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Diagram For Gas Or Oil Fired System With Tankless Domestic Coil
X
X
24 VAC
GAS VALVE
HIGH LIMIT
TRANS.
The R-B contacts of the low limit-circulator control main-
tain 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.
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.
W
1
4
2
3
B
R
JUMPER
W
BR
X X
TYPE 668 OIL
BURNER CONTROL
(LINE VOLTAGE)
3-WIRE
THERMOSTAT
(USE W-B FOR
2-WIRE THERMOSTAT)
IGNITION
TRANS.
BURNER
MOTOR
CIRCULATOR
MOTOR
LOW LIMIT
CIRCULATOR
HIGH
LIMIT
TYPE
809 RELAY
HOT
LINE
N
Controls With Adjustable Differential
1. Insert a screwdriver in the centre slot and turn the dial
until the right hand indicator “B” points to the lowest
temperature of the cycle.
2. Turn the differential adjusting screw “C” until the left
hand indicator “D” points to the highest temperature
of the cycle.
The left-hand indicator points to the temperature at which
the contacts open on high limit and low limit applica-
tions. On circulator applications, the left-hand indica-
tor points to the temperature at which the circulator will
start.
On combination low limit and circulator applications,
the left-hand indicator points to the temperature at which
the low limit stops the burner and permits the circulator to
run.
Controls with a Fixed Differential
Insert a screwdriver in centre slot “A” and turn the dial until
the fixed indicator “B” points to the highest desired tem-
perature of the cycle.
The fixed indicator points to the temperature at which the
contacts open on high limit and low limit applications.
On circulator applications, the fixed indicator points to
the temperature at which the circulator will start.
On combination low limit and circulator applications,
the fixed indicator points to the temperature at which the
low limit stops the burner and permits the circulator to run.
SETTING THE CONTROL
WIRING (CONT.)
“B” FIXED INDICATOR
“C” DIFFERENTIAL
ADJUSTING SCREW
“D” MOVABLE INDICATOR
“A” ADJUSTING
SLOT
“B” FIXED
INDICATOR
“A” ADJUSTING
SLOT