Hi All, For reasons that I will spare you from (unless you INSIST :-) I am installing a 16k Atwood RV furnace in a box mounted on the receiver hitch of my BB bus and using flexible duct work to run it into the bus from the rear of the box into the back wall of the bus - (6" or less). The box also houses, in a separate compartment, a gas bottle, a small generator and probably a small wheelchair battery to run the furnace (or I may just wire it to the house batteries)
So my question is this: - the furnace is installed in the top left section of the box - vent facing the drivers side of the box and heat ducted out the rear - So what would be the best place to get the "make up" air from? If I pulled it from the top or front (which is actually the rear- facing part of the box?) would that be okay? Usually it is pulled from inside the RV - I'm guessing because it is slightly warmer than the frigid outside air?
Any other considerations? - I understand the general issues of gas and spark/ flame and batteries in proximity etc but feel free to express your concerns :-)
will you be using this while driving ?
Collision alert Bob! Lvmci...
:o
Let me make some popcorn.......
That set-up won't provide much heat at all. With no return air to draw the cooler air to the furnace, the warmed air won't be able to move efficiently into the bus.
16k btu is not a very large furnace-like 3 electric heaters. Propane furnaces are made to be mounted inside since they have sealed combustion out the side. This will allow air from the inside to be recirculated and heated rather than trying to heat out door cold air.
I am mounting my furnace (Suburban NT40, since they have just a small intake/exhaust vent outside wall mounted) in the basement. It will be in a sealed cabinet with air being drawn from the inside of the living space and distributed by 4-4" ducts. Good Luck, TomC
It may work but you won't like it when the fresh air being heated and fed into the rv picks up some sort of odd smell near by and pumps it into your rv. Stray diesel fumes, gas fumes from cars and who nose what other fume/smell it may pick up when the wind blows. Attempting to heat air that may be 20 to 30 degrees with 16k will only give you marginal heat.
There are a number of reasons a cold air return pulls the air from the heated space, one is heating pre-heated air, and the second is not allowing the heated space to become pressurized and resist intake of heated air, plus the heated air needs to be encouraged to circulate inside the space. 16K is well on the small side for a bus, 30K to 40K is more appropriate. A small wheel-chair battery won't run a furnace long, they are real current hogs when the fan is on.
Brian
As others have pointed out, drawing the air from outside is an issue. Any force air heater only has the capacity to raise the temperature of the intake air by a limited number of degrees. Just suppose that your heater can discharge air that is 40 degrees hotter than the intake air (this figure is just for example sake). If the intake air was 20 degrees, the discharge would be only 60 degrees. Now if the the intake air comes from the interior space, it is gradually heated up, so when it reaches 30 degrees the discharge will be 70 degrees. When it reaches 40 degrees, the discharge will be 80 degrees, etc. Therefore your heater will gradually bring the inside temp up to your thermostat set point of say 70 degrees and shut off. If you are only processing cold outside air, your heater, depending on capacity, may never be able to reach the temp you want.
First, ??? ::). Now that that's out of the way, mounting in back like that might pull engine exhaust fumes into it. Unless you aren't planning on driving it. You may get too much bouncing on the unit over rough roads.
I forgot about the exhaust and the bouncing. BB Transit FE is a front engine, short wheelbase (front axle behind the door) flat nosed schoolie with a long rear overhang, the back of that thing is going to ride as rough as an 8 year old kid would want. It's going to be a problem, without a doubt, you could probably launch stuff off the back of that bus... Exhaust would normally be right under this box, and the rear low pressure area will trap it there and try to push it inside the bus.
Brian
I am always open to new ideas, but a heater on the outside of the bus (especially with 14-17 BTU's) is totally unworkable. Previous posts have indicated problems with using new cold air to heat the interior-- what you want is the previous warm air to feed the heater so it gets that much warmer.
I installed a Webasto diesel fired heater that incorporates the already existing heating system to warm the bus.
--Geoff
Geoff I would like the details of the unit you used as I am thinking that way myself but getting very little help from people up here.Webasto head tec called me and then said get a aquahot they use our burners and hung up.
It sounds like you have a reason for not installing it as it's intended, and it may be a very valid one. If it were me though, I'd certainly give installing it as the manufacturer intended some more thought - even if it meant relocating something else. Heat, for me at least, would be a pretty high priority.
Hi Bob, there are addons for overhead AC units, heat strips, under counter or under sofa, as an example, that are electric, if propane flames are an issue, actually they are pretty simple to install, lvmci...
Quote from: dbldragon on January 30, 2015, 12:10:33 AM
Geoff I would like the details of the unit you used as I am thinking that way myself but getting very little help from people up here.Webasto head tec called me and then said get a aquahot they use our burners and hung up.
