Melting Snow with Jetboil

Last weekend on an attempt on Whitney I learned my system might not be quite as good as it seemed on day hikes.

First, arriving at the trailhead at 8,000', temp around 40F I encountered two guys doing a Jetboil boil-off. One with the new Jetboil Sol (aluminum version), the other with the older PCS. The Sol had a much stronger flame and boiled much sooner.

Up the mountain I had my PCS and my partner had the inverted canister Helios system. Set up on a rock with strong gusty wind mine took a long time to boil snow. His did much, much better.

My bottom cover/bowl had cracked so bad that I couldn't use it to hold water, so my method of keeping the canister in a water bath didn't work.

I'd like to try a Sol and bring a supplemental windscreen, but for serious winter use I concur that inverted canister is the way to go.

I'm still 100% sold on the heat exchanger concept though.

"Last weekend on an attempt on Whitney I learned my system might not be quite as good as it seemed on day hikes."

How were conditions on the mountain? Which route?

–B.G.–

Bob,

Intended trip was up Mountaineer's Route. To "Frog Ponds" between Upper Boy Scout and Iceberg Friday, summit Saturday, hike out Sunday.

There was several feet of week-old snow which was still consolidating- soft, slushy, voids around rocks. We started hiking about a mile below the Portal trailhead at approx. 7900'. Friday was warm (too warm) with the lower section of North Fork being a solar oven with slushy snow. At least the willows and creek were covered so we could snowshoe instead of zigging up the ledges.

Last year I did the same route and plan while being in somewhat worse condition (I think). Piece of cake. Difference was walking on firm surfaces (rock & snow) plus being able to drive to Portal. This year I was rather beat upon reaching camp. Extra mile, soft snow, and weight of snowshoes was probably the difference. Friday night my legs were aching. Saturday morning was windy with gusts in the 40 mph range- big snow banners blowing off ridges. Salvation for my legs- it would definitely be too windy past the notch for my skill level. Headed back down.

Jim

Question —

The temperature of the snow on this trip would be 32F right? If so, why not pack a lot of snow around the canisters? That would keep it at 32F correct?

In winter I have used several MSR white gas stoves and an inverted Windpro this year with good results. But the fiddle factor of heat reflectors and windscreens versus the Jet Boil is something to think about. Also, in winter the weight of the newer Jet Boil is not a negative, versus what others are using (Whisperlite, Dragonfly, Windpro, etc.).

Steel is a solid at very high temperatures, but not all solid steel is hot.
Similarly water is solid at 32F, but not all solid water is 32F, it can be much colder.

"Similarly water is solid at 32F, but not all solid water is 32F, it can be much colder."

Right. But Jim said the snow was soft and slushy. I don't know the answer, but it seems that it might work. Also a pouring some water into something like a margarine container and placing the canister in it might be an option. Just thinking out loud here.

I am not going to buy a Jet Boil, already have way too many stoves :)

As you run the canister, it releases heat due to evaporation of fuel inside canister

You have to transfer heat from the environment, into the canister, to keep it from getting too much colder

If there's snow around the canister, this heat transfer will be inhibited, because the snow is an insulator

I'm not saying you shouldn't try it, but this effect may make this not work

Water in tub works – you probably have to add some water heated from the stove to keep it from freezing, if it's below freezing air temp

Finally it's snowing in California so I'm thinking of winter trips. Bringing me back to deciding whether I 'need' a new winter stove.

So I did some tests to try and approach a decision on upright canister vs. inverted, and if upright, do I keep my existing Jetboil or get something with more heat.

First, over simplifying some of the basics as I comprehend them: (My apologies for any confusion due to my mixing of units). If I got any of this horribly wrong do tell and I'll edit (with attribution of course) to reduce confusion.

Upright canister stoves use a pressurized flammable gas (liquid under pressure, gas in use). They shoot it through a small orifice, mix it with air, then burn it. Pressure differential between the two sides of the orifice determines flow velocity through the orifice. The orifice size (cross sectional area) times the flow velocity determines the gas flow volume. A valve regulates the pressure at the orifice from 0 (valve off) up to a maximum of the pressure in the fuel can (presuming that the valve and fuel lines are oversized compared to the orifice.) Normally the air inlets are non-adjustable.

