Trane 80% problem, need help

Kevin_12

I went on a late night call, it was an upflow Trane 80% Model TUD080R936 2 stage 1995, any way the roll out link was blown. This is a typical install in a basement. I jumped out the link to see what was going on. The low speed flame came on and low speed inducer also. Then the blower came on and the flames were coming out of the chamber. It was late and i assumed the heat exchanger was bad. I put a new exchanger in it 2 days later and it still rolls out when the fan comes on. its fine before fan.
HELP

Tom K

trane

> I went on a late night call, it was an upflow

> Trane 80% Model TUD080R936 2 stage 1995, any way

> the roll out link was blown. This is a typical

> install in a basement. I jumped out the link to

> see what was going on. The low speed flame came

> on and low speed inducer also. Then the blower

> came on and the flames were coming out of the

> chamber. It was late and i assumed the heat

> exchanger was bad. I put a new exchanger in it 2

> days later and it still rolls out when the fan

> comes on. its fine before fan. HELP

Paul Mitchell

Oh boy that is brutal...

changing a heat exchanger is bad enough...Here is a couple guesses and what not. Is the chimney clear? Is there enough secondary air to the basement? Maybe the basement is sealed off and the blower is actually pulling the flame out? What did the customer change? Ran fine till the other day? I think it is something external of the furnace. Keep us up on this one would like to know the outcome.
Paul

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Contractor"

Dale

I agree with Paul

also I would just pull the vent outlet off temporarily and open the basement door and fire it up, if it rolls out then I think you have a bad fit where the top or bottom of the sections mate to the front bulkhead.

Pat Clark

Trane 80%

Removing the flue and checking will tell you if the problem is in the furnace or the flue. If in the flue, first check to make sure the flue is installed to the manufactures specs in regards to size length, type of pipe (if you can't find that information, feel free to email me and I will send it to you). If so check to see if the termination is correct, then check to see if the flue is dirty and needs to be cleaned.

If the problem is in the furnace, make sure there is no obstruction in the flue connection from the heat exchanger, if not, the next thing to check is the inducer motor itself, check for an obstruction in the housing, check the amp draw, and if possible the rpm to verify it is working correctly.

It is important to find the problem before replacing parts whenever troubleshooting a problem. I always ask myself "Why" once you find the answer your problem is solved.

Hope this helps.

Pat

masterplumb

Did you check

the gas pressure (assuming gas) with a manometer?

jim lockard

Are your

Are your filters clean how about your return? what happens when you run the furnace with the lower door off ? does the fire still back out of the box? Did you check the pressure on the inducer draft fan? is the pressure switch stuck? can not recall if that model is radient senser or flame sensor? good luck let us know

jim lockard

fuel

are you burning Nat or LP in the furnace if LP with 2 stage gas valve you must set/check the pressure. could gas valve have failed or been toyed with?

tim smith_2

Trane 80% furnace.

I am suspecting a return air is open to furnace room and when the blower comes on you get back out of flames. The flue idea would not make sense as it does not happen until the blower comes on. I too would have made the assumption of a bad heat exchanger but I would have 1st checked for any negative drafts in room or I would have pulled heat exchanger and checked for any defects before replacing heat x. Good luck. Tim

Kevin_12

1st of all, this was a late night call and I don't know how it is where you work but where I work you work 11-13 hours a day. Ok, I was tired and yes, I should of checked into this furnace even farther, but it did seem like a bad x-changer. Our company has sent over another tech and he said that the circuit board is bad and when the blower comes on the voltage to the inducer went way down, and slowed down and caused low vacuum through the furnace. Thanks for all your help.
Now get this one, I went on the same type furnace the other day for a noise. I walk up to this furnace and the flue is pretty rotten. It goes to a masonary chimney with a flue liner kit and a water heater on it. Natural gas. I turn it on and the inducer shook unbeileably bad. I took the flue down and the square to round adaptor crumbled. There were more than half the blades missing on the wheel. The heat chambers collector plate was fried too. No a/c so I took a plenum register off and the heat exchanger looked new still. The water heater flue was fine. I found that this furnace was running high speed inducer with low fire. Any one else seen this? This one was a 1997 model.

jim lockard

metal fan blades

Kevin--I have seen the metal fan blades on inducter draft fans crumble. The draft fans with plastic blades seem to fare better.

rob

Curious....

as to why the pressure switch did not pick up the drop negative pressure? I quess it must be a ported type or have a slow response time to prevent nuisance trips. BTW- I has a call the other day (Amana 80%) where the ignition sequence was ok. About two minutes after the fan came on, the burner would shut down. Troubleshoot till I was ready to throw in the towel. Voltage dropping out to gas control and dropping out to IC module. To make a long story short and to add to my learnning experience, the evaporator coil was soiled enough to raise the deltaP through the heat exchanger that the p/s was tripping. Open up the plenum and problem solved. Turns out the htex must have a pin hole(s) that allowed ther elevated delta P to trip the p/s.
We recommended a new furnace and installed. Like Rosanna Rosanna Addana- "it's always something".......

Kevin_12

rob

I guess because it was the low flame pressure switch and even with some blades missing, it was running high speed. These folks bought a new furnace.