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SEQUENCE OF OPERATION (cont.)
On the initial power to the EconoMi$er IV control, it will
take the damper up to 2 1/2 minut es before it begins to
position itself. After the initial power --up, further changes
in damper position can take up to 30 seconds to initiate.
Damper movement from full closed to full open (or vice
versa) will take between 1 1/2 and 2 1/2 minutes. If free
cooling can be used as determined from the appropriate
change over com mand (switch, dry bulb, enthalpy curve,
differential dry bulb, or diffe r ential enthalpy), then the
control will modulate the dampers open to mai ntain the
mixed air tem perature setpoint at 50_F(10_C) to 55_F
(13_C). If there is a further demand for cooling (cooling
second stage -- Y2 is energized), then the control will
bring on compressor stage 1 to maintain the mixed air
temperature setpoint. The EconoMi$er IV damper will be
open at maximum position. EconoMi$er IV operation is
limited to a single compressor.
Heating
The sequence of operation for the heating is the same as
an electromechanical unit with no economizer. The only
difference is how the economizer acts. The economizer
will stay at the Economizer Minimum Position while the
evapora tor fan is operating. The outdoor air damper is
closed when the indoor fan is not operating.
Optional Perfect Humidity System
Units with the factory equipped Perfect Humidity option
are capable of providing multiple modes of improved
dehumidification as a variation of the normal cooling
cycle. The Perfect Humidity option includes additional
valves in the liquid line and discharge line of each
refrigerant circuit, a small reheat condenser coil
downstream of the evaporator, and Motormaster
variable--speed control of some or all outdoor fans.
Operation of the revised refrigerant circuit for each mode
is described below.
NOTE: x = refrigerant circuit A, B, or C.
Normal Cooling
Refrigerant flows from the outdoor condenser through the
normally open Cooling Valve (CV.x) to the expansion
device. Reheat1 Valve (RH1.x) and Reheat2 Valve
(RH2.x) are closed.
Reheat1 (Subcooling Mode) -- 580J04--16
This mode increases latent cooling and decreases sensible
cooling compared to normal cooling. Refrigerant flows
from the outdoor condenser, through the normally open
Rehea t1 Valve (RH1.x), and through the reheat condenser
coil to the expansion device. Cooling Valve (CV.x) and
Reheat2 Valve (RH2.x) are closed.
Reheat2 (Hot Gas Reheat Mode) -- 580J04--16
This mode provides maximum latent cooling with little to
no sensible capacity. This mode can operate to provide
dehumidification when there is no c ooling demand. L ike
Rehea t1 mode, refrigerant flows from the outdoor
condenser, through the norma lly open Reheat1 Valve
(RH1.x), and through the reheat condenser coi l to the
expansion device. The Cooling Valve (CV.x) is closed.
Rehea t2 Valve (RH2.x) is open which provides some
compressor discharge gas to the reheat condenser to
further increase the reheat of the eva porator airstream.
COMP
COND COIL
PERFECT HUMIDITY
COIL
EVAP COIL
INDOOR ENTERING
AIR
OUTDOOR AIR
METERING
DEVICE
CLOSED VALVE
OPEN VALVE
RH1.x
RH2.x
CV.x
a48-8172
C09455
Normal Cooling Mode -- Perfect Humidity System (580J04--16)
580J