P470 Electronic Pressure Control with Display Product/Technical Bulletin2
Application
Application Options
The P470 Electronic Pressure Control with Display is
designed for On/Off control (direct or pilot duty) of
refrigeration and HVAC loads based on system
pressure.
The P470 control’s overall setpoint range is
0 to 750 psi. The available operating ranges are:
0 to 100 psi, 0 to 500 psi, and 50 to 750 psi, depending
on which P499 transducer is wired to the control. See
Table 2 for more information.
Note: Each of the P470 control’s three field-
selectable, operating pressure ranges require a
specific P499 transducer to operate properly. See
Table 2 for more information.
The P499 transducer may be used with any fluid or
vapor that is compatible with 17-4PH stainless steel.
This includes all non-corrosive refrigerants and
ammonia.
The P470 control may replace a variety of
electromechanical pressure controls, and provides a
clear LCD display of the controlled equipment
pressure. The transducer may be mounted up to
100 ft (30.5 m) away from the control using three-wire
shielded cable, providing greater installation versatility,
and eliminating many of the constraints of capillary
tubes found on electro-mechanical pressure controls.
You may use a maximum of four P470 controls wired to
a single P499 transducer. For example, high-pressure
control and condenser fan cycling can use a common
transducer in conjunction with two P470 Controls to
control high-side pressure. The P470 Controls may be
connected to a single transducer on the suction
manifold to stage four compressors on a refrigeration
rack. See Figure 7.
Operation Overview
The P470 control uses a P499 Electronic Pressure
Transducer to sense pressure. The control’s operating
pressure range depends on the transducer model
selected and the position of the pressure range
jumpers. See Positioning the Jumpers
and Table 2.
The P499 transducer is mounted to a pressure tap
point on the refrigerant system. The transducer
generates a 0.5 to 4.5 VDC ratiometric signal that the
P470 pressure control converts to a psi value. Refer to
the P499 Electronic Pressure Transducer Product/
Technical Bulletin (LIT-12011190).
The sensed psi value is refreshed every two seconds
and displayed on the Liquid Crystal Display (LCD),
along with other control status information, during
normal operation. See Figure 3.
When the pressure at the transducer reaches the cut-in
setpoint, the output relay is energized, the front-panel
LED lights, the Normally Open (N.O.) contacts close,
and the Normally Closed (N.C.) contacts open. When
the cutout setpoint is reached, the output relay is de-
energized, the LED goes off, and the contacts return to
their normal positions.
IMPORTANT: Use this P470 Electronic Pressure
Control only as an operating control. Where failure
or malfunction of the P470 control could lead to
personal injury or property damage to the controlled
equipment or other property, additional precautions
must be designed into the control system.
Incorporate and maintain other devices, such as
supervisory or alarm systems or safety or limit
controls, intended to warn of or protect against
failure or malfunction of the P470 control.
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