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Calculating Charge Using the Weigh-In Method
STEP 1 - Measure in feet the distance between the
outdoor unit and the indoor unit. (Include the entire
length of the line from the service valve to the IDU.)
Subtract 10 ft from this entire length and record on
line 1.
STEP 2 - Enter the charge multiplier (0.6 oz/ft).
Each linear foot of interconnecting tubing requires
the addition of 0.6 oz of refrigerant.
STEP 3 - Multiply the total length of refrigerant tub-
ing (Line 1) times the value on Step 2. Record the
result on Line 3 of the Worksheet.
STEP 4 - This is the amount of refrigerant to weigh-
in prior to opening the service valves.
STEP 2 - Stabilize the system by operating for a minimum of 20 minutes.
At startup, or whenever charge is removed or added, the system must be operated for a minimum of 20 minutes
to stabilize before accurate measurements can be made.
STEP 3 - Check the liquid line temperature and liquid gage pressure to obtain a minimum of 10º subcooling in
heating mode.
Measured Liquid Line Temp = __________ º F
Liquid Gage Pressure = __________ PSIG
STEP 4 - Add charge if a minimum of 10º subcooling is not obtained with the namplate charge plus additional
charge previously added.
STEP 5 - Return to site for adjustment.
Important: Return in the spring or summer to accurately charge the system in the cooling mode with outdoor
ambient above 55º F.
Section 15. Checkout Procedures and Troubleshooting
15.1 Operational And Checkout Procedures
Final phases of this installation are the unit Operational and Checkout Procedures. To obtain proper performance, all units
must be operated and charge adjustments made.
Important: Perform a final unit inspection to be sure that factory tubing has not shifted during shipment. Adjust
tubing if necessary so tubes do not rub against each other when the unit runs. Also be sure that wiring connections
are tight and properly secured.
After installation has been completed, it is recommended that the entire system be checked against the following list:
1. Leak check refrigerant lines. ........................................ [ ]
2. Properly insulate suction lines and fittings. ................... [ ]
3. Properly secure and isolate all refrigerant lines. ........... [ ]
4. Seal passages through masonry.
If mortar is used, prevent mortar from coming
into direct contact with copper tubing. .......................... [ ]
5. Verify that all electrical connections are tight. ............... [ ]
6. Observe outdoor fan during on cycle for clearance
and smooth operation. .................................................. [ ]
16
1. Total Line length (ft) – 10 ft ______________
2. Charge multiplier
3. Step 1 x Step 2
4. Refrigerant (oz)
CHECKOUT PROCEDURE
7. Be sure that indoor coil drain line drains freely. Pour water
into drain pan. ............................................................... [ ]
8. Be sure that supply registers and return grilles are open
and unobstructed. ......................................................... [ ]
9. Be sure that a return air filter is installed. ..................... [ ]
10. Be sure that the correct airflow setting is used.
(Indoor blower motor) ................................................... [ ]
11. Operate complete system in each mode to
ensure safe operation. .................................................. [ ]
x ___0.6 oz _____
= _____________
= _____________
88-A4HP4001-1G-EN
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