Page 61
F-Gravity Exhaust Dampers
LAGEDH03/15 dampers (figure 30) are used in downflow
and horizontal air discharge applications. Horizontal
gravity exhaust dampers are installed in the return air
plenum . The dampers must be used any time an economizer
or power exhaust fans are applied to LCH units.
Gravity exhaust dampers allow exhaust air to be discharged
from the system when an economizer and/or power exhaust is
operating. Gravity exhaust dampers also prevent outdoor air
infiltration during unit off cycle. See installation instructions for
more detail.
FIGURE 30
PEF POWER
EXHAUST FAN ASSEMBLY
(ORDERED SEPARATELY)
GED GRAVITY
EXHAUST DAMPERS
GED AND PEF
G-K1PWRE10B Power Exhaust Fans
Power exhaust fans are used in downflow applications only.
Fan requires optional down flow gravity exhaust dampers and
economizer. Power exhaust fans provide exhaust air pres
sure relief and also run when return air dampers are closed
and supply air blowers are operating. Figure 31 shows the
location of the LAPEF. See installation instructions for more
detail.
FIGURE 31
POWER EXHAUST FAN
POWER EXHAUST
FAN ASSEMBLY
RETURN AIR
OPENING
P18/P24
H-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.
I-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.
J-Blower Proving Switch S52
The blower proving switch monitors blower operation and
locks out the unit in case of blower failure. The switch is
N.O. and closes at .14" W.C. (34.9 Pa) The switch is mount
ed on the upper left hand corner of the blower deck. Wiring
for the blower proving switch is shown on the temperature
control section (C2) wiring diagram in back of this manual.
K-Dirty Filter Switch S27
The dirty filter switch senses static pressure increase indi
cating a dirty filter condition. The switch is N.O. and closes
at 1" W.C. (248.6 Pa) The switch is mounted on the top filter
channel corner. Wiring for the dirty filter switch is shown on
the temperature control section (C2) wiring diagram in back
of this manual.
L-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.
M-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.O. overflow switch is controlled by K220 and DL46 relays,
located in the unit control panel. When the overflow switch
closes, 24VAC power is interrupted and after a five-second
delay unit compressors are de-energized. Once the conden
sate level drops below the set level, the switch will open. Af
ter a five-minute delay the compressor will be energized.
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