Skip to main content ↑ ↓
Topic: Front Furnace Recommendations Needed (Read 690 times) previous topic - next topic

Front Furnace Recommendations Needed

In the midst of remodeling, I discovered the current front furnace is too far gone to be repaired cost effectively. It's an Atwood 853x-ii (I'll double check the model this afternoon).

I'm tight on space under the bench I built in place of the jack knife sofa, but left enough room for a similarly-sized unit (the depth into the coach is the limiting factor).

Recommendations on Dometic/Suburban/other that will be relatively drop in replacement?

Thanks!
Chip
1994 Grand Villa U300 40' Build: 4396
6V92TA Detroit 350HP
Allison 4 Speed w/jake

Re: Front Furnace Recommendations Needed

Reply #1 –
A quick search of the Forum brought up a recommendation from Well Known and Much Respected Forum member Kenhat.

Links below to the old posts, and a current source of the model he likes.  Ad states this is a direct replacement for 85xx Series.

"Installation requirements for the Atwood 2-Stage Furnace are the same as for all 8500 series furnaces. No special installation requirements mean that the Atwood 2-Stage Furnace can be installed as a replacement to Atwood's popular 8500 Series"

Need Hydro Flame Furnace Burner

Noisy Hydro Flame (Atwood) Furnace

https://www.my12voltstore.com/Atwood_38542_Excalibur_23_000_34_000_BTU_Furnace_p/38542.htm
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Front Furnace Recommendations Needed

Reply #2 –
Thanks Chuck!
1994 Grand Villa U300 40' Build: 4396
6V92TA Detroit 350HP
Allison 4 Speed w/jake

Re: Front Furnace Recommendations Needed

Reply #3 –
Looks as if that Atwood Excaliber isn't available any longer.

Is it worth finding a 2 stage furnace? It seems like many (all?) of the Dometic models are only single stage.
1994 Grand Villa U300 40' Build: 4396
6V92TA Detroit 350HP
Allison 4 Speed w/jake

Re: Front Furnace Recommendations Needed

Reply #4 –
Quote from: Chip7 –
Looks as if that Atwood Excaliber isn't available any longer.

Is it worth finding a 2 stage furnace? It seems like many (all?) of the Dometic models are only single stage.
I was way off base recommending the Excaliber.  Shoulda looked closer.  Seems it has been out of production for several years.

If it were me, I would not worry about finding a 2-stage furnace.  In fact, after doing some more reading of old Forum posts, I think I would avoid the 2-stage models if at all possible.  Sounds like there is a requirement for a new thermostat to accommodate the 2 blower speeds, which just adds more expense to the swap.  If your coach was equipped the same as ours, your front furnace was probably a 35K BTU model.  I would just try to find a similar BTU rated single speed model that will fit into the same mounting hole and space as the old one.  I am continuing my reading on this matter, because although both our furnaces are still working fine, they could crater anytime.  See thread below for some more info:

Atwood (now Dometic) Hydroflame Furnace replacement
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Front Furnace Recommendations Needed

Reply #5 –
What exactly is wrong with your old front furnace?  Are you positive it cannot be repaired by replacing parts?  I have replaced the motors and the burner heads on both of our OEM furnaces.  They still work great.

It's starting to look like you may have a tough job ahead of you (finding a suitable replacement).  I was looking at the current Dometic furnace models.  They now make a single speed "medium" sized model with 35,000 BTU called the DFMD 35111.  It is close to the same size as your OEM furnace, except it is 2" deeper.  The cutout for the outside door looks the same size.

PROBLEM IS:  The reviews on newer Dometic furnaces (in general) are terrible!  See the product page linked below:

Dometic DFMD 35111 Medium Furnace - Doored Furnace 35,000 BTU, Uses
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Front Furnace Recommendations Needed

Reply #6 –
That's not encouraging news on the Dometic reviews. I suspect the dimensions may be closer to the Atwood than it seems, but I am not certain. Perhaps they measure to the extent of the vent for the unit depth?

I've done some additional reading and agree single stage is best (avoiding the expensive thermostat).

On a potential rebuild, I would definitely need a blower, motor, and cover. The sail switch and high temp limit switches both tested good. Probably need a new burner and igniter. Not sure about the board yet. Additionally need new mounting hardware and outside cover, as the current is so bent it will be difficult to get a solid seal for keeping water out.

