5320779-UIM-A-0417
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Johnson Controls Unitary Products
SECTION VI: SYSTEM CHARGE
To ensure that your unit performs at the published levels, it is important
that the indoor airflow is determined and refrigerant charge added
accordingly.
MEASURE INDOOR AIR FLOW
To determine rated air flow for a specific match, consult the technical lit-
erature at www.upgnet.com. When attempting to match this air flow,
select the lowest possible speed tap, measure the actual flow, and
adjust as necessary.
To measure actual air flow, it is not an acceptable method to just
check the jumper pin setting tables and is to assume 0.5” water
column total external static pressure.
To determine indoor air flow, first measure the static pressure with a
manometer between the filter and blower. On a single-piece air handler,
take a second reading after the coil. On a furnace or modular air han-
dler, take the second reading after the heat exchanger but before the
indoor coil. Add the negative return static to the positive supply static to
determine the system total static pressure. Treat the negative return
static as a positive pressure (even though it is a negative reading). If
there is static pressure on the blower (i.e. -.10) return, add it to a supply
static (.40) which equals a (.50) total system static pressure. Compare
this value to the table for the indoor unit's static pressure vs. CFM or to
a curve chart.
SYSTEM CHARGING
The factory charge in the outdoor unit includes enough charge for the
unit, a 15 ft. line set, and the smallest indoor coil match-up. Some
indoor coil matches may require additional charge. See tabular data
sheet provided in unit literature packet for charge requirements.
The “TOTAL SYSTEM CHARGE” must be permanently stamped on the
unit data plate.
Total system charge is determined as follows:
1.
Determine outdoor unit charge from tabular data sheet.
2.
Determine indoor coil adjustment from tabular data sheet.
3.
Calculate the line charge using the tabular data sheet if line length
is greater than 15 feet.
4.
Total system charge = item 1 + item 2 + item 3.
5.
Permanently stamp the unit data plate with the total amount of
refrigerant in the system.
Use the following charging method whenever additional refrigerant is
required for the system charge.
If a calibrated charging cylinder or accurate weighing device is avail-
able, add refrigerant accordingly. Otherwise, model-specific charging
charts are provided on the access panel of the unit.
SUBCOOLING CHARGING METHOD - TXV INDOOR
For cooling operation, the subcooling values are shown in parentheses
on the charging charts provided with the unit.
1.
Set the system running in cooling mode by setting the thermostat
at least 6°
F below the room temperature and operate system for at
least 10 – 15 minutes.
2.
Refer to the technical guide for the recommended indoor airflow
and verify it is correct (it should be about 400 SCFM per ton).
3.
Measure and record the indoor wet bulb (WB) and the outdoor
ambient dry bulb (DB) temperature.
4.
Using the charging chart located on the unit, find the intersection
of the indoor wet bulb and the outdoor dry bulb. This is the recom-
mended liquid pressure (and subcooling value).
5.
Measure and record the pressure at the liquid valve pressure port
and compare to the value obtained in step 4.
6.
Add charge if the measured liquid pressure is lower than the rec-
ommended value. Remove / recover charge if the measured liquid
pressure is above the recommended value.
Condenser subcooling is obtained by calculating the difference of the
saturated refrigerant temperature of the pressure measured at the liquid
base valve and the liquid tube temperature as measured at the liquid
base valve.
Subcooling Temp. (TC) = Saturated Temp. (TS) – Liquid Temp. (T)
CAUTION
R-410A refrigerant cylinders are rose colored. Always charge the
system slowly with liquid R-410A refrigerant.
CAUTION
Do not leave the system open to the atmosphere.
WARNING
DO NOT attempt to pump “Total System Charge” into outdoor unit for
maintenance or service. This may cause damage to the compressor
and/or other components. Recover and weigh “System Charge” into
an appropriate recovery cylinder for any instances requiring evacua-
tion.
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CAUTION
Refrigerant charging should only be carried out by a qualified
air conditioning contractor.
CAUTION
Compressor damage will occur if system is improperly charged. On
new system installations, charge system per tabular data sheet for
the matched coil and follow guidelines in this instruction.
Example: The liquid pressure listed at the intersection of the indoor
WB and the outdoor DB 320 psig. Pressure at the liquid valve is 305
psig. It would be necessary to add refrigerant to increase the liquid
pressure to 320 psig.
CAUTION
IT IS UNLAWFUL TO KNOWINGLY VENT, RELEASE OR DIS-
CHARGE REFRIGERANT INTO THE OPEN AIR DURING REPAIR,
SERVICE, MAINTENANCE OR THE FINAL DISPOSAL OF THIS
UNIT.
WHEN THE SYSTEM IS FUNCTIONING PROPERLY AND THE
OWNER HAS BEEN FULLY INSTRUCTED, SECURE THE
OWNER’S APPROVAL.
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