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NOTE: I ndoor-air cfmnmst bewithin normal operating
range of
unit. Alloutdoor fans m ust beoperating.
5OOO
4500
4000
3500
3000
©
25OO
i
2000
1500
1000
5OO
LEAK IN
r_
VACUUM TIGHT
TOO WET
TIGHT
DRY SYSTEM
2
3
4
5
6
MINUTES
Fig. 30 - Deep Vacuum
Graph
C06264
The TXV (thermostatic
expansion
valve)
is set to maintain
between
10 and 15 degrees
of superheat
at the compressors.
The valves
are
factory set and cannot be adjusted.
Do not use a TXV designed
for
use with R-22
refrigerant.
Puron®
Refrigerant
Puron refrigerant
operates
at 50 to 70 percent
higher pressures
than
R-22.
Be
sure
that
servicing
equipment
and
replacement
components
are designed
to operate
with Puron refrigerant.
Do not
mix with
components
that have been
used with
other refrigerants.
Puron
refrigerant,
as with
other
HFCs,
is only
compatible
with
POE oils.
Recovery
cylinder
service
pressure
rating
must be 400 psig. Puron
systems
should
be
charged
with
liquid
refrigerant.
Use
a
commercial-type
metering
device
in the manifold
hose. Manifold
sets should
be 750 psig high-side
and 200 psig low-side
with 520
psig low-side
retard.
Use hoses
with
750
psig service
pressure
rating.
Leak
detectors
should
be
designed
to
detect
HFC
refrigerant.
Filter
Drier
Replace
whenever
refrigerant
system
is exposed
to atmosphere.
Only
use factory
specified
liquid-line
filter
driers with
working
pressures
no less than 650 psig. Do not install a suction-line
filter
drier in liquid
line. A liquid-line
filter drier designed
for use with
Puron®
refrigerant
is required
for each circuit.
Protective
Devices
Compressor Rotation
Overcurrent
Each compressor
has internal
line break motor protection.
Overtemperature
Each
compressor
has
an internal
protector
to protect
it against
excessively
high discharge
gas temperatures.
High-Pressure
Switch
If the high-pressure
switch
opens,
the compressor
will shut down
and the compressor
lockout
(CLO)
device
will energize
to block
further
compressor
operation.
The high-pressure
switch
will reset
automatically
as the refrigerant
pressure
drops below
its reset level.
The CLO will remain energized
until manually
reset.
Low-Pressure
Switch
If the low-pressure
switch
opens,
the compressor
will shut down
and the compressor
lockout
(CLO)
device
will energize
to block
further
compressor
operation.
The low-pressure
switch
will reset
automatically
as the
refrigerant
pressure
rises above its reset level.
The CLO will remain energized
until manually
reset.
Freeze Protection
Switch
This switch
is installed
on each evaporator
coil section
to provide
protection
against
continued
unit
operation
with
a
frosted
evaporator
surface.
If the
freeze
protection
switch
opens,
the
compressor
on this circuit
will
shut down
and
the compressor
lockout
(CLO)
device
will energize
to block
further
compressor
operation.
The freeze protection
switch will reset as the evaporator
tube temperature
rises above
its reset level.
The CLO will remain
energized
until manually
reset.
Compressor
Lockout
(CLO)
Device
The CLO prevents
automatic
recycling
of the compressor
as safety
controls
reset. If the high-pressure
switch,
low-pressure
switch
or
freeze
protection
switch
opens,
the CLO
device
will energize
to
block
further
compressor
operation.
To reset the CLO
(after
all
safety
switches
have reset),
either open the themmstat
to remove
the cooling
demand
signal (and then re-close)
or cycle the control
power
in the unit,
Evaporator Fan Motor Protection
A manual
reset, calibrated
trip, magnetic
circuit breaker
protects
against overcurrent.
Do not bypass
connections
or increase
the size
of the breaker
to correct trouble. Determine
the cause and correct it
before resetting
the breaker.
Condenser-Fan
Motor Protection
Each
condenser-fan
motor
is
internally
protected
against
overtemperature.
Fuses
are also located
in the control box
and feed power
to the
condenser
fan motors.
Always replace
blown
fuses with the correct
size fuse as indicated
on the unit fuse label.
Relief Devices
All
units
have
relief
devices
to
protect
against
damage
from
excessive
pressures
(i.e., fire). These
devices protect
the high and
low side and are located
at the
suction
line service
port. Protect
joint during
brazing
operations
near joint.
Control Circuit, 24-V
Each control
circuit is protected
against
overcurrent
by a 3.2 amp
circuit breaker.
Breaker
can be reset. If it trips, determine
cause
of
trouble
before resetting.
See Fig. 34-36
for wiring
diagrams.
Replacement
Parts
A complete
list of replacement
parts may be obtained
from
any
Carrier distributor
upon request.
PM20 CHARGING CHART - R410A REFRIGERANT
COOLING MODE - ALL OUTDOOR FANS MUST BE RUNNING
_0
,o
l
20
I I
11
80
i'i[i'°-i
60
4O
20
..........
I00
150
200
250
300
350
400
450
500
550
Compressor
Dischsrge
Pressure,
Ipsig]
I
600
Fig. 31 - Charging
Chart
- 50PM20
C08047
39
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