Charging - Lennox HP21 Series Installation Instructions Manual

3 − After evacuation is complete, open the liquid line and
vapor line service valves (counterclockwise) to release
refrigerant charge (contained in outdoor unit) into the
system.
4 − Replace stem caps and secure finger tight, then tight-
en an additional (1/6) one-sixth of a turn.
5 − Check voltage supply at the disconnect switch. The
voltage must be within the range listed on the unit
nameplate. If not, do not start the equipment until the
power company has been consulted and the voltage
condition has been corrected.
6 − Set the thermostat for a cooling demand, turn on power
to indoor blower unit and close the outdoor unit discon-
nect to start the unit.
7 − Recheck voltage while the unit is running. Power must
be within range shown on the nameplate.

Charging

Units are factory charged with the amount of R22 refrigerant
indicated on the unit's rating plate. This charge is based on a
matching indoor coil and outdoor coil with a 15 foot (4.6 m)
line set. For varying lengths of line set, see table 3 for adjust-
ing the refrigerant charge.
Table 3
Liquid Line Set Oz. per 5 ft. (grams per 1.5 m) adjust
Diameter
3/8 in. (10 mm)
*If line length is greater than 15 feet (4.6 m), add this amount. If
line length is less than 15 feet (4.6 m), subtract this amount.
The outdoor unit should be charged during warm weather.
However, applications arise in which charging must occur
in the colder months. The method of charging is deter-
mined by the unit's refrigerant metering device and the
outdoor ambient temperature.
Measure the liquid line temperature and the outdoor ambi-
ent temperature as outlined below:
1 − Close manifold gauge set valves. Connect the man-
ifold gauge set to the service valves.
low pressure gauge to vapor valve service port
D
high pressure gauge to liquid valve service port
D
Connect the center manifold hose to an upright cylin-
der of R22.
2 − Set the room thermostat to call for heat. This will create
the necessary load for properly charging the system in
the cooling cycle.
3 − Use a digital thermometer to record the outdoor ambi-
ent temperature.
4 − When the heating demand has been satisfied, switch
the thermostat to cooling mode with a set point of 68_F
(20_C). When pressures have stabilized, use a digital
thermometer to record the liquid line temperature.
5 − The outdoor temperature will determine which charg-
ing method to use. Proceed with the appropriate charg-
ing procedure.
from 15 ft. (4.6 m) line set*
3 oz. per 5 ft (85 g per 1.5 m)
Weighing in the Charge Fixed Orifice or
TXV Systems – Outdoor Temp. < 65_F (18_C)
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 re-
paired.
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 proce-
dures outlined below.
Charging Using Normal Operating Pressures
and the Approach Method
TXV Systems – Outdoor Temp. > 65_F (18_C)
The following procedure is intended as a general guide and
is for use on expansion valve systems only. 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 and operate unit for
several minutes to allow system pressures to stabilize.
3 − Compare stabilized pressures with those provided in
table 5, Normal Operating Pressures." Minor varia-
tions in these pressures may be expected due to differ-
ences 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.
4 − Use the same digital thermometer you used to check
the outdoor ambient temperature to check the liquid
line temperature.
5 − The difference between the ambient and liquid temper-
atures should match values given in table 4. If the val-
ues don't agree with the those in table 4, add refriger-
ant to lower the approach temperature, or recover re-
frigerant from the system to increase the approach
temperature.
Approach Temperature
Liquid Line
HP21−36
9 + 2
NOTE − For best results, use the same thermometer to check both
outdoor ambient and liquid temperatures.
Page 15
Approach Method
Table 4
Approach Temperature
_ _
F − Outdoor Ambient
HP21−48
7 + 2
F
HP21−60
10 + 2