Direct vent fireplace fogged glass

[scosta]

What do you think is causing the inside of the glass on this direct vent fireplace to fog? Poor venting? Pilot was lit, it vents directly out the back to the exterior.

Thanks, Steve

[Larry D. Kage]

Water is in gas. The condensation is a by product of combustion. It will probably disappear when the burner is ignited.

Did you try the burner?

[scosta]

Yes, and it fired up. I did not run it long though. Were you gonna say after leaving it run a while the fog would go away?

Thanks, Steve

[Larry D. Kage]

Yes, once the fireplace heats up the moisture should go away.

[Russel Ray]

It's more than moisture.

Be right back with great info for you.

[Russel Ray]

Here you go:

White film on glass panels. According to Mr. Dale W. Feb, Executive Director of the Fireplace Investigation, Research, and Education Service (Moorpark, California), the white film is sulfuric acid. All fossil fuel produces sulfur during the combustion process, and when this sulfur is mixed with moisture, sulfuric acid is created. The white film (acid) may permanently etch the glass and should be removed on a regular basis. Permanent damage might already have occurred to the glass panels and replacement may be necessary. Recommend further evaluation by licensed fireplace professional. Information obtained from http://inspectionnews.com/ubb/Forum7/HTML/000129.html.

There's also a picture in the very first post in that thread.

Sometimes the link doesn't work; tonight it did.

[Larry D. Kage]

Originally Posted by rray

It's more than moisture.

Be right back with great info for you.

Yes, good info Russel. It may be that, however I've noted many fireplace glass fronts that cleared, what appeared to be moisture, after it was heated up. These were all pilot lighted units I'm talking about. I had one for years that acted that way and never damaged the glass. It always cleared.

[Russel Ray]

They do clear up. I've never seen one that didn't clear up. However, the damage from the sulfuric acid remains, even though it might, indeed, take years before the damage is noticeable. It depends on the quality of the gas and how often the fireplace is used.

I had a one-year-old house a couple of weeks ago that had a direct vent fireplace. When I flipped on the switch, the glass fogged up and the Client got upset. We let it burn awhile and I showed her the damage that had already been caused by the sulfuric acid. They have requested from the seller a new glass front for the fireplace. Our gas out here is pretty oogy.

[Larry D. Kage]

Originally Posted by rray

It depends on the quality of the gas and how often the fireplace is used.

Yes, that may be it.

Originally Posted by rray

Our gas out here is pretty oogy.

I've heard that about more things than gas in CA.

[Russel Ray]

By the way, if anyone ever has an opportunity to attend a seminar by Dale Feb, one should jump at the opportunity. One will never look at, or think about, fireplaces and chimneys the same way again. They are eye-opening seminars.