GF - G 2
Flame Roll-Out Limit Switches
Purpose of the flame roll-out limit switch
Flame roll-out limit controls (Figure 1) protect against
abnormally high temperature in the furnace burner area.
Figure 1
These limit switches are 24 volt operated automatic
reset switches that open when the temperature they
sense exceeds the switches open setting. The open
temperature of the switch is normally not listed on the
part.
Electrical circuit
The flame roll-out switch circuit is powered by 24 volts.
The flame roll-out switch is wired in series with other
furnace limit switches (Figure 2.)
Integrated furnace controls (IFC) monitor the position
of limit switches during a call for heat via a connection
to a 15 pin plug (Figure 3) located on the IFC board.
Figure 3
The plug has several pins that connect to the furnace
limit devices. One pin sends 24 volts potential to the
limit switches and the other pins receive the 24 volts
potential back to the IFC. When a call for heat is
received by the IFC, the IFC sends 24 volts out to the
high limit circuit. If the limit switch is open, the IFC
will not receive 24 volts back.
If the limit or any of the other limits open, the furnace
will shut down burner operation and run the furnace
blower and induced draft blower in an attempt to cool
down the furnace.
Figure 2
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