Manufacturer: Johnson Controls
Category: Electrical Controls
Sub Category: Pressure Controls
P74 Series Differential Pressure Controls
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.
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.
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.
All Series P74 differential pressure controls are designed for use only as operating controls. Where an operating control failure would result in personal injury and/or loss of property, it is the responsibility of the installer to add devices (safety, limit controls) or systems (alarm, supervisory systems) that protect against, or warn of, control failure.
Replaces Part Numbers: P74HA-9, CARP74HA-9