Dual Pressure Control P70 Series
4-Wire, 2-Circuit Contact Block
P70 single and dual function pressure controls are used in commercial air conditioning and refrigeration applications. The load-carrying contacts provide direct control of A.C. motors within the control’s rating. (See cover label for the electrical rating.) The controls can be used with R- 12, R-22, R-500, or R-502 refrigerants. Specific models for ammonia applications are also available. The MICRO-SET construction of low pressure controls and low side of dual models permits differentials to a minimum of 5 psi (34 kPa).
! WARNING: On ammonia applications, the ammonia P70 pressure control must be mounted separately from the electrical cabinet.
All Series P70 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) that protect against, or systems (alarm, supervisory
systems) that warn of control failure.
These controls are available with either main contacts (LINE-M2) CLOSE high - OPEN low, or main contacts (LINE-M2) OPEN high - CLOSE low contact action. The controls have a four-wire, two-circuit contact block that operates from a pressure actuated bellows. The controls have a single “sight-set” calibrated scale which shows cutout setting and the differential. Adjustments can be made readily without removing the control cover.
Mount the control on a flat surface or panel board by two screws or bolts through the holes in the back of the case. The control should be mounted above the element connections to provide drainage from the sensing elements. The pressure connection on the bellows should be above the liquid level of the equipment on which the control is used. This reduces possible accumulation of foreign matter inside the bellows.
! CAUTION: Do not mount the control in a position where dirt, sediment, or oil
will affect the operation of the control. Universal mounting bracket No. 271-51 is available, if required.
(Note: When using any bracket, use only mounting screws supplied with the control to prevent damage to internal components.)
1. Avoid sharp bends or kinks in the capillary tubing.
2. Be sure pressure controls installed on ammonia systems are built for ammonia service.
3. Purge all tubing and lines before connecting pressure controls.
4. Make sure the control is not installed on equipment to handle a load in excess of the switch’s electrical rating.
5. Coil and secure excess capillary length to avoid vibration but allow some slack in the capillary to avoid “violin string” vibration which can cause tubing to break. Do not allow tubing to rub against metal
Replaces Part Numbers: P70LB-25