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14
Multi-zone Heat Pump Condensing Units
STARTING THE UNIT
• Before starting the unit in cool weather,
power the system 24 hours before at-
tempting to start.
• Do a final system check using the super-
heat/subcooling method. Record results
on
Test Unit Performance Data
sheet
(next page).
- Cooling mode superheat is set with a proper
sized piston and charge, using the field
charging charts.
- Heating mode superheat is set with a TXV
and should be 5°F. When charging a system
in heat mode, use the subcool method field
charging charts.
FIELD CHARGING
Example
(Using the 12,000 Btuh cooling
chart):
1. Suction pressure is 65 psi. which equals
38
°
F on
The R-22 Scale of the Low-
Side Gauge.
2. Suction line temperature taken at the
unit is 70
°
F. 70
°
F minus 38
°
F equals
32
°
F superheat.
3. Outdoor temperature is 90
°
F; indoor
temperature is 80
°
F.
4. Intersection of the indoor-temperature
and outdoor-temperature lines occur on
the 12
°
F superheat line.
5. Add charge to obtain 12
°
F superheat.
Instructions:
1. Measure suction pressure and determine
evaporator-refrigerant temperature on
R-22 scale of low-side gauge.
2. Measure suction-line temperature on
suction line of the unit.
3. Measure outdoor and indoor tempera-
tures.
4. Determine from the table what the super-
heat should be for the indoor and outdoor
temperatures. (Example indicates 12
°
F
superheat.)
5. Adjust charge if needed. Be sure unit is
running at stabilized condition.
NOTE:
If operating superheat is more
than 5°F above the chart value, add
refrigerant. If below the chart value
remove refrigerant. If below the limit
line, remove refrigerant.
REFRIGERANT PIPING INSTALLATION SECTION
NOTE:
For installation of the indoor unit
and start-up of the system, please refer
to the appropriate installation manual
for your indoor product to complete the
installation.
• Remove gauge set. Mount all access panels
and make sure they are properly secured.
• Make final visual inspection and repair
any deficiencies.
(Proceed to the
Sequence Of Operation
on the following pages)
