# Major Furnace And Insulation Mods!!



## Insomniak

We're on our third Outback, and every one of them has had a noisy furnace. Noisy to the point where we want it to run as infrequently as possible during the night, or it will wake everybody up - especially those in the bunkhouse. The 301BQ is also our largest Outback ever, and not surprisingly, the coldest. I started thinking of ways to quiet the furnace, including moving it to the underbelly area, but there just isn't enough room. I decided to leave the furnace where it is, but to modify the huge intake grille under the fridge. I read somewhere that the 30,000 btu furnace requires about 60-70 sq inches of supply air, so I figured I'd close off the front grille completely, and provide supply air from a few ducts placed throughout the trailer (like a home HVAC system). The only problem was there's not enough room to run 6" ducts where I wanted to. Finally, I realized that I could use a hollow wall as a single, large duct, and the shower wall was a perfect candidate.










After removing the furnace (easy - only 4 screws), I cut out and framed a hole between the furnace compartment and the underside of the tub/shower. I sealed as many gaps as possible, so the furnace could draw air from the top of the shower wall, under the tub, and into its compartment. I didn't go too crazy sealing everything, as I figured that any extra air from little gaps wouldn't be a problem, and would just let the furnace run more efficiently.










I then installed adjustable metal duct elbows to make connecting the existing ducts a little easier once the furnace was back in place. This also allowed me to seal the 5" holes in the floor once the 4" elbows were in. This step is where I noticed the VAST amount of cold air that was being blown through these big holes from the underbelly, from just a bit of wind outside. If you think the edges of your corrugated plastic underbelly are sealed well, think again!!










Once the furnace was back in place, I connected the ducts to the collars, taped everything up and framed the opening for the solid panel that I made from 3/4" plywood. Not a good idea to use regular plywood as it's very difficult to get stain to match the existing cabinetry in the trailer. Oak or alder would probably be better choices. I replaced the bathroom wall and cut a hole at the top for a 6" x 12" air intake grille. I painted the grille ivory white to better match the wall. When the furnace is running, you can really feel air being sucked into the vent.



















How effective was this little project? Before I began, I measured the interior sound level with a little app for the iPad. With nothing running in the trailer, the ambient sound level was about 32-34dB. With the stock furnace running, it was about 55-57dB, and with the modified furnace running, it's about 42-44dB. HOORAY!!! We took our first trip last weekend, and we barely noticed the furnace running. We could watch TV and not have to increase the volume, and nobody was woken up at all. It's a bit louder in the bathroom now, since the furnace compartment opens under the tub, but that's ok.



















The last part of the project was to drop the underbelly and stuff in R-13 (3-1/2") insulation on top of the plastic cover. This size works well as it gives enough room for the water pipes, wiring and furnace ducting, but prevents cold air from seeping into the the "basement" space. I also cleaned up Gilligan's mess of wires, shortened the ridiculous excess water pipe and furnace duct lengths, and put foam insulation on all of the water pipes. This will not only keep the pipes from getting cold, but will also eliminate most of the banging noise when flushing etc. This insulation mod was a MAJOR pain in the butt. It's very difficult to crawl around under the trailer and shove the insulation in place while keeping eveything where it belongs. It's also not easy to get the underbelly cover back in place, especially when it's cold out - it shrinks!! Here's a photo of the insulation as I neared the back of the trailer.










Overall, these two mods have really paid off. The trailer is not only warmer and quieter, but the furnace is also running less often. We're planning a trip in January to some freezing mountain temps, so we'll see how well everything works then.


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## Oregon_Camper

Dang...that is one kick a$$ mod bro!!


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## CamperAndy

With the high intake you will be sucking in your warm air instead of the cold air near the floor. I would normally say that is a bad plan and it would be for a house but in the trailer I think it would be okay. Can you say if you think the fan is running more or less? I could not tell for sure from the way you wrote it up but did you seal the holes in the floor for the tub drain?

BTW - Love the effort, I think it would be a good plan for my trailer also and may actually do this next spring.


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## cdawrld

Very nice mod!!!


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## hautevue

WOW! Impressive mod. Thanks for sharing, and especially for the great photos.


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## DeanHeck

Just curious, has anyone ever tried drawing outside air for furnace?


