# CountryPlans Design/Build Forum

## General => General Forum => Topic started by: MountainDon on January 29, 2011, 09:54:36 AM

Title: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on January 29, 2011, 09:54:36 AM
I've know for a very long time that temperature affects propane, that at -44 degrees F or colder it will not turn to a vapor. I also knew that some propane fueled construction heaters would perform poorly or maybe not at all when used on 20 pound cylinders. I did not realize just how seriously the low temperatures affect the propane output from small cylinders. So I've complied some information in the form of tables and have placed them below.

First, a chart with the relationship between temperature and the vapor pressure of propane. Most propane appliances require 11" to operate properly. The chart states "Outside Temperature". I should have labeled that "Temperature of Liquid Propane" to be 100% correct, but since the tank should be outside it is in all likelihood the same.

(https://images2.imgbox.com/a3/b9/m3QgsaHG_o.jpg)

The next table shows the performance of 100 pound cylinders at various temperatures. The left column shows the 100 pound tank with various amounts of propane, measured in pounds. The body of the table shows the maximum continuous draw measured in BTU/hr, at zero degrees and at 20 defrees F. There are columns for single, dual and triple tanks, connected together with a manifold of some kind. Parts are available to make up whatever is needed.

(https://images2.imgbox.com/49/01/C3t677CU_o.jpg)

The third table is similar to the above, but is based on what the maximum output would be when a tank is 25% full. The maximum continuous output of different size cylinders at a range of temperatures is shown in the body of the table.

(https://images2.imgbox.com/9e/24/QeudT9U9_o.jpg)

From the two above tables one should be able to get a good idea of how they may fare if using small cylinders with devices that use various amounts of propane. Many heaters require an input of 10,000 BTU/hr or greater to operate properly. With lower volumes they will perform poorly or perhaps not at all. It is readily apparent that 20 pound cylinders are not adequate to power many devices when the temperature gets down to 10 degrees F or lower.

The last table is a compilation of propane properties.

(https://images2.imgbox.com/05/3e/frOOjbRB_o.jpg)

Notes:

Propane is stored as a liquid under pressure and boils to produce a vapor that is drawn off at the top for the heater or other device to use as fuel.  Because propane boils at -44° (below zero), the gas will freeze if it can not absorb enough ambient heat to compensate for the boiling process.  The bigger the cylinder is compared to the amount of load, the warmer it is outside, the warmer the cylinder is kept, all are a determining factor in the likelihood of a cylinder freezing up.

If a sweat or frost line forms around the cylinder at the level of the fuel, this is a telltale sign that the cylinder is over worked and is in the process of freeze up.  If the gas does freeze, it will stop producing vapor and the pressure inside the cylinder will drop to as low as zero psi which will cause the device to stop running.

If a tank of cold propane is warmed it will perform better. The exhaust from a propane fueled generator could be used to warm a tank. Proper cautions to prevent overheating must be taken as propane expands when heated. That is why propane tanks are filled to 80%.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: bayview on January 29, 2011, 02:09:51 PM

A lot of great information!

I’ve noticed that the propane flame is more yellow in the winter.   Now I see why. . .    The appliance is receiving less than one third of the pressure compared to a 100 degree summer day.   (Even with a pressure regulator)

Thanks.

/.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: ajbremer on January 29, 2011, 02:16:27 PM
Thanks MountainDon and BayView. I have been using those little, what are they called, 5-gallon tanks - the same ones barbecues use. I was wondering, would it be better to have one big one and then 'Y' off to different heaters and appliances from it?
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on January 29, 2011, 04:00:49 PM
5 gallon = 20 lb, more or less

What to use depends a lot on the outdoor temperature and the volume (BTU's/hour) needed by the appliance. It seems to me the 20# cylinders begin to get into the potential trouble zone around +30 F.

My propane dealer has fittings for manifolding two or more tanks together. It's similar to connecting batteries in parallel to increase electrical capacity. As the charts show, larger tanks combined, equals more available vaporized gas.

