Primary Controls Flashcards
The safe, automatic operation of an oil heat system is dependent on the interaction between what devices?
- thermostat
- primary control
- limit controls
What are the three main functions of a primary control?
- To respond to thermostat
- To respond to the limit controls
- To control start up,run cycle & shutdown of the oil burner.
How does the primary control accomplish its mission?
- Reacting to pressure or a sense of flame.
- managing oil burner startup by checking for flame before energizing ignition transformers etc
- burner shutdown once the thermostat is satisfied or the limit control opens.
Do primary controls also have low voltage circuits?
Yes 24v to accommodate thermostats and other devices.
For the primary control to activate the oil burner what must happen with line and low voltage?
Both circuits must be closed. (If either the thermostat or limit control is open/satisfied the primary control will not activate the burner.
If a primary detects a flame what will it do?
It will not activate the oil burner for startup if the control senses flame during the off cycle.it prevent fuel being pumped into the unit that has a fire before start up.
What are the two types of primary controls?
-Thermal Mechanical
(Stack switch)
-Cad Cell (Newer/Modern)
How does a thermal mechanical switch work?
Utilize bimetals to detect flame and to mechanically open or close electrical contacts to provide burner control.
If a stack relays bi metals are not sufficiently heated what will happens?
A safety switch will shit the burner off in 75-120 seconds and cannot be started again until ten safety switch cools down and is manually reset.
If the control does not have TT terminals what terminals do you then connect to?
W & B
What two components are the cad cell primary’s control circuits composed of?
- Flame Detector
- Primary Control
