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Old 01-30-2011, 03:32 PM   #1
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Which Size Propex Propane Heater?

I did not have a heater installed when my build was done last year because SMB Indiana balked at a Propex since it was not a listed RVIA manufacturer. Fine. I spent more time since then thinking about the pros and cons of it vs diesel and concluded based on cost, maintenance, and pure bias I still like the propex. I had a propane tank, stove top and outlet for external BBQ installed as part of the build to keep my options open. I thought that if I ended up with diesel, I would have some redundancy built-in. And I kept enough room under the seat/bed unit of my EB50'ish floor plan for either of the two sizes available, the HS2000 (6500 BTU/hr = 2000 W) and the HS2800 (10,000 BTU/hr = 2800 W). I have made a measurement of the steady state temperature rise that a rated 900 W electric heater achieves when the outside temperature was 39 F on a night when there was very little wind. It got to 66 F or a temperature difference of 27 F.

Assuming that the thermal resistance a constant, that would mean to keep the van at 60 F when it is 10 F out side it would take 900*(60/27) = 2000 W, which is exactly what the output is for the smaller Propex. However, if it were quite windy, the thermal resistance would decrease making it necessary to output more heat to keep the van at 60 F. How much is difficult to say, but it appears that if you camp in cold, windy weather, or if you want to use your heater to keep the pipes from freezing (you know those pipes runn in places that can be quite a bit colder than it is where you are having a sip of wine) this experiment seems to point toward getting the larger heater that puts out 40% more heat. We all have felt what wind/chill factor is, and it would not be surprising if on a windy night much of that extra 40% would be needed in a worst case scenario.

One disadvantage of getting a heater larger than is needed is that it would cycle on/off more frequently, which could result in a larger temperature difference from when it turns off until when it turns on, but the is pure speculation.

Does anyone have other ideas on how to choose a size of heater, or better yet, does anyone have enough experience in weather that could lead to more insight into the choice? It seems whenever the Propex is mentioned it is in terms of the smaller unit, which it appears VW owner are happy with. But that vehicle is quite a bit smaller than an E-350 or Sprinter. If you know the listed output of your SMB propane (Suburban?) heater or one of the diesels, that would be good info too!
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2008 E-350 6.0L diesel: Bought new in 2010, 4x2, 4.10 LSD, HD spring-lift all 'round,
Cruiser II Top, 6'7" inside, full-time upper bed w/ kind'a EB50 layout, cozy 4-season rig
Solar: 540 W of Kyrocera w/ Blue Sky 3024iL, 3x100 AmpHr AGM's
Electrical: 4 cf fridge, nuker, water heater, compressor
Propane: stove top, furnace Travel: https://www.lugnutlife.wordpress.com
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Old 01-30-2011, 03:49 PM   #2
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Re: Which Size Propex Propane Heater?

I believe the Suburban in my van is 12,000 BTU. And it is more than enough to keep it warm with the top up - even in the 'teens. At 18 outside, it will heat the interior up to 65-70 in just a few minutes.

Without a doubt, the larger unit will do the job. The smaller one will probably work quite well down into the 20's.

You can increase the heat retention of the van by insulating the soft wall. Do a search on this site for penthouse insulation. Some have used Reflectix - kind of industrial bubble wrap - and other have used Thermarest mattresses to insulate the soft walls.

Good luck,

Mike
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Old 01-30-2011, 05:44 PM   #3
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Re: Which Size Propex Propane Heater?

I believe the smallest suburban propane heater available now is 16,000 btu. the 12,000 has been discontinued
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Old 01-30-2011, 08:21 PM   #4
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Re: Which Size Propex Propane Heater?

First thing is to carefully read the specifications for INPUT heating capacity and OUTPUT heating capacity. Most heaters are sold based on heating INPUT value. I believe the Suburban we had in our van was 12,000 btu/hr input and about 9,000 btu/hr output. The Propex literature gives input and output heating values. The output value is the one to compare to the electric heater. (the ratio of output and input values would be the efficiency of the heater)

When we had the RB van with 24" hard top and 12,000 btu/hr Suburban, it would stay warm under most any conditions with minimal furnace operation. One time it got down to +10F with 30 mph winds, and the heater would only turn off for about 5 minutes before starting again.

