The DPDT relay has Normally closed contacts from S1 and S2-FS (Red Dots) to the Flame Sense Voltage Terminals (Blue Dots).
S2-FS should have 90 volts to ground all the time (except when the ignitor is energized) to detect a Flame when no call for heat.
The Top Blue Dot is connected to S1, but the top blue dot is a dead terminal.
The bottom Blue Dot has 90 volts AC connected to S2-FS, which sends voltage to the HSI (Hot Surface Ignitor).
The voltage will go to S1 through the HSI (Hot Surface Ignitor)(Orange Line), but there will be no current because the top blue dot is not connected to a ground or neutral.
So, if you measure from S1 to Ground or S2 to ground, you should get 90 volts AC.
If you measure from S1 to S2, you should get 0 volts.
During the 20 second ignitor heatup, S1 connects to 120 volt line power and S2 connects to Line Neutral and the HSI should use 3.9 amps (450 watts).
Then the relay switches back to Flame Sense mode.
S2-FS should have 90 volts to ground all the time (except when the ignitor is energized) to detect a Flame when no call for heat.
The Top Blue Dot is connected to S1, but the top blue dot is a dead terminal.
The bottom Blue Dot has 90 volts AC connected to S2-FS, which sends voltage to the HSI (Hot Surface Ignitor).
The voltage will go to S1 through the HSI (Hot Surface Ignitor)(Orange Line), but there will be no current because the top blue dot is not connected to a ground or neutral.
So, if you measure from S1 to Ground or S2 to ground, you should get 90 volts AC.
If you measure from S1 to S2, you should get 0 volts.
During the 20 second ignitor heatup, S1 connects to 120 volt line power and S2 connects to Line Neutral and the HSI should use 3.9 amps (450 watts).
Then the relay switches back to Flame Sense mode.
