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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8391
Experience:  Furnace, A/C and heat pump specialist.
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, I recently sucked in a lot of water into my trane

Customer Question

JA: Thanks. Can you give me any more details about your issue?
Customer: I recently sucked in a lot of water into my trane xe90 when snow went over the air intake it flooded the system and sucked water into the pressure switch it was full of water and i got a two flash error had a guy come look at it, he fixed two flash and it became three flash i bought a new pressure switch and installed and it fired up fine but when I put the cover back on the furnace i'm getting a three flash error again when i pulled the tube to pressure switch from the box where the burners are it worked fine again so it seems like the switch is sensing pressure in that box
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Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Did you or tech drain all water from inducer vent motor if it had water inside?

Customer: replied 1 year ago.
there was no water in the inducer vent motor
Customer: replied 1 year ago.
furnace runs fine if the plate is off the furnace (that is what you call the box that contains the burners and igniter correct?)
Expert:  airheatman replied 1 year ago.

OK. now at this point if you remove hose from inducer to pressure switch is there any water in it?

Customer: replied 1 year ago.
no, all water out
Expert:  airheatman replied 1 year ago.

OK next check the drain hoses and make sure no water is backing up in drain.That will cause same vacuum issue.

Customer: replied 1 year ago.
checking now
Expert:  airheatman replied 1 year ago.

Take your time. Make sure man drain line is free and clear and no water backed up in any hoses.

Customer: replied 1 year ago.
no backup
Expert:  airheatman replied 1 year ago.

OK did you use excact replacement switch as what was there from factory?

Customer: replied 1 year ago.
exact honeywell c341825p24
Customer: replied 1 year ago.
switch is only triggered when hose is connected to burner box and cover is on. when cover is off it runs fine
Customer: replied 1 year ago.
also runs fine with cover off and hose taken away from box and plugged
Customer: replied 1 year ago.
sorry, last one was cover on
Expert:  airheatman replied 1 year ago.

Ok now we know we either have an issue with vacuum or switch since it works with cover off.The usual causes are:

Blocked vent

Obstructed intake

Water or debris blocking hose

Defective pressure switch

Defective inducer not pulling sufficient vacuum

Defective gasket causing vacuum loss

Defective secondary heat exchanger

Next step in verifying is going to be to get a vacuum pressure gauge and that reads water column and see if the issue is with switch or vacuum. Possible you got a bad switch improperly calibrated.

Customer: replied 1 year ago.
where would the defective gasket be located? Checked vent and intake, they look clear outside. Vent seems to be venting right in furnace. Inducer motor seems to be doing job when furnace panel is off. I found and patched small hole in hose to pressure switch (thought I had found the problem there but unfortunately same results after hole closed).
Expert:  airheatman replied 1 year ago.

Gasket will be where inducer mounts to unit.Did you cycle power off and back on after repairing hose to reset board?

Customer: replied 1 year ago.
to reset board you just need to do on/off, on/off, on within 30 secs? I went for more on/offs than that.
Customer: replied 1 year ago.
went with on/off switch on the furnace rather than at the thermostat
Customer: replied 1 year ago.
something interesting happened when i went to make sure board was reset. have plate to furnace unscrewed. it won't trigger the switch if the plate is in the bracket but loose. when the furnace fired up, i noticed that the plate was pushed out by air right after the gas ignited. After that, I pushed the plate flush to see if the switch would be triggered when the furnace is heating. it has been running for about 5 minutes sealed without triggering the pressure switch.
Expert:  airheatman replied 1 year ago.

Watch and see if it stays running .

Customer: replied 1 year ago.
Stayed running until it got thermostat up to 70 in house. Once 70 was reached it shut down. Turned up to 71 to see if it would restart and pressure switch was triggered. Think its safe to say that air pressure from gas ignition is tripping switch.
Expert:  airheatman replied 1 year ago.

So will switch close and stay running now?

Customer: replied 1 year ago.
Expert:  airheatman replied 1 year ago.

Excellent.

If you have further questions, please let me know.

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Customer: replied 1 year ago.
no, it only will start if i leave plate open a little bit. if i leave plate closed i get three flash error when heat kicks back on.
Expert:  airheatman replied 1 year ago.

Sounds like you are still losing vacuum then.I would either get someone to check the actual vacuum with a gauge or try a different pressure switch.