Pressure switches from Johnson Controls
Published:  January 2008
Johnson

Versatile pressure control — the P77 series of pressure switches from Johnson Controls.

Johnson Controls has launched a range of pressure switches for refrigeration, air-conditioning and heat-pump applications that conform to PED 97/23/EC Cat IV.

P77 series single pressure controls have a range of 3 to 42 bar and can be used in a variety of applications involving high- or low-pressure refrigeration. They are IP54 classified. These switches can be used with R22, R134a, R404A, R410A and all other non-corrosive refrigerants within the operating range of the control — plus other high- or low-pressure applications such as air and water.

The controls are provided with a special power element, with external pressure on the bellows instead of internal pressure like the present standard versions. All models have alarm contacts, and standard models have phosphor-bronze bellows and brass pressure connections. They can be used for control functions or limit functions.

SPDT contacts are standard, so the P77 series can be wired for alarm functions. Trip-free manual reset ensures over-ride is not possible in the control function.


For more information on this story, click here:Jan 08, 168



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