HVAC Level-Master Control

{0 Comments}

HVAC Level-Master Control

The level-master control is a positive liquid-level-control device suitable for application to all flooded evaporators (see Fig. 11-45). The level-master control is a standard thermostatic-expansion valve with a level-master element. The combination provides a simple, economical, and highly effective liquid-level control. The bulb of the conventional thermostatic element has been modified to an insert-type bulb […]

Read More…

Level Control Valves Float valve

{0 Comments}

Level Control Valves Float valve

A hollow float is sometimes used to control the level of refrigerant (see Fig. 11-43). The float is fastened to a lever arm. The arm is pivoted at a given point and connected to a needle that seats at the valve opening. If there is no liquid in the evaporator, the ball-lever arm rests on […]

Read More…

Level Control Valves Capillary tubes

{0 Comments}

Level Control Valves Capillary tubes

Capillary tubes are used to control pressure and temperature in a refrigeration unit. They are most commonly used in domestic refrigeration, milk coolers, ice-cream cabinets, and smaller units. Commercial refrigeration units use other devices. The capillary tube consists of a tube with a very small diameter. The length of the tube depends on the size […]

Read More…

Discharge-Bypass Valves Hot Gas

{0 Comments}

Hot gas may be required for other systems functions besides bypass capacity control. Hot gas may be needed for defrost and head pressure control. Normally, these functions will not interfere with each other. However, compressor cycling on low suction pressure may be experienced on system start-up when the discharge-bypass valve is operating and other functions […]

Read More…

Discharge-Bypass Valves Installation

{0 Comments}

Discharge-Bypass Valves Installation

Bypass valves can be installed in horizontal or vertical lines, whichever best suits the application and permits easy accessibility to the valves. However, consideration should be given to locating these valves so that they do not act as oil traps. Also solder must not run into the internal parts during brazing. The DBV should always […]

Read More…

Externally Equalized Bypass Valves

{0 Comments}

Externally Equalized Bypass Valves

The primary function of the DBV is to maintain suction pressure. Thus, the compressor suction pressure is the control pressure. It must be exerted on the underside of the valve diaphragm. When the DBV is applied as shown in Fig. 11-38, where there is an appreciable pressure drop between the valve outlet and the compressor […]

Read More…

Discharge-Bypass Valves Application

{1 Comment}

Discharge-Bypass Valves Application

DBVs provide an economical method of compressor capacity control in place of cylinder unloaders or of handling unloading requirements below the last step of cylinder unloading. On air-conditioning systems, the minimum allowable evaporating temperature that will avoid coil icing depends on evaporator design. The amount of air passing over the coil also determines the allowable […]

Read More…

Discharge-Bypass Valves Operation

{0 Comments}

Discharge-Bypass Valves Operation

Discharge-bypass valves (DBV) respond to changes in downstream or suction pressure (see Fig. 11-37). When the evaporating pressure is above the valve setting, the valve remains closed. As the suction pressure drops below the valve setting, the valve responds and begins to open. As with all modulating-type valves, the size of the opening is proportional […]

Read More…