Lennox 13HPX Series Unit Information page 11

NOTE-The preferred method is to use an electronic leak or
Halide detector. Add a small amount of R−410A (3 to 5 psig
[20kPa to 34kPa]) then pressurize with nitrogen to 150 psig.
4− Release nitrogen pressure from the system, correct any
leaks and recheck.
WARNING
Fire, Explosion and Personal Safety
Hazard.
Failure to follow this warning could
result in damage, personal injury or
death.
Never use oxygen to pressurize or
purge refrigeration lines. Oxygen,
when exposed to a spark or open
flame, can cause damage by fire and
/ or an explosion, that can result in
personal injury or death.
WARNING
Danger of explosion!
When using a high pressure gas such
as dry nitrogen to pressurize a refriger-
ant or air conditioning system, use a
regulator that can control the pressure
down to 1 or 2 psig (6.9 to 13.8 kPa).
C − Evacuating the System
1− Attach gauge manifold. Connect vacuum pump (with vac-
uum gauge) to center port of gauge manifold. With both
manifold service valves open, start pump and evacuate
indoor coil and refrigerant lines.
IMPORTANT
A temperature vacuum gauge, mercury vacuum
(U−tube), or thermocouple gauge should be used.
The usual Bourdon tube gauges are not accurate
enough in the vacuum range.
IMPORTANT
The compressor should never be used to evacu-
ate a refrigeration or air conditioning system.
2− Evacuate the system to 29 inches (737mm) vacuum. Dur-
ing the early stages of evacuation, it is desirable to stop
the vacuum pump at least once to determine if there is a
rapid loss of vacuum. A rapid loss of vacuum would indi-
cate a leak in the system and a repeat of the leak testing
section would be necessary.
3− After system has been evacuated to 29 inches
(737mm), close gauge manifold valves to center port,
stop vacuum pump and disconnect from gauge man-
ifold. Attach an upright nitrogen drum to center port of
gauge manifold and open drum valve slightly to purge
line at manifold. Break vacuum in system with nitro-
gen pressure by opening manifold high pressure
valve. Close manifold high pressure valve to center
port.
4− Close nitrogen drum valve and disconnect from
gauge manifold center port. Release nitrogen pres-
sure from system.
5− Connect vacuum pump to gauge manifold center
port. Evacuate system through manifold service
valves until vacuum in system does not rise above
.5mm of mercury absolute pressure or 500 microns
within a 20−minute period after stopping vacuum pump.
6− After evacuation is complete, close manifold center port,
and connect refrigerant drum. Pressurize system
slightly with refrigerant to break vacuum.
D − Charging
This system is charged with HFC−410A refrigerant which
operates at much higher pressures than HCFC−22. The
recommended check expansion valve is approved for use
with HFC−410A. Do not replace it with a valve that is de-
signed to be used with HCFC−22. This unit is NOT ap-
proved for use with coils that include metering orifices or
capillary tubes.
The unit is factory−charged with the amount of HFC−410A
refrigerant indicated on the unit rating plate. This charge is
based on a matching indoor coil and outdoor coil with a 15
foot (4.6 m) line set. A blank space is provided on the unit
rating plate to list the actual field charge.
IMPORTANT
Mineral oils are not compatible with HFC−410A. If oil
must be added, it must be a polyol ester oil.
CHECKING INDOOR AIRFLOW
NOTE − Be sure that filters and indoor and outdoor coils are
clean before testing.
COOLING MODE INDOOR AIRFLOW CHECK
Check airflow using the Delta−T (
HEATING MODE INDOOR AIRFLOW CHECK
Blower airflow (CFM) may be calculated by energizing
electric heat and measuring:
S
temperature rise between the return air and supply air
temperatures at the indoor coil blower unit,
S
measuring voltage supplied to the unit,
S
measuring amperage being drawn by the heat unit(s).
Page 11
DT)
process (figure 4).