Some testing of heat exchanger pot (eta power)

I put my new Primus 1.0L eta pot to the test against a regular kitchen pot. Both are heated with a MSR pocket rocket running on almost full can of Primus gas, with 0.5L of tap water. Eta pot also has the Primus clip on windshield, thou the test was conducted indoors (too cold outside for upright canister stove), so it may only function as a poor heat reflector.

Regular stainless kitchen pot came to rolling boil at 2 minutes and 15 seconds, eta pot came to rolling boil at 1 minute and 45 seconds. So in the end that's only 30 seconds of time saved, or around 25% efficiency increase, a far cry from Primus' claim of 50%.

The price of Eta pot is about 60% higher than Primus litech, which is essentially the same stuff without heat fin, and perhaps even closer to eta's efficiency compare with the stainless kitchen pot.

So is it worth it, I don't know, from pure cost saving POV it's going to take a whole lot burn to make up the price difference. But on the other hand you can squeeze a few more boil/meal out of the same fuel canister when there is no spare, and that could come in helpful depends on the situation.

Thanks for the tests / review.

I have the Primus Litech Kettle / pot and really like it. When I purchased it about 2-3 years ago, I also looked at the EtaExpress pot you tested and decided at the time, that the addition of the heat exchanger and subsquent extra cost was not worth the investment to gain only 10's of seconds of claimed heat time.

Thanks for the figures. I suspect the difference would be even less if your standard pot had a typical cobbled up, aluminum foil wind screen, not as highly efficient, but light, cheap, and versatile.

Thanks for the review, it confirms typically the same 25-30% improvement in fuel consumption that I have found for gas burners of a medium heat output such as the MSR pocket rocket. I have found that slightly higher efficiency (by comparison) is available using the 1.7 litre pot with gas burners with much higher output such as the Coleman F1 Power stove, which will produce almost twice the heat output of the MSR pocket Rocket. Using conventional pans with the Coleman F1 at the maximum heat output tends to send a lot of the heat up and around the pan, where as the Primus Eta Power seems to 'capture' the heat much more effectively giving boil times less than 1 minute for 0.5 litre of water.

Typically if you can get around 12 Litres of Boiling water with a conventional SS pan and an 220 gm cartridge the 25% improvement in efficiency will get an you an extra 3.75 Litres giving almost 16 Litres in total. Thats equivalent to an extra day or two in cooking capability out in the wilderness all for an extra 40 grams of heat exchanger.

With the larger 500 gm cartridge the differences are even greater giving an extra 3-4 days extra cooking/boiling capability.

The 1 Ltr Etapower pot is certainly appears to be lot more expensive to purchase since they initially appeared on the market though. The Etapower 1.2 Litre pot is available for much less cost though.

http://www.amazon.com/Primus-Eta-PackLite-Litre-Colander/dp/B003EM75EK/ref=pd_sbs_sg_5

Rather than spending around $58 for the 1 Litre Etapot I would spend the extra $15 and get the EtaPacklite stove system instead.

http://www.amazon.com/Primus-354083-PACK...155&sr=1-15

http://www.youtube.com/watch?v=JF-TxE20m9c

In an indoors test, a windscreen won't make too much difference unless it can be made to function as a skirt where hot air is channeled up along the sides of the pot.

In the field, in wind, I'd take a windscreen over a heat exchanger pot pretty much any time unless the particular heat exchanger pot were to provide some wind protection. The Jetboil PCS offers some, and the MSR Reactor offers a lot of wind protection.

On the other hand, a Jetboil GCS's heat exchanger is exposed. Heat exchangers cut both ways. A strong wind can suck heat out via a heat exchanger just as much as a flame can put it in. I've read posts where a person burned an entire canister of gas but couldn't get their water to boil.

Manufacturers typically say "never use a windscreen with an upright canister stove." Of course those warnings are primarily to prevent lawsuits. The reality is that in temperate conditions, a windscreen with something like 270 degrees of coverage around a canister stove probably won't overheat a gas canister if you know what you're doing, particularly if it's windy.

