Fig. 40 — Perfect Humidity™ System

Normal Design Cooling Operation

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. 41).

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 fur- ther subcooled to a temperature approaching the evaporator leaving-air temperature. The liquid then enters a thermo- static 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.

The liquid enters the evaporator coil at a temperature lower than in standard cooling operation. This lower temperature increases the latent capacity of the rooftop unit. The refriger- ant passes through the evaporator and is turned into a vapor. The air passing over the evaporator coil will become colder than during normal operation. However, as this same air passes over the subcooling coil, it will be slightly warmed, partially reheating the air.

Subcooling mode operates only when the outside-air temper- ature is warmer than 40 F. A factory-installed temperature switch located in the condenser section will lock out subcool- ing mode when the outside temperature is cooler than 40 F.

The scroll compressors are equipped with crankcase heaters to provide protection for the compressors due to the addi- tional refrigerant charge required by the subcooling/reheat coil.

When in subcooling mode, there is a slight decrease in sys- tem total gross capacity (5% less), a lower gross sensible capacity (20% less), and a greatly increased latent capacity (up to 40% more).

Hot Gas Reheat Mode

When the humidity levels in the space require humidity con- trol, a hot gas solenoid valve (specific to hot gas reheat mode only) will open to bypass a portion of hot gas refrigerant around the condenser coil (see Fig. 42).

This hot gas will mix with liquid refrigerant leaving the con- denser coil and flow to the subcooling/reheat dehumidifica- tion coil. Now the conditioned air coming off the evaporator

Fig. 41 — Perfect Humidity System

Subcooling Mode Operation

will be cooled and dehumidified, but will be warmed to neu- tral conditions (72 F to 75 F) by the subcooling/reheat dehu- midification coil.

NOTE: The 551B090-150 rooftop units can operate one cir- cuit in subcooling mode and one circuit in hot gas reheat mode or both circuits in hot gas reheat mode, or both in nor- mal design cooling mode.

The net effect of the rooftop when in hot gas reheat mode is to provide nearly all latent capacity removal from the space when sensible loads diminish (when outdoor temperature conditions are moderate). When in hot gas reheat mode, the unit will operate to provide mostly latent capacity and extremely low sensible heat ratio capability.

Similar to the subcooling mode of operation, hot gas reheat mode operates only when the outside air temperature is warmer than 40 F. Below this temperature, a factory-installed outside air temperature switch will lock out this mode of operation.

See Table 29 for the Perfect Humidity dehumidification sys- tem sequence of operation.

Fig. 42 — Perfect Humidity System

Hot Gas Reheat Mode Operation

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Bryant 551B installation instructions Perfect Humidity System Normal Design Cooling Operation
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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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