Lennox HP29 Series Unit Information page 15

IMPORTANT
The following procedures require accurate
readings of ambient (outdoor) temperature, liquid
temperature and liquid pressure for proper
charging. Use a thermometer with accuracy of
+2°F( + 1.1°C) and a pressure gauge with accuracy
of +5PSIG ( + 34.5kPa)
1 − Expansion Valve Systems
The following procedures are intended as a general guide
for use with expansion valve systems only. For best results,
indoor temperature should be between 70 °F and 80 °F
(21.1 °C and 26.6 °C) . If outdoor temperature is 60 °F (16
°C) or above the approach method of charging is used. If
outdoor temperature is less than 60 °F (16 °C) the
subcooling method of charging is used. Slight variations in
charging temperature and pressure should be expected.
Large variations may indicate a need for further servicing.
APPROACH METHOD (TXV SYSTEMS)
(Ambient Temperature of 60_F [16_C] or Above)
1 − Connect gauge manifold. Connect an upright
HCFC22 drum to center port of gauge manifold.
2 − Record outdoor air (ambient) temperature.
3 − Operate indoor and outdoor units in cooling mode.
Allow outdoor unit to run until system pressures
stabilize.
4 − Make sure thermometer well is filled with mineral oil
before checking liquid line temperature.
5 − Place thermometer in well and read liquid line
temperature. Liquid line temperature should be
warmer than the outdoor air temperature. Tables 11
and 12 shows how many degrees warmer the liquid
line temperature should be.
Add refrigerant to lower the liquid line temperature.
Recover refrigerant to raise the liquid line
temperature.
Add refrigerant slowly as the unit approaches the
correct temperature. This will allow refrigerant to
stabilize allowing the correct temperature to be read.
TABLE 11
APPROACH METHOD
AMBIENT TEMPERATURE OF 60 _F (16 _C) OR
Model
HP29−211
HP29−261
HP29−311
HP29−411
HP29−461
HP29−511
HP29−651
Liquid Line °F Warmer Than Outside
ABOVE
(Ambient) Temperature
10°F (5.6°C)
13°F (7.2°C)
16°F (8.9°C)
12°F (6.6°C)
13°F (7.2°C)
16°F (8.9°C)
18°F (10°C)
AMBIENT TEMPERATURE OF 60 _F (16 _C) OR
Model
HP29−018
HP29−024
HP29−030
HP29−036
HP29−042
HP29−048
HP29−060
SUBCOOLING METHOD (TXV SYSTEMS)
(Ambient Temperature Below 60_F [16_C]
NOTE- It may be necessary to restrict air flow in order to
reach liquid pressures in the 200-250 psig range which
are required for checking charge. The indoor temperature
should be above 70_F(21_C). Block equal sections of air
intake panels as shown in figure 16, moving obstructions
sideways until liquid pressures in the 200-250 psig range
are reached.
1 − Connect gauge manifold. Connect an upright
HCFC22 drum to center port of gauge manifold.
2 − Operate indoor and outdoor units in cooling mode.
Allow outdoor unit to run until system pressures
stabilize.
3 − Make sure thermometer well is filled with mineral oil
before checking liquid line temperature.
4 − Read liquid line pressure and convert to condensing
temperature
conversion chart.
Condensing temperature (read from gauges) should
be warmer than the liquid line temperature.
5 − Place thermometer in well and read liquid line
temperature. Tables 13 and 14 shows how much
warmer the condensing temperature should be.
Add refrigerant to lower liquid line temperature.
Recover refrigerant to raise liquid line temperature.
6 − When unit is properly charged liquid line
pressures should approximate those given in
tables 15 and 16 .
Page 15
TABLE 12
APPROACH METHOD
Liquid Line °F Warmer Than Outside
ABOVE
(Ambient) Temperature
10°F (5.6°C)
13°F (7.2°C)
8_F (4.4_C)
13°F (7.2°C)
13°F (7.2°C)
15_F (8.3_C)
8_F (4.4_C)
BLOCKING OUTDOOR COIL
Block outdoor coil one side at a time
with cardboard or plastic sheets until
proper testing pressures are reached.
CARDBOARD OR PLASTIC SHEET
FIGURE 16
using temperature/ pressure