Bryant 551C, 551B Cooling, Heating, Safety Relief, Ventilation Continuous Fan, Operating Sequence

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Cooling

Set the space thermostat to the OFF position. Set the system selector switch at COOL position and the fan switch at AUTO position. Adjust the thermostat to a setting below room temperature. The compressor starts when contactor closes.

Check cooling effects at a setting below room temperature. Check the unit charge. Refer to Refrigerant Charge section.

Reset the thermostat at a position above room temperature. The compressor will shut off.

TO SHUT OFF UNIT - Set the system selector switch at OFF position. Resetting the thermostat at a position above room temperature shuts off the unit temporarily until the space temperature exceeds the thermostat setting. Units are equipped with a Cycle-LOC™protection device. The unit shuts down on any safety trip and remains off; an indicator light on the thermostat comes on. Check the reason for the safety trip.

Compressor restart is accomplished by manual reset at the thermostat by turning the selector switch to OFF position and then to ON position.

Heating

To start unit, turn on main power supply.

Set system selector switch at HEAT position and set thermostat at a setting above room temperature. Set fan at AUTO position.

First stage of thermostat energizes the first-stage electric heater elements; second stage energizes second-stage electric heater elements, if installed. Check heating effects at air supply grille(s).

If electric heaters do not energize, reset limit switch (located on evaporator-fan scroll) by pressing button located between terminals on the switch.

TO SHUT OFF UNIT - Set system selector switch at OFF position. Resetting thermostat at a position below room temperature temporarily shuts unit off until space temperature falls below thermostat setting.

Safety Relief

A soft solder joint at the suction line fitting provides pressure relief under abnormal temperature and pressure conditions.

Ventilation (Continuous Fan)

Set fan and system selector switches at ON and OFF positions, respectively. Evaporator fan operates continuously to provide constant air circulation.

Operating Sequence

Cooling - Units Without Economizer

When thermostat calls for cooling, terminals G and Y1 are energized. The indoor-fan contactor (IFC), reversing valve solenoid (RVS) and compressor contactor are energized and indoor-fan motor, compressor, and outdoor fan starts. The outdoor fan motor runs continuously while unit is cooling.

Heating - Units Without Economizer

When the thermostat calls for heating, terminal W1 will be energized with 24v. The IFC and heater contactor no. 1 (HC1) are energized.

Cooling - Units With EconoMi$er IV

When free cooling is not available, the compressors will be controlled by the zone thermostat. When free cooling is available, the outdoor-air damper is modulated by the EconoMi$er IV control to provide a 50_ to 55_F supply-air temperature into the zone. As the supply-air temperature fluctuates above 55_ or below 50_F, the dampers will be modulated (open or close) to bring the supply-air temperature back within the set point limits.

Integrated EconoMi$er IV operation on single-stage units requires a 2-stage thermostat (Y1 and Y2).

For EconoMi$er IV operation, there must be a thermostat call for the fan (G). This will move the damper to its minimum position during the occupied mode.

If the increase in cooling capacity causes the supply-air temperature to drop below 45_F, then the outdoor-air damper position will be fully closed. If the supply-air temperature continues to fall, the outdoor-air damper will close. Control returns to normal once the supply-air temperature rises above 48_F.

If optional power exhaust is installed, as the outdoor-air damper opens and closes, the power exhaust fans will be energized and deenergized.

If field-installed accessory CO2 sensors are connected to the EconoMi$er IV control, a demand controlled ventilation strategy will begin to operate. As the CO2 level in the zone increases above the CO2 set point, the minimum position of the damper will be increased proportionally. As the CO2 level decreases because of the increase in fresh air, the outdoor-air damper will be proportionally closed. Damper position will follow the higher demand condition from DCV mode or free cooling mode.

Damper movement from full closed to full open (or vice versa) will take between 1-1/2 and 2-1/2 minutes.

If free cooling can be used as determined from the appropriate changeover command (switch, dry bulb, enthalpy curve, differential dry bulb, or differential enthalpy), a call for cooling (Y1 closes at the thermostat) will cause the control to modulate the dampers open to maintain the supply air temperature set point at 50_ to 55_F.

