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ELECTRIC HEATERS
The 50FC units can be equipped with field-installed accessory
electric heaters. The heaters are modular in design, with heater
frames holding open coil resistance wires strung through ceram-
ic insulators and control contactor(s), using a combination of
24-v control side break/auto-reset or line-break/auto-reset limit
switches and a pilot-circuit/manual reset limit switch to protect
the unit against over-temperature situations. All 50FC model
electric heaters are one module containing either one or two
banks of electric heat coils. Heaters may be installed on both
Standard SCCR and High SCCR rated units.
Heater modules are installed in the compartment below the indoor
(supply) fan outlet. Access is through the indoor blower access
panel. Heater modules slide into the compartment on tracks along
the bottom of the heater opening. See Fig. 46-48.
Each kit (CRHEATER454A00 to CRHEATER471A00) con-
tains the heater module, wire ties, and three 1/4-20 nuts. Refer
to "Electric Heater Accessory, Single Package Rooftop Units,
Select 17.5 to 27.5 Tons" for unit electrical data and kit usage.
Not all available heater modules can be used in every unit. Use
only those heater modules that are UL listed for use in a specif-
ic size unit. Refer to the label on the unit cabinet regarding
approved heaters.
NOTE: All vertical supply units with electric heat require a field-
supplied 90-degree elbow. The elbow must be installed in the sup-
ply ductwork below the unit discharged connection.
Refer to accessory instructions for the correct single point kit to
use when single point power entry is desired. The single point kit
required varies with the specific heater accessory used.
For units equipped with a non fused disconnect switch, the discon-
nect must be adequately sized for the electric heater. If the discon-
nect switch supplied with the equipment is not sized to handle the
ampacity of the electric heater accessory kit for cooling units or the
electric heater accessory kit plus the unit ampacity for heat pump
units, the electric heater kit must be wired to a separate disconnect
switch sized to handle the electric heater accessory kit ampacity. Re-
fer to the unit's nameplate or the product data for the unit.
Heater Installation (All Units)
Perform the following procedure to install the accessory elec-
tric heaters:
1.
Turn off power to the unit.
2.
Remove electric heater section access panel, control box
access panel, filter access panel, and blower access panel
from base rooftop unit. (See Fig. 46.)
3.
Remove the block-off plate and save screws. Remove post
adjacent to control box and post located between filter access
and blower access. (See Fig. 47.)
4.
Insert heater assembly through opening where block-off plate
was previously removed. Let back end of heaters slide along
support rails beneath fan deck. (See Fig. 48.)
5.
Slide heaters until completely installed such that heater con-
trols are completely in the unit. Using screws saved from Step
3, secure heater assembly. (See Fig. 49.)
6.
Route heater power wires through grommeted notches in ver-
tical fan deck support. (See Fig. 48.) Continue routing wires
under coil and filter support through the bottom notched sec-
tion of the control box. Avoid sheet metal edges and any pro-
truding screws.
7.
To be used with Standard SCCR (5ka) Units Only. Refer to
Fig. 53 for wiring single point kit accessory when required.
Using three 1/4-20 nuts, connect power wires to the load side
of terminal block.
If single point power entry is desired, a single point kit must
be used. See "Electric Heater Accessory, Single Package
Rooftop Units, Select 17.5 to 27.5 Tons" for details on
selecting the correct single point kit for the accessory heater
being installed. Terminal block and fuse holder can be
mounted using screws provided, locating the combination
below unit terminal block. (See Fig. 52.) Heaters will be con-
nected to the load side of the terminal block provided with kit.
Load side of fuses to be connected to terminal block of main
unit, at factory-installed option non-fused disconnect switch
and molded case switch for 230v units with the High SCCR
(Short-Circuit Current Rating) option or fuse holders for 460v
units with the High SCCR option.
For dual power entry, purchase terminal block HY11UC313
for 208-230 volt applications. Six 1/4-20 field supplied lock
nuts required (P/N AT56AB171). For 400v-50 Hz, 460v and
575v-60Hz
applications
HY11UC125. Three 1/4-20 field-supplied screws required
(P/N AA45AB167). Mount in pre-drilled holes using field-
supplied fasteners. Connect power leads from heaters to field-
supplied terminal block.
8.
Connect low voltage control plug from heater to the control
plug from unit.
9.
Re-install posts previously removed. When re-installing
screws verify that wires do not come into contact with
screw tips.
10. Re-install blower access, heater access, filter and control box
access panels.
11. Mark nameplate with a check mark next to heater installed.
460V HIGH SCCR UNIT INSTALLATION
(65KA SCCR)
1.
Remove shroud screws and shroud. Install fuse block
assembly in location shown in Fig. 50.
2.
Route heater wires to fuse holders.
3.
Insert wires in top holes of lugs.
4.
Tighten screws in lug to clamp down on wires.
Torque to 7.9 Nm (70 in.-lb).
5.
Repeat for all heater wires.
6.
Reattach shroud with 2 screws.
230V HIGH SCCR UNIT INSTALLATION
(60KA SCCR)
1.
Install terminal block assembly in location shown in Fig. 51.
2.
Remove cover from terminal block assembly.
3.
Route heater wires to terminal block assembly.
NOTE: There may be 2 or 4 wires per leg depending on heat-
er configuration.
4.
Heater wires will be either 2 wires per leg or 4 wires per leg.
Component assembly order is important for maintaining
secure assembly and maximum distancing between compo-
nents on each leg.
For 4 wire/leg assembly: add lock washers (Item 5), turn bot-
tom two wires so barrel of terminal is down as shown in
Fig. 51. Add nut (Item 4) and tighten to 9-10 Nm (79 in.-lb).
Add second lock washer (Item 5), the top two wires shall be
installed with barrels "up." Add second nut (Item 4) and
tighten to 9-10 Nm (79-88 in.-lb).
For 2 wire/lug assembly: add lock washers (Item 5), wire ter-
minal barrels may be up or down. Add nut (Item 4) and tight-
en to 9-10 Nm (79-88 in.-lb).
5.
Repeat for all heater wires maintain wire color continuity -
black to black; yellow to yellow; blue to blue.
6.
Remove leg cover from line side of control box main fuse
block. Install line side power wires into bottom holes of fuse
block lugs. Maintain wire color continuity. Torque set screw
in lug 42 Nm (375 in.-lb). Reinstall cover.
37
purchase
terminal
block
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