Automation and Control Solutions
Honeywell International Inc. Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North 35 Dynamic Drive
Golden Valley, MN 55422 Toronto, Ontario M1V 4Z9
customer.honeywell.com
L4188A,B; L4189A,B; L6188A-C; L6189A-C AQUASTAT® CONTROLLERS
® U.S. Registered Trademark
© 2007 Honeywell International Inc.
68-0061—1 J.I. Rev. 10-07

To Set Adjustable Differential (if provided)

Use a screwdriver to turn the differential dial until the slot
molded into the case lines up with the desired degrees of
differential.
Fig. 12. Twist the Screwdriver Slightly to turn the
Differential Dial.

To Set Temperature Limit Stop (if provided)

CAUTION
Follow these instructions carefully to avoid
placing the limit stop pointer on the wrong side of
the setting indicator. In a high limit application,
incorrect positioning of the pointer will cause
system operation above the limit stop setting,
potentially resulting in overheating or related
conditions.
• Remove the knob.
• Turn the controller shaft all the way counterclockwise
when setting a high limit. Turn it all the way
clockwise when setting a low limit.
• Find the metal limit stop on the back of the knob.
• Lift the limit stop slightly with a pencil or screwdriver and
push to move to desired setting.
• Read the setting from the front of the knob.
• Place the knob on the shaft.
• Turn the knob to make sure it: (1) turns through the desired
adjustment range, and (2) stops at the limit setting.
DO NOT FORCE.
• Return knob to desired setting.
Fig. 13. Adjust the Limit Stop with a Screwdriver and
check Orientation when Replacing Knob on Shaft.

CHECKOUT

Turn the system on and observe it through several cycles to
make sure the controller operates as desired.
Teflon® is a registered trademark for E.I. Du Pont De Nemours and Company.
CONTROLLER
SETTING
INDICATOR
DIFFERENTIAL
ADJUSTMENT
DIAL
M25425
LIFT AND PUSH
TO CHANGE LIMIT
SETTING
AJUST LIMIT STOP
REPLACE KNOB ON SHAFT
LIMIT STOP
POINTER
KNOB
KNOB
SHAFT
SETTING INDICATOR:
LIMIT STOP MUST
BE ON RIGHT SIDE OF
SETTING INDICATOR FOR
HIGH LIMIT; ON LEFT
SIDE FOR LOW LIMIT
FOR LOW LIMIT STOP:
TURN SHAFT
FULL COUNTERCLOCKWISE
(SHOWN) BEFORE
REPLACING KNOB.
FOR HIGH LIMIT STOP:
TURN SHAFT
FULL CLOCKWISE
BEFORE REPLACING
KNOB. M25426