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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22679
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I keep getting an FLU error code on my boiler. The vent is

Customer Question

I keep getting an FLU error code on my boiler. The vent is not blocked, it happens not matter what troubleshooting I do or what the manual says and there's no problem with the condensate cup and drain not sure where to go now add sometimes it will fire up and run but most of the time the error comes up within seconds
Submitted: 2 years ago.
Category: HVAC
Expert:  BillyHvac replied 2 years ago.

have you tried bypassing the vent switch?

Customer: replied 2 years ago.
I've tried that as well as the float switch for the condensate cup. It will fire up and work briefly and then the flu code comes up. I can't seem to narrow it down to a specific issue. The total exhaust and intake runs are well under the max distance for 2 inch pipe and the exhaust is angled to allow the condensation to drain to the cup where it drains out and is flowing fine.
Expert:  BillyHvac replied 2 years ago.

so bypassing the vent switch did not result in proper operation?

Customer: replied 2 years ago.
No only a brief fire up and then it quits again with the error
Expert:  BillyHvac replied 2 years ago.

if the vent switch is bypassed it should not code that there another safety in series in this loop?

Customer: replied 2 years ago.
In the troubleshooting guide it says that code comes up if the flue vent is blocked or damaged, if the vent pressure switch is not working, the condensate cup is excessively full and not draining or the float switch is not working and to make sure the 2 pin condensate cup connector is securely plugged in to the socket on the bottom of the heater. I have made sure all the wiring is intact and have good connections.