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K-Optional Cold Weather Kit (Canada only)
Electric heater is available to automatically control the
minimum temperature in the gas burner compartment.
Heater is C.G.A. certified to allow cold weather opera
tion of unit down to ‐60° F (‐50° C ).
The kit includes the following parts:
1- A heater assembly is installed on the vestibule of the
heating compartment. Included in the box are the fol
lowing:
a - Electric strip heat (HR6).
b - Thermostat switch (S59) is an auto‐reset SPST N.C.
switch which opens on a temperature drop. The
switch is wired in series with 24v power and the com
bustion air blower switch. When the temperature
drops below ‐30° F (-35° C) the switch opens and the
gas heat section is de‐energized. The switch automati
cally resets when the heating compartment tempera
ture reaches -10° F (-12° C).
c - Thermostat switch (S60) is an auto‐reset SPST
N.C. switch which opens on a temperature rise.
The switch is wired in series with HR6. When the
temperature rises above 20° F (‐7° C) the switch
opens and the electric heater is de‐energized. The
switch automatically resets when the heating com
partment temperature reaches ‐10° F (23.3° C).
d -Thermostat switch (S61) is an auto‐reset SPST
N.O. switch which closes on a temperature drop.
The switch is wired in series with HR6. When tem
perature drops below 20° F (‐7° C) the switch clos
es and electric heater is energized. The switch au
tomatically opens when heating compartment
temperature reaches 76° F (24° C).
2- K125 heat shutoff relay de-energizes HR6 heaters
when S60 or S61 thermostat switches open. K125 must
be installed in the control section.
3- Wire harness is routed between the heat section com
ponents and the unit control box. Follow instructions
provided with kit for wire connections.
L-Control Systems
The A55 Unit Controller provides all control function for the
rooftop unit. Default operation requires a standard room
thermostat or direct digital controller (DDC). The A55 can
also control the unit from a zone temperature sensor. The
A55 Unit Controller is a network controller when daisy-
chained to the L Connection
®
Network Control System. For
ease of configuration, the A55 can be connected to a PC
with Unit Controller PC software installed.
M-Indoor Air Quality (CO
2
) Sensor A63
The indoor air quality sensor monitors CO
2
levels and re
ports the levels to the A55 Unit Controller. The board ad
justs the economizer dampers according to the CO
2
levels.
The sensor is mounted next to the indoor thermostat or in
the return air duct. Refer to the indoor air quality sensor in
stallation instructions for proper adjustment. Wiring for the
indoor air quality switch is shown on the temperature con
trol section (C2) wiring diagram in back of this manual.
N-Drain Pan Overflow Switch S149 (optional)
The overflow switch is used to interrupt cooling operation
when excessive condensate collects in the drain pan.
The N.C. overflow switch is connected to the M2 Unit Con
troller (A55) through DI-3. When the switch opens, the Unit
Controller will shut off the unit. After a five-minute time out,
the Unit Controller will verify the overflow switch position
and restart the unit (if the switch has closed). The Unit Con
troller has a three-strike counter before the unit locks out.
This means the Unit Controller will allow the overflow switch
to open three times per thermostat demand. If the unit locks
out, a reset of the Unit Controller is required after the switch
has closed to restore unit operation.
O-Smoke Detectors A17 and A64
Photoelectric smoke detectors are a factory installed op
tion. The smoke detectors can be installed in the supply air
section (A64), return air section (A17), or in both the supply
and return air section. Wiring for the smoke detectors are
shown on the temperature control section (C2) wiring dia
gram in back of this manual.
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