Note the charts are for vertical tanks. Horizontal tanks perform better as the surface area of the liquid propane is increased. But beware, a cylinder designed for vertical use will not work properly. Do not try that.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: Shawn B on January 30, 2011, 07:49:58 AM
Yep known about the small tank and torpedo heater issues for awhile now. MtnDon mentions that appliances need 11" w.c.  Keep in mind that this is burner manifold pressure, or outlet of the gas valve/regulator. Most appliances, especially central forced air furnaces need 14" w.c. on the inlet pressure to appliance. Most house regulators are set at 14" w.c. Not sure if R.V. appliances are the same. Also keep in mind that "propane" or L.P. gas is not an exact mixture region to region or batch to batch. It is a man made gas of several natural and other man made gases. This is one reason why propane has a history of burning dirtier and with more CO2 an CO than natural gas. This is one reason the price changes so much and in some areas of the Nation electric is a cheaper energy source.  In colder climates such as the northern tier states it is common to bury the propane tanks to avoid the temp issues. Also colder areas use a different mixture of butane and iso-butane.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: rick91351 on January 30, 2011, 08:00:30 AM
MD or Shawn B what is W.C.?  Guessing I can eliminate wall clearance and water closet.  ??? ???
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on January 30, 2011, 08:07:41 AM
water column

As for the required vapor pressure I was going by what the various appliances we have require; Servel refrigerator (11), Housewarmer wall heater (11-13), Water heater (11), range (I don't remember, but it works on 11)     :-\
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: rick91351 on January 30, 2011, 10:10:54 AM
Thanks, I sort of knew what you guys meant but is there a simple way of measuring this for some of use that really just do not care to get into the laws of evaporating gas and displacement.  Or is it just safer to say best get a 100 lbs tank if your ambient temps are going to be -20 or below for any length of time and wanting to keep the basics of a cabin sort of on standby (pilot light lit) and not trust the smaller twenty lbs tanks in the winter time. Okay I am sort of leading the witness...... ;)
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on January 30, 2011, 10:33:24 AM
The lazy mans way would be 100# cylinders. Or larger tank on the ground.  I wanted to avoid 100#ers as they are just plain heavy!

I will be considering the options of manifoilding 40#ers, buying 100#ers, or even a 200 -250 gallon on ground tank. I'm not in a rush as nobody can drive up for a few months yet.

IF the task was to simply keep a pilot light burning that would not be an issue with even a 20#er. It's when the burner kicks in.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: Shawn B on January 31, 2011, 03:21:56 PM
In my opinion for a seasonal or part time cabin that has a propane range, heat, and water heater I would use either 2--100 lb vertical cylinders or a 200-300 gallon buried tank. The vertical cylinders could be manifolded together or used as singles, that way you could haul one back for a refill. But as MtnDon pointed out there very heavy to load, unload and get in position; especially if you have to lift the tanks onto a platform. The buried tank option is the most appealing to me. Makes it much harder for someone to carry it off, protects from damage, don't have it out taking up the view, in extreme cold you maintain much better vapor flow. Another point of buying a bigger tank is that the propane dealer would come to fill it as needed, and you can take advantage of low prices in the propane market, hopefully avoiding price spikes.

Rick,  This is what I use to measure water column.

http://www.testersandtools.com/Yellow-Jacket-78060-Gas-Pressure-Test-Kit.php

Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: davidj on January 31, 2011, 04:24:23 PM
Great info - thanks.

