| Subject: | Re: Propane pressure facts |
| From: | Randy Charrette |
| Date: | Thu, 1 Nov 2001 21:50:26 -0500 |
<html><div style='background-color:'><DIV> <P>I guess I started this thread and the truth is I am not happy at all with the performance of my coleman black cat. I go Skiing and ice climbing in the winter and arrive at my destinations very late at night. This heater can not keep up for the cold that I encounter. However it was affordable,and I had read good things about it. I would gladly pay a couple of hundred dollars for a good ventilated system that would fit in a vanagon. Looking on RV sites I have not found a system under $400, and even at that they are to big to fit reasonably behind the front passenger seat and still have room(I have 2 dogs and a wife that crash in there too.). So anyone that has found a good system PLEASE let me know. I am willing to install a propane tank and/ or aux. battery (plan too anyways). Thank for the propane education!</P> <P>Randy Charrette</P> <P>87' Syncro weekender</P> <P>Longmont, CO<BR><BR></P></DIV> <DIV></DIV> <DIV></DIV>>From: Dennis Haynes <DHAYNES@OPTONLINE.NET> <DIV></DIV>>Reply-To: Dennis Haynes <DHAYNES@OPTONLINE.NET> <DIV></DIV>>To: vanagon@GERRY.VANAGON.COM <DIV></DIV>>Subject: Propane pressure facts <DIV></DIV>>Date: Thu, 1 Nov 2001 20:54:47 -0500 <DIV></DIV>> <DIV></DIV>>There has been a lot of talk about the use of propane heaters these past <DIV></DIV>>few days so I though I would clear the air! <DIV></DIV>> <DIV></DIV>>The pressure in the propane tank is a function of the propane and <DIV></DIV>>temperature. As long as there is liquid in the tank, the pressure will <DIV></DIV>>be close to that stated in the chart. <DIV></DIV>>http://www.gasplants.com/property.htm A bulk tank and portable cylinder <DIV></DIV>>will have the same pressure at the same temperature. Note that propane <DIV></DIV>>and butane are great for carrying in small containers because they <DIV></DIV>>compress to a liquid easily. The latent heat of vaporization explains <DIV></DIV>>why a propane tank gets cold as the gas is being used. Yes, heat has to <DIV></DIV>>be absorbed in order to create the vapor you burn to make heat. Yes the <DIV></DIV>>relatively low pressure needed to compress to a liquid also makes it <DIV></DIV>>possible to use as a refrigerant. <DIV></DIV>> <DIV></DIV>>Most propane appliances need the vapor pressure reduced to 11" water <DIV></DIV>>column pressure. This is the job of the regulator. Appliances designed <DIV></DIV>>to work with portable cylinders rely on an orifice to limit the flow, <DIV></DIV>>thus reducing the pressure during use to a level appropriate for the <DIV></DIV>>device. The major advantage of propane as compared to other fuels is <DIV></DIV>>it's extremely wide flammability range. Air fuel mixture is not critical <DIV></DIV>>for a clean burn. The down side here is that any propane out of control, <DIV></DIV>>(a leak), presents a real hazard since the vapor is easy to ignite and <DIV></DIV>>reducing the oxygen supply will not extinguish it. You would never see <DIV></DIV>>an electric pump placed inside a propane tank like we frequently see in <DIV></DIV>>gasoline tank. Yes. The pump in the gas tank relies on the fact that <DIV></DIV>>there is little oxygen so there is little chance of ignition. Another <DIV></DIV>>problem with a propane fire is the fact that the tank is already under <DIV></DIV>>pressure. As the tank is heated in a fire, the vapor pressure will rise <DIV></DIV>>rapidly, especially as the propane tries to boil. This can cause a <DIV></DIV>>BLEVE, (Boiling Liquid Expanding Vapor Explosion). <DIV></DIV>> <DIV></DIV>>Using a non vented heater in a Vanagon is not very smart. I did this <DIV></DIV>>many years ago and now consider myself lucky. These heaters need proper <DIV></DIV>>ventilation to ensure a safe oxygen supply for you and to ensure no CO2 <DIV></DIV>>accumulates. I believe the recommendation is two 12" X 12" openings for <DIV></DIV>>each 5,000 Btu. One opening high, one low. Not much is going to remain. <DIV></DIV>>Remember, most of these things are designed for tents. If you must use <DIV></DIV>>these, get a good propane alarm and CO2 alarm and mount according to the <DIV></DIV>>directions. You should also make sure the heater has low oxygen cut off. <DIV></DIV>>Do not rely on the battery operated units. Go to an RV supply and get <DIV></DIV>>the permanently installed 12 volt models. <DIV></DIV>> <DIV></DIV>>All combustion produces water vapor as a by product. In the winter this <DIV></DIV>>will accumulate behind the interior panels of the van and never dry out. <DIV></DIV>>It will even get inside the square tubes in the sides and roof of the <DIV></DIV>>vans. My 1970 van rusted in places I never though possible in only 2 <DIV></DIV>>years of occasional camping this way. <DIV></DIV>> <DIV></DIV>>If you really need to add heat your van, you should go with a <DIV></DIV>>permanently installed, vented heater. Do it right. It is your life at <DIV></DIV>>stake here. As for connecting the portable heaters to a bulk cylinder, a <DIV></DIV>>good RV supply can get you the needed fittings and adapters. Marshall <DIV></DIV>>Brass makes a great T that goes between the tank valve and the <DIV></DIV>>regulator. (Extend a Stay). <DIV></DIV>> <DIV></DIV>>Last spring, I posted a line of portable heaters that stayed outside and <DIV></DIV>>used a 3" hose to pipe in the heat. I forgot what brand they were. I'll <DIV></DIV>>look some more and repost when I find it. <DIV></DIV>> <DIV></DIV>>Hope some of this helpful. Remember, be very careful suing propane and <DIV></DIV>>these portable heaters. It only takes one mistake or unknown situation <DIV></DIV>>to make a disaster. <DIV></DIV>> <DIV></DIV>>Dennis <DIV></DIV>> <DIV></DIV></div><br clear=all><hr>Get your FREE download of MSN Explorer at <a href='http://go.msn.com/bql/hmtag_itl_EN.asp'>http://explorer.msn.com</a><br></html>
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