York YPAL 051, YPAL 061 Refrigerant Charge, Checking Superheat and Subcooling, Subcooling R-410A

Startup

INITIAL START-UP

After all of the preceding checks have been completed and the control panel has been programmed as required, the unit may be placed into operation.

1.Place the Unit Switch in the control panel to the ON position.

2.With a demand, the supply fan will cycle on, and permit compressor operation if the air proving pressure switch for the supply fan has closed.

3.The first compressor will start. After several minutes of operation, a flow of refrigerant will be noted in the sight glass, the vapor in the sight glass will clear, and there should be a solid column of liquid visible in the sightglass when the TXV stabilizes.

4.Allow the compressor to run a short time, being ready to stop it immediately if any unusual noise or adverse conditions develop.

5.Check the system operating parameters by checking evaporator superheat and condensing subcooling. Connect a gauge manifold set to the Schrader ser- vice valve connections on the liquid and common suction line in the condensing section of the unit. After the system is running and the pressures have stabilized, measure the temperature at the liquid and common suction lines near the Schrader ser- vice valves. Calculate evaporator superheat and condensing subcooling. The subcooling, should be approximately 15.0 ˚F and the superheat should be 12.0 ˚F. Repeat the above process for each of the refrigerant systems.

6.With an ammeter, verify that each phase of the con- denser fans, compressors, supply fan, and exhaust fan are within the RLA/FLA as listed on the unit data plate.

Refrigerant Charge

This rooftop unit comes fully charged from the factory with refrigerant R-410A as standard.

CONDENSER COIL PRESSURE DROP

YPAL050	YPAL051	YPAL060	YPAL061
33 PSIG	39 PSIG	24 PSIG	27 PSIG

FORM 100.50-NOM6 (1207)

Checking Superheat and Subcooling

An R-410A temperature and pressure chart lists the associated saturation temperature in one column, with the associated pressure in another column. As a result, only one temperature/pressure column is needed to show the relationship.

Subcooling (R-410A)

When the refrigerant charge is correct, there will be no vapor in the liquid sight glass with the system operating under full load conditions.

The subcooling temperature of each system can be calculated by recording the temperature of the liquid line at the outlet of the condenser and subtracting it from the saturation temperature listed in Table 3-1, for the corresponding discharge pressure. If the rooftop unit does not have an access port for liquid access, subtract the condenser coil pressure drop value from the table on this page from the discharge pressure to determine the equivalent saturation temperature.

Example:

On a YPAL 050 the discharge pressure is 388 PSIG and the

liquid temperature is 95 °F

Liquid Pressure = Discharge Pressure (388 PSIG) - 33.0 PSIG

Saturation Temperature for 355 PSIG	= 108°F
Minus the liquid line temp	= 95°F
Liquid Line Subcooling of	= 13°F

The subcooling should be 15°F at design conditions.

Superheat (R-410A)

The superheat should be checked only after steady state operation of the unit has been established, the discharge air temperature has been pulled down to within the control range, and the unit is running in a fully loaded condition.

The superheat is calculated as the difference between the actual temperature of the refrigerant gas in the suction line and the temperature corresponding to the Suction Pressure as shown in Table 3-1.

50 JOHNSON CONTROLS