Minimum temperature for inverted canister stove

That's what I was thinking (not very hard) until someone corrected me

If you look at Roger's article http://www.backpackinglight.com/cgi-bin/backpackinglight/effect_of_cold_on_gas_canisters.html

Figure 2, shows the pressure at different temperatures. This is for upright, but for inverted, the pressure will stay at the 100% full level for the entire canister.

For -10 C, pressure is 1.7 bar, -20C 1.2 bar, so 1 bar would be about -24 C – this is the point where the pressure would exactly match atmosphere (1 bar). This is -11 F. So, the common mixtures will work inverted down to about -11 F. Maybe you need a little warmer so there's a bit of pressure.

hmmm – it doesn't matter whether you have butane or iso-butane as long as you have about 20% or 30% propane??? But this is just for inverted. For upright, you definitely want iso-butane instead of n-butane.

I have used inverted canister stoves down to -15f with no issues at all.

so much for theory : )

How would altitude affect this?

Well, yes and no. Your canister pressure should be at least as high as the air pressure outside and that outside pressure can be lower then 1 bar e.g. at 6500 ft. the air pressure is ± 0,8 Bar.

I can't match Stephen's temperature, but this morning I tested my Windpro II and my Caffin stove on the patio at a bracing +4* F (no wind), and both stoves functioned quite well. Not as efficient as if it was +50* F, but certainly well enough to boil water. I only ran each stove for 10 minutes, as it was too cold and boring for me to just sit there and watch things.

"Since the inverted canister stove depends on propane vaporizing"

As sort of stated above, the fuel in the canisters is not propane. Some (most?) canisters have some propane, but most of the fuel is butane (either "n" or "iso") with a much higher boiling point and therefore a must higher temperature required to maintain enough pressure to work. Even inverted you need some pressure to force the liquid out of the canister and into the stove.

yeah, if at altitude, then the air pressure is less, so you can be colder and the pressure inside canister will still be greater than air

it doesn’t matter whether you have butane or iso-butane as long as you have about 20% or 30% propane??? But this is just for inverted.

Well, not exactly. Remember you’ve typically got to get the stove hot first and then invert the canister or you’ll get a flare up. It takes a period of operation to get the pre-heat mechanism hot enough to properly vaporize the fuel.

Here’s the drill:
1. Start with a warm canister (sleep with it, put inside your coat, etc.)
2. Fire up the stove in the normal (upright) position; let it run for a bit (30 seconds?)
3. Turn it down and invert the canister
4. In really cold weather, take steps to keep the canister warm (bowl of water, hand warmer, etc.)

Since you’re running the canister upright for part of the time, your propane content as a percentage of the overall content will decrease over time (recall that propane has a higher vapor pressure and will evaporate from the fuel mixture at a faster rate than isobutane or n-butane). This decrease in the percentage that is propane will be significantly less than in upright operation but it will occur. The amount will vary with how long you run the canister upright and how many times you start up the stove per canister.

All that to say, toward the end of the life of the canister, the vapor pressure may not be as good as it was with a full canister. I therefore am conservative. I usually say that the lower operating limit for inverted canister use is 0F/-18C at sea level (subtract approx 2 degrees F for every 1000 feet elevation or 1 degree C for every 300 m) with an 80/20 isobutane/propane mix. You can go lower than that with a fresh canister and quite a bit lower if you employ canister warming techniques.

HJ
Adventures In Stoving
Hikin’ Jim’s Blog

Jim is only partly right. You can start your stove with the canister inverted. If you are using Powermax canisters you will do this anyhow. I do, often.

* Keep the canister 'warm' – anything around or above freezing is fine. Store it next to your waterbottles in your pack for instance.
* Keep the stove itself as warm as possible too.
* Start with the canister inverted and a very low throttle. It will splutter a bit – ignore that and put your pot on the stove anyhow. In addition to being more fuel efficient, doing so will reflect some heat back towards the stove at least.
* When you have some luke warm water, put a few spoonfuls into the bowl at the base of the canister.
* Get the coffee/cocoa ready in your mug.

