furnace technical help needed

[John Arnold]

This is a 10 year old Nordyne furnace.
Can someone tell me what this tube is called and why it might be burned?

[Steven Saville]

The photo doesn't show where the tubing terminates so I would guess that it is connected to a diaphragm switch above which closes when the draft inducer produces enough differential between atmosphere and combustion chamber indicating proper draft and allowing the gas valve to open.

I don't see any scorching around the tubing connection on the draft inducer, so it may just be discolored due to long term exposure to hot combustion gas.

[John Arnold]

Thanks. My photos of this furnace are somewhat lacking.
Here is a similar plastic tube with foil on the ends just lying there. At first I thought it was a crack pipe or something. Hey, maybe the installer was smoking crack! That could explain the dimmer switch that controls the fan (see separate thread).

[Bob Cone]

My vote would be for a pressure switch input- need better pictures to tell for sure- but 10 year old furnace, with obviously a inducer blower assembly right there would need some sort of safety check strategy, typically via a pressure switch monitoring negative pressure in the collector box vs atmospheric pressure

[John Arnold]

My vote would be for a pressure switch input- need better pictures to tell for sure- but 10 year old furnace, with obviously a inducer blower assembly right there would need some sort of safety check strategy, typically via a pressure switch monitoring negative pressure in the collector box vs atmospheric pressure

Bob - Thanks. Any particular worries about that scorching at the bottom?

[Bob Cone]

The tubing used is often a high temp variety- I have never seen the tubing in a translucent material.

My question is if someone may have substituted a generic tube for a quick fix... Best get a HVAC guy in there to take a look...

[Bob Harper]

The amber colored tubing in the first pic looks like latex such as used in medical applications. That would explain the heat damage. Depending upon the location of the sensing port, tubing should be silicone or neoprene.

I would recommend an HVAC inspection with combustion analysis. Having this along with a goofy modification such as a dimmer on an inducer is a red flag.

[John Arnold]

...a goofy modification such as a dimmer on an inducer is a red flag.

Bob H. - Thanks. The dimmer is actually on the air handler blower, though.

[Bob Harper]

Dimmer on the blower sounds like they are trying to get more heat by driving up the delta T with a lower fan speed. That would account for the heat damaged tubing. All the more reason to get a tech in their who knows combustion analysis.

good pickup!