American Standard Freedom 80 - Furnace Flame Size Problem

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American Standard Freedom 80 - Furnace Flame Size Problem

Postby tchad2012 » Wed Dec 26, 2012 4:04 pm

I'm new to the forum and have had problems since a recent power failure. Had to replace HSI and control board after power company caused an instantaneous power failure.

Everything is working ok now, except for one problem. My furnace is mounted horizontally, and the flames on the burners are okay until I put the louvered furnace cover on. Once I do this, the flames immediately spread outside of the proper distance (spread maybe 2 or 3 inches out). Anyway, this is enough to burn part of the insulation off of the HSI wires. If I remove the cover, the flames retreat to the proper size. So, I'm currently running the furnace with the louvered cover off until I can determine what is causing this strange situation.

Any suggestions would be most appreciated.
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- American Standard Freedom 80 * Furnace Flame Size Proble

Postby Freon » Wed Dec 26, 2012 4:24 pm

From your description it appears you have a draft problem. How old is the furnace and when was the heat exchanger last cleaned. Check the complete flue system for any obstruction like bird's nests or other debris. Not knowing this model I do not know if it has an inducer blower to establish the correct draft. If it does, there may be a problem with the inducer and, or the pressure sensor. For now keep the front off. I would also have someone call for heat while you observe the furnace starting. See if, when the burners first ignite, any flame rolls out of the combustion chamber.
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- American Standard Freedom 80 * Furnace Flame Size Proble

Postby tchad2012 » Wed Dec 26, 2012 7:04 pm

Thanks for the reply Freon.

It does have an inducer blower. Prior to the power failure, I wasn't having any problems. So I'm guessing something else electrical was damaged by the power failure and the subsequent power surge. I've watched the furnace startup process, and when the burner ignites everything is fine....there is no flame rollout. It's only when I put the louvered cover on that I see the flames creep outside of the heat exchanger and get to the HSI wires. Only about 2 to 3 inches of insulation is burned on the wires.
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- American Standard Freedom 80 * Furnace Flame Size Proble

Postby Freon » Thu Dec 27, 2012 12:09 pm

I will assume the new HSI and control board are identical replacement parts. If not, please tell me.

I am still thinking it's improper draft. Try this test. On the furnace locate the draft pressure sensor. It should be close to the draft inducer assembly. Follow the wires to where it connects to the control board. I will assume that when proper draft is established this switch closes completing a circuit that the control board senses. If you unplug the sensor from the control board you'll force an open sensor state. Therefore the ignition process should not happen... no HSI glow or anything. See if this is the case. I want to make sure the draft inducer pressure switch is working correctly.

Who did the change_out of the control board and HSI? If it was an HVAC company you might want to get them involved since they should bear some responsibility.
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- American Standard Freedom 80 * Furnace Flame Size Proble

Postby tchad2012 » Thu Dec 27, 2012 2:12 pm

Thanks for the resply, Freon.

I've discovered something rather interesting. I went into the attic just a few minutes ago to watch the flames after the heat came on. The louvered cover has been off for a couple of days and I've been running the heat intermittently. I don't run it at night because of my fear of a fire.

Anyway, I put the louvered cover back on and the flames immediately crept out to the sides of the holes in the heat exchanger. So, I removed it, again.

I've owned this house for 3 years, and this is the first time I've had trouble with the heat. I've been putting the cover back on the way it came off each time. The reason I know I've put it back on the same way is because there's a sticker on the top of it that has the name of a local HVAC company.

Anyway, just for the heck of it, I tried rotating the cover 180 degrees and putting it back on. Well, guess what....the flames are staying confined to the holes in the heat exchanger. There is no flame creeping out the sides now. The only difference is that the louvers are angled opposite of what they were before. The HVAC company's sticker is now upside down and at the bottom.

So, does this make any sense. Does the direction of the louvers make a difference. The louvered cover has been in the other position for at least 3 years.
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- American Standard Freedom 80 * Furnace Flame Size Proble

Postby Freon » Thu Dec 27, 2012 3:25 pm

It makes sense because you've changed the flow direction of air into the combustion chamber. However I would never expect a main burner flame to be so sensitive to the flow direction of the combustion air entering the combustion chamber.

Does the main burner flame appear to waver easily. Who did the HSI replacement and did they play with the gas pressure at the gas valve. It is possible the gas pressure could be an issue and the power problems are just a coincidence. See if the gas company can come, free of charge, to verify the pressure to your house. I will assume no technician messed with the gas valve settings. At least now you have a useable furnace that won't ruin the HSI. There should also be a flame roll-out safety but double check.
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- American Standard Freedom 80 * Furnace Flame Size Proble

Postby tchad2012 » Thu Dec 27, 2012 9:18 pm

Thanks again, Freon for your comments and suggestions.

I replaced the HSI and control board myself with American Standard (now Trane) OEM parts. I didn't fool with anything else. So, I'm at a complete loss to explain the flame problems. Nothing was adjusted or fiddled with other than the HSI and control board. Both were quite easy to replace.

The main burner flames appear to be strong and shoot right into the heat exchanger, so in my opinion, they do not waver easily.

I will call the gas company and see if they will check the pressure.

Regarding the flame roll out safety, this unit is supposed to have such a shut off switch, but the safety mechanism has never activated.
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- American Standard Freedom 80 * Furnace Flame Size Proble

Postby Freon » Fri Dec 28, 2012 4:18 pm

I am coming back to the draft and flue system. The draft inducer is on the flue side of the heat exchanger. Possibly something is impeding the air flow through the heat exchanger. Depending on the material the heat exchanger is made from there could be debris of some kind. See if accessing the heat exchanger is easy. Usually there is a clean-out access plate.

Another possibility is a crack in the heat exchanger allowing house air into the flue system and thereby making the pressure switch close but due to air flow not 100% from the combustion chamber. This is a long shot.

I would jumper the inducer sensor to make sure it is working and the true draft pressure is being established. Check the chimney and anything along the path from the combustion chamber to the open air outside. Sorry I can't be more help.
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- American Standard Freedom 80 * Furnace Flame Size Proble

Postby tchad2012 » Thu Jan 03, 2013 7:36 pm

Thank you Freon for your reply. I intend on removing the burners and cleaning them and will inspect the heat exchanger. I'll also check the flue.

Regarding "jumping" the inducer sensor, I must admit that I don't know how to do that.
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- American Standard Freedom 80 * Furnace Flame Size Proble

Postby Freon » Fri Jan 04, 2013 12:09 pm

We need to test the draft pressure switch.

If you look around the draft inducer assembly you should find 2 wires going to an object located on a flue pipe close to the furnace. That is the pressure sensor. Hopefully the 2 wires connect using spade connections so you can simply pull them off and tape them together TEMPORARILY. Turn off the furnace power, remove the 2 wires from the pressure switch and tape them together so they make a good electrical connection.

You have now jumped the draft pressure switch so it will be closed and tell the control board to run the furnace as usual. Using your multimeter, check the continuity of the pressure switch. With the furnace off and the inducer not running, there should be no continuity, infinite resistance. The switch is open.

Now turn on the power and call for heat. Check the switch again for continuity. It should now show continuity, zero resistance. The switch is closed.

After this test, turn off the power to the furnace and reconnect the wires to the pressure switch.

Let us know what you find.
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