The Suburban was quite loud and I would rather have it running the minimal amount of time. Many times we would "almost" wake up when the furnace came on. Hopefully the Propex is quieter.
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Old 01-31-2011, 12:29 AM   #5
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Re: Which Size Propex Propane Heater?

Quote:
Originally Posted by dhally
First thing is to carefully read the specifications for INPUT heating capacity and OUTPUT heating capacity. Most heaters are sold based on heating INPUT value. I believe the Suburban we had in our van was 12,000 btu/hr input and about 9,000 btu/hr output.

When we had the RB van with 24" hard top and 12,000 btu/hr Suburban, it would stay warm under most any conditions with minimal furnace operation. One time it got down to +10F with 30 mph winds, and the heater would only turn off for about 5 minutes before starting again.
The numbers I gave were very close to the official heat output specs: Propex HS2000 output is 1,900 W = 6,484 BTU/hr and for the HS2800 it is 2,800 W = 9,556 BTU/hr (http://www.propexheatsource.co.uk/heatsourcespec.php).

If indeed your experience exactly equaled my made-up worst case and if the output of your Suburban was indeed 9,000 BTU/hr, that is exactly the kind of data I needed, especially since we have a fixed top too. In addition, we have an EB and a higher fixed top. Based on that the HS2800 is definitely the way to go, and PH top would probably need even more output for winter camping.

I hope some folks with Espar Airtronic D2's and D4's chime in, because their high outputs (not boost mode) are 6150 BTU/hr (D2) and 10,200 BTU/hr. These are fairly comparable to the two Propex units. Almost true for the Webasto Airtop 2000 (7,000 BTU/hr) and the 3900 (12,000 BTU/hr).
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2008 E-350 6.0L diesel: Bought new in 2010, 4x2, 4.10 LSD, HD spring-lift all 'round,
Cruiser II Top, 6'7" inside, full-time upper bed w/ kind'a EB50 layout, cozy 4-season rig
Solar: 540 W of Kyrocera w/ Blue Sky 3024iL, 3x100 AmpHr AGM's
Electrical: 4 cf fridge, nuker, water heater, compressor
Propane: stove top, furnace Travel: https://www.lugnutlife.wordpress.com
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Old 01-31-2011, 09:00 AM   #6
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Re: Which Size Propex Propane Heater?

the propex hs2000E looks interesting. works on both propane and elecytic hook up
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Old 02-01-2011, 12:17 AM   #7
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Re: Which Size Propex Propane Heater?

have you considered some type of catalytic heater?
http://ventedcatheater.com/6.html
they seem very interesting yet folks don't talk about them very often.
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Old 02-01-2011, 12:37 AM   #8
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Re: Which Size Propex Propane Heater?

Quote:
Originally Posted by gerrym51
the propex hs2000E looks interesting. works on both propane and elecytic hook up
It requires 230 volts AC doesn't it? Although you would be on shore power when using the AC, the transformer need to convert 1500W from 230 to 110 might be quite substantial, e.g. 24 lbs 13x7x9" and $80.00 (http://www.220-electronics.com/Transfor ... verter.htm). Also need to verify if 60 Hz is o.k. Would love to know what you can find out.
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2008 E-350 6.0L diesel: Bought new in 2010, 4x2, 4.10 LSD, HD spring-lift all 'round,
Cruiser II Top, 6'7" inside, full-time upper bed w/ kind'a EB50 layout, cozy 4-season rig
Solar: 540 W of Kyrocera w/ Blue Sky 3024iL, 3x100 AmpHr AGM's
Electrical: 4 cf fridge, nuker, water heater, compressor
Propane: stove top, furnace Travel: https://www.lugnutlife.wordpress.com
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Old 02-01-2011, 10:54 AM   #9
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Re: Which Size Propex Propane Heater?

Quote:
Originally Posted by windguy
have you considered some type of catalytic heater?
http://ventedcatheater.com/6.html
they seem very interesting yet folks don't talk about them very often.

catalytic heaters are very good-except for the danger warnings mof carbon monoxide. I see many people using them. the one you put link to is vented and supposedly does not have the carbon monioxide warning.

having said this I can't get over my own fear of it. that is why i;m going suburban nt regular rv furnace.

gerry
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Old 02-06-2011, 07:24 AM   #10
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Which Size Propex Propane Heater?

IMHO:

Bigger is better

Propex appear to be finicky especially at high altitudes

Suburban is old school but work great

I am specing out a new rig
It will get a suburban
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