RV furnace vent is 190 degrees. I’m afraid something will catch on fire!

Dear Dave,
My Atwood furnace, model number 8536-IV-DCLP, seems like it’s getting too hot coming out of the vents at 190°. I measured it with my manual thermostat gadget. The temperature outside is around 70–72°. On the front vent opening it measured 180° or more. That seems awfully hot. If you touch the vent opening, it will literally burn your hand. I’m worried about the ducting. I think they are rated at 190°.

Is it because it’s summer and these things actually get hotter? When it gets colder do they cool down a little bit so there is a more normal temperature coming out of the vents? Right now they’re blasting hot. I’m worried that something’s going to melt or catch on fire.

I called Atwood, now owned by Dometic, and I got no help.

Pinched duct hose

I found one of the duct hoses to the bathroom is slightly pinched, but it might be enough to where dirt or dust is accumulating and preventing full pressure in the heat to go into the bathroom. I’m going to take out the support in that wall and cut it out a little bit so there’s more room and it’s not pinched. Another problem is that all the other vents are getting very, very hot, to 190°. You can cook a hot dog or a marshmallow on them. LOL. —Larry, 1999 Fleetwood Southwind 35S model

Dear Larry,
Your Atwood 8500 series furnace has a temperature limit switch on the back side of the burner assembly that is designed to shut the furnace down if it gets over a predetermined temperature. Most of these are set at approximately 190 degrees, as you have stated.

You stated the temperature at the back of the furnace is 190 degrees and also 190 degrees at the vent, which is odd. Typically the air will cool slightly as it flows through the hose and to the vent. However, the temperature is at the high side of the limit and there is typically a buffer of a few degrees either way.

How an RV furnace works

The furnace draws interior air through the cold air return and pushes it over the burner assembly to the hoses and vents. It draws outside air through the vent, which goes through the burner chamber and out the exhaust vent. So, hotter days will make the furnace run at a higher temperature without the cold air being drawn in.

I do believe that the kinked hose can also be part of the issue. Limited airflow to that vent means a restriction and excess heat to the other vent or vents.

Since the unit is more than 25 years old, I would suggest replacing the limit switch with one rated at 190 degrees, fix the duct hose, and then take the temperature again at the limit switch and the vents.

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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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