Lennox HP29 Series Unit Information page 14

IV − CHARGING
Unit charge is based on a matching indoor coil and
outdoor coil with a 15 foot (4.5 m) line set. For varying
lengths of line set, refer to table 10.
TABLE 10
Liquid Line Ounce per 5 foot (ml per mm) adjust from
Set Diameter
5/16 in. (8mm) 2 ounce per 5 feet (60 ml per 1524 mm)
3/8 in. (10 mm) 3 ounce per 5 feet (90 ml per 1524 mm)
*If line set is greater than 15 ft. (4.5m) add this amount. If line set is less than
15 ft. (4.5m) subtract this amount
A − Pumping Down System
CAUTION
Deep vacuum operation (operating compressor at 0
psig or lower) can cause internal fusite arcing
resulting in a damaged or failed compressor. This
type of damage will result in denial of warranty claim.
The system may be pumped down when leak checking
the line set and indoor coil or making repairs to the line
set or indoor coil.
1 − Attach gauge manifold.
2 − Front seat (close) liquid line valve.
3 − Start outdoor unit in cooling mode.
4 − Monitor suction gauge. Stop unit when 0 psig is
reached.
5 − Front seat (close) suction line valve.
B − Leak Testing (To Be Done
Before Evacuating)
1 − Add small amount of refrigerant (3 to 5 psig) to the
system.
2 − Attach gauge manifold and connect a drum of dry
nitrogen to center port of gauge manifold.
3 − Pressurize the system to 150 psig.
CAUTION
When using dry nitrogen, a pressure reducing
regulator must be used to prevent excessive
pressure in gauge manifold, connecting hoses, and
within the system. Regulator setting must not
exceed 150 psig (1034 kpa). Failure to use a regulator
can cause equipment failure resulting in injury.
NOTE−Electronic leak or Halide detector should be
used. Add a small amount of HCFC22 (3 to 5 psig
(20kPa to 34kPa)) then pressurize with nitrogen to 150
psig.
15 ft. (4.5 m)*
C − Evacuating the System
IMPORTANT
The compressor should never be used to
evacuate a refrigeration or air conditioning
system.
1 − Attach gauge manifold. Connect vacuum pump (with
vacuum 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.
2 − Evacuate the system to 29 inches (737mm) vacuum.
During 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
indicate a leak in the system and a repeat of the leak
testing section would be necessary.
3 − After evacuating system to 29 inches (737mm), close
gauge manifold valves to center port, stop vacuum pump
and disconnect from gauge manifold. 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 nitrogen 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
pressure 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
Charging must be done in the cooling mode. If system is
completely void of refrigerant, the recommended and most
accurate method of charging is to weigh the refrigerant into
the unit according to the total amount shown on the unit
nameplate.
If weighing facilities are not available or if unit is just low on
charge, the following procedure applies.
Separate discharge and vapor line service ports are
provided outside the unit for connection of gauge manifold
during charging procedure as well as a suction line service
port.
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