PGC's 800-1200 CFM system is a durable, high quality piece of humidity/temperature conditioning equipment for scientists and engineers whose research, testing, or quality control applications require environmental simulation and control within extremely narrow tolerances.

PGC conditioners are two-temperature generators. Within the unit, a water spray temperature and a leaving air temperature are precisely controlled. A portion of the air always passes through a water spray where it is cooled to the temperature of the water and saturated. The air is then reheated to the desired dry-bulb temperature and returned to the conditioned area. The temperature of the water spray will approach the dew point of the process air. By controlling dew point temperature and dry-bulb temperature, a very constant relative humidity is maintained.

How it works

If the area to be conditioned has changing internal loads or requires make-up air, the Cascade System should be selected. This system adds a humidity sensor to the control loop that will reset the water spray temperature to compensate for load changes.

Air Flow

Air returning from the conditioned space passes through a return duct and, depending on the position of the face and by-pass damper, a portion is directed through a water spray and the balance by-passes the spray. The portion of the air subjected to the sprayed coil is cooled to within approximately 1.0ºC of the spray water temperature. This essentially saturated air passes through a mist eliminator and mixes with air that by-passed the sprayed coil. The mixed air is forced across an electric air heater by a fan. The conditioned air is then supplied, via ductwork, to the work or test area.

Air Control

A proportioning control system compares the dry-bulb temperature, measured by an RTD, to the air temperature set point. A pulsed output, which is ordinarily "on" 50% of the time when stabilized, is supplied to the air heater control circuit. A second analog output positions the by-pass damper so that the amount of air by-passed is directly proportional to the percentage of air heat applied. If the air temperature drops below the selected set point, the controller calls for more heat; i.e., the "on" time of the heater increases. The face and by-pass damper begins to compensate so that more returning air by-passes the spray coil, returning the pulsed output to the normal 50% "on" condition. Conversely, if the air temperature increases above the set point, the heater is pulsed less and more air is directed through the spray chamber.

RH Control

A platinum RTD in the water line is measured by a proportioning controller, the output of which adjusts a refrigeration capacity control valve and a water heater. Water spray temperature is controlled within ±0.1ºC.

Cascade System

The desired relative humidity is set to within ±0.1%. The proportioning controller receives an input signal from a relative humidity sensor/transmitter and, if necessary, adjust the water temperature. The output of the RH control loop is the water temperature set point. If the relative humidity drops by as little as 0.2%, the output of the RH controller will increase the water temperature set point by approximately 0.1ºC. This will, in turn, increase the relative humidity to the selected set point, returning the controller output to steady-state level.

Benefits:

·Precise

Better than ±0.5ºC and ±1.0% RH is provided by the 800-1200 CFM unit.

· Easy

The 800-1200 CFM unit sits on casters and can be rolled right up to the area to be conditioned.

· Durable

316 stainless steel interior with heliarc-welded seams.

· Proven

PGC has been building humidity chambers since the mid-1970s using a principle established and proven since the 1930s.

Standard Features:

· Mechanical, conditioning, and control components come complete in one unit

· Adjustable over-temperature safety thermostat

· High quality solid state control circuit

· 316 stainless steel

· Pebbled exterior finish

· Automatic liquid-level device

· Magnetic drive chemical pump for water spray circulation

· Centrifugal fan for circulating air through conditioned area

· Low watt density heaters to ensure long life

· Low water safety cutout