Has Furnace Fails to Ignite Intermittently

Gumby77

https://youtu.be/9a-LrE7eq2k


The draft inducer on my furnace sometimes starts and stops before the burner and blower finally go. Other times the furnace works perfectly normal. This is a Lennox 193UHE. It's only a couple months old and in a new house. No other exhausts on the furnace pipe. I have replaced the honeywell thermostat with a nest but the problem was there before the switch. I have changed the thermostat recently but the problem was there before that change. 

HVACNUT

New house to you or new construction?
At only a couple months old, the installer, and or GC is responsible. 
Why are you here? Have you contacted them?

Gumby77

Yeah it's new construction. I'm going to contact them Monday. It was pretty cold here this weekend and I just wanted to kick start things just in case it went out and I couldn't get anyone in here right away. I really like learning about issues so at least I'm familiar when the pro comes in, plus it's good knowledge for future reference. Thanks. 

EBEBRATT-Ed

Sounds like your original installer should take care of this.

On a call for heat the draft inducer starts first
Then he hot surface ignitor glows
then the burner starts
then the main blower comes on

Check the flue pipe for any obstructions, could be the pressure switch that proves that the inducer is running might be faulty or it's connections plugged.

Is this a high efficiency furnace with PVC exhaust pipe?

Make sure the condensate drain is clear and the furnace isn't holding water

But in any event you need a professional to look at this

Gumby77

I've had hvac company out 4 times. They've replaced the control board, pressure switch, gas valve and inducer motor to no avail.  It still throws code 11 "pressure stuck closed prior to inducer motor startup". I continually bring up the condensate piping to them cause the pitch of the piping after the trap is negative and it holds water in the drain pipe. I noticed also that there is no vent tube on the vent outlet of the trap. The instructions explicitly state vent tube must be minimum 1" above condensate outlet and max of 2" above. My wisdom is could this cause issues with the pressure switch? They don't seem concerned with this. 

pecmsg

Where's the pipe that goes up from the "T" go to?

Gumby77

pecmsg said:

Where's the pipe that goes up from the "T" go to?

Sorry I should have labeled that. That is the drain from the ac evaporator. There is another vent above this for that drain line.