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Old 12-13-2009, 07:37 PM   #1
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Water heater vs Propane pressure....

Grrrr...i just wrote this all up and then hit "preview" instead of "submit"...grrrrr...

We've been in the cold, cold hills of Martinsburg, WV (Rick's still working here) and this weekend we have been a wee tad miffed by our water heater. Seems that when we use the smaller tanks (20#) they stop working when the tank is only half empty. This doesn't seem to happen with the larger tanks (30#)...only the 3 smaller ones. We know lots is still in them as we weighed 'em!

Is this a matter of not enuf pressure sending the propane back to the water heater? Or should I be suspicious of the regulator? Or is this a function of the small tanks? I hate to sound so ignorant of all things propane, but...well.....I am!

Why would the pressure go so low that it wouldn't get back to the water heater???

You just can't imagine the frustration of getting up for a shower before work ot find no hot water, and having to get out in the wind/ice/snow/rain in the teens to change over the tank!

Any suggestions, other than throwing the tanks over the cliff???? I've got it made...I'm heading home to teach this week, but my man has gotta figure this out! Else i may find a frozen stick when I return next Friday!
Susan
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Old 12-13-2009, 08:27 PM   #2
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It may be too cold for the smaller tanks to convert the liquid propane to gas. The smaller the tank the worse the problem. Also, a full tank will perform better then a 1/2 full tank in extream cold weather.
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Old 12-14-2009, 09:11 AM   #3
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slow propane??

ah....so extreme cold (well, in the teens) makes the propane slow down? I'm sorry to admit I did not know that....
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Old 12-14-2009, 11:18 AM   #4
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If you are going to continue camping in the cold consider getting an electric strip heater and winding it around the lower half of the tank. Something around 1-200 watts should do it.
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Old 12-14-2009, 11:37 AM   #5
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Wrapping the tank with some sort of insulation would also help - not too tight, of course, as all propane tanks will vent just a bit. And be sure the heat tape you use will not create a spark at any time.

You guys are hardy folks! Keep at it.

Pat
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Old 12-31-2009, 09:46 PM   #6
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The best thing to do is get rid of your changeover valve and put in a T that connects both tanks at once. If you don't have a changeover valve, you just have to switch to bigger tanks.

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Wrapping the tank with some sort of insulation would also help
I respectfully suggest that that would make it worse. Propane tanks cool while in operation and have to be heated by the surrounding air in order to continue to vaporize (boil) the liquid propane. Any insulator, including an accumulation of snow or frost, will prevent the propane from being heated by the surrounding air.

Here are the standard industry recommendations for tank size. If you have two tanks, and they are both full, and you don't have one of those changeover valves that only runs one tank at a time, you can double the BTUs. The water heater uses 10,000 BTUs. I'm not sure what you have for a furnace, but it's probably 30,000 BTUs, if you're running it:

Temp 20 lb. 30 lb. 40 lb. 100 lb.
60F 24,000 32,000 40,100 79,700
50F 21,200 28,300 35,500 70,600
40F 18,450 24,700 31,000 61,500
30F 15,700 21,000 26,400 52,400
20F 13,000 17,300 21,800 43,300
10F 10,250 13,700 17,200 34,200
0F 7,500 10,000 12,600 25,000
-10F 4,780 6,400 8,000 16,000
-20F 2,050 2,700 3,400 6,800

Output in BTU's per hour - Vertical Cylinder 25% full - Minimum Cylinder Pressure 10 PSI

So you can see that you really need a pair of 40 pound cylinders T'ed together (no changeover valve) if you're going to run extensively in weather below freezing. Not sure what they used in 1975 but I believe 40 pound cylinders are standard in the 30 foot+ trailers being sold today.

Also shows why people who use their trailer in the snow all winter are fond of the 100 pound tanks, and the 100 gallon "pigs."
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Old 01-03-2010, 02:17 PM   #7
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Might try to change your supplier

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Any suggestions, other than throwing the tanks over the cliff????
Kudo's to Jammer for giving a good dissertation on the subject.

One thing to add to comments already given - try a different supplier.

Common "Propane" (or "Butane") is usually a mixture of the two gasses - sometimes the blends could be severe, considering the altitude and temperature as to where they are intendended to be used.

By all means, combine the two tanks (or get a larger tank), but also talk to your supplier to ascertain if the store is selling a "winter blend" or a "summer blend" for your area.
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Old 01-03-2010, 02:29 PM   #8
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Stay away, far far away from Butane, especially during the winter months, as it freezes at about the same temperature as water.

Andy
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Old 01-03-2010, 03:54 PM   #9
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Quote:
Originally Posted by Jammer View Post
The best thing to do is get rid of your changeover valve and put in a T that connects both tanks at once.."
So.. you then use a single regulator connected to the T ?
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Old 01-03-2010, 06:30 PM   #10
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LPG system

A good, "automatic changeover" valve system, is highly desireable.

First of all, it's a safety device.

With that valve, you can turn the red flag to the tank your using, and remove the other (empty) tank, without blowing off any LPG.

If you simply use a "T" with a regulator, you cannot do that, You would have to shut both tanks off, then remove the empty tank. When you disconnect that empty tank, you will lose the LPG pressure that's in the LPG plumbing. When that happens, you will then need to purge the LPG lines, everytime to remove a tank.

Also, if an automatic changeover LPG valve was no good, why then, has Airstream used them for over 50 years.

Andy
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Old 01-03-2010, 10:41 PM   #11
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Andy, you are correct, I misunderstood how the valves work. I found a PDF explaining them in greater detail. If they are working properly, they will end up drawing from both cylinders if the temperature is low enough that vaporization is a problem.
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Old 01-03-2010, 10:45 PM   #12
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Stay away, far far away from Butane, especially during the winter months, as it freezes at about the same temperature as water.
I think you meant to say that it boils at about the same temperature as the freezing point of water. Butane boils at 31 degrees. It freezes at around -200 degrees F.
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Old 01-03-2010, 10:53 PM   #13
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I think you meant to say that it boils at about the same temperature as the freezing point of water. Butane boils at 31 degrees. It freezes at around -200 degrees F.
I was taught that Butane freezes about the same temperature as water, as you pointed out, 31 degrees F, and that Propane freezes at a much colder temperature than an Airstream could ever be subjected to.

I have experienced "no flow" from pure Butane, at 25 degrees F.

I would look up those temps tomorrow.

Andy
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Old 01-03-2010, 11:35 PM   #14
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Thanks to all of you for helping on this...we brought the AS home last week...he'll have a break for three weeks and work nearby while awaiting some parts, then have to go back up to WV for a bit more. I'm glad he's down here in central VA now as the weather in the Mid-Atlantic region this year is really brutal by our standards (in the last couple of decades we have warmed a LOT). Now it's down in the teens at night but feels way lower due to strong winds/ wind chill.

Wrapping the bottom of the two 40-lb tanks did the trick...they are T'd and you have to change them over by hand, so I'll print yourr posts off and make sure we get the other connection....if I understand you correctly, thereby making it a much stronger pressure/btu's in really cold weather? He also erected a wind barrier/box..not close-fit, but more a a wind blind, and that helped as well.

It has been an incredible experience...wintering over is an experience! These last two months have afforded him an opportunity to REALLY get to know the Excella on an intimate basis :=) Previously it was mostly me playing with it and constantly showing him things from the internet and this forum, but now there is not an inch he hasn't poked, prodded, sealed, caulked, etc..... When he returns it'll only be for a month or so, so I thought he'd just want to get a room, but NOOOOO, he's taking it back up! I do think this guy who never camped as a youngsta has been firmly "converted"!!!

Thanks again!
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