So, on a cold day (10F), with my 200K BTU/hr on-demand propane heater, I'm gonna have to parallel up 20 five gallon propane tanks to have a shower!  Makes the on-ground 250 gallon tank seem pretty good value.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: upa on February 02, 2011, 08:27:34 AM
I have been using a 45Kbtu propane heater in various settings outside of my cabin for a few years now.
When in gets to 0 degrees or colder a 20-30 pound tank is useless. The heater runs but it blows luke warm air. The regulator typically only limits max pressure, if you don't have minimum pressure there is not much the regulator can do to compensate. The only thing that has worked for me so far in extreme cold temperature as Don's pressure charts confirm is a larger tank. I currently run a single 100# tank with the option to manifold two of them. The heater works like a son of a gun, solid blue flame even in the coldest temps the Canadian Praries have thrown at me this winter. 60# tank may have been enough but the 100# definitely works.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: ajbremer on February 02, 2011, 08:34:16 AM
I use the small 20# tanks and I have a pretty large Blue Flame heater. Last night it got to 7 degrees here in mid-oklahoma and the heater has had no problems. BUT, I'm going to graduate to the 100# tanks really soon - then I won't have to mess with those little tanks no more.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on February 02, 2011, 09:54:13 AM
It all depends on the BTU/hr rating of the heater and how full the cylinder is, as well as temperature.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on February 04, 2011, 11:38:24 AM
I found some heater blankets that are made for keeping cylinders warm. Very pricey. I never copied the location. VERY Pricey items. It would work if one had grid power though.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: ajbremer on February 06, 2011, 02:44:56 AM
Seems to me that it would be advantageous to build a little insulated wooden box/shed on or near the house that would contain the propane cylinders. Then you could maybe put a light bulb in there in severe temperatures to keep them warm, kind of like a well-house.

I've thought that those 100# cylinders would be way better than those huge white propane tanks you see in the yards of so many people. I drive a very small Ford Festiva (I collect them and have three of them) and those 100 pounders fit in the back seat when I take them to my propane man!
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on February 07, 2011, 11:34:45 AM
The issue I have with trying to warm them up is there is no power grid connection at the cabin. That could work for you or others.   :)

A SAFETY NOTE on propane cylinders. Do NOT transport or store propane cylinders on their side unless they have been designed as a horizontal tank.

All portable propane cylinders are equipped with a safety pressure relief valve. In order for this valve to work safely it must be located above the level of the liquid propane in the tank. If the tank becomes overheated and the pressure rises too high the relief valve will vent propane in vapor form.

When the tank is placed on its side the safety valve will most likely vent liquid propane. This is very dangerous. Liquid propane changes to a vapor at -44 F. If the vented liquid contacts skin it will freeze the skin instantly. If it contacts an eye, kiss the eye goodbye. When liquid propane changes to a vapor its volume increases dramatically. A liquid discharge inside a car could fill the interior with propane vapor in an instant. If the propane/air mix is right (2.3 to 9.5%) and there is an ignition source... Big Fireball; maybe Big Boom!!

My propane dealer has some pictures of the burnt out shell of an auto after a propane fire. The tank can be seen horizontal on the floor.

They will not refill a cylinder if they see it come in in a horizontal mode and there is no provision to transport it vertical once filled.

The necessity to transport vertical is yet another reason why I did not buy 100 pounders in the first place. I can strap the 40 pounders inside the Jeep but not a 100 pounder. The hundred pounders will require the trailer and I'll have to make something to secure them vertically. More bother, but better than a fire/explosion or maybe some frozen body parts.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: ScottA on February 07, 2011, 12:16:23 PM
Good info Don. I can tell you that 2- 40lb. bottles half full will just barely run our tankless WH at 0 degrees. Thats with just 1 fixture running. Turn on a second fixture and it dies. at 20+ degrees we have no problems until the tanks get almost empty.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: ajbremer on February 07, 2011, 06:13:16 PM
Wow Don, thank you, I never knew about the danger of propane cylinders on their side. I guess I'll have to get a sun-roof in my Festiva!
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on February 07, 2011, 06:31:44 PM
A sunroof will do it. That what I need in the Cherokee too!

I actually don't think the odds of a propane vent event is all that great. But the consequences could be very bad, so it's not worth the risk. I have to admit to having transported tanks on their side until I changed propane dealers about 4 years ago.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: wvrammer on April 01, 2011, 08:36:47 AM
Maybe there is another way to make this work...