Pressure in the fuel can is based on the boiling point of the gas(ses) and the temperature. Pressure outside the fuel can is… whatever the local atmospheric pressure is, and varies mostly by altitude, slightly by weather/temperature.

Commercially available stoves are designed to not explode or flame out at the upper range of possible environmental conditions. If too much gas is delivered it won't mix with enough air before reaching the burner and the flame will "lift off" or blow out, resulting in a dangerous condition of how stove and unburned, heavier than air, fuel. The way manufacturers generally do this is by sizing the orifice so that at the upper pressure range it doesn't allow an excessive amount of gas to flow.

Another method, standard on all modern propane stoves, is to use a pressure regulator. In the US, domestic and RV propane systems use either a single or two-stage regulator. The first drops from tank pressure to about 10 psi (69 kPa), the second drops to "11 water column inches" or 0.4 psi (2.7 kPa). Camping stoves and BBQ's generally have a single stage "high pressure" regulator which drops pressure to about 10 psi. The regulator uses a spring loaded diaphram to limit pressure on the downstream side.

Welding gas and air compressor regulators are somewhat similar but are adjustable.

A few butane backpacking stoves use a regulator- MSR Reactor, Soto Regulator, and Jetboil Sol are three. With a stable pressure differential between the valve and atmosphere, the designer of the stove doesn't have to compromise the designed orifice size/air inlet/burner configuration based on the maximum working canister pressure.

A final point on regulators- it's not a pump so it can't increase pressure from the can to the valve. It won't make isobutane jump up and dance at -10.

Bla bla bla.

What it comes down to is delivering butane gas and air to the burner. At low temperatures it means low pressure gas which means you need a bigger orifice to get much heat.

At 68F/20C a 30/70 propane/isobutane mix sits at about 4 atmospheres (bars) of pressure (per http://www.bushwalking.org.au/FAQ/FAQ_Mixtures.htm read Roger Caffin's whole article if you haven't already) At 32F/0C it drops to 2.5 bar. Under cold use the propane boils off much faster than the isobutane, so we need to see the pressure of pure isobutane or maybe a 10/90 formula. Pure isobutane is at 1.6 bar, 10/90 is at 1.8. Then of course at 12F/-11C the isobutane is at 1 atmosphere and happy to take a nap in an open container at sea level.

Remember, it's not the absolute pressure that's important, rather the differential between the fuel and atmospheric pressure. At sea level, room temperature there is 4-1= 3 atmospheres or roughly 45 psi pressure differential. At freezing (32F/0C) there's only 0.6 atmosphere or 9 psi pushing that isobutane out. Get up in altitude to 3,000 meters and the basic barometric pressure drops to 70% so you get 0.9 bar 13 psi.

OK. On to the D&#* Jetboil PCS. It was designed to be super efficient. The burner output is low so it doesn't waste energy up the sides of the pot. Also because of the built-in wind screening effect of the fins and base plate, too much gas would probably flame out. Finally the neoprene cozy would get burned up if too much heat blows past.

I'm not sure of the jet size, but the jet does have "21" stamped on top so I think it may be 0.21 mm. This is based on the Jetboil website mentioning that the Helios jet is 0.25 mm, and the Helios is close to double the PCS output.

All this means that the rated power level is low. Originally advertised as 5200 btu, I seem to recall one of the ads for the Sol mentioned that the PCS is 4500 btu. And it is probably rated at STP (70F, sea level), with a fresh can of "Jetpower" Isobutane/propane mix. That means the rating is based on having 3 bars, or 44 psi pressure across the jet orifice. At freezing (32F/0C), with a partly depleted canister the pressure differential drops to 0.6 bar or 9 psi. Basically 1/5 of the rated amount.

At least that's my theory. Time for a test. I don't think air temperature is a critical part of the test. Most important are canister temperature and cooking water temperature/volume.

