0.84
DUCT DESIGN
The design of the duct system must account for the added
restriction of the heater. Table 4 lists the static pressure
drop of the heaters. Usually it will be necessary to add
additional outlets to account for the added restriction,
particularly for the systems requiring more than 800
CFM (378 L/s). For these systems it is not unusual to
have 7 outlets per ton.
TABLE 4: PRESSURE DROP, INCHES OF WATER (PA)
External Electric Heater Models
CFM (m
3
/min) 2 Kw 5 kW 7.5 kW 10 kW 15 kW 20 kW
100(2.83) 0(0.64) 0(0.64) 0(0.8) 0(0.8) 0.01(1.28) 0.01(1.28)
125(3.54) 0(1.0) 0(1) 0.01(1.25) 0.01(1.25) 0.01(2.01) 0.01(2.01)
150(4.25) 0.01(1.44) 0.01(1.44) 0.01(1.79) 0.01(1.79) 0.01(2.89) 0.01(2.89)
175(4.96) 0.01(1.96) 0.01(1.96) 0.01(2.44) 0.01(2.44) 0.02(3.93) 0.02(3.93)
200(5.66) 0.01(2.55) 0.01(2.55) 0.01(3.19) 0.01(3.19) 0.02(5.14) 0.02(5.14)
250(7.08) 0.02(3.99) 0.02(3.99) 0.02(4.98) 0.02(4.98) 0.03(8.02) 0.03(8.02)
300(8.50) 0.02(5.75) 0.02(5.75) 0.03(7.17) 0.03(7.17) 0.05(11.56) 0.05(11.56)
350(9.91) 0.03(7.82) 0.03(7.82) 0.04(9.76) 0.04(9.76) 0.06(15.73) 0.06(15.73)
400(11.33) 0.04(10.22) 0.04(10.22) 0.05(12.75) 0.05(12.75) 0.08(20.54) 0.08(20.54)
450(12.74) 0.05(12.93) 0.05(12.93) 0.06(16.14) 0.06(16.14) 0.1(26) 0.1(26)
500(14.16) 0.06(15.97) 0.06(15.97) 0.08(19.92) 0.08(19.92) 0.13(32.1) 0.13(32.1)
550(15.57) 0.08(19.32) 0.08(19.32) 0.10(24.1) 0.10(24.10) 0.16(38.84) 0.16(38.84)
600(16.99) 0.09(22.99) 0.09(22.99) 0.12(28.68) 0.12(28.68) 0.19(46.22) 0.19(46.22)
650(18.41) 0.11(26.98) 0.11(26.98) 0.14(33.66) 0.14(33.66) 0.22(54.25) 0.22(54.25)
700(19.82) 0.13(31.29) 0.13(31.29) 0.16(39.04) 0.16(39.04) 0.25(62.91) 0.25(62.91)
750(21.24) 0.14(35.92) 0.14(35.92) 0.18(44.82) 0.18(44.82) 0.29(72.22) 0.29(72.22)
800(22.65) 0.16(40.87) 0.16(40.87) 0.20(51.00) 0.20(51.00) 0.33(82.17) 0.33(82.17)
850(24.07) 0.19(46.14) 0.19(46.14) 0.23(57.57) 0.23(57.57) 0.37(92.76) 0.37(92.76)
900(25.49) 0.21(51.73) 0.21(51.73) 0.26(64.54) 0.26(64.54) 0.42(104.00) 0.42(104.00)
950(26.90) 0.23(57.64) 0.23(57.64) 0.29(71.91) 0.29(71.91) 0.47(115.87) 0.47(115.87)
1000(28.32) 0.26(63.87) 0.26(63.87) 0.32(79.68) 0.32(79.68) 0.52(128.39) 0.52(128.39)
1050(29.73) 0.28(70.41) 0.28(70.41) 0.35(87.85) 0.35(87.85) 0.57(141.55) 0.57(141.55)
1100(31.15) 0.31(77.28) 0.31(77.28) 0.39(96.41) 0.39(96.41) 0.62(155.35) 0.62(155.35)
1150(32.56) 0.34(84.46) 0.34(84.46) 0.42(105.38) 0.42(105.38) 0.68(169.80) 0.68(169.80)
1200(33.98) 0.37(91.97) 0.37(91.97) 0.46(114.74) 0.46(114.74) 0.74(184.88) 0.74(184.88)
1250(35.40) 0.40(99.79) 0.40(99.79) 0.50(124.5) 0.5(124.50) 0.81(200.61) 0.81(200.61)
PRESURE DROP, INCHES WC (Pa)