Figure 4-3. Typical Setup For Testing Pressure Switches Hp1, Hp2 And Hp3; Adding A Partial Charge - Carrier 40 Operation & Service Manual

4.10.3 Adding A Partial Charge

a. Place refrigerant cylinder on scale and note weight.
b. Connect charging line from the cylinder to the receiv-
er valve. Purge the line at the cylinder valve.
c. Start the unit with the road compressor turning at
2400 rpm.
d. Front seat the liquid line service valve.
CAUTION
Refrigerant R404A must be charged as a liq-
uid. Refrigerant R404A is a blend. Charging
as a vapor will change the properties of the
refrigerant.
e. Add a small quantity of refrigerant.
f. Back seat the receiver valve.
g. Follow the procedures of paragraph 4.10.1 and add
refrigerant as required to clear the sight glass.
4.11 REPLACING THE COMPRESSOR
a. For the road compressor, remove the refrigerant
charge. Refer to paragraph 4.7.1. For the standby
compressor, pump the unit down. Refer to paragraph
4.7.2.
WARNING
Ensure power to the unit is OFF and power
plug is disconnected or vehicle engine is
OFF and negative battery cable is discon-
nected before replacing the compressor.
WARNING
Slowly open the plug on the suction and
discharge valves to vent the nitrogen hold-
ing charge.
b. for the standby compressor, follow wiring diagrams
provided herein and on inside of terminal box cover.
c. Installation
d. To install the compressor, reverse the removal proce-
dure. Refer to paragraph 1.5 for torque values.
e. Evacuate and dehydrate, see paragraph 3.5 then
charge system, see paragraph 4.10.
4.12 HIGH PRESSURE OR CONDENSER
PRESSURE SWITCH
4.12.1 Removing Switch
a. A schreader valve is located under each switch to al-
low removal and installation without removing the re-
frigerant charge.
b. Remove switch and test in accordance with para-
graph 4.12.2.
c. Replace or reinstall switch.
4.12.2 Checking Pressure Switch
Do not use a nitrogen cylinder without a
pressure regulator. (See Figure 4-3.) Cylin-
der pressure is approximately 2350 psi (160
bar). Do not use oxygen in or near a refriger-
ant system as an explosion may occur.
a. Remove switch as outlined in paragraph 4.12.1.
b. For the High and condenser pressure switches, con-
nect switch to a cylinder of dry nitrogen (see
Figure 4-3.). For the low pressure switch, connect to
a vacuum pump and gauge. Test low pressure switch
using method similar to that described in the following
steps for the pressure switches.
c. Set nitrogen pressure regulator higher than cut-out
(HP--1 or HP--3) or cut in (HP--2) point on switch being
tested. Pressure switch settings points are provided
in paragraph 1.3.
d. Close valve on cylinder and open bleed-off valve.
e. Open cylinder valve. While observing indicator (light
or meter), slowly close bleed-off valve and increase
pressure until the switch opens (HP--1 or HP--3) or
closes (HP--2). Slowly open bleed-off valve (to de-
crease pressure) until switch reverts to normal posi-
tion.
f. If switch does not activate within tolerances provided,
replace switch. Test new switch before installation.
1
2
1. Cylinder valve and gauge
2. Pressure regulator
3. Nitrogen cylinder
4. Pressure gauge (0 to 400 psig = 0 to 28 bars)
5. Bleed-off valve
6. 1/4 inch connection
Figure 4-3. Typical Setup For Testing Pressure
Switches HP1, HP2 and HP3
4-5
WARNING
4
5
3
6
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