Gas fireplace almost burnt place down

[walter3ca]

My friend moved into a condo. There was a pre-existing Montigo Phenom PL42DFNi direct vent gas fireplace built into the wall. It was old, so they replaced it with a new one. Same make and model. After it was professionally installed, the next day they flipped the switch, heard the piezo electric kick in, and the fire started. No problems. After about an hour, they heard a crackling inside the wall above the fireplace. They turned the switch off. Crackling continued. Then smoke started coming out of recessed light in ceiling. So they called 911 and ran. The fire department pulled the wall apart and drowned it. The inside, above the fireplace, was charred all the way to the ceiling. the installers moved the vent pipe from the top to the back and it vented outside, about 20 feet above the ground. What could have caused the fire? My friend never smelled gas.

 

[begreen]

Hard to say without eyes on the scene. Maybe improper installation clearances initially for the original fireplace? If pyrolysis built up, and more heat was generated by the new fireplace, then that could ignite surrounding wood.

 

[walter3ca]

Hard to say without eyes on the scene. Maybe improper installation clearances initially for the original fireplace? If pyrolysis built up, and more heat was generated by the new fireplace, then that could ignite surrounding wood.

I do know that there was some vent in the wall to the left of the fireplace, about level with the height of the fireplace. I call it a vent because when the FD pulled the wall apart, there was an 8 inct pipe from the ceiling going to it. But when they put the new insert in, they covered up that vent I think that they opened up that vent box because the new box was slightly taller than the old one. The new one had a couple of upside down V's on the top. So, if the entire wall was sealed, that could concentrate the heat and cause the fire? The manual says that the back and sides are 0 clearance, but the top needed 9 inches. Stupid question. There seems to be an internal and external metal cover over the holes. What would happen if the internal cover were not installed or if the back inside one were never removed so that the vent in the rear was blocked and there was only one cover covering the hole in the top?

 

[walter3ca]

Here are photos. You can see the "vent" above the Before fireplace, to the left. After, no mantel or vent. You can see the hole in the back wall where the fireplace vent protruded to the outside, with the burn hole above it. The bridcage and the firebreak were not melted or anything. You can see the alligator burn on either side of the firebox, which starts above the level of the top of the firebox and the two strange pipes. I know that the pipe on the left goes up, through the wall of the condo above, and protrudes out the roof. You can see the clearance and offsets from the top of the firebox. That should be the 9 inches of non-combustable clearance. We have no idea what caused the fire.

 

[walter3ca]

Apparently, the photo captions didn't come out. The top photo is the old fireplace in the wall. The second photo is the new fireplace in the wall. The third photo is the new fireplace with the wall covered up. The fourth photo is the inside of the wall after the fire. I have no idea what those hanging pipes are for. And the last photo is the old fireplace before we removed the drywall to pull the insert out.