WIRING
All wiring should be done in accordance with local and national electrical codes and ordinances.
If the boiler or burner manufacturer recommends a wiring diagram, then follow such recommendations. If none is offered, this diagram shows a suggested circuit.
LOW LIMIT APPLICATION — This diagram shows a common circuit on an oil fired heating system that also heats domestic hot water which is stored in a tank.
Low limit control maintains domestic hot water temperature all year round.
When thermostat calls for heat, burner and circulator operate.
| FIELD | THERMOSTAT |
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| |
| INSTALLED |
|
TYPE 668 OIL | JUMPERS |
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|
| |
BURNER CONTROL | TYPE |
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(LINE VOLTAGE) | 829A RELAY |
|
T |
|
| T |
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| |
T |
|
|
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HIGH LIMIT |
|
| T |
5 | 3 | 1 | |
CONTROL |
|
| HOT |
IGNITION |
|
| LINE |
TRANS. |
|
| |
|
| 2 | |
| 4 | N | |
|
| ||
| 6 |
|
|
| LOW LIMIT |
|
|
| CONTROL |
|
|
BURNER |
|
|
|
MOTOR | CIRCULATOR MOTOR |
| |
|
| ||
SETTING THE CONTROL
CONTROLS WITH ADJUSTABLE DIFFERENTIAL
The movable indicator points to the temperature at which the contacts open. The fixed indicator points to the temperature at which the contacts close. The difference between these two indicators is the differential.
“B” FIXED INDICATOR
“C” DIFFERENTIAL ADJUSTING SCREW
“D” MOVABLE INDICATOR 
(CUT-OUT POINT)
“A” ADJUSTING
SLOT
To set the control:
1.Use a screwdriver in the adjusting slot (A) on the front of the control to turn the dial so that the fixed indicator (B) points to the temperature at which the contacts will close.
2.Turn the differential adjusting screw (C) until the movable indicator (D) points to the temperature at which the contacts will open.
2
