Quieting the Suburban furnace model NT-16SE, same as the NT-20SE

[floyd]

Originally Posted by David Morgan

Yes that is correct, I have tried Various combinations with the little dials, and it does change to cycling times, but not in a seemingly beneficial way. I am going to give the digital house Tstat a try. And see what happens. It should be noted that while I was running on the reduced power, the cycle times were more appropriate. And the unit ran slightly longer but without the huge extremes in temperatures.

I have not yet moved my thermostat to prove my suspicions, since the problem with temperature swings is a minor one for me, but I suspect that placing the thermostat on the side of the cabinet which houses the furnace may be a contributing factor. The furnace heats up the cabinet and the warm cabinet delays the cooldown of the thermostat, thus exaserbating any temperature swing. The solution may be as simple as relocating the thermostat.

[David Morgan]

I have my T-stat on the dinette side of the closet in the exact middle height. So I can save you moving it there . A small fan running that pulls the hotter air down towards the floor helps tremendously. An insulated floor in my opinion would make all the difference in the world! My trailer is now currently up for sale. But if I end up keeping it I am going to do some experimenting with floor heating. Since I have hot water I was considering some hydronics on the underbelly!

[David Morgan]

Originally Posted by GeorgeR

I found these two 3A and 6A 12VDC regulators. Waterproof feature is nice. Fan RPM at 12V could be reduced by approximately 13% from 13.6V or 17% from 14V. In noise level this reduction could be more significant. I am contemplating getting one of these and measure the sound at 12V and 13.6V. Furnace noise is very annoying. Additional RPM reduction could be easily done by a resistor in series.

George.

DC-DC Stable Converter Voltage Regulator 8V-40V Step Down 12V 6A 72W waterproof | eBay
DC-DC Converter Regulator 8V-40V Step Down 12V 3A 36W Voltage Stabilizer | eBay

That would probably work perfectly! Now if you were to add some resistance behind one of those, that would work. Drop the final voltage to about 11.5V or so and it would run tons quieter. Once you have a regulated input you can use resistors to drop the voltage to exactly where you want it. And the units seem to run just fin at 10V as long as you have the amps. I may order one of those myself and do some testing, Thanks for the links!

[Kelly K]

I would like to float an idea that I am going to do to my trailer. Tap into the hot water heater with a circulation pump. Run it through a base board heater that I am going to make out of 3/8 soft copper and get as much length as possible. Control the pump with a thermostat. Another idea is run the hot water through a coil like a car heater and add a low amp Quiet computer fan. circulation pumps use less than 1 amp and is very very quiet.

[cpaharley2008]

Originally Posted by Kelly K

I would like to float an idea that I am going to do to my trailer. Tap into the hot water heater with a circulation pump. Run it through a base board heater that I am going to make out of 3/8 soft copper and get as much length as possible. Control the pump with a thermostat. Another idea is run the hot water through a coil like a car heater and add a low amp Quiet computer fan. circulation pumps use less than 1 amp and is very very quiet.

I think you will get tired of hearing your hot water heater come on/off as the water cools down circulating. Is it possible you can circulate it thru plastic tubing under the floor, radiant heat is better than convection heat and more efficient.

[David Morgan]

Originally Posted by cpaharley2008

I think you will get tired of hearing your hot water heater come on/off as the water cools down circulating.

I would trade the water heater noise over the furnace any day.

The bast way to do the hydronic system is if you have one of the coach style water heaters with the heat exchanger in it. You can run a closed loop system with glycol or the like. This solves a bunch of problems with air accumulation and other issues with recircing your water heater water. Also the glycol mix absorbs and releases heat much better than the plain water. Both of the systems you mentioned work. I have seen both. Floor heating is very nice and Most even. But really difficult in a small fiberglass trailer with a simple plywood floor. If you have the coach water heater, you can modify a home base board (water not steam I believe) radiator to work for you. It sounds like you are quite aware that anything you use with you're drinking water needs to be food grade, Copper or stainless. Sounds like a really fun project.

Ken - I believe did the in floor radiant heating in his big foot renovation/extension. He has some good info in his log on it as I recall.

[DavidSo]

The frustrating thing I guess is that a much better heating system could be designed and built. Most of the elements of that system have been discussed in this thread. These campers are small, and their heat requirements are small. One of the fatal flaws of these Suburban type units is their requirement for large airflow. You barely need a whisper of air to circulate around a 16 foot trailer. Instead of cycling on and off to control the temp, there should be a variable flame. Imagine if your BBQ only operated on high, and you had to continually turn the thing on and off to regulate the heat <_<. That is how stupid and inefficient these things are. If you had a small PWM controlled fan and a variable flame, the furnace would barely run overnight to maintain a nice sleeping temp. It would only speed up when you demand a higher thermostat setting. It would probably double the run time on a battery and fuel tank too.