The trick is to feel the canister. If it feels hot (hot, not warm) to the touch, then you need to take immediate corrective action. As long as the canister is no more than warm, then it's perfectly safe to use a windscreen. You just need to be diligent and repeatedly feel the canister. This is not something that you light and then go set up the rest of camp while dinner cooks. You need to feel the canister and keep a close eye on things.

In cold weather, you can go with a lot more coverage, probably more like 315 degrees of coverage, just leaving enough gap that you can adjust the flame. The heat of the flame can work to your advantage, keeping the gas in your canister warm.

Using a windscreen with an upright canister stove is not without risk. If you know the risks and are a diligent person, you shouldn't have a problem. If you're easily distracted, maybe you shouldn't use a windscreen with an upright canister stove. For the easily distracted, a remote canister set up can be used with a windscreen and will never need checking. The windscreen with a remote canister set up protects the fuel from the heat rather than transferring heat to the fuel.

I've got an article coming out in the April edition of Seattle Backpacker's magazine that will discuss remote canister stoves further.

The times where it might be really worthwhile to have a heat exchanger pot are:
a) Snow melting. Snow melting can take a long time. If you have a certain amount of time alloted before you turn in for the night, it may be worth it to have a heat exchanger pot so that you can get everything done in the time between the time you arrive at camp and the time you need to turn in. In really cold weather, your sleeping bag may be the only thing able to keep you warm enough. You don't want to spend a lot of time outside the bag messing around with melting snow.
b) Big groups. If you're cooking for big groups, you may have larger quantities of water to boil or food to cook. A heat exchanger pot can certainly speed things up.
c) Fuel availability restrictions. Say you're doing a longer hike. You need your fuel to last "X" number of days. A heat exchanger pot might help you do that. On a Sierra backpack in 2009, I got by with about 100g (one 4 oz canister) of gas for five days for three people (four hot suppers, four hot breakfasts, cold lunches). That's 25g of fuel per "day," (day = 1 breakfast + 1 supper) which is pretty danged good. I was using a Jetboil GCS (which has a heat exchanger pot) and a windscreen.

HJ

That's one of the reasons I picked the primus windshield, it will not reflect any heat down to canister, and everything in the photo will pack into the pot with room to spare.

I'm not so sure about that windshield. I notice that I can see the heat exchanger over the top of the windscreen.

On the plus side, I don't think that it would cause any heating of the fuel.

HJ

Yes some heat exchanger is exposed but burner isn't. Now that you mentioned it I see the problem, looks like I need to tweak it more.

One problem might be that the windscreen was designed to work with the Primus Eta Express stove. The burner height on a PR might be different. If the burner height on a PR is higher, then the windscreen might not reach high enough. I would think that for sure you'd want to have the windscreen go a little higher than the top of the heat exchanger. You could extend the windscreen a little bit with a couple of paper clips and heavy gauge aluminum foil or similar material. It wouldn't be pretty, but when you're hungry, who thinks about how pretty their stove is?

HJ

I've tried additional windshield by adding piece of aluminum to cover the heat exchanger. It actually made efficiency lower, boiling is back to 2 minutes. I think because the shield is so close to the pot, it's interfering with airflow through the fins, which they need in order to function properly.

Yeah, I wouldn't cover the fins, I'd extend the windscreen a bit.

HJ

Wrong choice of words, I didn't actually cover the fins. What I did was wrap heavy duty aluminum foil around the pot to form a skirt, which connects with the windscreen and block any wind from cooling the fins.

Needs more tweaking I guess.

Photo?

The original had a full skirt, I cut it down a bit last night while testing.



I cannot just extend the windscreen, because while it's larger diameter than the heat exchanger, it's actually smaller than the pot itself, so extension wouldn't go over the pot.

I think the original design of the windscreen is only to protect the flame anyway, which it does pretty well. It's not the screen off eta express, it's similar but intended as a stand alone product.

