Assessments - 4, GPA: 4
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Facilidade de uso
Without accessory economizer — Upon a request for cooling from the space thermostat, terminals Y1 and G will be energized with 24 v. As a result, the indoor-fan contactor (IFC), outdoor-fan contactor (OFC) and Compressor contactor no. 1 (C1) will be energized, which in turn will energize the indoor fan, outdoor fan and Compressor no. 1, respectively. If the space thermostat calls for a second stage of cooling by supplying 24 v to Y2, Compressor contactor no. 2 (C2) will be energized, thus energizing Compressor no. 2. When the space thermostat is satisfied, Y2 will be de- energized first, which will deenergize Compressor no. 2. Upon a further drop in space temperature, Y1 will be de- energized which will deenergize Compressor no. 1, and the outdoor and indoor fans. HEATING — Upon a request for heating from the space thermostat, terminal W1 will be energized with 24 v. On units with economizer, the economizer damper blade will move to minimum position regardless of the outdoor-air temperature, and the unit will operate as described in Cooling, Without Accessory Economizer section above. The IFC, OFC, C1 and C2 will be energized. The reversing valves switch position and the indoor fan, outdoor fan, Compressor no. 1, and Compressor no. 2 are energized. If the space temperature continues to fall while W1 is energized, W2 will be energized with 24 v, and the heater contactor( s) (HC) will be energized, which will energize the electric heater(s). When the space thermostat is satisfied, W2 will be de- energized first, and the electric heater(s) will be deenergized. Upon a further rise in space temperature, W1 will be de- energized, and the reversing valve solenoids (RVS1 and RVS2) will be energized. On units with economizer, the economizer damper blade will move to the fully closed position. DEFROST — When the temperature of the outdoor coil drops below 28 F as sensed by the defrost thermostat (DFT2) and the defrost timer is at the end of a timed period (adjustable at 30, 50 or 90 minutes). RVS1 and RVS2 are energized and the OFC is deenergized. This switches the 17 NOTES: 1. In heating mode, economizer damper blade will move to the minimum position, and unit will operate as described for units without economizer, regardless of outdoor air temperature. 2. The temperatures given in the graph are for demonstration purposes only and may vary depending on which thermostat is used. LEGEND C— Contactor HC — Heater Contactor IFC — Indoor-Fan Contactor OAT — Outdoor-Air Thermostat OFC — Outdoor-Fan Contactor RVS — Reversing Valve Solenoid W— Heating Stage X— Contact Energized Y— Cooling Stage UNITS WITH ECONOMIZER AVERAGE OUTDOOR-AIR TEMPERATURE GREATER THAN OAT SETTING Thermostat Demand G Y1 Y2 W1 W2 C1 C2 IFC OFC RVS1 RVS2 HC Second Stage Cooling First Stage Cooling Deadband (Offset) First Stage Heating Second Stage Heating X X X X X X X X X X X X X X X X X X X X X X X X X X AVERAGE OUTDOOR-AIR TEMPERATURE LESS THAN OAT SETTING, BUT GREATER THAN .2 C (28 F) Thermostat Demand G Y1 Y2 W1 W2 C1 C2 IFC OFC RVSI RVS2 HC Second Stage Cooling First Stage Cooling Deadband(Offset) First Stage Heating Second Stage Heating X X X X X X X X X X X X X X X X X X X X X X X UNITS WITHOUT ECONOMIZER AVERAGE OUTDOOR-COIL TEMPERATURE LESS THAN .2C (28 F) Thermostat Demand G Y1 Y2 W1 W2 C1 C2 IFC OFC RVSI RVS2 HC Second Stage Cooling First Stage Cooling Deadband (Offset) First Stage Heating Second Stage Heating X X X X X X X X X X X X X X X X X X X X X X X X X X AVERAGE OUTDOOR-COIL TEMPERATURE GREATER THAN .2 C (28 F) Thermostat Demand G Y1 Y2 W1 W2 C1 C2 IFC OFC RVSI RVS2 HC Second Stage Cooling First Stage Cooling Deadband (Offset) First Stage Heating Second Stage Heating X X X X X X X X X X X X X X X X X X X X X X X X X X Fig. 20 — Typical Operating Sequence 18 position of the reversing valves and shuts off the outdoor fan. The electric heaters (if installed) will be energized. On units with economizer, the economizer damper blade will move to the fully closed position. The unit continues to defrost until the coil temperature as measured by DFT2 reaches 65 F or the duration of defrost cycle completes a 10-minute period. During the defrost mode, if circuit 1 defrosts first, RVS1 will oscillate between heating and cooling modes until the defrost mode is complete. At the end of the defrost cycle, the electric heaters (if installed) will be deenergized; the reversing valves switch and the outdoor-fan motor will be energized. On units with economizer, the economizer damper blade will move to the minimum position. The unit will now operate in the heating mode. If the space thermostat is satisfied during a defrost cycle, the unit will continue in the defrost mode until the time or temperature constraints are satisfied. SERVICE When servicing unit, shut off all electrical power to unit to avoid shock hazard or injury from rotating parts. Cleaning — Inspect unit interior at the beginning of each heating and cooling season and as operating conditi...
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