This thing is really beat up and hasn't been well maintained.

I'm not opposed to a rebuild, but thought I would replace with new if it was going to be several hundred dollars in parts.

1994 Grand Villa U300 40' Build: 4396
6V92TA Detroit 350HP
Allison 4 Speed w/jake

Re: Front Furnace Recommendations Needed

Reply #7 –
Quote from: Chip7 –
I'm not opposed to a rebuild, but thought I would replace with new if it was going to be several hundred dollars in parts.
I agree with your approach.  I would feel the same way.  It's still several months until Winter approaches where you are (Knoxville?), so not yet a emergency.  I will keep looking around (online) for a replacement unit, and you should do the same.  Surely there is a modern furnace out there somewhere that will drop into the same sized hole and hook up without too much difficulty.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Front Furnace Recommendations Needed

Reply #8 –
Don't rule out looking at salvage yards for parts or a complete unit.
It's possible that an almost "new" unit could be found.

Speculation at best here....
Frank & Connie Williams
1999 U320 '36
Build: 5466
MC: 18335

Re: Front Furnace Recommendations Needed

Reply #9 –
Would any of the diesel heaters on the market work?


Just in
FinditParts discount 10%.

Use code take10

I have no relationship with them. Just prior customer
1999 U270 40 #5518
USN. USPS.

Re: Front Furnace Recommendations Needed

Reply #10 –
Quote from: Texhub –
Would any of the diesel heaters on the market work?
Diesel heaters were discussed here couple years ago in some depth.  I think Pierce was doing some experimentation.  Don't know how far he got.  Perhaps he will see this and add his comments.

Diesel Heater To Replace OEM Furnaces

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"It goes without saying..."

Re: Front Furnace Recommendations Needed

Reply #11 –
Quote from: Phranko –
Don't rule out looking at salvage yards for parts or a complete unit.
It's possible that an almost "new" unit could be found.

Speculation at best here....
Looks like several Atwood 853x-ii  listed here: Furnaces & Heaters Category | Colaw RV Used Parts

Good Luck, Dave A
Dave and Nancy Abel
'00 U320 36' WTFE  Build #5669
'10 Jeep Wrangler Unlimited Rubicon
Livingston, TX  SKP's Fulltiming

Re: Front Furnace Recommendations Needed

Reply #12 –
Check PPL in Houston,and /or wait and go to Quartsite in Jan. and get one there can maybe get a free install.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Front Furnace Recommendations Needed

Reply #13 –
To close this out and maybe help someone in the future:

I ended up sourcing a new Hydro Flame/ Dometic 32668 from amazon. This unit is only 20k BTU (primarily because it was the model immediately available). The outside dimensions are nominally the same for the height/width as the old Atwood, but the depth is 2" more for the new unit. This is due to the heat exchanger being bent tubing rather than a welded assembly. The result is a quieter furnace because of less turbulence around the exchanger.

The newer Dometics have terrible reviews on their website, but most reviewers rated low because the furnace was difficult to get to for repairs. This caused simple furnace maintenance to be expensive because several labor hours to get access may be needed. This is a function of RV design rather than the furnaces, though. Time will tell, but this thing looks extremely similar to the Atwoods from 30 years ago. I suspect not much has changed overall.

A couple of notes:
- the furnace does not ship with any flange, plastic seal door, or external metal door
- the Atwood outside cover and door does not fit the new unit without modifications, but the old mounting flange worked fine.
- I cut a couple of small clearance notches around the Atwood plastic cover/seal and was happy with the fit and seal.
- the outer doors were not readily available so I heavily modified the old Atwood door to work for now. The exhaust port location/size is too different to make it a smooth fit. I used aluminum and bondo to make it work temporarily and will replace it with the proper door soon.
- I used the old Atwood thermostat successfully.
1994 Grand Villa U300 40' Build: 4396
6V92TA Detroit 350HP
Allison 4 Speed w/jake

Re: Front Furnace Recommendations Needed

Reply #14 –
Check with Tristate rv parts , they are in Michigan he did have some nos still in the box atwood , I got one from him for 600 delivered.
Andy & Eileen
Riverton Wyoming
1992 U300  40' 6V92 TA
2007 Honda CRV
1998 Jeep Grand Cherokee) Build # 4135 Skp# 122921