Feeling a lot of heat on outside furnace vent

From the Atwood installation manual for the 8500 series IV:

Atwood wrote:
: Furnace efficiency rating is a thermal rating determined under
continuous operating conditions, independent of any installation. Efficiency
rate is given at 77% minimum, actual efficiency rating may be higher.

Don't touch that vent either, you can get a nice burn. Don't ask the wife how she knows this!

TucsonJim wrote:
On cool mornings, I love to have my coffee while the DW is getting her beauty sleep. I like to sit near the exterior vent and enjoy the "wasted" heat.

x2

Hi beemer,

I find no ratings for input btu's vs output btu's at Attwood for the Hydroflame series. I did see a number of 77% based on continuous output. That could easily be lower with cycling. It also indicates it is a brand new redesigned unit which mine is not.

I don't know where you guys got those numbers. Most RV furnaces are 78-80% efficient which means 20% of your LPG is wasting heating the outdoors through the exhaust.

Want to determine the efficiency? Look at the label on the furnace. Divide the output BTU by the input BTU to determine efficiency.
example;
24,000 output BTU
divided by
30,000 input BTU
equals
0.8 which is 80%

On my OFF-ROAD POPUP this heater vent is just inches away from my normal fabric window flap. Amazing amount of heat going up the outside wall of the POPUP. I have to make sure this flap is tucked up high all the time...

pianotuna wrote:

I wish there were a way to use that heat--but I've not found anyone who has come up with a safe solution.

X2

On cool mornings, I love to have my coffee while the DW is getting her beauty sleep. I like to sit near the exterior vent and enjoy the "wasted" heat.

The furnace heats the heat exchanger and exhaust out just like a house furnace. They are not high efficiency type so they do waste some heat but your duct temperatures are higher than the high efficiency so they do heat the rig up fast!

Hi Trudi,

The furnace approaches 65% efficiency. The other 35% goes "out the chimney".

I wish there were a way to use that heat--but I've not found anyone who has come up with a safe solution.