A thing to remember is that even if the stove splutters a bit, with some liquid butane/propane fuel coming out the jet, that liquid fuel will vaporise VERY fast as soon as it reaches the flame region. This is a bit different from white gas or kero, where you can have the liquid fuel spitting for some distance before it vaporises. You might as well use the fuel to heat your pot.

Yes, I am quite sure one could happily use a canister stove when the ambient temperature is -40 F/C – if the canister is kept up around freezing, along with your water bottles.

And yes, the higher you go, the lower the air pressure and the more likely the canister will be to push out gas.

Cheers

To the OP: if you had a canister containing 100% propane, then yes, it would work down to -30 something F. But canisters for stoves contain a mixture of propane and butane. This has two related effects: in summer temps, the pressure in the canister is less than for pure propane, so the canister does not need to be very strong and heavy. 2nd, the boiling point is higher. The mixture of propane and butane has a boiling point inbetween that of pure propane and pure butane, dependant on the prooportions of each.
The whole point of our article http://www.backpackinglight.com/cgi-bin/backpackinglight/effect_of_cold_on_gas_canisters.html was to calculate this boiling point for different mixtures, taking into account the effect of using the canister with an upright stove. When the canister is used inverted the mixture doesn't change much and so neither does the boiling point.

Tested out a Kovea Spider inverted at 1*F and 7000'. It ran ok if I only opened the valve half way. If I turned it up too high it flamed out. As long as I kept it out of the wind it ran good enough to use for about 15 minutes. I gave up on the cold before the stove did!

you’ve typically got to get the stove hot first and then invert the canister or you’ll get a flare up.

Jim is only partly right. You can start your stove with the canister inverted. If you are using Powermax canisters you will do this anyhow. I do, often.

Well, yes, but do note the use of the word “typically,” above. :)

And, yes, one can of course start with the canister inverted, particularly if one starts slowly. Interestingly, with the Coleman PowerMax, I’ve had relatively few problems with flaring. I’ve always put it down to the higher propane content.

HJ
Adventures In Stoving
Hikin’ Jim’s Blog

Hi Jim

> with the Coleman PowerMax, I've had relatively few problems with flaring. I've always
> put it down to the higher propane content.
I will disagree here.

The Coleman Xtreme stove was a bit of a genius design. There were features in it which the company never bothered to explain to the customers – possibly to prevent the commercial opposition from waking up to what Coleman were doing, or, depressingly, maybe Sales and Marketing never understood the message they were given. The cynic in me goes for the latter, but you know me.

That straight brass fuel line going to the flexible hose, with the funny little brass rod inside it? THAT was the real heat exchanger. Liquid fuel never reached the bit going over the flame. All the bit over the flame did was heat the straight bit. That realisation was part of what led to my creation of the flat aluminium heat exchanger on my stoves.

Cheers

My thanks to all who replied.

I had lost track of Roger & Stuart's fine article. I was unsure whether propane would cause the same pressure whether or not it was part of a mixture. I now see that, depending on the mixture, the low temperature at sea level should be around 0F.

It looks to me as if an inverted canister stove would generally work fine in the Sierras. Assuming 8000' altitude and Jim's 2F degrees per 1000', that would be about -16F. Since it is generally at least a little warmer in your tent that outside it should be pretty rare that this would not work in the Sierras.

Now some other areas … more dubious. Northern Minnesota, for example. Also winter in the northeast mountains — Adirondacks or White Mountains — where -20F or a little colder when it is time to cook supper is pretty common. It sounds to me as if you'd better have a good plan for introducing some extra heat to the canister if you want to use it places like that.

–MV

> It sounds to me as if you'd better have a good plan for introducing some extra heat
> to the canister if you want to use it places like that.
Certainly, and planning ahead for that is key to an enjoyable trip.

Do you carry water in your pack at -20 F? Of course.
Why does the water stay liquid even though it is -20 F ambient?
Because you carry it in your pack next to your back, where it gets lots of nice heat.
If you carry your canister around the same place – it too will stay above freezing.
Dead easy.

Cheers

"Do you carry water in your pack at -20 F? Of course."

