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Author Topic: Things to look for when buying a furnace?  (Read 3645 times)
WEC4104
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« Reply #15 on: March 11, 2009, 05:39:30 AM »

Sean provided some really excellent information, with a nice logical flow. However. I think there is one point I'd like to clarify and/or reemphasize.

First, I believe the BTU/hr ratings of most propane furnaces are expressed in input values, not the output in BTUs/hr.  For example, an 80% efficient 35,000 BTU model will produce only 28,000 BTUs/hr.  This would be the equivalent output of between five and six of the 1500 watt cube heaters.

Using Sean's figure of 90,000 BTUs in a gallon of LPG, and a 4.7 gallon tank, that yields a total of 423,000 BTUs/tank.  At an input consumption of 35,000 BTUs/hr, that translates to a smidgeon over 12 hours of continuous run time.  That figure will be independent of the furnace efficiency.  The efficiency will only determine what percentage of the 35,000 BTUs will actually reach your room.
« Last Edit: March 11, 2009, 05:41:03 AM by WEC4104 » Logged

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Oregonconversion
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« Reply #16 on: March 11, 2009, 06:16:30 AM »

Thanks Sean, you gave me much more to think about. Sounds like I will need electric and a furnace.  Im sure both will come in handy. I am not sure what the rate here in the NW is for electricity but I will be on private land.

Now I have to figure out if I want LP or Diesel. I am leaning towards LP for when fuel reaches the $5/gal mark.
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« Reply #17 on: March 11, 2009, 06:19:03 AM »

Sounds like I am going to go with 2 20,000 BTU LP furnaces.
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WEC4104
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« Reply #18 on: March 11, 2009, 07:16:23 AM »

Oregon:

Do I gather from your comments that you plan to spend a considerable amount of your time at a "home base" on private land?  Owned by you, or someone else?

Here is where I am headed with those questions....  If I knew I was going to stay at a particular location for extended periods, I might factor that into my heating design. Such as, would it be feasible to install a large LPG tank at the site with the ability to connect your bus to it as needed?

Or, I was also wondering about the possibility a dedicated 220VAC connection, solely for heating purposes.  When you were on the road travelling, you would use the LP furnace(s) and your 110VAC system.  But when back home, there would be a small separate system with a 220 power line, simple breaker box, and a high output electric heater or two.  Just kickin' ideas around in my head.
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« Reply #19 on: March 11, 2009, 07:18:05 AM »

Oregon,
I think you'll be very happy by going that route.  I have 2 sf-25 suburbans and they work great.  They install from the inside so they only need exhaust/intake holes put into the side of the bus.  You just have to be sure that you clear any structrual parts.  Just build around them so that you can service them.  Good luck!

Glenn
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« Reply #20 on: March 11, 2009, 08:24:49 AM »

Years ago, I was working on the road, living in a 35' trailer, generally in one place for 4-6 weeks.  In the winter, I would always call a local propane company to install 2 - 100 lb. tanks. Otherwise, I was refilling the 30's every other day.  Life was so much simpler then.
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Sean
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« Reply #21 on: March 11, 2009, 09:16:31 AM »

...
First, I believe the BTU/hr ratings of most propane furnaces are expressed in input values, not the output in BTUs/hr.  For example, an 80% efficient 35,000 BTU model will produce only 28,000 BTUs/hr. ...

Using Sean's figure of 90,000 BTUs in a gallon of LPG, and a 4.7 gallon tank, that yields a total of 423,000 BTUs/tank.  At an input consumption of 35,000 BTUs/hr, that translates to a smidgeon over 12 hours of continuous run time.  That figure will be independent of the furnace efficiency.  The efficiency will only determine what percentage of the 35,000 BTUs will actually reach your room.


Aha...  I learn something every day.  I did not realize that RV LP furnaces are rated by input.  And, you're right, all my earlier math assumed that the rating was for the output.  (Been a long time since I owned an LP furnace.)

