GF - G 4
Flame Roll-Out Limit Switches
Using voltmeter
Step 1
Call for heat.
Step 2
Place your voltmeter leads across the limit switch
terminals (Figure 9.)
Step 3
You should measure 0 volts if the limit is closed (Fig-
ure 10.) If the limit is open, you will measure 24 volts.
Causes of flame roll-out trips
• Low gas pressure
• A lack of combustion air
• Plugged burner orifice
• Plugged heat exchanger
Figure 9
Figure 10
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