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Outdoor Air Damper and Economizer Operation (continued)
Y3 demand:
1st-Economizer is at maximum open and compressor operates at first stage. If economizer stays at
maximum open for 3 minutes (default unit controller setting) compressor switches to second stage
operation while supply fan stays on high speed
SINGLE STAGE UNIT OPERATION (6 TON):
Modulating Outdoor Air Damper:
Damper minimum positions are adjusted during unit setup to provide minimum fresh air requirements at the indicated supply
fan speeds per ASHRAE 62.1.
-Supply fan is off and the outdoor air damper is closed
-Supply fan is on and the outdoor air damper is at minimum position
1
Outdoor Air is Suitable
Note: When outdoor air is not suitable during the occupied time period, damper modulates to minimum position. When out
door air is not suitable during the unoccupied time period, damper modulates closed.
Cooling - Thermostat or Zone Sensor (Up to 2 stages Y1, Y2)
Y1 demand:
1st-Compressor is off, supply fan is on, economizer modulates (minimum to maximum open
position) to maintain 55°F supply air temperature (default unit controller setting)
Y2 demand:
1st-Economizer goes to maximum open position and if the damper stays open for three minutes
(default unit controller setting) the compressor is energized.
F-Power Exhaust Relay K65
(power exhaust units)
Power exhaust relay K65 is a DPDT relay with a 24VAC
coil. K65 is used in all LCH units equipped with the op
tional power exhaust dampers. K65 is energized by the
Unit Controller after the economizer dampers reach
50% open (adjustable). When K65 closes, exhaust fan
B10 is energized.
G-Power Exhaust Fans
E1PWRE10A available for LCH 3 and 4 ton units and
ET1PWRE10N available for 5 and 6 ton units, provide ex
haust air pressure relief. See figure 24 and installation in
structions for more detail.
H-Optional UVC Lights
The Healthy Climate
®
germicidal light emits ultraviolet (UVC)
energy that has been proven effective in reducing microbial life
forms (viruses, bacteria, yeasts, and molds) in the air.
UVC germicidal lamps greatly reduce the growth and prolif
eration of mold and other bio-aerosols (bacteria and vi
ruses) on illuminated surfaces.
Germicidal lamps are NOT intended to be used for removal of
active mold growth. Existing mold growth must be appropriate
ly removed PRIOR to installation of the germicidal lamp.
Refer closely to UVC light installation instruction warnings
when servicing units.
I-Smoke Detectors A171 and A172
Photoelectric smoke detectors are a factory- or field-
installed option. The smoke detectors can be installed in
the supply air duct (A172), return air section (A171), or in
both the supply duct and return air section.
J-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.
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 in the supply
air section on the evaporator coil seal.
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