ARSCROFT P-Series Snap Action Switches for Differential Pressure Control Instruction Manual
- June 3, 2024
- ARSCROFT
Table of Contents
ARSCROFT P-Series Snap Action Switches for Differential Pressure Control
DIMENSION
INTRODUCTION
The Ashcroft pressure control is a precision device that features a snap action switch. Fixed Deadband is available with single or dual SPDT Independently adjustable switches with various electrical ratings. An adjustable headband is available with an SPDT switch with various electrical ratings. Several wetted material constructions for compatibility with pressure media may be obtained. The “P” Series Ashcroft snap action pressure switch is available in both standard NEMA-4 and explosion-proof NEMA 7 & 9 configurations. The enclosure is an epoxy-coated aluminum casting.
INSTALLATION
This control is a precision Instrument and should never be left with internal
components exposed. During installation ensure that covers are in place and
conduit openings are sealed.
MOUNTING
Four holes in the bracket supplied are used in surface mounting of the
control. Location of these holes is shown on the general dimension drawings.
An optional pipe mounting bracket is also available. Mount on a vibration tree
surface or pipe. When tightening control to pressure line, always use the
wrench flats or hex on the pressure connection. Never tighten by twisting the
case.
PRESSURE CONNECTIONS
For operation as a differential pressure control-connect the high pressure to
the side port marked “H” and the low pressure to the side port marked “L.”
ELECTRICAL CONNECTION
Remove top cover, cover unscrews (CCW). On all units except one with terminal
blocks – wire directly to the switch according to circuit requirements. Units
with terminal blocks – wire directly to terminal blocks as required. Terminals
are marked common, norm open and norm closed.
CONDUIT CONNECTIONS
Two 3⁄4 NPT holes are provided, one fitted with a plug, the other with a cap.
It is recommended that Teflon tape or other sealant be used on conduit bushing
or plug threads to ensure integrity of the enclosure. NEMA 7 & 9 enclosures
require proper conduit seals and breathers as per the National Electrical
Code.
SETPOINT ADJUSTMENTS
Series PD-S Single Switch – Remove front cover, held in place by two screws.
For setpoint adjustment to within ±1% of the nominal range, use a suitable
reference such as an Ashcroft Duragauge or test gauge. Monitor switch with a
suitable pilot light or meter. Apply LOW pressure. Then apply HIGH pressure to
the required setpoint and turn the adjusting wheel until the switch changes
mode. When the setpoint has been achieved, raise and lower the HIGH pressure
to insure that the differential pressure between HIGH and LOW pressures is
correct.
Series PD-D Dual Switch – Remove the front cover, held in place by two
screws. There are two range-adjusting wheels. The adjusting wheel on the left
(labeled A) controls the left switch, and the adjusting wheel on the right
(labeled B) controls the right switch. The switches are set independently.
Note: The units are calibrated at the factory such that for proper operation
switch B setpoint must be set higher than the switch A setpoint.
For setpoint adjustment to within ±1% of the nominal range mount the switch on
a calibration stand, and use a suitable reference such as an Ashcroft
Duragauge or test gauge. Monitor the switch with a suitable pilot light or
meter. Apply LOW pressure. Then apply HIGH pressure to the required setpoint
and turn to adjust wheel until the switch changes mode. When the setpoint has
been achieved raise and lower the pressure to insure the setpoint is correct.
This must be done for both setpoint A and setpoint B.
Series PD-A Adjustable Deadband Switch – Remove the front cover, held in
place by two screws. The adjusting wheel labeled controls the re-setpoint of
the switch. The adjusting wheel labeled B controls the setpoint of the switch.
Note: The units are calibrated at the factory such that for proper operation
setpoint B is always higher than re-setpoint A.
For accurate setpoint adjustment, mount the switch on a calibration stand, and
use a suitable reference such as an Ashcroft Duragauge or Test Gauge. Monitor
switch with a suitable pilot light or meter. Apply low pressure. Then apply
high pressure to the required setpoint. Move the adjusting wheel for switch B
until switch changes mode. Then lower the HIGH pressure to the reset point and
move adjusting whee: for switch A until the switch changes mode. Raise and
lower the HIGH pressure to insure that the differential pressure between HIGH
and LOW pressure is correct. Repeat as necessary.
© 2007 Ashcroft Inc., 250 East Main Street, Stratford, CT 06614-5145, USA,
Tel: 203-378-8281, Fax:
203-385-0499,
www.ashcroft.com
All sales are subject to standard terms and conditions of sale.
I&M009-10011-10/00 (250-2550) AMR 12/07