Please forgive the instant transition into a technical sounding definition…

The specific latent heat of vaporization is the amount of heat required to convert unit mass of a liquid into the vapor without a change in temperature.  This definition sounds complicated to folks who don’t deal with it a lot.  It can be applied for propane pretty easily.

In other words, when propane vapor leaves the tank, it is taking the energy required to vaporize it to the place where the propane is burned in your appliance.  This energy needs to be replenished to cause more of the liquid propane to vaporize in the tank.  The propane needs energy from the air or ground outside of the tank to flow into the tank to change its state from liquid to a vapor.

It may be confusing – thinking that heat energy can flow from a 10 degree ambient temperature environment into your propane tank. Where there is more heat energy, it will always flow to where there is less heat energy.  By taking the vapor from the tank to burn it, the amount of heat energy in the tank is reduced to a point where the heat energy in the tank is lower than the heat energy available in the 10 degree environment around the tank.  So heat energy flows from environment into the tank. I bet if you check the temperature of the tank while you are using it, it will be lower than the temperature of the environment around the tank. The question to answer is: will the heat energy flow into your tank fast enough to replenish the heat energy taken away by moving the vapor (and its energy) to your appliance?

Pure propane takes 184 BTU’s/lb to change from liquid to a gas or vapor.

The higher the temperature you have around the tank, the more energy that is available to flow into the propane in the tank for the change from liquid to vapor.

The better the heat is transferred from whatever surrounds the tank into the tank, the more energy that is available to cause vaporization.  Cold air does not transfer heat energy well (doesn’t have much heat energy).  If you can’t get this heat of vaporization (energy) into the tank fast enough to cause the vaporization, the performance of the appliance suffers.

The beauty of this kind of fuel is that it has such a low heat of vaporization. Also, at relatively low pressures it becomes a liquid so you can transport a lot of it in a little tank.

Why does more volume of propane work better?  Heat energy at ambient temperature of 10 degrees flows into a 40 lb tank at a constant rate from the environment around the tank. Demand on the tank from the appliance remains the same.  Add a second tank of the same shape and size and you are doubling the amount of heat energy flowing into your reserve of propane with the demand remaining the same … and so on.  More heat flows into 2 tanks than one – your demand remains the same.

With all due respect, increasing the amount of propane or number of tanks is only one way of making your system work. It is sort of like adding a larger pressure tank to your water system to handle peak water demands.  You still need to use the same amount of energy to fill that pressure tank.

What is important is how fast the heat energy in the propane tank can be replenished (so it can make the vapor from the liquid) as it is taken away to your appliance.  Is there a safe place  where you could place the tank(s) to provide a constant and more adequate ambient temperature? Maybe a solar heated spot with “heat sink” like a rock wall or a water tank.  Bury it below the frost line…

Preaching to the choir again, but if I placed my tank in a remote location, I would insulate the tubing going through the cold environment to the appliance to prevent losing the precious energy gained from environment around the tank.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: Okie Bob on December 10, 2011, 06:43:04 AM
Forgive me for being so late to chime in, been busy last few months.
I have a 100# verticle propane bottle I bought last year to heat my garage from. Went to fill it up at my good buddies hardware store
and was told, they are not supposed to even fill a verticle tank laying in the back of a pickup and can geting in trouble for doing so.
I also have a 500 gal buried tank and had  100 gal of propane delievered last week at \$2.55 per gallon! We don't use much propane but, have a gas fireplace we love in cold weather.
Another question comes to mind also. What about the size of pipe runs from the tank to the appliance? I ran 1/2 black pipe and all seems well but, not sure my gas grill on the deck maybe 75' away is not getting as much gas as it needs. Can anyone tell me how to calculate
what pipe size I should have run? Only other appliances on the run are the gas cooktop on kitchen stove and the fireplace. Don't know off hand what the btu requirements on any of these appliances are if that is needed for the calculations.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on December 10, 2011, 07:07:39 AM
Yes you need to know the BTU input rating for each appliance.  Then go to this page (http://www.engineeringtoolbox.com/propane-gas-pipe-sizing-d_827.html) and use the graphs or tables for the type of pipe being used.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: Okie Bob on December 10, 2011, 01:20:12 PM
Thanks for the link, Don. Believe I'm in a border line situation and may go ahead and run a new line...pretty easy for me to do.
Bob
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: petergmauro on December 12, 2011, 02:45:07 AM
Folks, can I put three 40 pound tanks,  in parallel, to to achieve the same vaporazation of  one 100 pound tank?
My local grocery store will exchange 20 and 40 pound tanks, also a 40 pound tank is easily handled.
And, where can I get a manifold for three tanks?
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on December 12, 2011, 06:17:52 AM
Two or three parallel 40's help.

