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INSTALLATION CONT.
The R-B contacts of the low-limit circulator control maintain
domestic hot water at the desired temperature year-round.
When the thermostat calls for heat, the burner starts. The
circulator also starts if the R-W contacts of the low-limit circulator
control are closed.
If excessive boiler temperature causes the high limit to open, the
circulator continues to run but the burner shuts down until the
high limit recloses.
Pipe Insulation Should Cover Shield
Containing Element.
If low boiler temperature causes the R-W contacts of the low-
limit circulator control to open, the burner stays on but the
circulator stops until the R-W contacts reclose.
When the thermostat is satisfied, the circulator stops. The
burner also shuts down if the R-B contacts of the low-limit
circulator control are open.
Convenient Installation – May be mounted
vertically, horizontally, or on an angle. Will
not affect operation of control.
WIRING
All wiring should be done according to local and national electrical codes.
RED
WHITE
BLUE
COMMON
CLOSE ON RISE
OF TEMPERATURE
OPEN ON RISE
OF TEMPERATURE
This control has a single-pole, double-throw snap action switch.
The top left-hand terminal (red) is the common terminal. The top
right-hand terminal (blue) has open-on-rise switch action. The
bottom centre terminal (white) has close-on-rise switch action.
Diagram for Boiler with Tankless Domestic Coil
X
X
Diagram for
Gas-Fired System
24 VAC
GAS VALVE
HIGH
LIMIT
TRANS.
R
B
W
W
1
4
2
3
B
R
X X
3-WIRE THERMOSTAT
(USE W-B FOR
2-WIRE THERMOSTAT)
TYPE 668 OIL
BURNER CONTROL
(LINE VOLTAGE)
IGNITION
TRANS.
BURNER
MOTOR
CIRCULATOR
MOTOR
HIGH
LIMIT
JUMPER
JUMPER
TYPE 1127
LOW-LIMIT
CIRCULATOR
CONTROL
N
LINE
HOT
Refer to the wiring diagram supplied by the boiler or burner
manufacturer, or to the suggested circuits included with the
primary control. The information below shows the terminals to
use for the various applications.
Limit Control: When used as either a high limit control or as a
low limit control, use the open-on-rise terminals (red and blue).
Circulator Control: When used as a circulator control, use the
close-on-rise terminals (red and white).
Combination Low Limit and Circulator Control: For this
application, all 3 terminals are used. The wiring diagram below
shows a typical circuit for a hot water system having a boiler with
tankless domestic coil.