3 … 6
Annually check the switch for proper operation
Set Point Calibration
The set point dial of the GAO and GMH is factory calibrated
with increasing pressure (GML: decreasing pressure). Due
to hysteresis, the GAO switch will actuate at a slightly lower
point as the pressure decreases.
Adjusting the Set Point
• Remove the clear cover from the switch.
• Turn the dial until the desired trip pressure is opposite the
white arrow (mark) on the yellow dial face.
• After adjusting the set point for normal operation check to
see that the gas pressure switch operates as intended.
• Use an accurate pressure gauge connected upstream
from the switch to measure the actual pressure.
• Replace the clear cover.
OPERATION AND ADJUSTMENT
Automatic Reset
The NC contact of the GAO breaks when pressure rises
above the set point. It makes automatically when pressure
returns to the normal operating level.
Manual Reset
The NC contact of the GMH breaks when pressure rises
above the set point. The NO contact of the GML breaks
when pressure falls below the set point. Neither of the
switches will return to their former position automatically. To
reset, wait until the pressure returns to the normal operat-
ing level. Then press and release the clear cover over the
red reset button in the center of the yellow dial face; it is not
necessary to remove the cover. The neon light indicates a
fault condition for the GML and GMH series and for the GAO
series when used as a high gas limit. The lead for the light
wired to terminal #2 on the GAO series should be wired to
terminal #1 when used as a low gas limit.