A Coleman lantern running overnight would provide enough heat to keep the chill off most nights.

But no.......we have to light a MIG jet engine every 30 - 40 minutes and run it for 10

David

[cpaharley2008]

Originally Posted by DavidSo

The frustrating thing I guess is that a much better heating system could be designed and built. Most of the elements of that system have been discussed in this thread. These campers are small, and their heat requirements are small. One of the fatal flaws of these Suburban type units is their requirement for large airflow. You barely need a whisper of air to circulate around a 16 foot trailer. Instead of cycling on and off to control the temp, there should be a variable flame. Imagine if your BBQ only operated on high, and you had to continually turn the thing on and off to regulate the heat <_<. That is how stupid and inefficient these things are. If you had a small PWM controlled fan and a variable flame, the furnace would barely run overnight to maintain a nice sleeping temp. It would only speed up when you demand a higher thermostat setting. It would probably double the run time on a battery and fuel tank too.

A Coleman lantern running overnight would provide enough heat to keep the chill off most nights.

But no.......we have to light a MIG jet engine every 30 - 40 minutes and run it for 10

David

There are better propane furnaces available. Lance, a truck camper and now trailer manufacturer, offers Atwood's 2 speed furnace which is a variable low/high speed 15-22,000 furnace which can operate at the lower speed if the owner selects. It comes on high and then drops down to the lower setting and has the digital thermostat option.In addition there is the 12,000 low draw 1.2 amp Atwood Everest heater which has a slower speed. The digital thermostat and it's placement should allow the furnace to run longer and then remain off longer, depending on your trailer's insulation and windows. Unless you have better insulation and windows, replacing the thermostat is futile, all your heat is leaving the furnace as quick as you provide it, retaining the heat is a better solution, IMHO.

[DavidSo]

Here's an interesting factoid that puts the issue into perspective in easily understood terms. A 1500 watt electric heater running on high continously puts out only 5,118 BTU/hr. How cold would it have to get before you could even stand to be in the trailer?
David

[DavidSo]

Originally Posted by cpaharley2008

There are better propane furnaces available. Lance, a truck camper and now trailer manufacturer, offers Atwood's 2 speed furnace which is a variable low/high speed 15-22,000 furnace which can operate at the lower speed if the owner selects. It comes on high and then drops down to the lower setting and has the digital thermostat option.In addition there is the 12,000 low draw 1.2 amp Atwood Everest heater which has a slower speed. The digital thermostat and it's placement should allow the furnace to run longer and then remain off longer, depending on your trailer's insulation and windows. Unless you have better insulation and windows, replacing the thermostat is futile, all your heat is leaving the furnace as quick as you provide it, retaining the heat is a better solution, IMHO.

Harley,
The Everest may be a better starting point. What you said about rate of lose is exactly right, and one reason that a lower continous output makes more sense.
David

[honda03842]

I vote for continuous hot water heat, rather than intermittant hot air. A 'food grade' radiator with a low flow fan behind it.

The water heater would have catalytic propane heat, no jet engine, simply external silent heat as well as electric heat. Two thermostats are required, one for water temperature, the other for inside temperature.

I could imagine something not significantly larger than the present water heater eliminating the need for a seperate electric heater or propane furnace.

Throwing around ideas is fun

[cpaharley2008]

The new propane instant rv water heaters operate a little different than conventional water heaters. You only turn on the hot water and the amount of flow determines the temperature. You open all the way and it gets cooler, turn back the flow and it gets warmer. You do not turn on the cold side. Thus something that would pump the water thru a circuit may cause it to overheat. A conventional water heater would be better suited to a hydronic system.

[David Morgan]

Originally Posted by cpaharley2008

There are better propane furnaces available. Lance, a truck camper and now trailer manufacturer, offers Atwood's 2 speed furnace which is a variable low/high speed 15-22,000 furnace which can operate at the lower speed if the owner selects. It comes on high and then drops down to the lower setting and has the digital thermostat option.In addition there is the 12,000 low draw 1.2 amp Atwood Everest heater which has a slower speed. The digital thermostat and it's placement should allow the furnace to run longer and then remain off longer, depending on your trailer's insulation and windows. Unless you have better insulation and windows, replacing the thermostat is futile, all your heat is leaving the furnace as quick as you provide it, retaining the heat is a better solution, IMHO.

Agreed - The Atwood furnace is considerably quieter. Heap loads quieter, if you ask me. The suburban is cheaper, that is really all there is to it. The Everest Draws 1.2 amps like you mentioned, yet still boasts the impressive 12,000 BTUs. They are also significantly smaller in size, for the record.

