Air Techniques 87176 Guide

Pressure Switch Replacement Kit
Part Number: 87176
Replacement & Adjustment
Instructions
Figure 2. AirStar Membrane Compressor Pressure Switch Location and Connection Configuration
Table 1.
Pressure Switch Configuration by Model and Serial Number
Notes:
AirStar models with serial numbers lower than
those listed have an unloader connected.
AirStar models with serial numbers the same or
higher than those listed do not have an unloader
connected and do not use the tubing.
This includes models AS12, AS40 & AS100.
Model Serial
No. Model Serial No.
AS10 102716 AS30 316829
AS21 216147 AS50 512621
AS22 226244 AS70 706081
Introduction. This document provides the instructions to replace and adjust the Pressure Switch, part number 86436, used on
the AirStar membrane compressor product family using Pressure Switch Replacement Kit, P/N 87176. The switch controls the
compressor on (cut-in) and off (cut-out) cycling in response to system pressure level. It effectively keeps the system air pressure
within the rated operating range of 85 and 115 psi (5.8 and 7.9 bar). As shown by Figure 1, the parts supplied in the kit consist of
a Pressure Switch, P/N 86436 and a 10.25-inch length of 10mm Flamex Tubing, P/N 86726.
Flamex 10mm
Tubing
(1 piece, 10.25
inches long)
Pressure
Switch
AirStar AS50 Shown
Detail A - Current Design
Pressure Switch without an unloader
Membrane
Dryer
Pressure
Switch
Cooler
Pressure
Switch
Detail B - Original Design
Pressure Switch with unloader and extra hoses
Membrane
Dryer
Membrane
Dryer
Unloader with associated
connection hoses
Figure 1. Pressure Switch Replacement Kit, Supplied Parts
Item Description P/N
1. Pressure Switch
Assembly
86436
2. 10.25-inch, 10mm
Flamex Tubing
86726
2
1
© Air Techniques, Inc Copyright 2012 •P/N 86766, Rev. D •October 2017
www.airtechniques.com
DENTAL AIR SYSTEM
Air Techniques, Inc.
1295 Walt Whitman Road
Melville, New York, USA 11747- 3062
Unloader
Important Information. There are two pressure switch
connection configurations presently in the field; the original
design with an unloader connected and a newer one that
does not use an unloader. Replacement kit, P/N 87176, is
used to replace the pressure switch in both configurations
leaving the pressure switch installed without an unloader.
Table 1 lists the different configurations by model and
serial number. Figure 2 shows the pressure switch location
and connection configuration details. New AirStar models
including AS12, AS40 and AS100 do not have an unloader
and do not use the supplied Flamex tubing.
All personnel servicing the equipment must read and
understand the Installation and Operation Manual before
operating or performing any service of the unit. Only a
trained technician should perform any service.
CAUTION
Remove Power and Depressurize Tank
iNever work on equipment connected to live power. Remove power by disconnecting facility
power to the unit prior to performing any replacement procedures.
iPrior to performing the replacement procedures, make sure to depressurize the storage tank.

Caution: To avoid damage, do not exceed maximum allowable system pressure.
Always check the pressure switch operation after re-setting.
Pressure Adjustment
Adjusting the operating pressure range of the Pressure Switch is accomplished by the Range and Differential spring nuts located
under the pressure switch cover. The Range spring nut controls the cut-in or turn on pressure set point, while the Differential spring
nut sets the operation cut-out or turn off pressure set point. Since the range adjustment changes both the high and low operating
points, it is recommended to always adjust the Range spring nut first.
Adjustment Instructions
Set the switch pressure range by first removing the nut
securing the pressure switch cover and remove the
cover from the switch to access the adjustment spring
nuts. Refer to the Figure 4 and adjust the pressure
switch as follows:
Range – Adjust Range spring nut (A) until the
desired operating point (cut-in) of 85 psi (5.8 bar) on
falling pressure is obtained. Turning the Range nut (A)
clockwise will increase the setting.
Keep in mind the range adjustment changes both the
high and low operating points but should always be
adjusted for the low operating point.
Differential – Set the operating point (cut-out) on
rising pressure to maximum by adjusting the Differential
spring nut (B). Turning the nut (B) clockwise increases
the pressure difference between the high and low
operating points by increasing the high operating point
only.
Kit Replacement Procedure. Refer to Figures 2 through 4 and
replace the pressure switch by performing the following steps.
1. Use a Phillips head screwdriver to loosen the screw securing
the pressure switch cover and remove the cover.
2. Disconnect wires from the pressure switch. Tag if necessary.
3. Proceed to step 4 if no unloader is connected to the pressure
switch. If an unloader is connected perform the following:
a. Use a torx screwdriver to loosen the screw securing
the unloader to the pressure switch and remove the
unloader.
b. Remove the hoses connected between the Cooler
and Membrane Dryer. Discard the unloader and
associated hoses.
c. Replace the removed hose between the Cooler and
Membrane Dryer with the Flamex tubing supplied with
the kit.
4. Using a 15/16-inch open end wrench, loosen the pressure
switch by turning counter-clockwise. Remove and discard.
5. Install the replacement pressure switch and tighten by turning
clockwise using a 15/16-inch open end wrench.
6. Refer to Figure 4 and connect the wires to the pressure switch.
7. Turn on the compressor and check the pressure switch. Adjust
the switch by performing the Pressure Adjustment Procedures
below.
8. Install the cover onto the pressure switch and secure by
tightening the 5/16-inch acorn nut.
Figure 3. Pressure Switch Replacement
STEP 1
STEP 3.bSTEP 3.a STEP 3.c
Torx
Screw
Unloader Discard the unloader
and associated hoses.
Unloader
Flamex 10mm
Tubing
10.25 inches long
(1 piece)
STEPS 4 & 5 STEP 8
15/16-inch
Wrench
STEP 2
Figure 4.