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These differential pressure controls are for use as operating controls and/or indicating system functions through display lights or panels. They measure the difference in pressure exerted upon its two sensing elements. The controls are available for applications sensing air, oil or liquid. Typical applications are proof of flow across a chiller or water cooled condenser, proof of flow in a heating or cooling coil and lube oil pressure sensing on refrigeration compressors. On a proof of flow application the control measures pressure drop across two different points in either a closed water circulating system or a city water to supply system.

On a proof of flow application in a water chiller system the control activates a light or signal to indicate a loss of water.The control may also be applied as a lube oil pressure sensing control on refrigeration compressors. They may be used in combination with P28 and/or P45 oil pressure cutout controls on two compressor, single motor units to reduce the oil system cost. Special low pressure models are available for variable speed and screw compressor oil pressure applications.

Single and double pole models are available with contacts that open on a pressure differential increase or close on a pressure differential increase. Also available are models with single-pole, double-throw enclosed contacts or with main and separate reverse-acting auxiliary contacts. Controls with lockout feature require manual reset to reclose circuit after lockout. The ?trip-free? reset will not permit restart until reset button is pushed and released. The operation point of the control is readily adjusted by rotating the adjusting disk. The control set points are easily read on a calibrated scale.

Johnson Controls A19 Series temperature controls are designed to cover a broad range of uses for heating and general purpose requirements. Controls have SPST contacts which open on temperature increase or they may be supplied in single-pole, double-throw contact action. Various control ranges are available to cover working temperatures from -30 to 550° F (-34 to 288° C). Closed tank fittings and bulb wells are available for immersion applications. These controls are designed for open low and open high applications. Where critical or high value products are to be maintained within a specific temperature differential, a single control should not be applied to function as both an open low and open high control. In these applications, a separate backup control with alarm contacts should be wired to indicate when the back-up control operates.

The A419 series controls are single-stage, electronic temperature controls with a Single-Pole, Double-Throw (SPDT) output relay. They feature a lockable front-panel touchpad for setup and adjustment, and a Liquid Crystal Display (LCD) for viewing the temperature and status of other functions. A Light-Emitting Diode (LED) indicates the controls? output relay On/Off status. The A419 controls are available in 24 VAC or 120/240 VAC powered models. The A419 controls have heating and cooling modes, adjustable setpoint and differential, an adjustable anti-short cycle delay, and a temperature offset function. The setpoint range is -30 to 212°F (-34 to 100°C). The controls feature remote sensing capability and interchangeable sensors. The A419 controls are available in either NEMA 1, high-impact plastic enclosure suitable for surface or DIN rail mounting or NEMA 4X watertight, corrosion-resistant surface-mount enclosures.