I have a 2011 RV with the Atwood heater. It won't continue to run and after opening up I find the burner is falling apart. I don't know if I have a problem with the board or any other parts also. When I am looking at replacement parts it shows the burner is not available but another may fit which I am checking. All in all it appears I can replace most of the replacement parts for ~ $150-$175 with new units running ~ $500. Just wondering if I replace all the valves and burner/igniter and switches do I still have an old furnace and newer unit would heat my RV much better. I hate to put a bunch of new parts in an old furnace when for a few more dollars I could get a much more efficient unit that blows air much better. So what would you do if money was not a major issue? Thanks, Wally

Personally I would go for the new furnace. From my experience with a water heater, once you start down the repair road it never ends.

I have an 8531 in the 1991 Class C. (amazing you have an 8520 in your fairly new rig!) IMO get new!The burner in ours was rusting out so lots of trouble with it. (The screen with the little holes in it was mostly gone so the flame was all over the place, confusing the igniter/temp set.)No luck getting a burner at first and found out they are very different in different 85xx sizes so be careful there. I eventually found a used 8531 in a garage sale for low price, and swiped the burner out of that. The furnace still acts up a little. Sometimes the fan comes on and no heat, so have to go to the thermostat and switch off, wait, then switch on and now it ignites properly. Most of the time it works right though. I was on the point of getting a new replacement. I recommend doing that for sure. Do note that the new ones are longer in the back where the ducts go, so you need room back there so it will fit.

I am going the other way. If the unit is solid without any rust, I would be fixing it.These people in Portland should have the parts and expertise for you.Laurelhurst Distributors2011 model should not be in that bad of shape. Did you get rig new or used?

I bought the toy hauler used in 2012 so it was only with someone else for about a year. We have had it the last 6 years. It seems to work ok until this event happened this last weekend out. We camp in the trailer during ski season at the resort on weekends so I can't afford to have a problem allowing the trailer to freeze up and break things.

If the burner is falling apart I'd worry about the heat exchanger (The part that seperates the CO in the unit's exhaust from YOU keeping you alive) I'd go ahead and repalce.

Atwood Hydro Flame 8520, replace or fix? | Good Sam Community

mchero
Explorer
Nov 22, 2018
Combustion chamber A.K.A. Heat exchanger? If the heat exchanger is rusted thru then trash the furnace. I rebuilt two hydroflame furnaces on my 93 pace diesel pusher. Burner (rusted), sail switch and one blower motor.
Still running to this day. My rear furnace in my current rig needs new board. Think ill order a Dinosaur board for it.
7 degrees this am, better hustle.
enblethen
Nomad
Nov 22, 2018
the 8531-II takes a different one. Shows as a 32811
BFL13
Explorer II
Nov 22, 2018
enblethen wrote:
36043 fits a wide range of furnaces. It diffuses the propane to give a good flame pattern.

The "burner" on our 8531-II is like a tongue that sticks nearly straight out. I have seen one like it but with a big angle to it, not sure what model they are for.

The replacement I got came off an 8531-III. It is the same as the II's except it had an "extra" mounting bracket/bolt I had to cut off with a hacksaw so it would go on the II ok. Same two screw holes though, so that was easy.
lamopar
Explorer
Nov 22, 2018
Thanks Doug! Yep I agree I should have a larger unit. That will be another project to work on. I bet they designed the heating system based on the trailer being built in Southern California and being a toy hauler probably thought it would be used in nicer conditions. We use our for all conditions so I may need to work on it a bit.

Again, thanks for the guidance.
dougrainer
Nomad
Nov 22, 2018
lamopar wrote:
The unit is the Atwood 8520 IV. It seems the unit has been replaced by another unit but many of the parts interchange. I guess one thought I had was how well it heats our trailer. I saw someone posted the 1000 BTU per foot of length as a general thought. Mine is a 36' but the furnace is only a 20K BTU. When we camp below freezing it is a challenge to keep the unit warm. We keep a dehumidifier running inside and it really helps. Anyway it seems to work so far and I assume with the destroyed burner it was not running efficiently anyway. From time to time I could smell some propane inside and the monitor would randomly go off. I believe it was incomplete combustion due to the damaged burner unit. This morning after running it for quite a while there is no smell and it is heating up pretty well.

I posted the 1000 BTU per foot. THAT is not my opinion, but both Atwood(Dometic now) and Suburban is what they stated are the guidelines. One thing that 1000 does NOT cover is the addition of slide room/s. Each slide room will need to be thought of when spec'ing BTU's. Most large RV's above 30 foot with slide rooms will have 2 Furnaces. If you have a 36 foot and a 20 BTU furnace, you do not have the size to do a good job of heating up the RV. I made Cruiser(the OEM) upgrade 2 of our customers 20 BTU furnaces to 30 BTU furnaces a few years ago, on their 28 foot Trailers as the 20 BTU could not keep up in even 30 degree weather. They were both under warranty. Doug
enblethen
Nomad
Nov 22, 2018
36043 fits a wide range of furnaces. It diffuses the propane to give a good flame pattern.
BFL13
Explorer II
Nov 22, 2018
lamopar wrote:
It is P/N 36043 on model 8531.

Thanks. They kept changing those things over the years, so you have to get the right one. It was the "screen" on ours that had rusted away.
lamopar
Explorer
Nov 22, 2018
It is P/N 36043 on model 8531.
lamopar
Explorer
Nov 22, 2018
BFL13 wrote:
Hard to follow just what was replaced. "Burner assembly" was mentioned at first, but now "combustion chamber" --what exactly was replaced?

Parts list for our 1991 8531-II has a "burner box assembly" and also a "burner assembly"

Trying to understand in case it happens to ours.

For part numbers it is part number 30268. This is a metal and screen assembly that encases the area where the propane enters from the nozzle. The igniter is on the outside of the screen. I have tried to post the picture of the damaged unit but this process to do it makes no sense to me.
enblethen
Nomad
Nov 22, 2018
Did you look at parts breakdown on Laurelhurst site? Note they have different numbers.

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