Ashcroft B700 Pressure Switches - Manual

Installation and Maintenance Instructions for
B700 ASHCROFT
® Snap Action Switches
© Ashcroft Inc., 250 East Main Street, Stratford, CT 06614 USA, Tel: 203-378-8281, Fax; 203-385-0408, www.ashcroft.com
All sales subject to standard terms and conditions of sale. I&M009-10120-10/02 ATEX Rev. 06/13
NO (Normally Open) Blue
NC (Normally Closed) Red
C (Common) White
• 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.
8. Adjustment of Setpoint
Note – As indicated below, 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.
B700 Series – A single setpoint adjustment nut (7/8”) is locat-
ed 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 set-
point 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.
Note – Since vacuum models are already above setpoint at
atmosphere, the Normally Open (NO) circuit will be closed as
received.
D700 Series – A single setpoint adjustment nut (
7 ⁄
8
˝) is located
centrally at the bottom on the inside of the enclosure.
The direction of turning is indicated on a label affixed to the
inside of the control enclosure.
A typical calibration procedure would be as follows:
Static Working Pressure - 600 psig
Adjustable Differential Range - 5/200 psid
Differential Setpoint - 150 psi above static
working pressure.
Simultaneously raise the high and low side pressure to 600
psig. Maintain the low side pressure at 600 psig. Raise the
high side pressure to 750 psig to obtain 150 psi differential.
Turn the adjustment nut until the switch changes mode at 150
psi differential. When the setpoint has been achieved, raise
and lower the high side pressure to ensure that the differential
setpoint is correct.
D700 Series (low range differential) – A single setpoint
adjustment nut ( 7 ⁄
8
˝) is located centrally at the bottom on the
inside of the enclosure.
The direction of turning is indicated on a label affixed to the
inside of the control enclosure. XG5 controls have a setpoint
indication scale adjacent to the adjustment nut. To adjust the
control, align the top of the adjustment nut hex with the indica-
tor line on the scale. Do not force adjustment or attempt to
exceed the maximum setting shown on the scale or name-
plate.
For accurate setpoint calibration or for controls without a scale
mount the control on a calibration stand so that the HIGH and
LOW pressures expected under operating conditions may be
obtained. Suitable reference standards are necessary for each
pressure.
Note – Due to the sensitivity of these controls it is imperative
that the LOW pressure side volume be large to prevent a set-
point shift between calibration and field installation. If this is
not possible, an approximate setpoint under operating condi-
tions can be obtained by setting the operating point with the
low side open to atmosphere. A final setpoint adjustment can
be made after installation.
Apply LOW pressure. Then apply HIGH pressure to the
required setpoint and turn the adjustment nut until the switch
operates. When the setpoint has been achieved, raise and
lower HIGH pressure to ensure that the differential pressure
between the HIGH and LOW pressures is correct.
After installation of the control, replace the cover to ensure
electrical safety and to protect the internal parts from the
environment.
T700 Series – A single setpoint adjustment nut (
7 ⁄
8
˝) is located
centrally at the bottom on the inside of the enclosure.
The bulb of the control should be immersed in a bath at the
desired setpoint temperature. Optimum performance will be
obtained if the bulb is fully immersed. Allow five minutes for ini-
tial stabilization.
As received, the temperature switch will normally be set to
approximately 90% of the indicated range. After stabilization,
turn the adjustment nut until switch changes mode. Direction of
turning is indicated on a label affixed to the inside of the con-
trol enclosure. When setpoint jas been achieved raise and
lower temperature to insure that the setpoint is correct.
After installation of the control replace cover to insure electri-
cal safety and to protect internal parts from the environment.
B750, D750 and T750 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 decreas-
es deadband. Letters on the wheel may be used as a refer-
ence. Deadbands obtainable will vary from 0.5% to 9% of
pressure or temperature range depending on range segment
and type of diaphragm.
Adjustment of Setpoint – As received, the switch will normal-
ly be set to approximately 90% of range. Rotate the wheel on
the MICRO SWITCH all the way to the right; this will provide
smallest deadband. Pressurize, or increase bath temperature,
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.
SIRA 02ATEX1391X; II 2GD; Ex d IIC T6 Gb;
Ex t IIIC T85° C Db IP 6X; (Ta = –20°C to +60°C)