Furnace placement for heat distribution

[Tenor]

I've got a 19k BTU suburban furnace and I want to put it in the most efficient place possible.   Two of my choices put it about middle of the coach (front to back) and the 3rd puts it in the front 3rd.
1. Driver's side under the stove.  (middle of bus)
2. Passenger side under the fridge. (middle of bus)
3. Driver's side under the couch (front 3rd)

If it goes on the driver's side, (either under stove or under couch) I can run ductwork all the way back to the bedroom for one run, and then 2 separate runs for the front taking heat almost to behind the driver.

If it goes under the fridge, there is nothing else  to send heat through to the front (I can blow almost directly out of the furnace) but I can duct to the back bedroom.   

So, if it goes under the stove, it's center.  Would I lose heat to the bedroom by moving it forward under the couch?  If it goes under the fridge, it can blow into the whole front room.  Which of these will heat better? 

[Nick Badame Refrig/ACC]

Hi Glen,

I will always tell you, if only 1 furnace, In the middle...  for equal distrabution front and rear.

As far as which side of the bus, the side that will not interfear with the duct runs. ie, plumbing fixtures in bath, electrical lines..  etc.

Good Luck
Nick-

[Tenor]

Hey Nick, (and anyone else)
What is better, no runs and blowing to large open floor space or ducting to 2 points into the open space?  Will ducts improve air flow over a distance, or impede it?

[Nick Badame Refrig/ACC]

Glen,

Ducts are a must if you want to carry your heat all the way to the front and rear.

Just imagine sleeping in your bed in the rear and your head is closest to the coldest part of your bus without ducts.

Also do you plan on having colseable doors for privacy? if so, there is another reason...

Good Luck
Nick-

[TomC]

First off, Glen, one 19,000btu furnace is enough for the front half.  I would buy another for the rear.  I have a 35,000btu furnace that is mounted next to my stove with four vents evenly spaced from about the rear of my front sofa to the head of the bed in back.  I can tell you that 35,000btu works a bit when it gets down to the 20's-and that's with my bus having 2" of sprayed foam insulation and Penn windows.  Good Luck, TomC

[ChuckMC8]

Glenn, Mine is in the middle of the bus with ducts that run to the b/r (rear) and under the dinette (close to front) Plenty of heat for as cold as it gets here (usually no less than 15 degrees in Atlanta)
  The MOST IMPORTANT thing is to locate the furnace where the vent is between 2 bay doors when they are open.....or the vent heat will cook the open bay door......BTDT ;-)

[Tenor]

Well, based on all of your help, the best thing to do is center placement, where ducts can be run fully front to back without obstrucution, with a bigger furnace (since I only want to install one).  Here's an additional follow up question - would better flow be had buy building in wooden ducts under counters and other places that need construction or running 4" heater ductwork?  Also, I have heard that the little plastic round vents really don't allow heat out.  I have 2 boxes from my winnie that open a 4" duct out into an 8" vent.  Are these better?  Thanks!

[DavidInWilmNC]

For those who have these furnaces, especially the 30-35k BTU models, how powerful are the blowers?  I'm using the center tunnel as a supply with duct runs off this to various locations in the bus.  It reminds me of how I've seen some mobile homes and larger travel trailers ducted.  I'd imagine that the blowers are fairly strong to blow through the 4" round flex duct that is often used.

David

[jackhartjr]

My first question when I read it was this; Is 19,000 BTU enough for a bus?  I would think only if it were used in the south?
What's the opinion here folks??
Thanks
Jack

[Nick Badame Refrig/ACC]

Hi Jack,

40' bus... min. 35,000 btu's in the north.

Good Luck
Nick-

[edroelle]

Glenn,

"Better flow"  is dependent on duct size, distance, and friction in turns.   I would think you will need more than two, 4" ducts with the furnace blower.  Are there guidelines in the installation directions?   If you need 20 square inches of duct each direction, I think a rectangular duct would be more effective use of space.  A 4 inch round duct is a little more than 12 sq. inches.  You may be able to have a 4" duct to the front and back, and have another outlet or 2  near the furnace, dependent on the fan installation guidelines.

Because you want to use one furnace, you want to minimize friction.  When I had that situation, I ran PVC lightweight sewer pipe to the front and back.  The plastic had limited friction, and did not conduct heat away the whole length, like a metal duct would.  You will want to be able to throttle the flow to the individual outlet in whatever design you choose.

I am in agreement that 19,000 BTUs is not enough capacity.  Even if you don't plan on using your coach in very cold weather, I expect you will at some time.   I would believe TomC's guidance of 35,000 BTUs, is closer to your requirements.

Ed Roelle
Flint, MI

[TomC]

Personally would not use the A/C ducts because of the large size-you loose alot of heat and would take awhile to warm them up when in use.  On most furnaces, there are six possible openings using (if I remember right) 4" flexible and insulated hose per outlet.  My furnace warms up pretty much in about one minute for the air coming out of the vents.  You want the fastest warm up time when you're cold-I don't think you can achieve that with the original A/C ducts.  Now using them for A/C-great!  Good Luck, TomC

[Tenor]

This furnace came in a 33' travel trailer that I am recycling the appliances out of.  It's a suburban model.  My plan is to use it for now and continue to look for a suburban sf42 model.  I really like the mimimal opening needed for the side of the bus.  My 4905 had a 17k coleman that would keep the bus warmish down to about 30 degrees.  So it's a short term furnace hopefully, but the location and duct questions would still apply for a bigger furnace.  I really don't know how much winter use this bus will get.  We usually stop in October, but I am prefering to have too much of something than not enough!

Some posts occured as I was typing.  I believe that this furnace has 4 outlets in the case.  I had planned on only one to the bedroom, but I'll change that to 2.  In running the ducting down the drivers side I was planning on using at least 2 runs, but I need to think about "how do I fit that much duct work under my cabinets?".   I might want to build them in wood.

Unfortunatly, there is no paperwork with this particular furnace since it is being taken out of a trailer and it has been set up for floor ducting.

[DavidInWilmNC]

Why not keep the smaller furnace and add another later?  It would give you a bit better temp control.  I thought about putting in smaller unit for the bedroom and bathroom and another (small) one for the front of the bus.  It would be particularly nice if you did have a failure and had two units... at least you would still have some heat.

David

[Hartley]

I would say install the 19k unit for the bedroom and bathroom.
Then put a 35k or better up towards the front to heat the living area and kitchen.

I have a 35k in my kitchen that tries to heat the kitchen, hall and living area.
But the rub is that the front of the bus radiates away a lot of heat due to the glass, and the glass and front end metal gets mighty cold with 30 degree weather outside.

Just open the front door once and your heat is GONE.. For at least 5 minutes.

I had frost inside on the wall next to the door last week even with the heat on
full.... So keep that in mind..

I did a conversion for a guy from Idaho a few years back and put two 35K furnaces
in his bus. One for the bedroom and bath area. And one up front to cover the open kitchen and living area. He told me the next winter that it worked great.

Dave..