You don't need to spent the ton of money on what an Aqua-Hot system costs. The Webasto Scholastic Series is 45k BTU, and will warm up your engine as well as the interior by adding a few heater boxes. They primarily are used in school buses and the schematic for it is very simple. I use a couple of Gate valves to separate the Webasto interior heat from the engine cooling system. Plus you can use the heating system while driving down the road without the Webasto.
--Geoff
P.S. Call Webasto back and tell them you are interested in the Scholastic Series. There are a couple of bus parts companies on the internet that sell them at a discount, as well as eBay once in a while.
Link to manual. Look at 5.6 to see the basic system:
http://www.newyorkbussales.com/pdfs/Webasto%20School%20Bus%20Heater%20manual.pdf (http://www.newyorkbussales.com/pdfs/Webasto%20School%20Bus%20Heater%20manual.pdf)
Thank Geoff I will look into it further.
Chuck
There is one on eBay:
http://www.ebay.com/itm/WEBASTO-923326-SCHOLASTIC-12V-DIESEL-TRAY-KIT-/171581643642?pt=Motors_Car_Truck_Parts_Accessories&hash=item27f3101b7a&vxp=mtr (http://www.ebay.com/itm/WEBASTO-923326-SCHOLASTIC-12V-DIESEL-TRAY-KIT-/171581643642?pt=Motors_Car_Truck_Parts_Accessories&hash=item27f3101b7a&vxp=mtr)
But I would ask if it comes with the box cover as you can put sound proofing on the inside of the cover which is nice to have.
--Geoff
Geoff thanks for the info
Chuck
OK-$1695.00 on sale for the basic heater. Then there's the coolant lines, valves, at least three heat exhangers (about $150 each?), accumulator tank for hot water. So you may get by with as little as $3,000.
Let see-2-10gal electric water-$520.00. Electric block heater, $80.00. 40,000btu Suburban propane furnace-$800.00. Propane tank-$175.00. About $1,600.00. Good Luck, TomC
All kinds of ways of skinning that cat, me, when I bought the Foretravel, it came with the Aqua Hot system, I found after having the MC7 with the normal LP Gas water heater & furnace, the getting used to the Aqua Hot, was VERY easy, just the thermostat in the area you want and BINGO, ain't cheap, but oh so nice. I like unlimited hot showers and warmth overall.
Dave M
I don't like firing the system if you need hot water to wash dishes I am installing a water heater with the system
NewBob: Keep thinking outside box.. I'm one also! I think your biggest problem will be vacuum and basically poor air flow for combustion . The typical hvac is designed to take inside unit air and war it 20 to 22 degree. The loss in your tubing plus the cool temp of your combustion air( cold air for combustion even) will not let your heat exchanger preform to it's capability. Old Bob.
Quote from: TomC on February 01, 2015, 09:13:55 PM
OK-$1695.00 on sale for the basic heater. Then there's the coolant lines, valves, at least three heat exhangers (about $150 each?), accumulator tank for hot water. So you may get by with as little as $3,000.
Let see-2-10gal electric water-$520.00. Electric block heater, $80.00. 40,000btu Suburban propane furnace-$800.00. Propane tank-$175.00. About $1,600.00. Good Luck, TomC
Quote
Geoff,
That is why
I take mine to the Aqua Hot shop yearly, first, it s munted in a nearly impossble hle n front bay, I am too old & rigid to even get to it, so am dependant on youbg fellers. Why
I just purchased the newest model, had the Forrtravel factory install including total rewire as different control system, all including motel, fuel etc, $15,000. About like a twin airplane.
Dave M
I have found that is is cheaper to buy the parts and make your own system than buy the Aqua Hot.
--Geoff
Thanks All for the replies. My thought with the install was that if I did in fact find an issue with the make-up air I could always install an intake air duct - my thought was a 4" intake with a slow 12-volt powered fan to pull the air from inside the bus into the area around the furnace.
Here is a curious thought though for all who have an opinion on this: If "make up" air is so important - Why is there no place for it to come in? There is only the "intake" air grate around the exhaust pipe. There is no other place around the burn chamber just incidental spaces around the fans and such for the air to sneak in - no other grates or grills and I didn't see anywhere in the install manual where it said to leave space for such (although it is likely assumed it is a "typical" install in a living space.
The system is all installed but I have not fired it while hooked up yet. This afternoon I plan on firing it and seeing what kind of performance I get out of it (it is right around 0-10 degrees here lately). If it doesn't heat to satisfaction I can install the aforementioned make-up air intake duct from the bus (only 6" distance) with the intake fan if needed.
Edit - Oh, Yes, mostly used when the bus is just sitting and not running.
Your thoughts?? Did I miss anyones Q's or concerns?
- NewBob
Quote from: Newbob on February 04, 2015, 06:45:00 AM
Edit - Oh, Yes, mostly used when the bus is just sitting and not running.
Your thoughts?? Did I miss anyones Q's or concerns?
