3. 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).
4. If there is static pressure on the blower return (-0.1), add it to a supply static (0.4) which
equals a (0.5) total system static pressure.
5. Compare this value to the table for the indoor unit's static pressure against CFM or to a curve
chart.
Determining the total system charge
About this task:
The total system charge must be permanently stamped on the unit dataplate. Complete the
following steps to determine the total system charge:
1. Determine the base charge shipped in the outdoor unit by referring to the Tabular Data Sheet
included with the outdoor unit. (item 1)
2. Determine the charge adder for the matched indoor unit by referring to the Tabular Data
Sheet. (item 2)
3. If the refrigerant piping is longer than 15 ft (4.6 m), calculate the charge adder for actual
piping length by referring to the Tabular Data Sheet. (item 3)
4. When the charge adders for the matched indoor unit and for the refrigerant piping have
been weighed in, verify the system operation against the temperatures and pressures in the
charging chart for the outdoor unit. Refer to the charging charts on the outdoor unit or in the
Service Application Data on http://www.simplygettingthejobdone.com. Follow the subcool or
the superheat charging procedure in this section according to the type of indoor metering
device in the system and allow 10 min after each charge adjustment for the system operation
to stabilize. Record the charge adjustment made to match the charging chart. (item 4)
5. Verify that the total system charge = (item 1) + (item 2) + (item 3) = (item 4).
6. Permanently stamp the unit data plate with the total system charge as defined in these
instructions.
Use this method whenever additional refrigerant is required for the system charge.
If a calibrated charging cylinder or accurate weighing device is available, add refrigerant
accordingly. Otherwise, model-specific charging charts are provided on the access panel of
the unit.
41Installation Manual: R-454B Outdoor Split-System Air Conditioner
Johnson Controls Ducted Systems
To Next Page
Loading...