I had a mostly used Snopeak GigaPower 110 gram fuel can (24 grams fuel remaining). According to the Snowpeak website this fuel is 85% isobutane and 15% propane, though this can is a couple years old and some older reports had it at 80/20.

Conditions of test:
55F garage, no wind.
500 ml of ice cold water (32F/0C) per run, strained from pitcher filled with ice cubes and water.. PCS pot pre-chilled with ice cubes and water between runs.
I measured the time to raise temperature to 80C, using a dial coffee steaming thermometer.
Fuel consumption amounts using an empty fuel canister to set my scale tare. My scale is probably really only accurate to about 2 grams.

First test was mostly to attempt to boil off as much propane as possible from the canister. I used a Brunton Stove Stand to more easily maintain canister temperature.
Fuel Can attached to stove stand and a bowl of ice cubes was stored overnight in a -10F/-23C freezer, then wrapped in a towel for the test to maintain cold condition.
14 minutes 80C° temperature rise
4 g fuel used ending with 20g remaining
The flame was seriously weak! If outdoors any tiny bit of wind would have blown most of the heat away. Extrapolating from this test, going from snow to 0.5 liter of boiling water would take more than 1/2 hour!

Next test to see how the can would perform right at freezing, now that most of the propane is gone.
Cold 0C canister in ice and water bath
6:04 minutes 80C° temperature rise
5 g fuel used with 15 g remaining
Way better, but still weak. The canister might not have fully warmed up to 0C at the start. It did have a thin coating of ice on the bottom and one side after the test.

Next test with stove upright (no Brunton Stove Stand)
Cold 0° canister in ice and water bath
6:10 minutes with 80C° temperature rise
5 g fuel used with 10 g remaining

Next test to see if under warm conditions such an empty can would still deliver
Warm 25C° water bath
3:05 minutes with 80° temperature rise, 4:00 to full boil, canister ran out at 8:32

Final test with a half full canister (63 grams at start) in icewater bath
3:40 minutes for 80° temperature rise, boil at 4:30 minutes (My timing might be off on this run)

Back to my theory- that the pressure at 0C with only isobutane would be 1/5 of room temperature on a full can. I think this is off a bit as my 0C tests resulted in only double the heating time as the 25C test (though the 25 C test was on an almost empty can.) I may re-do the "standard temperature & pressure" test with a full can.

I do think that an upright canister could be a good performer in cold weather if you can keep the canister in a liquid water bath- even if that water is on the verge of freezing. The water acts as a big heat sink to keep the canister at a stable temperature.

In order to do this, one needs a bowl sized for the canister of choice. It seems that it would be best to have an insulating cozy, flat bottom, and perhaps three small feet so it isn't wobbly.

The questions I'm left with- Would replacing the jet with a larger orifice (maybe 0.25mm?) significantly boost winter performance? Some of the small canister stoves are rated at 9,000 btu or double the PCS. My PCS valve body has Primus stamped on the side. Do all Primus jets have the same threading? Is there a catalog somewhere?

Wow, that is some post. I generally agree with most of it, apart from:

"First test was mostly to attempt to boil off as much propane as possible from the canister"

You didn't have to do this. With only 24/110 = 22% gas remaining, the propane has already gone. The propane burns off regardless of what the temperature is, 50F or 20F, the propane still burns off faster than the butane. The weak flame you got is because of the low temp and because with 24g gas left, the propane has already gone.

"Would replacing the jet with a larger orifice (maybe 0.25mm?) significantly boost winter performance?"

The jet size is tuned to the burner assembly: the size and length of the mixer tube and the x-sectional area of the holes in the burner head. Changing the size of the jet will change the gas/air mix, most likely you will end up with a yellow flame.
I have seen two different threads on jets but I don't know what the jetboil uses.

Jim,

Pretty good write up (albeit long!). So, if I may play Devil’s advocate for a minute, why not just get a new stove? The regulator is there, and presumably the larger jet is already installed. Might just be easier. If you need greater capacity than the Sol’s 800ml mug, the 1000ml PCS mug should fit fine.

