Bryant R-22 service manual Millennium Scroll Compressor Features, II. Compressor Protection

PLASTIC CAP

BLUE SEALANT

PRONG

GROMMET

THERMAL GREASE	THERMOSTAT
	A90198

Fig. 30—Location of Discharge Thermostat

cause a rapid pressure equalization around the compressor, thus reducing the normal shutdown sound created by reverse rotation of the scroll. The solenoid valve is normally closed and is wired across high-voltage line 1 to load terminals of the contactor. (See Fig. 18.) The solenoid-valve assembly also requires a check valve piped in the discharge tube between the solenoid-valve tee and the condenser coil, or reversing valve on heat pumps. The purpose of the check valve is to prevent refrigerant from bypassing through the solenoid valve into the suction tube when the unit cycles off.

MILLENNIUM SCROLL COMPRESSOR

I. FEATURES

The scroll compressor pumps refrigerant through the system by the interaction of a stationary and an orbiting scroll. (See Fig. 29.) The scroll compressor has no dynamic suction or discharge valves, and it is more tolerant of stresses caused by debris, liquid slugging, and flooded starts. The Millennium scroll varies from the Copeland scroll in that the Millennium has a shutdown flapper valve located between the scroll plates and the discharge head, whereas the Copeland has a check device at the discharge connection after the discharge head. The Copeland discharge head unloads when the compressor shuts down. The scroll plate actually runs backwards while it unloads. A 1 to 3 second unloading of refrigerant occurs.

The Millennium flapper valve eliminates the refrigerant unloading by not allowing the discharge head to run backwards because of its location. The Millennium scroll compressor uses Zerol 150 oil with 3 percent Syn-O-Ad and is the only oil recommended for oil recharge. See Table 13 for recharge requirements.

II. COMPRESSOR PROTECTION

Millennium scroll compressors are protected by an internal line- break mounted on the motor windings. Internal protectors respond to overcurrent and high temperature. These protectors are automatic-reset devices containing a snap-action, bi-metal switch.

III. TROUBLESHOOTING

Troubleshooting mechanical and electrical problems in a scroll compressor is similar to a reciprocating compressor, except that a scroll compressor should never be allowed to pump into a vacuum.

—29—

The scroll compressor is capable of pumping into a vacuum very quickly, which could cause fusite arcing and compressor failure. See Step IV of Reciprocating Compressor section for removal and replacement.

IV. SCROLL COMPRESSOR, 3–PHASE MONITOR

CES0130075 — PHASE MONITOR

This control is factory-installed on all 3–phase, scroll compressor models. (See Fig. 31 and 32.) On start-up, the control will energize the pilot relay for 2 seconds. The monitor will check for correct compressor rotation. If rotation is correct, unit will continue to run. If rotation is incorrect, the control will break the 24vac power at the contactor and an LED light on the control will flash. If LED is flashing, turn off power, reverse L1 and L3 field-power leads, and restart unit. This control will check incoming power at every restart.

TWO-SPEED SYSTEM

I. CAUTIONS AND WARNINGS

CAUTION: For proper unit operation and reliability, the 2-speed units must be installed with the factory-supplied balance port, hard shutoff TXV. Do not install with indoor coils having piston or capillary-tube metering devices.

CAUTION: Do not install equivalent interconnecting tubing lengths greater than 100 ft. Do not decrease or increase interconnecting tubing diameters.

CAUTION: To avoid electrical shock, bleed resistor must be connected across run capacitor. Replace if missing or damaged.

CAUTION: Contactor is mechanically interlocked. Do not disable mechanical interlock. Compressor damage may occur.

WARNING: Contactor control voltage is 240vac.

WARNING: Do not attempt to operate this equipment below 55°F outdoor ambient temperature.

NOTE: Sections that follow describe the 598A Series B and 698A Series B products, which started production March, 1994. For 598A Series A and 698A Series A products, refer to the Split-System Service Manual dated 3–1–94, Catalog No. BDP 3356–115.

II. SYSTEM FUNCTIONS

COOLING OPERATION

The 2-speed products utilize a 2-stage-cooling indoor thermostat. With a call for first-stage cooling (Y1), the outdoor fan and low-speed compressor are energized. If low speed cannot satisfy the cooling demand, high speed will be energized (Y1 and Y2) by the second stage of the indoor thermostat. The thermostat has a 2° differential between first and second stages. After second stage is satisfied, the unit returns to low-speed operation, until first stage is satisfied, or until second stage is again required.