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Trane XV90 TUY080R9V3W4 Works fine without Viewport on Boiler Cover..Need Help

Trane XV90 TUY080R9V3W4 Works fine without Viewport on Boiler Cover..Need Help


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Old 01-31-20, 04:49 PM
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Trane XV90 TUY080R9V3W4 Works fine without Viewport on Boiler Cover..Need Help

Ok at this point I need to reach out to the pros..... My system stopped working just blowing cold air. Was giving three red lights--Pressure Switch. Checked pressure switches and they are working properly, 0.3 while inducer and flame on. This is the sequence....Unit calls for heat, inducer motor starts up, sends signal to ignitor which glows, gas valve opens, flame burners come on then stays for 3-5 sec and shuts down. Checked flame sensor cleaned, same thing. Had 1 in stock so I replaced it. Still happening. Checked safety and overload all fine. Ran it without the burner cover, it works fine!!! Removed all condensate lines and p-trap, cleaned all. Removed the blower, cleaned the secondary exchanger and blower. Check intake and exhaust all clear. What am I missing, I'm completely stumped. Your wisdom is greatly appreciated.
 
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Old 01-31-20, 05:09 PM
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Welcome to the forums.

Ran it without the burner cover, it works fine!!!
If you get the three flash fault that the pressure switch is open...... go no further.
You need to find the problem in the exhaust system. It's usually easier to have a manometer connected to that you can actually see the vacuum level to the pressure switch.

This is also a furnace..... not a boiler.

 
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Old 01-31-20, 07:17 PM
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Hi Pete,

Thank you for the reply. I will check the exhaust with my Buddys manometer and get back.
 
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Old 01-31-20, 07:42 PM
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Hey Pete,

Am I checking the pressure switch with my manometer or placing my manometer into the port of the heat exchanger?
 
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Old 01-31-20, 07:55 PM
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You want to tee in the line between the inducer and the pressure switch so that you can monitor the actual vacuum.
 
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Old 01-31-20, 08:43 PM
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Update: Checked both exhaust and intake both are clear. put viewport once unit has started up and unit is working properly. When the thermostat has reach the set temp it shuts the unit down. When the t-stat calls for heat again the system calls, inducer, ignitor, gas valve flame sensor and pressure switch all work but the burner will shut off after 3-5 sec. I will have the manometer tomorrow and check the pressure WC and heat exchanger pressure, incl exhaust. This is actually helping me be a better tech. Thanks for your help.
 
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Old 01-31-20, 08:48 PM
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Just double checked and the pressure switch has hoses from the back to the bottom heat exchanger (90% efficiency unit). From the front of the pressure switches (2 each) I have hoses from each to the gas valve and the burner box (1 stage). So correct me if I am wrong I tee from behind the pressure switches to the 2nd stage heat exchanger?
 
 

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