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## Bill & Kate

Drawing in outside air could get kind of tricky as you would also have to vent air out of the trailer at the same time. You could just let it blow out through a vent, but then you would be losing all the heat. When this is done in commercial applications, some sort of a heat exchanger is usually used to recover some of the heat from the air being exhausted. It is also common on commercial systems to try and recover some of the heat from the combustion exhaust. Both those features help make up for the inefficiency of having to heat up all that cold outside air rather than recirculating room temperature air.

Not saying you can't do it, and a properly designed system could help control the condensation that is often a problem when you get a bunch of people in a closed up trailer, but probably would be more complicated and expensive that a regular furnace.


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## willingtonpaul

Oregon_Camper said:


> Dang...that is one kick a$$ mod bro!!


x2 man, i am thinking about doing this too !!!


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## Insomniak

CamperAndy said:


> With the high intake you will be sucking in your warm air instead of the cold air near the floor. I would normally say that is a bad plan and it would be for a house but in the trailer I think it would be okay. Can you say if you think the fan is running more or less? I could not tell for sure from the way you wrote it up but did you seal the holes in the floor for the tub drain?
> 
> BTW - Love the effort, I think it would be a good plan for my trailer also and may actually do this next spring.


Well, the heat discharge ducts are in the floor, so warm air starts there and travels up to the return vent. Our house has all of the return air vents in the ceiling, and it seems to work just fine. I thought about putting the vent down low, but my goal was to reduce noise as much as possible. Every time the sound waves make a turn or run into something, they lose amplitude, so I decided to put the vent up high. We were only in 40 degree temps this weekend, but it seemed as if the furnace was running less and the trailer was heating faster. And, yep - I used spray foam to seal the tub drain area, and where the water lines come up through the floor. Got a little carried away with it too and encased the tub trap, lol....


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## johnp

A+ for that mod. I have hated the furnaces in every camper I've owned. Always noisy.

John


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## KTMRacer

johnp said:


> A+ for that mod. I have hated the furnaces in every camper I've owned. Always noisy.
> 
> John


x2. Fantastic update. I'll have to look at our 295RE, but I don't think I can pull the bathroom wall trick to get air to the furnace due to the slightly different layout. But the concept looks like the key to reducing fan noise.


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## clarkely

DAMN YOU!!!!

That is Nice!!!

I thought i was done doing things to my trailer........ But i like!!!! I may have to do this!!! Was already considering adding insulation underneath...... but seemed it would be a pain.......

My poor DW ..... something just got added to my Mod list in front of the Honey do list!!!

Great job and nice write up!!


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## Just Add Dirt

great mod....







one of the things I did not like about my TT was the level of noise when the furnace ran ( A/C too). THe only thing I would do different is to add heat trace to the external water lines, with a pig tail hanging just outside the insulation (so as to not add any load to the inverter/converter), so I could do some serious cold weather camping and wait longer in the year to winterize.


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## Insomniak

Hey guys, we took our first post-mod trip in cold weather a couple weeks ago, Jan 2-6. The temp at 4,500 ft elevation got down to 28 degrees, so we had ample opportunity to test the new furnace configuration. I have to admit that I expected the underbelly insulation to help keep the trailer warmer, but it's difficult to measure performance without side-by-side comparisons. We still needed to use our 2 electric heaters in addition to the furnace, but it did seem that the trailer was a bit easier to heat than in the past. The big winner though was how quiet the furnace is now. I'm not joking when I say that a couple of times while watching TV, I had to turn it down because I wasn't sure if the furnace was running or not!

As far as how well the underbelly and water line insulation are helping, I would probably say "somewhat". When taking showers, the cold "blast" when turning on to rinse after soaping up was still there, but didn't seem quite as bad as in the past - and the water from the campground faucets was COLD! With three kids taking back-to-back showers one night, we still ran out of hot water on the last shower. Probably didn't wait long enough for the water heater to recover, but I think I'm done with the 6 gallon Suburban. My next project will almost certainly be to install a 10 gallon Atwood, so if anybody wants a slightly used gas/electric water heater, let me know. For one or two people it's adequate, but for 4-5 it just doesn't cut it.


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