Perfect Humidity; Dehumidification System - Bryant 581J-17-28 Service And Maintenance Instructions

Service requires replacing the entire liquid header
assembly.
To check for possible blockage of one or more of these
metering devices, disconnect the supply fan contactor
(IFC) coil, then start the compressor and observe the
frosting pattern on the face of the evaporator coil. A frost
pattern should develop uniformly across the face of the
coil starting at each horizontal header tube. Failure to
develop frost at an outlet tube can indicate a plugged or a
missing orifice.
Refrigerant System Pressure Access Ports
There are two access ports in the system − on the suction
tube near the compressor and on the discharge tube near
the compressor. These are brass fittings with black plastic
caps. The hose connection fittings are standard 1/4 SAE
male flare couplings.

PERFECT HUMIDITY]

DEHUMIDIFICATION 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 design of the Perfect Humidity™
system allows for two humidity control modes of
operation of the rooftop unit, utilizing a common
subcooling/reheat dehumidification
downstream of the standard evaporator coil. This allows
the rooftop unit to operate in both a dehumidification
(Subcooling) mode and a hot gas Reheat Mode for
maximum system flexibility. The Perfect Humidity™
package is factory−installed and will operate whenever
there is a dehumidification requirement present.
The Perfect Humidity™ system is initiated based on an
input from a discrete input from a mechanical space or
return air humidistat.
The brass fittings are two−piece High Flow valves, with a
receptacle base brazed to the tubing and an integral
spring−closed check valve core screwed into the base (See
Fig. 14). This schrader valve is permanently assembled
into this core body and cannot be serviced separately;
replace the entire core body if necessary. Service tools are
available from RCD (p/n P920−0010) that allow the
replacement of the schrader valve core without having to
recover the entire system refrigerant charge. Apply
compressor refrigerant oil to the schrader valve core's
bottom o−ring. Install the fitting body with 96 ± 10 in−lbs
(10.85 ± 1.13 Nm) of torque; do not overtighten.
NOTE: The High−Flow valve has a black plastic cap
with a rubber o−ring located inside the cap. This rubber
o−ring must be in place in the cap to prevent refrigerant
leaks.
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Fig. 14 − CoreMax Access Port Assembly
Dehumidification Mode (Subcooling)
This mode will be engaged to satisfy part−−load type
conditions when there is a space call for cooling and
dehumidification. Although the temperature could have
dropped, decreasing levels of the sensible load in the
space, the outdoor and/or space humidity levels can be
higher. A typical scenario could be when the outside air is
85_F (29_C) with 70% to 80% relative humidity (RH).
coil located Desired sensible heat ratio (SHR) for equipment in this
scenario is typically from 0.4 to 0.7. The Perfect
Humidity™ unit will initiate Dehumidification mode
when the space temperature and humidity are both above
the temperature and humidity setpoints and will attempt to
meet both setpoint requirements.
Once the humidity requirement is met, the unit can
continue to operate in normal cooling mode to meet any
remaining sensible capacity load. Alternatively, if the
sensible load is met and humidity levels remain high the
unit can switch to Hot Gas Reheat mode to provide
neutral, dehumidified air.
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C08453