Well, give it a try, but if the heat exchanger is exposed to the wind, it can actually remove heat from the pot.

Have you tried attaching the extension to the windscreen and not the pot?

HJ

The windscreen is too narrow (it needs to fit inside the pot).

What I think I'll do with this setup is, I'll leave the skirt up when there's no wind (it's sort of attached to pot and can slide up and down easily), but if wind is strong enough to cause a problem I'll lower the skirt, and live with the air flow interference since it's the lesser of the two evils there.

The distance from skirt to pot, the gap, should be 10mm, otherwise it might choke your fire
Pot Skirt Investigation, ETHOS 2010

Nice diagram! And I would agree. There needs to be separation from the pot and the skirt or windscreen or it won't work right.

HJ

Yeah that's the problem, I need everything to fit inside the pot, so to make something that much bigger than pot is a bit beyond my available material and tools. And I don't like to use anything that folds repeatedly since the folds eventually break without warning.

Going to take a bit of brainstorming to see what I can come up with.

Don't be tellin' me how to wear my skirts.

Have you considered rolling the windscreen extension and placing it up against the walls of the pot? It can be rolled a bit tighter for storage and then loosened up for use.

HJ

I suppose that'll work too, even though I tried to make this set up self contained. But since I don't need a full height screen, I want to figure out something that will attach to the Primus screen and only cover the gap. Still working on it.

Also looking into the possibility of switching the stove to Gigapower or crux, which seem to have a lower burner height and may work better without addition of screen.

One thing I don't like about the Gigapower is lack of any real grip on the arms as compared to the Pocket Rocket. Pots do slip more easily off the Gigapower and nothing worse then seeing your dinner kiss the dirt if you are not real careful. I have seen this more then once with these stoves. Admittedly, it can happen with any stove though...

Also the height of the arms on the Gigapower are not much lower then the Pocket Rocket and I would surprised if it really would make any appreciable difference in cook/boil time to warrant the re-purchase of another stove. The Gigapower currently sells at MEC for $43.00. For that price, you can purchase 7 cannisters of Isopro for the Pocket Rocket and have hours of fuel burn time that would be very tough to beat, investment wise of only probable mere seconds of theoretical (and untested) extra burn time by the concept of the lower height arms on the Gigapower.

I have both the Pocket Rocket and the Giga Power GST-100. The GST-100 is definitely more compact. I'm not sure that the power is sufficiently greater to make a meaningful difference over the Pocket Rocket.

The Pocket Rocket's pot stands are far more easy to bend. The Giga Power is a lot more solid. Is the GST-100 sufficiently better that the increase in price justified? That's a judgment call for each individual to make.

Regarding the GST-100's pot supports being slippery, a simple file can take care of that. Rough 'em up a bit. It does help.

HJ

That's interesting regard the pot support, I just read another thread (on another forum) where people were complaining that pocket rocket's supports are slippery, and gigapower's support is better.

I have been using a PR for over ten years - basically it has become my main, "go to" stove. I have not had any problem with alleged slippery supports. If you ask me there is a lot of nit-picking out there.

I see a Mythbusters style of testing in the near future. Right Jim? (I nominate him as he has both types of stoves!)

Well, maybe, if I can get the time. And what's the objective testing protocol? Perhaps angle of slope? But I've got something coming up that takes precedence over pot support "slipperyness" testing.

My next gas project is to try to prove or disprove that the Soto Micro-regulator stove (OD-1R) has an advantage over conventional needle valved-stoves (Pocket Rocket, GST-100, etc.). That's going to take some planning and prep. God only knows what I'll find out, although I have my suspicions.

HJ

The Soto is bit pricey for a cannister stove and I don't know anyone who has one...which is uncommon in this area. For the cost (around $70.00) you would think that a better investment would be to purchase the Whisperlite for nearly the same price ($72.00 here.)

Anyway, looking forward to the comparison project.

Yeah eh? $70 is a bit too much for what I'd spend on a canister stove.