As the supply air temperature drops below the set point range of 50_ to 55_F, the control will modulate the outdoor-air dampers closed to maintain the proper supply-air temperature.

Heating - Units With EconoMi$er IV

When the room temperature calls for heat, the heating controls are energized as described in the Heating, Units Without Economizer section. During the occupied mode, whenever the indoor fan contactor is energized, the economizer damper moves to the minimum position.

Units With Perfect Humidity™ Adaptive Dehumidification

System

Normal Design Operation

When the rooftop operates under the normal sequence of operation, the compressors will cycle to maintain indoor conditions. (See Fig. 42.)

The Perfect Humidity adaptive dehumidification system includes a factory-installed Motormaster→ low ambient control to keep the head and suction pressure high, allowing normal design cooling mode operation down to 0°F.

Subcooling Mode

When subcooling mode is initiated, this will energize (close) the liquid line solenoid valve (LLSV) forcing the hot liquid refrigerant to enter into the subcooling coil. (See Fig. 43.)

As the hot liquid refrigerant passes through the subcooling/ reheat dehumidification coil, it is exposed to the cold supply airflow coming through the evaporator coil. The liquid is further subcooled to a temperature approaching the evaporator leaving-air temperature. The liquid then enters a thermostatic expansion valve (TXV) where the liquid drops to a lower pressure. The TXV does not have a pressure drop great enough to change the liquid to a 2-phase fluid, so the liquid then enters the Acutrol™ device at the evaporator coil.

551B,C

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Contents Installation Instructions Provide Unit Support Install External Trap for Condensate DrainField Fabricate Ductwork Rig and Place UnitRoof Curb Details Unit Leveling Tolerances 551C Unit Operating Dimensions Weight551B 551B 036-072 Base Unit Dimensions 551C 024-060 Base Unit Dimensions Field Control Wiring Field Power SupplyHeat Anticipator Settings Make Electrical ConnectionsBase Unit 551B Physical Data 551BBase Unit 551C Physical Data 551CPower Wiring Connections FLA MCA LRA Type Outlet Electrical Data-551CPerf ect Voltage FLA Crheater 008,009 23.4 30.1 40.8 FLA MCA LRA Electrical Data-551B414 508 Ton 004+005 19.9 24.3 55.2 76.3 86.9 168 34.9 173 002 13.6 A00 or Adjust Factory-Installed Options Typical Perfect Humidity t Adaptive Dehumidification System Outdoor-Air Damper With Hood Attached Outdoor-Air Damper Position SettingEconoMi$er IV Component Locations Optional EconoMi$er Supply Air Sensor Temperature Resistance Values Supply Air Temperature SAT SensorTemperature F Outdoor Air Lockout SensorEconoMi$er IV Sensor Usage EconoMi$er IV Control Modes Outdoor Dry Bulb ChangeoverDifferential Dry Bulb Control Differential Enthalphy Control Outdoor Enthalpy ChangeoverIndoor Air Quality IAQ Sensor Input Exhaust Set Point AdjustmentMinimum Position Control Damper MovementReturn Air Temperature or Enthalpy Sensor Mounting Location Outside Air Temperature Changeover Set PointsEconoMi$er IV Control CO2 Sensor ConfigurationCO2Sensor Standard Settings Adjust Evaporator-Fan SpeedDehumidification of Fresh Air with DCV Control Belt Drive MotorsUnit Motor Pulley Turns Open Evaporator-Fan Motor Data High-Static Motors Evaporator-Fan Motor Data Standard MotorMotor 551B Efficiency Evaporator-Fan Motor Efficiency024, 036 060 74/84 072 Airflow879 Rpm Bhp Watts 900 566 142 690 228957 522 1000 598 173 718 267 9031300 701 809 418 902 540 983 665 Rpm Bhp Watts 1200 666 252 778 361 873 476 956 5941400 737 355 842 481 932 610 875 551 962 6891600 828 412 931 536 1022 670 Rpm Bhp Watts 1500 790 353 897 471 991 6001700 866 478 966 608 1800 905 551 1001 6871472 1761 1600 1462 20671495 1858 1700 1463 1766 1520 1964 18002300 1104 1046 1185 1212 1260 1386 2200 1063 929 1147 1089 1224 1256 1295 14312400 1145 1174 1223 1346 1296 1526 2500 1185 1311 1262 14901900 945 638 1042 796 Rpm Bhp Watts 1800 907 558 1006 708 1092 8602000 984 727 1078 892 2100 1024 823 1115 9972200 1063 929 1152 1111 1230 1294 2100 1024 823 1115 997 1195 1173 1268 13502300 1103 1044 1189 1234 1266 1425 2400 1143 1168 1227 13671000 583 163 707 Rpm Bhp Watts 900 554 134 6811100 612 195 735 9191300 674 276 Rpm Bhp Watts 1200 643 233 762 3441400 706 324 1500 738 3791600 757 343 866 455 962 580 Rpm Bhp Watts 1500 724 295 837 402 937 524 1028 660719 1700 790 398 894 514 988 6431490 1873 1800 1474 1797 17001508 1957 1900 1467 1839 1527 2050 20002500 1069 1084 1149 1239 1223 1403 1293 1576 2400 1033 970 1115 1120 1192 1279 1264 1448Rpm Bhp Watts 1500 1188 970 1261 1143 1600 1208 1033 12792500 1061 1053 1148 1233 1226 1416 1297 1604 2400 1026 945 1115 1118 1195 1295 1268 14762600 1097 1169 1181 1356 1257 1546 2700 1132 1294 1214 1487 1289 1684Refrigerant Service Ports Internal WiringUnit Preparation Return-Air FiltersCooling Safety ReliefHeating Ventilation Continuous FanEvaporator Coil CleaningLubrication EconoMi$er IV Adjustment Condenser-Fan AdjustmentRefrigerant Charge No ChargeCooling Charging Chart Standard 551B Replacement Parts 551C 3 TON Charging Chart 551C 5 TON Charging Chart Economi$er IV Troubleshooting Unit TroubleshootingCooling Service Analysis EconoMi$er IV Troubleshooting CompletionProblem Cause Remedy Inputs Outputs EconoMi$er IV Input/Output LogicEconoMi$er IV Functional View Catalog No. II551B---C---36---1 Preliminary Information
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551C, 551B specifications