- NewBob
Then it might work.
UPDATE:
Ok, So I fired the furnace last night and everything seems "normal" - if that means anything. The heat comes out hot at the wall register which is about 12 -14 inches from the wall of the furnace itself. By hot I mean you can hold your hand in front of it and it wouldn't burn or force you to pull your hand away but it would not be comfortable.
Now, the bus is about 26 feet inside and just has the normal transit windows, not insulated at all and the front door closes only loosely. No other heat was running at ten degrees or less outside but the bus came up to temperature of about 60 degrees on the rear portion (where the heat register is) in about 15-30 minutes somewhere. (I was bust running in and out also to check the function and temperature of the housing "utility box" behind the bus. After that time the temp didn't seem to come up much more so after about an hour I started the bus and ran the front heater which doesn't blow very hot until the bus is run down the road a bit and the temp gets over 180 degrees. But the cabin was comfy and I imagine would get hot enough to have to dial it down while running down the road.
Does anyone know of and have experience with a T-stat that goes down to 30 -40 degrees or so? Id like to keep the bus warmed a little on some frigid nights but most T-stats I know of start around 50 degrees. I'll look to see if the electronic ones go down that low but would like to hear from someone who does this.
I will likely run some more tests then perhaps ad an intake air duct to the setup to see if it helps - I hate to cut another hole in the bus if I don't have to though :-\
Quote from: Newbob on February 05, 2015, 06:45:24 AM
UPDATE:
Does anyone know of and have experience with a T-stat that goes down to 30 -40 degrees or so? Id like to keep the bus warmed a little on some frigid nights but most T-stats I know of start around 50 degrees. I'll look to see if the electronic ones go down that low but would like to hear from someone who does this.
Paste and search this at Amazon.com ... Honeywell Manual 4 Wire Premium Baseboard/Line Volt Thermostat(YCT410B1000/U)
........................................................ Honeywell CT50K1028/E Low Temperature / Garage Non-Programmable Thermostat
were you looking for line voltage or low voltage.... ??
http://www.icmcontrols.com/Frost-Sentry-Garage-Thermostat-for-singlestage-heating-systems-Battery-operated-35F-to-75F-Vertical-design-Prodview.html (http://www.icmcontrols.com/Frost-Sentry-Garage-Thermostat-for-singlestage-heating-systems-Battery-operated-35F-to-75F-Vertical-design-Prodview.html)
or search further for " garage, farm or greenhouse thermostat " garage nets the best/most results :)
Cool - Thanks!
Newbob
I live in the mountains of NC on my bus i use a bunch of 100 watt light bulbs and one heat lamp.
bought up a lot of 100 watt bulbs when the gov. tried to make us use the new florescent that do not work when it gets cold.
0 degrees
I do not winterize the bus because it gets used a lot in the winter.
the only thing is it has to stay plugged up all the time.
uncle ned
My Honeywell wifi's will go down to 40, they are easily adapted to use in a coach ( wifi in the coach is needed of course for their intended use but they can be operated manually) they work great
Instead of cutting another hole is there any way to use some sort of double wall pipe? Heat going through the middle and return from living space going through the outer portion. Seems the heated air would stay warmer and the return would be preheated. Then insulate the outer pipe also. Just an idea.
Don
Quote from: bevans6 on January 29, 2015, 03:13:48 PM
I forgot about the exhaust and the bouncing. BB Transit FE is a front engine, short wheelbase (front axle behind the door) flat nosed schoolie with a long rear overhang, the back of that thing is going to ride as rough as an 8 year old kid would want. It's going to be a problem, without a doubt, you could probably launch stuff off the back of that bus... Exhaust would normally be right under this box, and the rear low pressure area will trap it there and try to push it inside the bus.
Brian
- I did do some tests on the bouncing - it has air suspension so it's not too bad - I added rather large, rugged braces on either side of the Reese hitch to support either side of the box mount base.
Also, I moved the exhaust to exit the driver side behind the rear wheels but back more. Mostly I will be running the heater when the engine is NOT running but I will be doing some stink-and dye testing to see if anything is creeping into the cabin through any means. In the end, I hope to have the furnace sealed mostly with only the hot air into the bus and the return air coming from the bus into the furnace "inlet" area.
As mentioned above - it seems to be working so far but I am curious to see if adding the "return" air duct will allow more heat into the bus (physics says "yes-duh") - But I just want to see if there is a noticeable difference.
Thanks to all who have posted and encouraged. If I haven't mentioned it before - this is as much a prototype test as anything to prove out some functionality ideas to make room for other ideas on the drawing board. I expect that I may move the furnace into an "underside tool box type" compartment (custom made) before next winter when I gat the bugs worked out of the other ideas in the works.
When I "finish" this project - I may be posting the build on the bus projects page for others amusement :-)