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I'm really just practicing posting pics, but here are a few from my last inspection.

If anyone has something to say about the flue arrangement, I'd be interested. Induced draft gas furnce, natural draft water heater.

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The "attic mold" looks like repeated frost build up and melting on the underside of the roof decking due to inadequate ventilation and or insulation. The "Tee" in the vent line needs a permanent seal at the base, appears to held in place by duct tape. Was there a rain cap at the top of the vent line, there looks to be mineral deposits on the joints and bottom of the pipe? Lots of double taps on the panel, but the #12 doubled up with the #6 needs some attention.

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The duct tape was the seal.

The attic had 6 12x12 vents, unfortunately none of them had rain caps so theye were really 6 12x12 holes. Two vents were missing completely.

The stuff on the sheathing was a mix of the frost residues..(there was only three inches of insulation) and mold.

The number 12 double tap was feeding a 60 amp subpanel for the dryer.

No ground what so ever was installed.

I'm ineterested in the flue configuration, with the furnace exhaust dumping into the horizontal run. Any thoughts?

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I think the installer probably installed it that way so that cleaning that flue will be a straight shot that only requires taking off the cap at the bottom, rather than disassemble the flue.

The horizontal run has a slight upward pitch that is probably enough, given the short run from that Tee, but the connection at the Tee before the flue violates the 'one bend of no more than 60° rule'. Also, the pipes from the furnace and water heater look like they are single-walled pipe. Is that basement heated? If not, single-walled pipe used in an unconditioned space in your climate will cause rapid cooling of exhaust gases that will impinge buoyancy.

The mineral salts are a clue to this last. The exhaust is cooling where those two 90° bends are slowing flow. The gas is cooling and the acid is eating away at the zinc in the galvanizing, creating the mineral residue. I don't see a lot of salts on top of that water heater (Is it new) or around the collar at the furnace (how about inside?), so maybe that stack configuration is meant to work like a drip leg.

It doesn't seem to be as bad as it could be though. I had a similar one the other day in a home that was only 8 years old. The joints of the single-walled pipe in the unconditioned space were heavily laden with salts and the furnace had piles of it inside around the inducer to fluepipe connection. The single-walled pipe was very badly corroded inside - damned near shot, in fact.

I wonder whether any HVAC guy ever calculated the flue size and draw needed based on the total BTU/HR requirements of both appliances and then tested the draw of that stack with both appliances hooked up to it, to ensure that it was drawing well enough?

Hmmm, I just looked at the picture again. Looks like the first section of pipe from the collar on both water heater and furnace, as well as the furst section of supply duct from the furnace, are newer, so I'm guessing both the water heater and furnace are newer but the flue configuration is not. In a situation like that, it would be kind of helpful to know how old the furnace that had been replaced was. Obviously, given the age of the house, it was probably not the first furnace, but I wonder if it managed to last its entire expected service life in your region or had a relatively short life due to this configuration?



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Off topic slightly, and maybe it's a regional thing because you guys don't have earthquakes, but I don't understand the solid soldered connections to the water heater (we use flex connectors here). How do you change the heater without hack-sawing the pipes?

Chad...I'm sure it's an optical illusion, but no matter how much I enlarge the photo it still looks like the gas piping goes up the darn flue. [:-bigeyes]

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Ron, the flue is a couple inches from the joist..that's about all that's right w/this house.

Richard, most people install a coupling and a shut off on both lines for the water heaters around here. They're almost never installed w/ flex. This one will have to be hacksawed out, nice touch, aye?

The gas line does look like it's going up the flue, but it's not..there is however, no fewer than six runs of romex in the cold air return including the furnace power supply.

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