Trane XR90 light codes and problem

[Bill Klika]

Hello

Went to turn on our Trane XR90 unit today, and no luck with heat!

Unit is propane run, about 5 years old.

When I try to turn the unit on, it display a series of 3 flashes on the light indicator. The guide code says this is a "draft pressure error." Not sure what this means.

If I set the fan to "on", it blows air in the house, but not hot air.

I have absolutely no experience with this - do I call the repairman or is this something I can do?

Thanks

[jb8103]

You have a pressure switch fault or a failing inducer fan motor. Model number?

[Bill Klika]

Thanks for the help - model number is "TUX1C100A9481AA".

[RegUS_PatOff]

... "draft pressure error."

does the Vent Motor run OK ?

Did any critters build a nest in your Vent system ?

[Bill Klika]

Sorry for the delay in getting back - snowstorm knocked out power until now!

Don't think there are any critters - will check vent motor. Can you provide any help on checking that? Is it as simple as turning fan to on?

Thanks

[RegUS_PatOff]

(burner) Vent Motor , not House Fan

[jb8103]

AKA "inducer fan motor". Do a Google image search for "inducer fan motor" so you'll recognize it inside the furnace door. It draws combustion air from outside, through the combustion chamber where the burners are, then through the heat exchanger, then exhausting to outside typically through 3" PVC or 4" metal duct.

This fan motor (IFM) will come on first when the thermostat calls for heat. It will run for a while, usually 30 seconds or more, before the ignition cycle begins. There are pressure switches (at least one) which will detect the negative pressure caused by the IFM.

In your case a pressure switch is apparently not closing, but this can have a variety of reasons besides a faulty pressure switch.

When you remove the furnace door, very likely there is a door interlock switch which will de-energize the furnace when the door is opened. You can hold this switch closed, but be very careful if you do, because now the exposed wiring is live 120VAC. The IFM should be running when the furnace is running or when trying to start. If not, there is the problem. Touch the motor casing carefully, it may be very hot. Keep your hands away from wires.

If the IFM is happily whirring away, then you may have stopped-up condensate lines. Flexible tubing leads from the pressure switch(es) to a collection box and/or to the IFM casing. Flexible tubing drains the collection box and/or casing into a condensate trap or to a pump or directly into a drain in the floor. Disconnect those one-by-one and see if any water comes draining out. If so that's a problem.

Post pics if you get crossed up about any of this.

[Bill Klika]

Well, I tried several of the options - and indeed, we had hornets make a nest in the exhaust. It now works fine.

Thank you to everyone who had a suggestion!

[kdog]

Did any critters build a nest in your Vent system ?

Good Call reg !!