inducer motor runs but only opens pressure switch sometimes


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Old 01-04-14, 04:39 PM
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inducer motor runs but only opens pressure switch sometimes

I have an aire-flo 125 BTU 90% furnace.

This is a model where the vacuum line for the pressure switch runs into a codensate drain along with a vacuum line from the inducer motor and a third hose coming from inside of the furnace box.

I have replaced the pressure switch with an OE switch from Lennox. This initially fixed the problem but now it is acting up again.

The inducer motor goes on and runs for minutes or sometimes hours before the pressure switch opens/closes and then the gas valve opens and the furnace operates normally.

This furnace is older and the local technician came out and basically refused to work on it. He says that it needs to be replaced....that I need to stop throwing money at at. The tech left two weeks ago and I found then that the problem was the reset switch up by the burners. I pressed it and the furnace worked....But it must have tripped for a reason. That is another issue but back to the inducer/ pressure issue.

From what I can find most pressure switches work off a vacuum directly from the inducer. That seems natural but mine goes into a condensate drain box. I have not seen this set up on any other furnace on the internet.

I have an open fitting on the inducer that I could hook the vacuum line to but that seems risky but then again that is how the more expensive units do it.

1) Do I need to replace the inducer motor
2) Do I need to replace the condensate drain box....FYI I removed it today and cleaned it out. It had rust in it. This furnace drains a lot of water. Not as much as the A coil but a lot of water. I added an electric pump for the water as it used to back up into the furnace ruining the last pressure switch. Today water backed up into the inducer motor housing that is why i cleaned out the condensate drain box
3) DO I need to get rid of this whole furnace. Not the recommended option

Any help from someone familiar with an older AIRE FLO furnace let me know. Also I replaced all of the hoses for the pressure switch thinking that one might have a leak....no change

Rick
 
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Old 01-04-14, 08:42 PM
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Rick, I'm not familiar with the furnace, but have one thought. Use a pressure meter (manometer, magnehelic, whatever) to measure the pressure at the condensate box, and compare to the set point on your switch. If the pressure is at or above the switch point, then you know that your switch is good, and there is something happening with the inducer motor, an obstruction, or perhaps a leak. If the pressure is below the switch set point, then you switch is not working properly.

Still leaves you with some work to do, but gets you closer to the answer. Is it possible there is an air leak into the condensate box due to the rust (ie has it rusted through somwhere)? That would certainly cause a problem with your inducer fan pulling enough of a negative pressure.
 
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Old 01-04-14, 09:19 PM
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The tech left two weeks ago and I found then that the problem was the reset switch up by the burners. I pressed it and the furnace worked....But it must have tripped for a reason.
That is the flame rollout switch and that needs to be addressed. That would indicate an airflow/exhaust problem or possibly even a heat exchanger issue.
 
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Old 01-05-14, 09:06 AM
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I think that I will pick up a manometer and check the pressure and or purchase a new condensate box. I have a feeling after seeing all of the rust that could be a culprit...not the culprit but one of

The tech that came out referenced a possible broken heat exchanger accounting for the flame roll out tripping.....I can see the flames and they are all the same color. Someone told me that I would see different colored flames.

They safety switch has not tripped in a couple of weeks soIi started to rule that out.

This furnace does not have any indicator lights on it so every bit of advice helps.
 
 

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