H E A D E R
0178-1737-000 Rev. A
7
4/OPERATOR MAINTENANCE
4.3 Testing the Switch Gauges
Use the following procedure to test the switch gauge cir-
cuitry. See Figures 6 through 8.
WARNING: This procedure requires a change of pres-
sure switch settings during the test. Readjust the alarm
trigger points after completing this procedure.
Tools required:
!
#2 Phillips screwdriver
!
1/16 hex wrench
!
Transparent tape
1.
Remove the left and right louvered panels by remov-
ing the Phillips head screws located at the top of each
panel (Figure 6).
2.
Verify that the readings indicated on each switch
gauge and the associated line pressure gauge match
to within:
6 psig for the nominal 50 psi gases, 18 psig for the 180
psi gases and 2 inches Hg. for the vacuum system.
3.
Place a suitable length of transparent tape across the
face of each switch gauge. The tape should be long
enough so that the ends of the tape clear the front
panel (Figure 8).
4.
Mark the exact location of the contact assembly’s
brass pins on the transparent tape (Figure 8B).
5.
Using the 1/16 hex wrench individually turn each low
(left side) contact so it just touches the gauge needle
(Figure 8C).
6.
The alarm must sound on contact. If no alarm
sounds, the panel needs repair (Figure 8D).
Note:
If remote alarms or monitors are connected, these
devices will be activated.
7.
Return each contact assembly to its original position
(mark placed on transparent tape. (Figure 8E).
8.
Repeat steps 5 through 7 to test high (right side)
pressure contacts.
9.
Remove tape and reattach the louvered access panels.
Note:
This test only checks switch gauge electronics; it
does not verify alarm trigger points. If the switch gauge
trigger points require adjustment, refer to the section
“Setting Alarm Trigger Points” in the Service Manual.
Figure 6
Louvered Panel Removal
Note:
Lip on louvered panel not shown.
When replacing, make sure lip is properly
positioned.
