Heat exchanger

[Marc M]

This look cracked? Kind of looks more like rust but just looking for other opinions.

[Nick Ostrowski]

It just looks like surface rust around the seams to me.

[Marc M]

Kind of what I thought, But its worth checking here in the event one of you experienced this already...
Thanks

[Eric Barker]

No visible crack to me. The ones I find tend to be a bit higher.

[Marc M]

No visible crack to me. The ones I find tend to be a bit higher.

Thanks, I've never actually seen a weld split, obviously wanting to error on the side of caution.

[Garry Sorrells]

Thanks, I've never actually seen a weld split, obviously wanting to error on the side of caution.

Did you run a CO test in the plenum or up stream from exchanger ?

Reason being that if it is a crack opens up on heating.

[Eric Barker]

Did you run a CO test in the plenum or up stream from exchanger ?
That approach can be misleading. Depending upon where a crack might be on the exchanger, a test for combustion gas may not point to a crack that is present. Being that the air flow is after the blower, it's under pressure and could be pushed into the exchanger rather than the gas leaking out.

[Garry Sorrells]

That approach can be misleading. Depending upon where a crack might be on the exchanger, a test for combustion gas may not point to a crack that is present. Being that the air flow is after the blower, it's under pressure and could be pushed into the exchanger rather than the gas leaking out.

Misleading if used as the only test, yes.
A CO reading would say something. No CO reading just says that there was not reading, not that all is fine. Like walking a roof. You may find nothing but it still may have defects. Just another test.

Typically is why the HI will beg off the furnace and suggest a HVAC do an exhaustive inspection. All about time and liability.

[Zibby Bujno]

CO test in plenum or EA (excess air) in exhaust will tell you if heat exchange has a crack.
CO test with furnace fan running. EA test with fan not running and then running, change in EA numbers will show leak. Again these tests should be performed by HVAC tech equipped with combustion analyzer.