If you just like experimenting (I can relate to that), then by all means have at it. I’d contact Jetboil, but probably the Sol’s jet and the PCS’s jet have the same thread.

Of course, you’d need to be careful with such experimentation. There’s a reason why the PCS has the jet aperture size that it does. Increasing the jet size in cold weather probably will be fine. Increasing the jet size in warm weather could be disastrous.

HJ
Adventures In Stoving

"why not just buy a new stove?"
Well there's this thing called money.
Anyhow I found a new Jetboil Sol aluminum on eBay last night for $90 shipped. Couldn't stop myself.

When it arrives I'll repeat the same test with another canister which also has 25g fuel remaining.

If all goes well I will probably buy the 1.8 l Sumo pot for winter and family trips. I like the fact that it will accept the stove still attached to a 230 or 450 gram fuel can. It's also a much better size for snow melting.

I repeated my tests above with my new Aluminum Jetboil Sol. PCS TIMES IN (parenthesis)

Conditions close but not identical. Canister had 25 grams left and spent the night in a -22C freezer. I skipped the first test with the can at that temp. Instead started with the ice and water bath. Used 500 ml of 0C water.

Jetboil Sol
4:02 for 80C temp rise (PCS 6:07)
5:07 to full rolling boil
(Avg of two tests, 6 sec variation)

Brought canister up to 25C and repeated.
1:58 for 80C temp rise (PCS 3:05)
2:28 to full rolling boil (PCS 4:00)

Clearly with low pressure in the can the Sol is much quicker. Still not a winter powerhouse though.

"Clearly with low pressure in the can the Sol is much quicker. Still not a winter powerhouse though"

Jim, I have not read this entire thread and too be honest I probably won't, however the Jetboil Sol was never intended to work in true winter conditions, let alone be a "winter powerhouse". Even their own website state that the Sol will only produce "consistent heat" down to 20F and in Colorado that is hardly scratching the surface of winter.

FWIW, I have an older Jetboil PCS for 3-season use. I like the ease of simplicity over alcohol stoves and my SP Giga Power for alpine conditions. In the winter it is the MSR XGK, my climbing partner uses the old Whisperlite– both of which can be found used online for $50-$80 these days and are much better winter stoves than both the Jetboil Sol and inverted canister stoves. If you want a winter powerhouse then IMHO, you are looking in the wrong direction.

> I'm not sure of the jet size, but the jet does have "21" stamped on top so I think it
> may be 0.21 mm. This is based on the Jetboil website mentioning that the Helios jet
> is 0.25 mm, and the Helios is close to double the PCS output.
The early models of the Jetboil were made by Primus under contract. Primus have confirmed to me that Jetboil asked them to limit the power output. A 21 micron jet would be about right.

. Would replacing the jet with a larger orifice (maybe 0.25mm?) significantly boost winter performance?
Hard to tell. What might happen is that the larger jet could mean a lower gas velocity, and hence lower air entrainment. That would give orange flames, less heat, and more CO.
You could try a 23 micron jet (say) – that small increase might work.

Cheers

Paul, Roger,

Thanks for your comments. I apologize for the long posts. I certainly could have edited better.

What I love about the PCS is its simplicity in use. I was hoping to stretch it to allow light winter use. At this point it's clear that the upright Jetboil is not a winter stove. When melting liter after liter of snow in cold weather I suggest a more appropriate stove.

That said, I have been pretty happy using my PCS for midday snow melting and drink brewing on day trips. Here in California the daytime temps are generally not much below freezing and altitude is usually at least 8,000 feet (2500 meters) lowering isobutane's boiling point to about minus 5F (-20C). Sol is much better than the PCS so where PCS worked, Sol should too.

ON EDIT: Adventures in Stoving page with Isobutane vaporization temp vs. altitude chart:
http://adventuresinstoving.blogspot.com/2011/11/how-cold-can-i-run-my-gas-stove.html?m=1

You might find this video interesting. He put the canisters in the freezer over night.

http://www.youtube.com/watch?v=ax4Oh_NpstU

They now make a windscreen for the Soto – I was able to fashion one similar our of an aluminum can.