The Bryant 551B and 551C are two highly efficient air conditioning units designed to provide optimal comfort in residential settings. Known for their reliability and performance, these models are part of Bryant's esteemed line of heating and cooling solutions.

One of the standout features of the Bryant 551B is its two-stage cooling system, which allows for better humidity control and increased comfort. This ensures that homeowners can enjoy consistent temperatures while reducing energy consumption. The unit operates quietly, thanks to its noise-reducing technology, making it an ideal choice for bedrooms and living spaces.

On the other hand, the Bryant 551C builds upon this foundation with its variable-speed compressor. This technology allows the unit to adjust its cooling output according to the specific needs of the home. This results in seamless operation and even greater energy efficiency. Both models also incorporate Bryant's advanced control capabilities, which allow users to monitor and adjust settings remotely via smart devices, adding a layer of convenience and modernity to home climate control.

With an emphasis on durability, both the 551B and 551C feature a galvanized steel cabinet that protects against weather-related damage. The powder coat finish further enhances their resistance to rust and corrosion, ensuring a long lifespan and minimal maintenance.

Another significant characteristic of these units is their excellent Seasonal Energy Efficiency Ratio (SEER) ratings. The 551B boasts a SEER rating of up to 16, while the 551C takes it even further with ratings exceeding 20. This efficiency not only translates to lower energy bills for homeowners but also contributes to a reduced carbon footprint, making these units environmentally friendly options.

Both models are also designed to operate with eco-friendly refrigerants, aligning with modern energy standards and regulations aimed at reducing greenhouse gas emissions.

In summary, the Bryant 551B and 551C are exemplary choices for homeowners looking for reliable, efficient, and high-performing air conditioning solutions. With features such as two-stage and variable-speed compressors, advanced smart technology, and robust construction, these models stand out in the competitive HVAC market. They promise a comfortable indoor environment along with significant energy savings, making them a wise investment for the future.
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