Make the manifold from pipe and fittings and good pipe dope (not teflon tape)
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: considerations on December 12, 2011, 06:33:14 AM
I seem to also be in a borderline situation.  I have a 100 gal upright tank, and a 20 gal as a reserve.  The cabin has a 100K on demand water heater, a freestanding range, and an 18K furnace.  When the temps were high 30Fs to low 40Fs, and the 100 gal tank was "full" I had hot water in the shower, the washer, and the kitchen sink...the stove and furnace works just fine.  Then the tank gauge dropped below 70%.  Hot water for the washer, but tepid water in the shower and kitchen.  Bummer.  Now its 28F, I'm wondering if the washing machine will still get hot water.  On the full 20gal tank there is never more than tepid water at any faucet.

The furnace and the stove continue to work just fine, surely because their demand is much lower.  Maybe the answer is another 100 gal tank running in tandem w/the first.  But maybe that is only a "step up" and not a absolute solution that will work when the temps get down to 8F at night.  Certainly I use more propane in the winter, and a hot shower to warm up in the AM is a sweet proposition.

This setup worked very well in the 5th wheel. Sigh
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on December 12, 2011, 07:00:09 AM
These two charts (also appears in the original post along with some others) explains what is happening when the tank level decreases and the temperature drops. The ability to supply propane in quantity diminishes. The RV water heater likely only drew 13 to 15 thousand BTU's. The on demand, demands many times more. You may be lucky that the burner works at all.

(https://images2.imgbox.com/49/01/C3t677CU_o.jpg)

(https://images2.imgbox.com/9e/24/QeudT9U9_o.jpg)

Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: considerations on December 12, 2011, 07:11:56 AM
Thanks. I did read them at the beginning of this thread and they clearly show the imbalance between supply and demand.  I need to put my math head on and figure out the most cost effective way to augment the system so it will work under all likely circumstances here.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: considerations on December 12, 2011, 07:17:54 AM
Just to be clear, the tanks are 20 gal, which I think is 100# and 100 gal which I believe would be 400 or 500#.  Still, though, borderline and not functioning well at these lower temps.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on December 12, 2011, 04:17:24 PM
FWIW, a horizontal tank will be capable of supplying a greater volume of gaseous propane than a vertical tank. This is because of the greater surface area of the liquid propane in the horizontal tank. The figures in the charts are for vertical tanks.

Note: it can be dangerous to place a vertical tank in the horizontal position for any reason as Okie Bob indicated, unless it is completely empty. The reason has been mentioned someplace here before, but bears repeating. The reason is the safety pressure release valve is located at the tank top. When laid on its side the relief valve may be in the liquid area. If the pressure rises and the valve releases pressure it would then release a stream of liquid propane. Liquid propane on the skin can freeze instantly as it evaporates. When liquid propane is released to the atmosphere it multiplies in volume and could cause a large fireball/explosion.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on January 01, 2012, 10:00:03 AM
This is as good a place as any to add this tidbit of information.

How much water is produced when propane burns?

Calculating this from the chemical formula for propane it looks like for every gallon of propane burned, 1.64 pounds of water is produced.

In liquid form that is 25 ounces of water per gallon of propane used.

