Commercial Air Conditioner
Model: heat pump, 10SEER UNITS
20
3.Push the tubing into the fitting until it stops. This prevents flux from getting into the system.
4.Remove the cap and Schrader valve core from the service port to protect the valve seals.
5.Wrap a wet rag around the valve stub before brazing.
6. Braze the joints of interconnecting tubing. Flow dry nitrogen into the shutoff valve port and
through the tubing while brazing.
7.After brazing quench with a wet rag to cool the joint. Reinstall the Schrader core in the
valve, if removed for brazing.
8.Pressurize the lines to 150 psi maximum with dry nitrogen. Check for leaks at all joints
with liquid detergent. If a leak is found, repair it after removing the nitrogen. Repeat the
process and re-check.
9.Do not purge the lines with refrigerant. Evacuate the lines and indoor coil.
Evacuation
All new installations must be evacuated to a deep vacuum in order that all noncondensible
gases and moisture are removed prior to charging the system. Air in a system causes high
condensing pressure, which increases power consumption and reduces performance. The
presence of moisture in a system can render it inoperable in a very short time. Proper
evacuation assures a dry, uncontaminated system. Here is the recommended evacuation
procedure:
1.Connect vacuum pump to both liquid and suction valve service ports.
2.Evacuate the interconnecting tubing and indoor coil to 500 microns or less for a minimum
of 30 minutes. Close the valve to the vacuum pump and wait 15 minutes. Vacuum should
not rise above 800 microns. If unable to obtain 500 microns, or vacuum rises above 800
microns over 15 minutes period, discontinue evacuation, pressurize and check for leaks.
Repair any leaks found and repeat the step 2.
3.Close valve to the vacuum pump and stop pump.
4.When sure of a tight, well evacuated system, charge with refrigerant.
8.7Charging the System
(For systems with capillary tube or fixed orifice metering device)
Before checking the system charge, make sure that the outdoor unit and indoor coil must
be an approved match per the unit specification. The indoor conditions should be within 2 F
of the desired comfort conditions.
! WARNING
-
Do not vent refrigerant to the atmosphere
! It is a violation of federal law to
do so. If the refrigerant needs to be removed from a system to correct the charge inside,
always use a recovery or recycling device.
! WARNING
- To prevent personal injury,
wear safety glasses and gloves when
handling refrigerant
.
1.Fully open both shutoff valves.
2.Connect service gage manifold to the valve service ports, being sure to evacuate lines.
3.Startup the system. Run system at least 10 minutes to allow pressure to stabilize.
4.Temporarily install thermometer on suction (large) line near condensing unit. Be sure of
good contact between thermometer and line. Wrap thermometer with insulating material to
assure accurate reading.
5.Refer to
Table 8-2
for proper system superheat. Add charge to lower superheat. Remove
charge to raise superheat. Carefully remove gage lines.
