Got the new furnace today and have started to install it. A few days ago I started taking the old one out and found quite a few things that were improperly done at the factory.

The rear of the furnace had no support, it was just hung by the attachment points on the side, This caused a few "popped" rivets. The furnace had pushed out at the bottom under the door.

Two heat ducts going thru the toilet area to service the living area were badly deformed. The duct to the kitchen cabinet wasn't to bad and air flow was just OK, the duct that went along the wall behind the sofa was badly crimped in at least two areas. when the sofa was installed, the relief was very small and crushed the hose. Airflow to the front of the coach was non-existent, Now I know why.

I have the sofa out and enlarging the passes and areas that were crushing the original duct and installing all new ducts. As soon as that is done, I will be able to install the furnace fairly easily because I can redo the attachment collars so that they will install easier in the tight space. I am also making up new mounts for the rear of the furnace to reduce the vibration and movement. I am taking pictures and will post them when I am thru.

I suspect that the combination of improperly hung furnace and reduced airflow may have contributed to the combustion chamber going bad.

OK here is a new twist! I get the new furnace and have replaced all the duct work, what a bear, but it is in and no more crushing and have very smooth bends, I have eliminated 1 bend in each duct.

I read the instruction carefully and suddenly realize that I do not have enough discharge area as required by the manufacturer! The Atwood 8535 (35K BTU) furnace requires 48 sq" of discharge area, the configuration in the coach is 36 sq". There are just three 4 inch ducts that were attached to the old furnace and one 2" duct. Per he instructions 2" duct does not count toward the discharge area and also this duct goes to the bathroom and has a shut off. Each 4 inch duct has 12 sq" of area. Sure I could enlarge the bathroom duct but if shut or reduced I still have less then required.

I have no clue where I am going to find the room to run another 4" duct!

Stay tuned, more to come I am sure!

Mine's only a 28K btu, and mine also has substantial revisions from earlier Breakaways, but I suspect the interior's close to the same. The furnace is on the left, under the reefer. There are three main ducts - two under the sofa and one in the bedroom.

On mine, it would be simple to run another duct to a register in the bedroom, on the left, or in the hallway just behind the furnace.

Frankly, with the de-kinked ductwork and considering you have about 40 sq.in. of forced-air exhaust, I suspect it might work fine. But I'm with you - I'd rather install more discharge area. Maybe the little ductwork in the bath could be enlarged.

"I read the instruction carefully and suddenly realize that I do not have enough discharge area as required by the manufacturer"

Your heater doesn't happen to be directly above your water tanks? If so, cut a hole in the bottom and send heat down.May be far-fetched, but check it out.

Unfortunately, it is mounted just above the wheel well and under the lav, that is what makes it so difficult. The main cabin ducts (2) run under the toilet pedestal. I think after, looking last night, that I can snake another 4" line thru that area and put a second outlet on the kitchen cabinet. If I can't then I probably will do what Rusty mentioned and increase the line size from 2" to 4" to the toilet area. I will have discussion with Atwood today 'cause I want to know what the air distribution is at the various furnace openings. Trying to get a better balance while I am at it, and if I have to increase the bath duct size I want it at the lowest flow area, not that I have many choices but the bath would be a very short run and would really get air flow!

More to come! Thanks for your thoughts and comments.

FINALLY, the furnace installation is finished. Had quite a few bends in this road however.

I extended the pedastal that the toilet sits on and got another run thru that area into the living area, so now I have the required 48 sq" of duct area. I installed all new duct hose and pulled them fairly tight so the restriction would be minimal. In scouting the internet, I found that Atwood make a much later updated model that is a two stage unit, sounded very interesting, did more research and thought, well now is the time to upgrade if I am going to do it. Talked with the supplier fo the furnace and they agreed to exchange the first unit (I hadn't installed it yet) for a two stage unit. Total increase in cost will be less then $150 for the upgraded unit. The two stage comes with a digital thermostat which has a fan only function as well as provisions to control A/C units or exhaust fans.

Fired it up tonight (literally) and it works very well. First thing that happened was the smoke detector went off due to some of the stuff that had to burn off and out of the system. I used aluminum tape to seal all the joints around the furnace and that puts off some bad stuff for the first few times but settles down quickly.

I really like the new unit, it is FAR quieter then the old unit and when it get to within 3 degrees of the target temperature it switches to low speed. The unit only draws 5 amps at low speed and the BTU is reduce to around 20K. It is REALLY quiet on low speed. There is virtually no combustion noise inside either in high or low speed.

I will be doing a write-up with pictures and post on my website in the near future.

Next week we are off to Seattle and BC, still have a few more things to fix but are very close now. Been a journey so far.

Great!!!

I love it when Righteousness triumphs over Evil!