Another good reason to use vented propane heaters in a cabin/building.

Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: considerations on January 02, 2012, 08:33:56 AM
"I have a 100 gal upright tank, and a 20 gal as a reserve.  The cabin has a 100K on demand water heater, a freestanding range, and an 18K furnace.  When the temps were high 30Fs to low 40Fs, and the 100 gal tank was "full" I had hot water in the shower, the washer, and the kitchen sink...the stove and furnace works just fine.  Then the tank gauge dropped below 70%.  Hot water for the washer, but tepid water in the shower and kitchen.  Bummer.  Now its 28F, I'm wondering if the washing machine will still get hot water.  On the full 20gal tank there is never more than tepid water at any faucet."

Ok, I'm not a plumber.  I figured out what the main problem is by accident.  My washing machine is a super compact and only has one inlet, so the hot and cold water hoses coming out of the wall are hooked to a "Y" which is subsequently attached to the washer inlet.  This is upstream from the shower and the sink.  If both of the washer faucets are open when I try to get hot water from the shower or sink, cold water gets through the Y joining up with the hot water, making the downstream hot water tepid.

This does not solve the problem of a low tank combined with low temps, but gives me a little more time to invest in another 100gal tank.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on January 02, 2012, 09:59:22 AM
Good sleuthing!!   :)
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: BrianN324 on February 06, 2013, 06:50:59 PM
A lot of useful information here I came across on a search on propane tanks. I recently installed a propane conversion kit on my backup power generator. It's working quite well so far. I've been looking at getting a 40# tank as soon as Costco gets them in again. On the other hand, it seems that having two 20# tanks might provide a couple of benefits: I can change a tank at a time when necessary without shutting down the generator, (if it's properly connected) and it seems it will provide that extra vapor that might be necessary at low ambient temps. I think there may be a connector that I could use from Mr Heater to attach two tanks to one appliance, but I need to verify that a single tank can be removed without leakage. A simple manifold would not work totally for this, but one with connections that will shut off might. The only regulator is a two stage on the generator, so I guess I could put a two outlet block on there and run two separate hoses, one from each tank. This would be full tank pressure, so anything I use needs to not leak during a tank switch.  Any suggestions would be appreciated. Thanks.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: flyingvan on February 06, 2013, 07:21:36 PM
Can't you just put ball valves in line past each tank?
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: rick91351 on February 07, 2013, 07:50:28 AM
Most RV supply stores have a selector valve that lets you chose which tank you want to run. You can disconnect the other side take it off the mount and take it down to refill.  When you run out in one tank it automatically switches to the other take and will display a red band and a green band in a sight glass.  Two red bands that is bad - no fuel available.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: GSPDOG on April 28, 2013, 03:25:29 PM
Thanks MountainDon that would actually explain an issue I have been having with my camper heater.  It is also a good jumping off point for me to ask my propane dealer before I bring in my two 500 gallon tanks.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: upa on February 10, 2014, 12:57:10 PM

Thought I would post a recent cautionary experience. I have automatic changeover regulator similar to the one pictured above and recently experienced an unexpected leak in the rubber hose at the juncture of the metal fitting. Apparently this is not an uncommon failure point. As luck would have it the leak occurred on the side that I had the switch set to, it slowy emptied my 100lb tank and then switched to the other full tank and then also started to drain it. Apparently if the regulator is auto switched(not manually)  there seems to be a pressure connection between the two sides. Probably lost around 80lbs before I noticed. The hoses were no more than 3 years old. Lesson here is check/leak test you rubber lines frequently and be sensitive to low flow propane symptoms especially in context to having propane still in the tank. This low flow rate is a feature built into the regulator when they perceive a leak. I obviously ignored mine. d*
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: aatos on August 23, 2016, 03:18:52 AM
Hello all,

I've just found this site as I was looking for vaporization rates.  I know this is a few years later, but I imagine propane hasn't changed much.  I have a question about the tables shown earlier. They seem to be quite approximate since one shows BTUs of about 25000 and the other of about 40000 for 100 lb cylinders at 25% and 0 degrees.  That is a 60% difference.  Which might be more accurate?

