Owner's manual

E
LECTRICAL CONNECTION
R
emove 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
Note:
Due to the sensitivity of this control it is imperative that
the LOW pressure side volume be large so that there is no
increase in LOW pressure when shut off and HIGH side pres-
sure is applied. If this is not possible, approximate setpoint
under operating conditions can be obtained by setting operating
point with LOW side open to atmosphere. Then make final set-
point adjustments after installation.
Installation and Maintenance Instructions for
ASHCROFT
®
P-Series Snap Action Switches
for Low Range Differential Pressure Control
TERMINAL BLOCK
SWITCH A
TERMINAL BLOCK
S
WITCH B
2
1
3
2
1
3
NC
NO
C
NC
NO
C
© 2007 Ashcroft Inc., 250 East Main Street, Stratford, CT 06614-5145, USA, Tel: [phone], Fax: [phone], www.ashcroft.com
All sales subject to standard terms and conditions of sale. I&M009-10014-10/00 (250-2525) AMR 12/07
A
B
0
20
40
60
0
20
40
60
Series PD-S Single Switch – Remove front cover, held in place
b
y two screws. For setpoint adjustment to within ±1 % of nomi-
nal 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 HIGH pressure to insure that differential pres-
sure between HIGH and LOW pressures is correct.
S
eries PD-D Dual Switch
–
Remove 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,
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
switch A setpoint.
For setpoint adjustment to within ±1 % of nominal range 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 and turn adjusting 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 front
cover, held in place by two screws. The adjusting wheel labeled
A controls the resetpoint 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 calibra-
tion stand, and use a suitable reference such as an Ashcroft
Dur
agauge or Test Gauge. Monitor switch with a suitable pilot
light or meter
.
Apply lo
w pressure
.
Then apply high pressure to
the required setpoint.
Move adjusting wheel for switch B until
switch changes mode. Then lower the HIGH pressure to the
re-setpoint and move adjusting wheel for switch A until the
switch changes mode. Raise and lower HIGH pressure to insure
that differential pressure between HIGH and LOW pressure is
correct. Repeat as necessary.