[DavidSo]

Originally Posted by David Morgan

Agreed - The Atwood furnace is considerably quieter. Heap loads quieter, if you ask me. The suburban is cheaper, that is really all there is to it. The Everest Draws 1.2 amps like you mentioned, yet still boasts the impressive 12,000 BTUs. They are also significantly smaller in size, for the record.

Harley and David,
Thankyou for that info!

[DavidSo]

I have done some sluething into these Atwood furnaces, including a call to Atwood. These furnaces have one huge advantage. They run all squirrel cage fans. That eliminates the crazy blade noise right there. Pretty much all blowers use squirrel fans for that reason. A little sound proofing on an Atwood is probably all that would be needed. The smaller 12Kbtu comes in 2 flavors. The multi-ducted 7912-II comes with a 3.4amp blower. The front discharge only 8012-II comes with a 1.2 amp blower. The only differences between the two with respect to parts are the motor, room blower wheel, and sail switch. I'm sure the sail switch could be adjusted for the lower blower output.

I also talked to the Atwood tech guy about BTU rating. He said that their rule of thumb was 1000btu per foot of trailer. 16ft trailer needs 16Kbtu. A lot depends on the trailer of course, and the conditions expected. It's also worth noting that the quoted btu ratings for all these furnaces are INPUT btu, not output. They typically run about 75% efficient so a "16K btu" unit is actually about 12K, and a "12k btu" is about 9K. I still say 9k output is plenty for my egg.

After spending alot of time working with this Suburban, I honestly think we are trying to spin silk from a sow's ear. This furnace has too many fundamental flaws. I do believe they can be overcome, but the cost/benefit gets mighty slim. I don't want to end up with a $1000 Suburban that works just fine. I've done that sort of thing in the past because I just don't know when to drop the bone once I lock on . I'd rather start with something more intelligently built and polish it a little. Now I'm reluctantly looking at shifting gears to another platform.

David

[Mike Magee]

Originally Posted by DavidSo

Here's an interesting factoid that puts the issue into perspective in easily understood terms. A 1500 watt electric heater running on high continously puts out only 5,118 BTU/hr. How cold would it have to get before you could even stand to be in the trailer?
David

RV furnace mfrs are not accustomed to FG eggs. They are thinking in terms of heating some big, drafty boxes. I had a 23' Rockwood for 3 years (bought new in 2005) and once in winter I tested a cube heater in the trailer while it sat in my back yard in 25 degree weather. After 2 hours on high, the cube only had the inside temp up to 38 degrees. And 23 footers are considered borderline between small and medium size trailers nowadays. So they design units that will adequately heat a poorly insulated stickie, and any small trailer just has to make do with the same unit.

I wonder if a person could take a basic design like a small catalytic or "buddy" heater, build a heat exchanger and venting, add some sort of thermostatic control, and create a custom furnace that will produce a worry-free trickle heater, properly sized for an egg.

[Mike Magee]

Originally Posted by DavidSo

David,
People have been using the cheap digital thermostats from Walmart, and that is what I plan to do. Don't buy an RV digital because they cost way too much! I've used cats before too and I like them. I especially like the quiet. I designed an exhaust hood for mine that eliminated most of the moisture. It came down over the top of the cat slightly and served as a heat exchanger as well as an exhaust. It was all made from aluminum sheet. My trailer came with the furnace but if I can't successfully quiet it, I will probably go back to using a cat.
David

Whoops, I missed seeing this post. Guess you've already been down that route! So much for any originality in my "idea".

[DavidSo]

Originally Posted by Mike Magee

Whoops, I missed seeing this post. Guess you've already been down that route! So much for any originality in my "idea".

Mike,
Great minds think alike right There are very few new ideas you know. We just keep thinking up the same stuff over and over. Interesting data on the sticky! These eggs do retain heat well actually. The fiiberglass does not conduct heat quickly which serves well in summer and winter. That thin insulation they use works very well too. I used it inside a truck camper once and heated that with the smallest cat I could get. In fact, I turned down the gas pressure at the regulator to drop it even lower than it was originally. The coldest nights I spent in there were 10 below zero. It is so hard to regulate a single setting heater though. I don't understand why they don't offer thermostats for cats. They could.
David

[David Morgan]

Originally Posted by DavidSo

. I don't understand why they don't offer thermostats for cats. They could.
David

I have wondered that too. Some of them have a standing pilot light, they could have a mechanical thermostat. Probably gets down to cost. Using the regulator to tune output is a little risky for CO potential I would think. But obviously you are still here to tell the tale .

[honda03842]

Originally Posted by David Morgan

I have wondered that too. Some of them have a standing pilot light, they could have a mechanical thermostat. Probably gets down to cost. Using the regulator to tune output is a little risky for CO potential I would think. But obviously you are still here to tell the tale .

There are CAT heaters with thermostats. It would be nice if they were more prevalent.