Thanks
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: ChugiakTinkerer on August 23, 2016, 10:40:11 AM
The rule of thumb used by Arrowhead suggests that for a 100 lb tank (47" x 14" or so) the 40,000 is closer.  Depending on your application, you might go by whichever is least advantageous.

Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: urbansurvivor on November 10, 2016, 07:20:43 AM
Question: I live in the city and my house is totally electric.  I am worried about having absolutely no source of backup heat.  I wanted to find a low-BTU freestanding ventless propane stove that I could run off of a portable propane tank (50 pounds or less).  It would be great if it could be visually appealing so that my better half would approve of the purchase  ;)  The Pleasant Hearth Vent-Free Dual Fuel Stove — 20,000 BTU, Model# VFS-PH20DT (you can find it at Northern Tool), seemed like a perfect fit.  However, they say that it will only run off of a 100 pound tank.  My initial reaction was one of disbelief, because most outdoor gas grills pull 30 to 40k BTUs and run off a standard 20 pound tank.  My conclusion, after some review, is that so long as the tank is kept indoors (I know that some of you all will freak out about this suggestion) at an ambient temperature of no less than 60F, I would be fine with a 30 or 40 pound tank, so long as I never let it drop below 30% full.  Any freeze-up concerns, were the tank to drop below this level for some reason, would be addressed by the standard safety valve.  Am I missing something here?

Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: flyingvan on November 10, 2016, 09:50:09 AM
Scary post!  If I were ever doing a primary search for victims during a house fire and encountered a 100# cylinder I'd immediately order all other firefighters to evacuate.  There are many, many cautionary tales of leaking cylinders.  The regulators bleed off fumes and are intended to be kept outside.   In fact, they must be 3' from any openings into the house.
Please do not put a vent free heating unit in living quarters!  If your house is very, very drafty you might not get CO poisoning.  If it IS very, very drafty, spend your money on making it less so...
I realize this isn't what you were asking.  However, there are some very attractive direct vent wall heaters and fireplaces that will keep you warm and safe.  Installation isn't difficult.  The vent system goes out the nearest wall and pulls combustion air in the same place. Options for your propane tank include burying, electric heat blankets, insulated storage, or multiple tank cascade systems (which increases your output when it gets cold)
Another option---have you considered a backup generator?
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: Mike 870 on November 12, 2016, 12:01:27 PM
Id really like to be able to hook my 40 lb propane tank up to my generator without using a cheapo 3/8 grill hose and lp regulator.  I'm not able to find the correct hardware to go from the larger threads on tank to a 1/2 ID pressure regulator.  Im wondering if I'm searching using the wrong terms or what, can anyone help me out?  My generator calls for a half inch supply.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on November 12, 2016, 01:19:27 PM
I have found some hard to find fittings here (https://gashosesandregulators.com/Brass-Fittings/40) and here. (http://bigway.com/index.php/propane-parts-products)

Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: Mike 870 on November 12, 2016, 06:46:48 PM
Bingo, just what I needed thanks Mt Don
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: flyingvan on November 15, 2016, 08:07:09 AM
http://www.namic.org/learn/FILP_manual/Chapter_4/4_6.htm  There may be a way or provision to direct the regulator vent outside while keeping the tank inside.  It's done on boats pretty often.  Come to think of it, we respond to quite a few boat fires...
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: jdindino on January 10, 2017, 06:41:15 AM
This thread sort of clicked a light bulb in my head. In colder climates, I am finding that instead of the 500lb above ground cylinders, many use in-ground 500lb or 1,000lb tanks. I thought this was purely for aesthetics. Is this for keeping the tanks at a much higher temperature in ground than above ground in the bitter sub zero cold?
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: flyingvan on January 11, 2017, 05:41:25 AM
That's exactly why.  The thermal mass below the frost line provides enough geothermal heat to make up for the heat lost in evaporation.  Metal tank exposed to subzero air, not so much
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: DaveOrr on January 14, 2017, 06:58:45 PM
Sadly, that's not really an option up here.
Our area is built on solid granite.
My propane tank is located where the snow blows in and covers it up.
This helps to keep it from getting too cold.
Others use heated blankets that cover their tanks.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: Dave Sparks on January 26, 2017, 07:31:22 AM
And others just use Diesel as it just becomes too difficult in your part of the world. I have few of them ::)
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: madracer2469 on February 10, 2017, 07:16:33 AM
Good Day,

