Atwood spontaneous combustion

[4549stiltz]

I was doing some checking on my Attwood 8535-IV furnace and found bare pine wood exposed in the floor ducting entrance at the exit of the furnace. I measured the temp in the area at 170 F. after running for a while. I know this not a good description and I don't have pictures. My concern is spontaneous combustion or a fire. The furnace is in the middle of the MH 2004 Monaco Monarc.

[Flyer15015]

Just the way they are made.

If you are concerned, you could get some aluminum flashing from the local hardware store and line the compartment. It would reflect the heat inward.

Mike in Colorado

[SafariBen]

Not right, but what are you gonna do? Borax is a decent fire retardant, spray it down with borax solution, then cover it like Mike stated. I would not want that directly exposed anywhere in the supply duct.

[jacwjames]

Download an installation manual for the furnace. It will have minimum clearance requirements. Make sure if there is a clearance listed the furnace is met. If not consider replacing with one that is zero clearance.





I have a Suburban furnace, it is rated as a zero clearance furnace. It was mounted on a piece of plywood that had been elevated at one end so the copper propane pipe feeding the refrigerator could be routed under it. When I removed the Norcold I lowered the furnace to the floor to gain the 1 5/8" the furnace had been elevated.

[Old-Biscuit]

The flash point of wood is around 482-572°F (250-300°C)
* lowest temperature at which wood vapors will ignite momentarily when exposed to a flame.

The ignition temperature of wood is around 572-752°F (300-400°C)
*lowest temperature at which wood will self-sustain combustion without an external ignition source.

Once ignited, the wood combustion temperature is around 752-1292°F (400-700°C)
*temperature range at which wood actively burns and releases heat.

[4549stiltz]

I read that too. What you are suggesting is I should be OK. The hot air exiting the furnace going into the plenum should not cause an issue with the bare wood. I feel I should be safe but I was wonder what other people feel. Thanks

[Sweetbriar]

Originally Posted by Old-Biscuit

The flash point of wood is around 482-572°F (250-300°C)
* lowest temperature at which wood vapors will ignite momentarily when exposed to a flame.

The ignition temperature of wood is around 572-752°F (300-400°C)
*lowest temperature at which wood will self-sustain combustion without an external ignition source.

Once ignited, the wood combustion temperature is around 752-1292°F (400-700°C)
*temperature range at which wood actively burns and releases heat.

What I was thinking. Long way to go from 170 deg plus there is a very high probability the furnace will cut off with an over temp fault long before the exposed material reaches critical temperatures.

[wff255]

Originally Posted by Old-Biscuit

The flash point of wood is around 482-572°F (250-300°C)
* lowest temperature at which wood vapors will ignite momentarily when exposed to a flame.

The ignition temperature of wood is around 572-752°F (300-400°C)
*lowest temperature at which wood will self-sustain combustion without an external ignition source.

Once ignited, the wood combustion temperature is around 752-1292°F (400-700°C)
*temperature range at which wood actively burns and releases heat.

This is true, wood generally has a high autoignition temperature. But it's worth noting that over time, high temperatures will begin to degrade wood and change it chemically, and there have been documented instances of autoignition of wood at temps as low as 256F. This was an extreme instance of an improper commercial range hood installation where wood members were heated to moderately high temperatures for long periods of time. Eventually it caused a fire.

These conditions were no doubt more extreme than the OPs. But I think a good rule of thumb concerning wood and heat is that if wood is exposed to temperatures that bare skin won't tolerate, it's probably getting too much heat.

If there are any other nerds like me who find this interesting, here's a link to the case study.

[4549stiltz]

I think from the opinions of the above I should be safe for a while, until I can find a way to repair or at least wrap the wood like stated earlier. If I am mistaken someone chime in and tell me so. I want to thank everybody that replied.