Table of Contents
Advertisement
CAUTION
Direct-expansion coils are shipped pressurized with dry air.
Release pressure from each coil split through valves in protec-
tive caps before removing caps.
Do not leave piping open to the atmosphere unnecessarily.
Water and water vapor are detrimental to the refrigerant sys-
tem. Until the piping is complete, recap the system and charge
with nitrogen at the end of each workday. Clean all piping
connections before soldering joints.
SUCTION PIPING
Connect suction piping as shown in Fig. 103 for face split coil or
Fig. 104 for row split coil.
NOTE: The lower split of face split coils should be first-on, last-
off. Row split coils utilize special intertwined circuits; either split
of these row split coils can be first-on, last-off.
Suction line from coil connection to end of the 15-diameter-long
riser should be same tube size as coil connection to ensure proper
refrigerant velocity.
Refer to Carrier System Design Manual, Part 3, and size remain-
ing suction line to compressor for a pressure drop equivalent to
2.0°F. This will provide a total suction line header pressure drop
equivalent to approximately 2.7°F.
To minimize the possibility of flooded starts and compressor dam-
age during prolonged light load operation, an accumulator can be
used in the suction line of first-on, last-off circuit.
The first-on, last-off circuits shown in Fig. 103 and 104 assume a
single condensing unit. Note that in both figures the last-on, first-
off circuit is looped above the common return line to prevent oil
entrapment in the non-operating coil at partial load.
TXV
UPPER
SENSING
SPLIT
BULB
AIRFLOW
15 DIAMS
MIN
10
DIAMS
LOWER
SPLIT
TXV
SENSING
BULB
AIRFLOW
15
DIAMS
MIN
10
DIAMS
LEGEND
TXV — Thermostatic Expansion Valve
Fig. 103 — Face Split Coil Suction-Line Piping
UNIT
COIL
CASING
CASING
SOLENOID
SIGHT
VALVE
GLASS
FILTER
DRIER
8
DIAMS
SOLENOID
MIN
VALVE
SIGHT
GLASS
FILTER
DRIER
TXV
INSIDE
CASING
(TYP)
DISTRIBUTOR
(TYP)
8 DIAMS
MIN
EVAPORATOR
COIL
FIRST-ON, LAST-OFF
TXV SENSING
BULBS
AIRFLOW
10 DIAMS
15
DIAMS
MIN
15
DIAMS
MIN
10 DIAMS
EVAPORATOR COIL
FIRST-ON, LAST-OFF
LEGEND
TXV — Thermostatic Expansion Valve
Fig. 104 — Row Split Coil Suction-Line Piping
Distributor Nozzle Change-Out
Distributor nozzles are factory supplied. Thermostatic expansion
valves (TXVs) are either field or factory supplied. Be sure that
correct nozzle is installed in each distributor before installing
expansion valve. See Table 11 for factory-installed distributor
nozzle sizes. Use AHUBuilder
best performance; replacement nozzles must be field-installed.
The correct nozzle is typically factory-installed.
Do not overheat distributor or cap. Failure to comply could
result in equipment damage.
Perform nozzle change-out procedure as follows:
1.
Remove plastic end cap by using an electric heat gun or a
torch (see Fig. 105).
2.
Clean off any grime.
3.
Remove nozzle retaining ring with screwdriver or needle
nosed pliers.
4.
Remove nozzle from distributor by inserting 2 no. 6-32
threaded rods (at least 4 in. long) into the threaded holes pro-
vided in the nozzle. See Fig. 106.
5.
Insert correct nozzle into distributor body.
6.
Re-insert nozzle retainer ring into distributor.
PLASTIC CAP
WITH VALVE
a39-4174
Fig. 105 — Distributor and Cap
138
COIL
CASING
SOLENOID
VALVE
SIGHT
GLASS
SOLENOID
VALVE
SIGHT
GLASS
8
DIAMS
MIN
TXV
8
INSIDE
DIAMS
CASING
MIN
(TYP)
DISTRIBUTOR
(TYP)
a39-2367
program to select nozzles for
®
CAUTION
UNIT
CASING
FILTER
DRIER
FILTER
DRIER
Advertisement
Table of Contents
