Lennox CHA16, Руководство по обслуживанию

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Page 43
FIGURE 43
PED16 CONTROL KIT
(ordered separately)
FILTER
ACCESS
PANEL
P24
J18
J24
J3
P18
from
PED16
2 BLUE WIRES TO
MERCURY SWITCH
TRANSFORMER AND FUSES
ON 575 VOLT UNITS ONLY
PED16 CONTROL KIT
PED16 AND ENTHALPY CONTROL INSTALLATION
UNIT FILTER SECTION
PED16 CONTROL KIT
(positioned behind
enthalpy control)
ENTHALPY CONTROL
ON MOUNTING BRACKET
FIGURE 44
c-Warm Up Kit
(units equipped with standard or
electronic thermostat and night
setback function)
An optional warm up kit may be added to the
REMD16M economizer (except CHA16 units using a
Honeywell W7400 control system).The warm up kit
holds the dampers closed during night setback and
morning warm up.When the first thermostat demand
of the day is satisfied,the warm up kit opens the out
door dampers to minimum position.The warm up kit
installs in the CHA16 filter access section.The kit
plugs into the unit wiring harness inline between the
unit and the economizer.For detailed wiring and op
eration, refer to the sequence of operation section of
this manual.
If a W973 system is used, the relay kit holds the out
door dampers closed during setback.If an electrome
chanical thermostat system is used, the relay kit
holds the outdoor dampers closed during setback,
de-energizes the indoor thermostat and energizes
the setback thermostat.
d-Differential Enthalpy
(all economizers)
Optional differential enthalpy control may be added
to any economizer to monitor both indoor and out
door air conditions. With differential enthalpy
installed, the economizer selects the lowest of the
two enthalpy conditions to satisfy cooling demand.
When differential enthalpy is installed, the second
enthalpy sensor is installed in the retrun air duct while
the original enthalpy sensor remains installed on the
outdoor air dampers.
Refer to the wiring diagram section of this manual for
wiring.
4-Economizer Operation and Controls
(all economizers)
a-Enthalpy Control: Setpoint Control
The key to economizer operation is the enthalpy con
trol.The enthalpy control senses total heat content of
outside air (temperature plus humidity) and uses that
information to control the amount of outside air
brought into the system.When the enthalpy of outside
air drops below the control setpoint and cooling de
mand is present, the control actuates a motor which
in turn adjusts outdoor dampers to meet cooling de
mand.With outdoor air dampers open, the indoor
blower draws in outdoor air for cooling and first stage
compressors are disabled.When heat content rises
above the setpoint, the control de-activates and the
dampers close to the preset minimum position. First
stage compressors are switched to handle all first
stage cooling.