No, we never did. We were exercising vigorously enough to use snow. Hold it in your bare hand until it is thoroughly wet, and then eat. If you wait until you are thirsty you can never catch up this way, but if you do it right along you can get all you really need for the day. I admit this method works better for snowshoeing than for skiing. It also works best when it is someone else's turn to break trail. And, yes, I know, this method will not be for everyone. Worked for us, though.

As to your main thought — it may well be that the interior of your pack is a warm enough place to solve the problem. If not there, then there are other places. The point we both are making is that you need to pay attention to that, not expect it to "just work" at those temperatures.

–MV

—if you had a canister containing 100% propane, then yes, it would work down to -30 something—

So besides the canister being heavier, why not use 100% propane fuel for temps below 10*F?

Wouldnt that solve a lot of the problems?

The Coleman Xtreme stove was a bit of a genius design. There were features in it which the company never bothered to explain to the customers – possibly to prevent the commercial opposition from waking up to what Coleman were doing, or, depressingly, maybe Sales and Marketing never understood the message they were given. The cynic in me goes for the latter, but you know me.

That straight brass fuel line going to the flexible hose, with the funny little brass rod inside it? THAT was the real heat exchanger. Liquid fuel never reached the bit going over the flame. All the bit over the flame did was heat the straight bit. That realisation was part of what led to my creation of the flat aluminium heat exchanger on my stoves.

Ah, now that is fascinating. I had noticed that, thought it odd, but thought no further. I mean if you have a pre-heat tube, that must be it, right? Apparently not.

I think people underestimated Coleman’s backpacking stoves. Coleman did it to themselves in a way by allowing the Coleman name to go on a lot of cheap crap, but some of their backpacking stoves were really nice products despite their image as more the “family camping” company. Of course since the buyout by Jardin I believe, they’ve almost entirely abandoned the backpacking stoves market.

The problem with Coleman is that they would have one product that is a really nice product, and then they’d have another product right next to it that was cheap crap, both with the Coleman name on it.

HJ
Adventures in Stoving
Hikin Jim’s Blog

So besides the canister being heavier, why not use 100% propane fuel for temps below 10*F?

Well, you can. But you do have to lug along one of those big heavy, generally green, propane canisters. They contain 16.4 oz/465 g of propane, and the canister empty probably weighs half a pound or more empty. Then you need an adapter if you want to use a backpacking stove. Car camping stoves are generally not suitable for backpacking.

There are various adapters available, like The Kovea Propane Adapter

HJ
Adventures in Stoving
Hikin Jim’s Blog

according to wikipedia, propane boiling point is -43 F, so it should work down to that temperature

the problem with propane, is that at normal temperatures, it has a lot of pressure, so you need a heavy container, like the one's they sell it in for camping

I think there are adaptors that you can screw onto a propane canister that has a Lindal connection for a canister stove. Or you could use a heavy stove designed for propane bottle

You could put 100% propane in a butane canister and as long as you kept it below some temperature, it wouldn't explode. Probably not smart to do this including transferring the propane, but make sure you have video running to capture the experience : ) and make sure you have health insurance (e.g. obamacare) and a will.

If you re using an inverted canister stove at very cold temperatures what happens if you apply a chemical hand warmer to the inverted bowl? Seems like it would help in an emergency without being dangerous?

Or…?

Bill

My understanding is that the whole point of inverted canisters is that they allow the propane to do it’s vapoury thing in the cold canister and force the liquid butane/propane mix into an environment (the warm stove) where the butane can gasify. This minimises the preferential loss of propane from the mix and so the canister still works until almost empty. No need for pure propane.

If you re using an inverted canister stove at very cold temperatures what happens if you apply a chemical hand warmer to the inverted bowl? Seems like it would help in an emergency without being dangerous?

Not dangerous at all.

The very (very) conservative DoT rating for canister temperature safety is 50°C (122°F) and there is no way in Hades that a chemical handwarmer by itself is going to overheat a canister.

The “Touch Test” is the quickest method to check: If the canister is not too hot to touch, you’re good to go. If at any point it gets too hot to touch, turn off the stove and let it cool while you assess the situation.

Good reading HERE, where this and other cold-weather canister warming techniques are explained clearly by Gary Dunckel.