I have called this out for evaluation by a qualified HVAC tech, but I wanted your opinion on what I think.
There was corrosion from a previous leak inside of the furnace. It had corroded a small hole in the plate under the induction fan. My thoughts are that with the hole the circulation fan in the base of the unit can now pull air (incl gases)from the combustion area of the furnace and circulate it around the home.
I would say you are correct, the hole is under the induction fan, the pic is was taken underneath in fan compartment right? IMO that furnace should be replaced unless it is possible to remove the rusted metal and replace it, probably not worth the trouble, but let the HVAC tech make the call as you did.
You are correct. But your only job is to observe and report what you see.
The rest is up to someone else. Fix/Replace, who gives a crap?
#1 It is broken, and a life threatening hazard. #2 I would red tag the thing and notify Agent/Home Owner - Tenant immediately.
What to do “NOW” is more important than what to do “Next”.
The return plenum has a much higher negative pressure than the flue. It’s not “if” , it’s about “how much” combustion gas is discharged into the house. When the induced draft fan shuts off, the blower keeps running and pulls everything backwards.
HE gas furnace have a sealed combustion/heat exchanger and that corrosion/hole shown in the picture is not in the combustion/heat exchanger. The mid efficiency doesn’t have a sealed combustion/heat exchanger and any CO leakage could get recirculated by the furnace circulation fan into the home.
Thanks for the info David!
In my initial response, I was thinking of a sealed combustion unit and not a unit where the endshot burners are open to the blower compartment (see attached) which is why I ask for a pic from further away.