So, yes, an LP furnace that burns 35,000 BTU/hr would run just over 12 hours on a 4.7 gallon BBQ tank.

Whether you apply the efficiency numbers to the input or the output side, though, makes very little difference to my analysis of which type of heat is most cost effective -- you still need to bump up the amount of LP needed in order to produce the desired amount of heat in the coach.

As for the LP vs. diesel argument, remember that these are both refined petroleum products (unlike, say, natural gas), and so they tend to rise and fall more or less together.  Just like gasoline vs. diesel, market and refinery factors mean they are not strictly tied together, but assuming that going with LP to "protect" against diesel rising back to the ~$4 level may not be the best strategy.

-Sean
http://OurOdyssey.BlogSpot.com
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« Reply #22 on: March 11, 2009, 10:02:44 AM »

This may be true, but from what I have seen, especially these days with diesel now being MORE expensive than petrol. (even though its less off a process to refine)




As for the LP vs. diesel argument, remember that these are both refined petroleum products (unlike, say, natural gas), and so they tend to rise and fall more or less together.  Just like gasoline vs. diesel, market and refinery factors mean they are not strictly tied together, but assuming that going with LP to "protect" against diesel rising back to the ~$4 level may not be the best strategy.

-Sean
http://http://OurOdyssey.BlogSpot.com

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« Reply #23 on: March 11, 2009, 10:33:31 AM »

Does Suburban an Atwood have web pages? I can not find them...
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Sean
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« Reply #24 on: March 11, 2009, 10:34:55 AM »

... diesel now being MORE expensive than petrol. (even though its less off a process to refine)


This is a common misconception.  The market price of retail petroleum products has very little to do with the number of processing steps.  It is much more a matter of market dynamics and transportation issues.

These dynamics can impact LPG just as easily as diesel or gasoline.  The major difference at the moment has to do with the fact that LPG is actually a "nuisance" byproduct for much of the petroleum production industry, where it is known simply as "condensate."  So there is a lot of headroom in LP pricing; as raw energy prices increase, it becomes more economical to capture, store, bottle, and sell condensate -- a good deal of it today is simply burned off as a waste product due to the economics of transportation.

At this moment, diesel averages $2.05 per gallon, which contains 130,000 BTU, while LPG averages $2.25 per gallon, containing 90,000 BTU (source: US DOE).  General consensus is that LP prices are continuing to drop, and I would expect that LP may again become competitive with diesel on a per-BTU basis.  However, there is absolutely no long-term trend data to support the notion that LP is a more cost-effective heating fuel than diesel; in fact, just the opposite is true.  The spike in retail motor fuel prices last year is probably the exception, and, again the market generally does not support such long-term disparities in the retail price of petroleum products.  Motor fuel happens to be more volatile (in the market sense, not the chemical sense) than cooking gas due to demand influence.

JMO and FWIW.  YMMV.

-Sean
http://OurOdyssey.BlogSpot.com
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Lee Bradley
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« Reply #25 on: March 11, 2009, 10:37:07 AM »

Does Suburban an Atwood have web pages? I can not find them...


http://www.atwoodmobile.com/

http://www.suburbanmanufacturing.com/
« Last Edit: March 11, 2009, 10:39:06 AM by Lee Bradley » Logged
TomC
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« Reply #26 on: March 12, 2009, 12:02:22 AM »

Just to touch on Diesel pricing- $1.97 for Diesel, 2.21 for regular at my cheapy station- and that is 15ppm ultra low sulphur Diesel.  Diesel fuel is no longer the crude nearly unrefined fuel of 20 years ago.  To create the 15ppm (parts per million) ultra low sulphur Diesel, the refining is sophisticated to remove the sulphur, then to compensate for the loss of lubricity, lubrication additives are added to make sure all our Diesel injection systems continue to be happily lubricated.  If you're old enough and dealt with Diesel fuel 20 years ago, it was brownish and rather stinky.  Diesel fuel now is a clear liquid with not nearly the smell to it.  Good Luck, TomC
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