Lennox XP16 Series Unit Information page 25

CHARGING INFORMATION FOR MODEL XP16−XXX−230−01 AND XP16−XXX−230−02
If the system is low on charge, follow the appropriate
procedure outlined below. Charging should be done with unit
operating in the cooling mode, if possible.
Charge Using The Weigh−in Method
Temperature < 65ºF (18ºC(
If the system is void of refrigerant, or if the outdoor ambient
temperature is cool, the refrigerant charge should be
weighed into the unit. Do this after any leaks have been
repaired.
1. Recover the refrigerant from the unit.
2. Conduct a leak check, then evacuate as previously
outlined.
3. Weigh in the unit nameplate charge. If weighing facilities
are not available or if you are charging the unit during
warm weather, follow one of the other procedures
outlined below.
Charge Using The Subcooling Method
Temperature < 65ºF (18ºC)
When the outdoor ambient temperature is below 65ºF
(18ºC), use the subcooling method to charge the unit. It may
be necessary to restrict the air flow through the outdoor coil
to achieve pressures in the 325−375 psig (2240−2585 kPa)
range. These higher pressures are necessary for checking
the charge. Block equal sections of air intake panels and
move obstructions sideways until the liquid pressure is in the
325−375 psig (2240−2585 kPa) range. See figure 16.
Block coil one side at a time with cardboard/plastic until
proper testing pressures are reached.
Figure 16. Blocking Outdoor Coil
1. With manifold gauge hose still on the liquid service port
and unit operating stably, use a digital thermometer to
record the liquid line temperature. At the same time,
record the liquid line pressure reading.
2. Use a temperature/pressure chart for HFC−410A to
determine the saturation temperature for the liquid line
pressure reading.
XP16
Unit Charging Sticker − 401193S, dated 02/06
Outdoor
Outdoor
CARDBOARD OR
PLASTIC SHEET
Page 25
3. Subtract the liquid line temperature from the saturation
temperature (according to the chart) to determine
subcooling. (Saturation temperature − Liquid line
temperature = Subcooling)
4. Compare subcooling values with those in table 1; if
subcooling is greater than shown, recover some
refrigerant. If subcooling is less than shown, add some
refrigerant.
Charge Using Normal Operating
Pressures/Approach Method
>65ºF (18ºC)
When outdoor ambient temperature is above 65_F (18_C),
use approach charge method. For best results, indoor
temperature should be 70°F (21°C) to 80°F (26°C). Monitor
system pressures while charging.
1. Record outdoor ambient temperature using a digital
thermometer.
2. Attach high pressure gauge set; operate unit for several
minutes; allow system pressures to stabilize.
3. Compare stabilized pressures with those provided in
table 3. Minor variations in these pressures may be
expected due to differences in installations. Significant
differences could mean that the system is not properly
charged or that a problem exists with some component
in the system. Pressures higher than those listed
indicate that the system is overcharged. Pressures
lower than those listed indicate that the system is
undercharged. Verify adjusted charge using the
approach method.
Use the same digital thermometer to check both outdoor
ambient temperature and liquid line temperature. Verify the
unit charge using the approach method.
4. The difference between the ambient and liquid
temperatures should match values given in table 2. If
values do not agree with the those in table 2, add
refrigerant to lower the approach temperature or
recover refrigerant from the system to increase the
approach temperature.
Using the Normal Operating Pressures Table
Use table 3 as a general guide when performing
maintenance checks. This is not a procedure for charging
the unit (see Charging/Checking Charge section). Minor
variations in normal operating pressures may be expected
due to differences in installations. Significant differences
could mean that the system is not properly charged or that a
problem exists with some component in the system.
Outdoor Temperature