Making an rv furnace quieter

2oldman wrote:
I'm not sure what the definition of 'loud' is for a furnace. Mine is fine. Electric space heaters are much louder, and annoying.

Agree. Portable electric space heaters are def. noisy due to the small propeller fan blades. Heaters with squirrel cage fans like the ones I used are waay quieter.

noteven wrote:
myredracer- I like your mod. I’d ask you how it’s done but then there might be a safety kerfuffle on the forum...

Forced air heat is like warming a rock with a hair dryer. It requires noise.

I boondock mostly. I use a Propane catalytic converter (Big Buddy) Not expensive, portable, quiet.

Requires some common sense “supplied by user.”

Here's a few pics. The one under the stove (Stelpro IIRC) was the exact width as the stove and all I had to do was remove a piece of wood between the stove and door below and it dropped right in. Each heater has it's own thermostat. The setup is just like in a house and is evenly heated throughout. The demand controller is under the dinette seating next to the converter/panel in the 4th pic and has a current sensing relay and the low voltage relays (24 VAC) for the t'stats. The bed & bath fans (King Pic-a-watt) are like in the last pic and you can see the squirrel cage fan. It has rubber vibration isolators which also helps. I ran all the wiring completely concealed in the ceiling and wall cavities. Looks like a factory install!

We never dry camp so this works well for us. Have never once tripped a 30 amp breaker. We're both hearing impaired and the TV is much easier to hear clearly without the furnace blasting away plus we sleep a lot better. Being an EE likely helped doing this mod... :)

Check the specifications for your furnace, usually stuck to the side of the unit, but certainly available online. It will tell you the minimum return air duct size, which is often 80 square inches. With that information, you can probably block-off most of the return-air grill except for 8 x 10 inches (80 square inches). Most RV grills are far bigger than that. Also check the specifications for minimum clearance. You may have enough room to add some fiberglass insulation as sound absorbent in the cabinet where the furnace is installed.

I added an electric fireplace under the TV in the living room, and run the cord through a weather tight electric box that I installed. This can be plugged directly into the post and places no additional load on the trailers electrical system. Then up in the bedroom we just have a small tower heater with a thermostat. This combination is nearly silent. We just turn the furnace about 5 degrees colder in case it gets cold enough that the electric system cant keep up but it very rarely ever kicks in. Now the A/C on the other hand is something I would like to figure out how to quiet down. That thing drives me crazy when I am trying to watch TV

ksbowman wrote:
Every rv furnace we have ever had was noisy. Has anyone done something to quiet there furnace.

My solution: Olympian Catalytic Heater, permanently mounted on the wall. Drilled one little hole in the floor and tapped copper tubing into black iron pipe underneath. The only part (other than 1/4" tubing) was a brass Tee to install onto black pipe where similar copper tubing was branching off to water heater.

Furnace is now "dead" quiet. Very easy on propane and zero 12V draw. Perfect for offgrid on solar.

A tip to those considering Olympian: if your temps are above freezing - SoCal, South AZ or wintering in Mexico - get the smallest 3,000 BTU model. I got 5,000 BTU for 26 ft trailer, this was too much, even on Low it raises temperature quickly, and there is no thermostat - only High-Med-Low.

Somebody mentioned Buddy heaters - I recall they are not catalytic, though I might be wrong.

If you are on hookups, you might consider electric heater. Fanned electric heaters can be annoying due to noise and feeling of "draft", but there are also fan-less heaters: 1500W Baseboard heater with thermostat. Amazon have some too. They are ~2ft long.

To my knowledge, the Buddy heaters are not catalytic but they are efficient. Still need to vent for safety as improper combustion results in CO.

They have had oxygen sensors in them since... 2000 I think? So if there is limited oxygen they're supposed to shut off.

What we hear is the blower. In most installations there's a direct line of sight to the blower on the furnace, that's what you hear. If you can "break" that line of sight without choking off air flow you will greatly reduce the sound, sound travels in a straight line and doesn't "bend". On residential furnaces I've used fiberglass ductboard to redirect the air, place the board so the fiberglass faces the blower which helps absorb the sound. Sometimes there's enough distance behind the return grille to suspend a piece of ductboard, directing the air around the edges and blocking line of sight.

In a living room of a trailer the blower is usually very close. In a small box of trailer the sound of blower reverberates from the walls and also transmitted through the vibration of the wall where this evil machine is sitting, and through the floor too. Maybe in a 5-er in a bedroom it will be quieter because you are on a different "floor" and are sheltered by interior wall. Cycling in the night is most annoying, worse than a steady noise.

On hookups I would use fan-less electric convection heater like a small baseboard heater or electric fireplace. On offgrid - propane heater, with one CO detector in living room and another one added in bedroom, with windows and/or vents slightly open as per instructions. In warmer climates you can often avoid running heater (or furnace) in the night, it's only needed from sunset to bedtime, and another hour in the morning. Get a good warm duvet.

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MNGeeks61 wrote:
To my knowledge, the Buddy heaters are not catalytic but they are efficient. Still need to vent for safety as improper combustion results in CO.

They have had oxygen sensors in them since... 2000 I think? So if there is limited oxygen they're supposed to shut off.

Buddy heaters are catalytic.

I use a Big Buddy - it has 1lb disposable cylinder connections, and quick connect for trailer system direct connection with a hose, or you can connect to a cylinder. It stands on it’s own so is portable. You can direct the heat where you want it. It would be bulky in a small floor space. The catalytic reaction consumes oxygen and produces water vapour so you must vent the space. I open a lee side window a bit and a roof vent. It is very efficient. I test my CO detector above stove burner from time to time. It registers a steady 0 held above the cat heater. It is a great heater in low RH weather. If raining or foggy you need to manage the humidity properly.

Mine cost around $200 for the heater and to rig with a hose and quick connects.

Fizzles a bit on low, pretty much silent on mid or high setting.

Low technology.

the more "bends" you can make for the air the quieter it will be but too many adds pressure drop and may reduce air flow. Keep the velocity below 400 ft/min and all will be fine.