Ashcroft B700 Pressure Switches - Manual (Page 2)

2 SPDT – Dual switching elements consist of two SPDT switches
mounted together in a bracket. Switches are calibrated to have
simultaneous operation within 1% of range either on increasing
or decreasing pressure but not in both directions. Wire directly to
the front and rear switch according to circuit requirements.
Leads are provided on rear switch color coded as follows:
Common
– White
Normally Closed – Red
Normally Open
– Blue
See SPDT instructions for pilot light hook-up.
When hermetically sealed switch elements(s) are supplied, the
lead color coding is as follows:
Common
– White
Normally Closed – Red
Normally Open
– Blue
B700 SERIES
SPDT – Wire directly to the switch according to circuit requirements.
2 SPDT – Wire to front switch terminal block (left) and rear
switch terminal block (right) as marked. Strip insulation 5 ⁄
16
˝,
insert in proper terminal connector and tighten clamping screw
to secure.
ADJUSTMENT OF SETPOINT
B400 & B700 Series – A single setpoint adjustment nut (
7 ⁄
8
˝) is
located centrally at the bottom on the inside of the enclosure.
For accurate setpoint calibration, mount the switch on a cali-
bration stand, a pump or catalog No.1305 deadweight gauge
tester. A suitable reference standard such as an Ashcroft
Duragauge or Test Gauge is necessary to observe convenient
changes in pressure.
As received, the pressure switch will normally be set to
approximately 90% of the indicated range. Pressurize the
system to required setpoint and turn the adjustment nut until
switch changes mode. Direction of turning is indicated on a label
affixed to the inside of the control enclosure. When setpoint has
been achieved raise and lower pressure to insure that setpoint
is correct.
After installation of the control replace cover to insure electri-
cal safety and to protect internal parts from the environment.
B450 and B750 VARIABLE DEADBAND SWITCHES
Deadband is varied by rotating the wheel on the precision
switch. When viewed from the front of the enclosure, rotation to
the left increases deadband – rotation to the right decreases
deadband. Letters on the wheel may be used as a reference.
Deadbands obtainable will vary from 0.5% to 9% of pressure
range depending on range segment and type of diaphragm.
ADJUSTMENT OF SETPOINT
As received, the pressure switch will normally be set to approxi-
mately 90% of range. Rotate the wheel on the MICRO SWITCH
all the way to the right; this will provide smallest deadband.
Pressurize the system to the required setpoint and turn the
adjustment nut until the switch changes mode. Lower the
pressure to reset the switch. Rotate the wheel on the MICRO
SWITCH until the desired deadband is obtained. The upper
setpoint will be changing upward with this adjustment. Lower the
pressure to reset the switch. Then increase the pressure to the
desired setpoint and turn the adjusting nut until the switch
changes mode. Lower the pressure and check resetpoint and
deadband.
Note – As indicated above, adjustment of setpoint is made by
use of 7 ⁄
8
˝ nut. Precision switch element mounting screws
and bracket adjusting screw are factory sealed and
should not be tampered with.
CAUTIONS TO OBSERVE
Switch Applications On Continuous Static Pressure:
Pressure switches that contain BUNA, VITON or TEFLON
diaphragms can experience some amount of compression set of
the diaphragm in high static pressure applications. This compres-
sion set has the potential to shift the switch setpoint while in ser-
vice. The setpoint can shift by approximately 2% (typically less
than 1%) from the original setting. To assure optimal long term
setting accuracy, Ashcroft recommends the switch setting be
checked after 30 Days in service and reset if necessary. As with
any calibrated instrument, Ashcroft recommends regular inspec-
tion of operation and setpoint setting.
Installation and Maintenance Instructions for
ASHCROFT ® High Pressure B400 & B700
Snap Action Switches with Buna N, Viton and
Teflon Diaphragms for Pressure Control
© 2014 Ashcroft Inc., 250 East Main Street, Stratford, CT 06614-5145, USA, Tel: 203-378-8281, Fax: 203-385-0499, www.ashcroft.com
All sales subject to standard terms and conditions of sale. I&M009-10210-Hi Prsr 3/14