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L4188A,B; L4189A,B; L6188A-C; L6189A-C AQUASTAT® CONTROLLERS
7 68-0061—1
Fig. 9. High Limit and Low Limit/Circulator Application in
an Oil-Fired Hydronic System with domestic hot water.
Fig. 10. High Limit and Separate Low Limit and Circulator
Application in an Oil-Fired Hydronic System with
Domestic Hot Water.
OPERATION
As the liquid filing the sensing bulb and capillary expands and
contracts, it moves a diaphragm. Movement of the diaphragm
is transferred by a lever to the snap-acting switch in the
controller.
High or Low Limit Action (L4188, L4189)
The normally closed C-1 contacts open on temperature rise to
the set point, shutting off power to the controlled circuit. On
auto recycle models, the switch closes C-1 after the
temperature falls past the set point and through the differential
(See Fig. 11).
Low Limit/Circulator Action (L6188, L6189)
The low limit is connected to the normally closed C-1 contacts,
and the circulator to the normally open C-2 contacts. As long
as the temperature at the sensing bulb is above set point, the
circulator runs. If sensing bulb temperature falls past the set
point and through the differential, the switch breaks C-2 to turn
off the circulator, and makes C-1 to turn on the burner. When
the temperature rises to the set point, C-2 makes to turn on the
circulator, and C-1 breaks to turn off the burner.
On manual reset models, the reset button must be pushed
before contacts C-1 will close (See Fig. 11).
Fig. 11. Aquastat Controller Switch Action on Temperature
Change.
ADJUSTMENTS
To Set Temperature
KNOB MODELS
Line up the desired temperature setting with the temperature
setting indicator behind the knob.
SCREWDRIVER SLOT MODELS
Line up the pointer on the shaft with the desired temperature
setting printed on the case.
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
1
L4188 OR L4189 USED AS HIGH LIMIT.
2
24V THERMOSTAT
PROTECTORELAY
CONTROL
BLACK
T
CIRCULATOR
L1
(HOT)
L2
2
3
HIGH LIMIT
BURNER MOTOR
IGNITION
ORANGE
WHITE
T
LOW LIMIT
RELAY CENTER
CIRCULATOR
MOTOR
RG
C1
2
L6188 OR L6189 USED AS LOW LIMIT/CIRCULATOR CONTROLLER.
3
M25422
PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS
REQUIRED.
1
24V
THERMOSTAT
PROTECTORELAY
CONTROL
BLACK
T
CIRCULATOR
L1
(HOT)
L2
BURNER
IGNITION
ORANGE
WHITE
T
TT
XX4
1
2
L4188.9
CIRCULATOR
L4188.9
LOW LIMIT
L4188.9
HIGH LIMIT
SWITCHING RELAY
RA832A
LINE VOLTAGE
LOW VOLTAGE
1
M25423
SET POINT
DIFFERENTIAL
TEMPERATURE
SETTING
SCALE
L4188.9
HIGH OR LOW
LIMIT
L6188.9
LOW LIMIT/
CIRCULATOR
SET POINT
SET POINT
LESS
DIFFER-
ENTIAL
BREAKS
MAKES
AUTO
RECYCLE
C-1 BREAKS
C-2 MAKES
C-1 MAKES
C-2 BREAKS
MANUAL
RESET
MAKES C-1
C1
C
1
2
C1
C
1
2
2
C
1
220 F
100 F
M25424