Spark Ignition only fires on Emergency/Aux setting


Old 12-13-18, 10:21 AM
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Spark Ignition only fires on Emergency/Aux setting

Iím a new DIYer and have been working on an older Bryant 90+ furnace with heat pump and spark ignition.

Just the other day I started noticing that it was blowing cool air on the heat setting. Opened the panel and found no flame. Reset the system and waited a bit before re-firing.

This time it worked - things ran fine until late that evening and no flame again. After some cleaning and trying to reach the flame sensor (which unfortunately I could not get to) I put it all back together and tried again. No luck.

So, just out of options I tried my Emergency/Aux setting. And sure enough, it ignited and I had heat again. I let it get the house back up to temp, and then switched back over thinking maybe itís going to fire now since it did on emergency. Nope.

Admittedly, Iím new to this, but does anyone have a reason why it only ignites on the emergency setting?

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Old 12-13-18, 10:59 AM
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Welcome to the forums.

You have what is called a dual fuel system.
You need to be using a thermostat that specifically says for dual fuel use. With a heat pump and a gas furnace..... they cannot run at the same time. The heat from the furnace will damage the heat pump.

With a typical thermostat.... when used with a heat pump...... if the room temperature is 3 or more degrees below the set point..... the AUX heat turns on. With a standard system.... that would mean the electric coils are activated and run WITH the heat pump until the room temperature rises. Then the electric coils are shut off and the heat pump runs on. If you have a gas furnace.... that means they both run at the same time. That's bad. E heat is the gas furnace only.

With a dual fuel stat..... when the room temperature is 3 degrees or more under the set point.... the heat pump is shut down and the AUX/gas furnace is run. When the room temp gets close to the set point..... the furnace shuts off and the heat pump takes back over. E heat is the gas furnace only.

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