It clearly shows that the regulator on the Soto makes a big difference. That video was instrumental in convincing me to upgrade to the JB Sol which also has a regulator.

Hi Jim

> It clearly shows that the regulator on the Soto makes a big difference.
Pity the laws of physics don't agree with you.

A regulator is no different from a needle valve as far as physics is concerned. It will not increase the gas pressure, ever. Anything you can do with the SOTO can be done with most any other upright stove.

That's not to say a bit of clever showmanship can't make it look different. I can do that, dead easy. But it would be fraud.

Cheers

I completely agree that "It will not increase the gas pressure, ever." That's not the point- what it does is eliminate high gas pressure reaching the burner.

That way the designer can specify valve size, jet, burner, air inlets, etc. for a fairly narrow pressure range and gas velocity through the jet.

I'm certainly no stove designer, but it seems with a regulator they can design a stove to work best at something like 1 atmosphere of gas pressure (about 5C or 40F at sea level), not having to consider hot summer pressure of 6 or more atmospheres.

Or maybe my mistake is in buying underpowered stoves! The Jetboil PCS is spec'd as 5200 btu in the best case. Obviously it will only go down from there. If I had a stove that maxed out at 12,000 btu it could certainly stand to lose some power.

Roger,
Are you saying the guy that did the freezer test faked it some how?

I can only give my personal experience. I didn't take notes on conditions …

I have the Brunton Raptor 11,000BTU and was using it when hiking Colorado 14ers in the winter – March. It would do what was expected – under cold condition – once the propane was burned off – no fire.

I then got the Soto – under similar conditions as the Raptor – it works.

Here are some more tests on the Soto
http://www.backpackgeartest.org/reviews/Cook%20Gear/Stoves/Soto%20OD-1R%20Micro%20Regulator%20Stove/

If you want to see more tests on stoves and other things:
http://www.backpackgeartest.org/reviews/Cook%20Gear/Stoves/

> That way the designer can specify valve size, jet, burner, air inlets, etc. for a
> fairly narrow pressure range and gas velocity through the jet.
Yes, he could.
But he could also design the burner so it is not critical.
Look, almost every other upright stove on the market does just fine (or really well) with a simple needle valve – and that over a wide range of outputs and a wide range of temperatures and pressures.
Spin…

Yes, at 5k BTU the stove is seriously underpowered. White gas stoves get up to 10k (maybe!), while many good canister stoves get up to 12 k. Go buy a GST-100 for comparison. It is still our Gold Standard.

Cheers

Hi Paul

> If you want to see more tests on stoves and other things:
I know. I am an Editor at BGT.
But you can't buck the laws of physics.

Cheers

"Yes, at 5k BTU the stove is seriously underpowered."
Roger, A lot depends on how you look at things. At ~4500BTU I consider that too much heat for good fuel efficiency. Simmering/boiling/melting water on low behind a wind screen uses the least amount of fuel for the maximum heat transfer. All pots and heat exchangers will suffer from delays in transfering heat. The Jet boil is no different. Otherwise the wasted heat slides up the sides and out. The same as putting it in the wind.

On gas pressure, note that everyone seems to think that boiling point is the absolute minimum. Not true. Water, for example, vapourizes into the air at all temps, even directly from ice, though it exhibits a very low vapour pressure. This rule applies to butane, n-butane, too…or any miscible liquids. Like water and alcohol distilations, a eutectic mixture will occcur at some point below the boiling boint of n-butane. Regardless of the starting temperature (at the gas pressure of the jet or regulator) there will always be some n-butane mixed with the propane. It is not possible to seperate the two by boiling off one gas, in this case propane, by freezing the cannister below the boiling point of n-butane.

Try a hand warmer in cold weather. Tape one to the side or beneath the canister – let it heat up some before igniting the stove. They are also good in case of an hypothermia emergency – place them under the arm pits and/or the inner thigh. Serra Trading post usually has them also.

http://www.rei.com/product/760936/grabber-hand-warmers-10-pairs

I keep them in my emergency kit.