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All wiring should be done in accordance with local and national electrical codes and ordinances.
RED
COMMON
WHITE
CLOSE 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 center terminal (white) has
close-on-rise switch action.
Diagram For Gas Or Oil Fired System With Tankless Domestic Coil
24 VAC
GAS VALVE HIGH LIMIT
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.
BLUE
OPEN ON RISE
OF TEMPERATURE
TRANS.
X
X
Refer to the wiring diagram supplied by the boiler or
burner manufacturer, or to the suggested circuits in-
cluded 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 on the next page shows a typical circuit for a hot
water system having a boiler with tankless domestic coil.
3-WIRE
THERMOSTAT
(USE W-B FOR
2-WIRE THERMOSTAT)
TYPE
809 RELAY
R
B
1
2
W
3
4
JUMPER
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.
3
WIRING
TYPE 668 OIL
BURNER CONTROL
(LINE VOLTAGE)
IGNITION
TRANS.
X
X
BURNER
MOTOR
CIRCULATOR
R
B
W
HIGH
LOW LIMIT
LIMIT
CIRCULATOR
MOTOR
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