[Bob Harper]

Homeowner called me into case where gas water heater recently replaced. Original WH pilot kept going out so after replacing several thermocouples, he replaced entire WH but pilot still kept going out. Had gas company in: held match near top WH and extinguished flame. Called me suspecting blocked flue. Cat. I fan assisted furnace common vented with WH manifolded then into breeching. Pull vent connectors and see aluminum liner full of masonry rubble. Chip away and pull manifold with liner attached: liner only about 3 ft. long and turned upwards at end. When alum. connector filled with masonry rubble, blocked flue so vented out WH draft hood.
Why didn't furnace vacuum switch or the fusible link and two high limit spill switches shut down furnace? Why so signs of backdrafting, flame roll out or condensation at furnace? Because it was venting out the draft hood. Why was the WH pilot shutting off? There was a masonry curb around the WH and furance to protect them from wet basement. When the fumes vented out the draft hood, the CO2, being heavier than air, fell to floor displacing oxygen thus suffocating the pilot. Amazing they were still alive.

Note: plastic bushings melted on top brand new WH. Lack of signs on furnace. Raised curb. Galvanized connector cemented into masonry wall yet liner attached inside wall. All clues something wrong. Look at how much the acids ate up this aluminum liner.

One technique to test for CO2 spillage snuffing out pilots is to use your combustion analyzer. When the ambient O2 drops from 20.9% down around 16-18%, this is dangerous and you will begin making CO as the CO2, being heavier than air, displaces the O2.

Furnaces common vented with draft hood equipped WHs defeats the primary safety controls in the furnace by providing a relief opening.

Enjoy!

[Kevin Stewart]

Bob

How old was the reline and did it once go to the top?

[Bob Harper]

The entire liner was about 3 feet! There was a Gelco 8x8 cap up top but other than that it was NOT a full reline. Someone either defrauded the 90 yr old previous owner openly telling them they relined it or the HVAC guy defrauded him by telling him he "fixed" it below. They are trying to locate the old guy to see if he can find his paperwork. The current owner inherited this abortion and lived with it for FIVE years! The only reason I can come up with why they are still alive is the wide open basement window and leaky upstairs. I'm pretty sure the HVAC tech did this because I found another section of this "liner" used as a warm air duct in the basement.