Thank you for the extremely detailed and helpful information. I would like to gather some more information and poll the audience on using a 40# LP tank with a heatnglo fireplace with a 23,500 max BTU.

According to the 25% full diagram this system should operate fine to about 25', does that sound accurate? My remaining questions are:
> Does that mean that when the tank is greater than 25% full and it’s warmer than 25’ that this system would operate completely normal?
> If the tank is less than 25% full and it is 25’ then would there be any safety concerns or could this damage the tank, regulator, or fireplace?
> Do you have any experience with a similar 40# tank and gas fireplace system and how has it functioned for you? I’m in North Carolina where it rarely gets below 25’.
May you have a great day!
-Mike
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: ChugiakTinkerer on February 10, 2017, 08:37:14 AM
Welcome to the forum Mike.  I don't have any experience with 40# tanks but I have had a portable grill crap out at about 32 F.  The issue then wasn't the tank but the regulator.  They are not all the same, so you want to be sure you've got one that will provide the flow you need at the anticipated temps.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: MountainDon on February 10, 2017, 12:53:57 PM
Good Day,

Thank you for the extremely detailed and helpful information. I would like to gather some more information and poll the audience on using a 40# LP tank with a heatnglo fireplace with a 23,500 max BTU.

According to the 25% full diagram this system should operate fine to about 25', does that sound accurate? My remaining questions are:
> Does that mean that when the tank is greater than 25% full and it’s warmer than 25’ that this system would operate completely normal?
> If the tank is less than 25% full and it is 25’ then would there be any safety concerns or could this damage the tank, regulator, or fireplace?
> Do you have any experience with a similar 40# tank and gas fireplace system and how has it functioned for you? I’m in North Carolina where it rarely gets below 25’.
May you have a great day!
-Mike

I'd say those assumptions should be correct.  As for what happens if the tank gets lower than 25% or the temperature gets colder.... the flame may go out or maybe just burn at low efficiency.
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: madracer2469 on February 13, 2017, 08:15:23 AM
Very helpful! Thank you for your time and feedback. Checking the pressure in the lines now and I'll report back.

Have a great day!
-Mike
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: flyingvan on February 13, 2017, 10:44:00 AM
Pressure is irrelevant.  Flow is what you need.  That said, if you watch for pressure drop from static to demand, you could probably figure out available BTU's at whatever temperature you are at.  Even a little puddle of propane in your cylinder on a cold day will generate pressure, around 140 psi or so--but once you try to do something with it there won't be much evaporation to maintain that pressure
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: madracer2469 on March 15, 2017, 04:01:42 AM

Update: I've been using the 40# tank for an hour or two every other day for about a month and it seems to work very well for this purpose. It was especially cold this morning at 25 F' and I used it for about 30 minutes. For future reference, I'll try to update with more findings if we have any other cold mornings as the tank gets lower. Thanks for all your time, collaboration, and feedback all!
Title: Re: What I've Learned About Propane and Portable Cylinders
Post by: jumbo on April 07, 2017, 09:57:29 PM
A lot of great information!

I’ve noticed that the propane flame is more yellow in the winter.   Now I see why. . .    The appliance is receiving less than one third of the pressure compared to a 100 degree summer day.   (Even with a pressure regulator)

Thanks.

/.

Yes, you are correct! Colour of flame changes and now I know why it happens. First I thought our regulator is having some issues.
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