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Discussion Starter · #1 ·
I have an American Standard Freedom 80 LP furnace. When it tries to fire the bottom burner will not always light, so it shuts down and tries again. Most of the time it will light on the second try, but sometimes it times out after the third try. I have removed the burners and have clean them with a thin knife. I have removed the orifices and made sure they were clean. I finally hooked up a manometer and got 9.5 to 10"WC inlet pressure. The manifold pressure is the same. The furnace calls for 11"WC. Obviously I can't adjust the regulator to get a higher manifold pressure.Would the lower pressure cause my furnace not to light properly? What should my LP inlet pressure be?
 

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Don't think I have ever seen a furnace that had the same manifold pressure as its inlet pressure.

Should still light okay at 10" manifold. But on horizontal applications, it can cause a problem.

Why can't the reg be turned up to 11"?
 

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Tank low? Sounds silly, but I've have enough calls to empty tanks.....

It doesn't light at all the first time or 2, or lights but then shuts off, retrying after that? Spark ignition or hot surface igniter? (hsi will glow red hot, instead of sparking) if you have a hsi, check the amps to it when it's trying to fire. Hsi's get old and can start to fail to light when the current draw is low. (resistance is climbing due to the stresses that it endures)

Cheers!
 

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Discussion Starter · #6 ·
Tank low? Sounds silly, but I've have enough calls to empty tanks.....

It doesn't light at all the first time or 2, or lights but then shuts off, retrying after that? Spark ignition or hot surface igniter? (hsi will glow red hot, instead of sparking) if you have a hsi, check the amps to it when it's trying to fire. Hsi's get old and can start to fail to light when the current draw is low. (resistance is climbing due to the stresses that it endures)

Cheers!
This is how I actually discovered that it was not lighting the first time. The hot surface igniter was dead. I suspect from having to continually cycle. I replaced the igniter and discovered that the top 3 burners always light initially but the bottom burner does not always light in enough time that the system senses a problem and shuts down. Even when the bottom burner does light it is always somewhat delayed. I have tried moving the bottom burner to the top with the same results, so ruling out a problem with the burners.
 

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Because i only have 9.5 to 10" going into the regulator.
If you only have 9.5 to 10" going into the regulator. You have a gas supply problem between the tank and regulator.

Oh, your calling the gas valve a regulator. It has a reg built into it. But its not considered a regulator.

Your house reg/secondary regulator can be turned up to get a higher pressure to your gas valve.
 

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Discussion Starter · #10 ·
If you only have 9.5 to 10" going into the regulator. You have a gas supply problem between the tank and regulator.

Oh, your calling the gas valve a regulator. It has a reg built into it. But its not considered a regulator.

Your house reg/secondary regulator can be turned up to get a higher pressure to your gas valve.
Sorry for my terminology confusion. Is the secondary regulator something I can adjust? I assume the primary reg is the one on the tank and the secondary is the one where the gas line enters the house. Does it adjust just like a normal gas valve? (clockwise to increase pressure)?
 

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Sorry for my terminology confusion. Is the secondary regulator something I can adjust? I assume the primary reg is the one on the tank and the secondary is the one where the gas line enters the house. Does it adjust just like a normal gas valve? (clockwise to increase pressure)?
Yes, CW to increase.

Tank reg knocks the pressure down to 10PSIG, secondary/house regulator brings it down to 12".

After adjusting it, you need to recheck that all other gas appliances are working correctly.
 
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Take your time doing it. Check both static lockup pressure, and working pressure. (SP= no appliances running, WP = every appliance running, measured at the appliance) SP is always higher, but can't exceed the rated "max inlet pressure" of anything in your house.

Cheers!
 

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Discussion Starter · #14 ·
OK, the static pressure was 10wc. I raised it to 13wc. I adjusted the manifold pressure on the furnace to 11wc. I still have the same problem! I had another identical gas valve and installed that. While I had it apart I cleaned the burners again and reinstalled the bottom burner on top, and the top burner on the bottom. unfortunately it is still doing the same thing!. I tried to take a video of the bottom burner not lighting, but of course it lights when I try to take the video. I think you can get the idea from the video how the bottom burner has a delayed ignition though. Here is the link:
I have no idea what else to check. Any ideas??
 

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And clean the crossover channels?

They are the little burner bars to the top and bottom of each burner. There should be a flame from them during operation.

The flame looks clean and burning well. That's a fairly normal light off, just a hair delayed. Something is distorting the gas flow before lighting.

Cheers!
 

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Discussion Starter · #18 ·
And clean the crossover channels?

They are the little burner bars to the top and bottom of each burner. There should be a flame from them during operation.

The flame looks clean and burning well. That's a fairly normal light off, just a hair delayed. Something is distorting the gas flow before lighting.

Cheers!
Yes. I thought this was going to be the problem from the very beginning. The very first thing I did was to remove them and cleaned the wings on the burner bars. The reason I swapped the bottom and top burner was to see if I had an issue with the burner. Unfortunately, the results were the same.
 

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Inspect the heat exchanger for a crack. Also check the draft the inducer is pulling on the pressure switches.
 
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