July 2012 / Bulletin 90-30 Head Pressure Control Valves For High and Low Ambient Stability ® OROA ORI-6 LAC-4-DS
Page 2 – Bulletin 90-30 The design of air conditioning and refrigeration systems utilizing air cooled condensing units involves two main problems that must be solved if the system is to operate reliably and economically. . . high ambient and low ambient operation. If the condensing unit is properly sized, it will operate satisfactorily during extremely high ambient temperatures.
Bulletin 90-30 – Page 3 LAC-5, LAC-10 – The LAC-5 and LAC-10 are also threeway modulating valves but they respond to receiver pressure. As shown in Figure 3, the receiver pressure acts under the diaphragm. As the receiver pressure drops below the valve setting, the seat moves away from the discharge port allowing discharge gas to bypass the condenser. This discharge gas warms the liquid in the receiver and raises the pressure to the valve setting.
Page 4 – Bulletin 90-30 ORD – (cont.) Due to its function in the control of head pressure, the full stroke can be utilized in selecting the ORD. Figure 6 ORD Refrigerant Migration – During an off cycle there is a potential for refrigerant to migrate from the warm receiver to the cold condenser. An auxiliary check valve should be used in the liquid line between the LAC and the receiver to prevent this from occurring. See Figure 7.
Bulletin 90-30 – Page 5 ORI/ORD – (cont.) As long as sufficient refrigerant charge is in the system, the two valves modulate the flow automatically to maintain proper receiver pressure regardless of outside ambient temperature. While valve capacity ratings and basic selection procedures are given later, two other factors affect the proper selection of head pressure control valves . . . paralleling valves for larger systems and pressure settings.
Page 6 – Bulletin 90-30 Piping Suggestions – (cont.) This is available in this manner for two reasons — to allow the bypassed hot gas to flow through the OROA to maintain the element temperature and to eliminate the need of a separate tee connection in the liquid drain line. Compared to the ORI and ORD combination, the OROA-5 installation process is simplified as the ORD-4 is included as an integral part of the OROA assembly. Inlet strainers are available for all head pressure control valves.
Bulletin 90-30 – Page 7 HEAD PRESSURE CONTROL VALVE CAPACITIES HIGH AMBIENT (SUMMER) CAPACITIES — TONS OF REFRIGERATION Capacities are based on 0°F evaporator, 110°F condenser, 10°F subcooled liquid. — — — — — — — — — — — — — — — — 404A 507 1 2 3 4 5 6 8 10 1 2 3 4 5 6 8 10 ORD-4 10.4 14.7 17.9 20.7 23.1 25.3 29.2 32.6 9.31 13.1 16.1 18.5 20.7 22.6 26.1 29.2 OROA-5 19.7 27.2 32.8 37.5 41.6 45.3 51.8 57.5 12.2 16.8 20.3 23.2 25.8 28.0 32.1 35.6 ORI-10 ORD-4 7.35 10.7 13.3 15.5 17.5 19.4 22.
Page 8 – Bulletin 90-30 SPECIFICATIONS LAC-10 ORI-6-65/225-H 120 ORI-10-65/225-H 120 ORD-4-20 20 100, 180, or 210 OROA-5 B C D 1.78 1.87 3.02 2.38 1.78 1.87 3.02 2.38 1.65 1.74 2.23 2.38 1.60 1.69 2.18 2.33 3.77 3.86 4.35 4.50 2.99 3.08 3.57 3.72 2.67 4.39 3.43 2.56 4.83 3.87 5.04 6.37 — 7/8 E F G H I Net Ship 0.77 0.80 0.82 0.87 0.94 2.50 2.55 2.60 2.75 0.85 0.88 0.90 1.02 1.09 2.65 2.70 2.75 2.90 6.40 3.20 3.42 6.84 3.28 3.50 1.00 1.25 1.25 1.50 2.
Bulletin 90-30 – Page 9 VALVE DESIGNATION/ORDERING INSTRUCTIONS To eliminate shipment delays, specify complete valve designation. LAC-4 LAC-4-DS 3.62 LAC-5 and LAC-10 1.94 1.94 R3L 3.62 D3L Discharge Discharge Discharge Receiver Receiver E 4.00 E Receiver E .
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© 2012 Parker Hannifin Corporation. Parker Hannifin Corporation Sporlan Division 206 Lange Drive • Washington, MO 63090 USA phone 636 239 1111 • fax 636 239 9130 www.sporlan.