I was able to pick up a new Soto for $48.00 total. Still more than I wanted to pay, but I'm curious about the stove. I need to run a series of comparative tests on it.

I suspect that at 5C above the vaporization point of a given fuel, both a conventional needle valved stove and a regulated stove (i.e. the Soto) will run equally well.

It's the range between about 1C to 2C above the vaporization point of the fuel up to 5C above vaporization where I think the regulated burner will have an advantage.

Now is the ability to operate in temperatures that are only 2 or 3 degrees C lower than what a conventional stove can operate a meaningful advantage, and does that ability justify the Soto's high price? Well, that's mostly a judgment call, but for me, I don't think 2 to 3 degrees C difference justifies paying $30.00 more than something like a Pocket Rocket.

To me fuel selection (propane and isobutane only, no n-butane) and putting the canister in a pan of (liquid) water are better, cheaper options. As long as a canister of propane-isobutane is kept in liquid water, a needle valved stove will continue to operate. Isobutane boils (vaporizes) at -12C/11F. Liquid water has to be above 0C/32F. At 12C/21F above the vaporization temperature, you should have plenty of gas pressure.

But, that's just what I think based on the chemistry and technology involved. I won't know for sure without some testing.

HJ

Okay this is the final iteration of this set up. The additional shielding is stored on the pot itself and only installed when necessary. I would like to seal the gap between it and windscreen but see no easy/compact way of doing it. Still I think this is about as windproof as it gets and still fit everything inside the pot.

Looking good! Have you tested it at all?

HJ

P.S. Nice adapter.

Still too cold outside for a canister stove to work properly, going to set up a fan indoors to try it tonight.

Haha, thanks for telling me about the pick up tube, otherwise there's no way I'd known about it!

Yeah, in order to use that adapter, you have to orient it correctly. If not, you've got a liquid feed which is a problem if you're stove doesn't have a pre-heat loop. Actually, any adapter that uses the 100% butane bayonet connector type canisters needs to be oriented notch up.

HJ

Oh boy, this is not good, my new discovery just put a big kink in this setup I just completed.

Primus express spider plus a fuel canister will fit inside the pot! So for no size increase and minimum weight addition I can have a remote canister stove with pre-heat loop. So now I'm thinking revamp the setup to around that stove instead, but that would mean my current windshield and butane adapter would be useless.

Urg, I need to learn to be happy with what I have...

The butane adapter will still work with the Primus Express Spider remove stove (although I doubt the butane adapter will fit into the Eta pot with the rest of the gear) and you can make your own custom wind shield and bottom heat reflector using titanium foil available from;

http://www.titaniumgoat.com/windscreens.html

You can also peg out the wind shield using a couple of titanium tent stakes to keep everything in place for the new stove.

It would work but there are much smaller ones without the legs and plate from Kovea.

I'll see, going to wait till the store have one of their regular sales to get one.

Having a remote canister stove with a pre-heat loop doesn't buy you all that much in warm weather. An upright canister set up is pretty quick and easy and is the most popular configuration.

For windy or cold weather, though, the remote canister set up sure is nice.

HJ

You might hold off on getting the Kovea adapter for a remote canister set up, at least for cold weather. The remote set up in cold weather really needs a propane-isobutane gas mix to work well. The adapter is for just 100% butane which is a poor cold weather fuel. For temps under 5C/40F, I'd stay away from the adapter and 100% butane.

HJ

Not in warm weather, but it would greatly extend the flexibility of the set up into colder temperature.

Good call on the adapter, no point really in getting one.

If one were to get only one stove and try to do everything with that one stove, then a remote canister stove with a pre-heat loop would cover everything from about 0F/-18C on up (that's canister temperature, mind you, not ambient temperature). I'm assuming of course that one is using a propane-isobutane fuel canister. Regular butane just isn't good for cold weather. One can go colder than 0F/-18C if one employs canister warming techniques.

In other words, one can cover a whole lot of "territory" temperature wise with a single stove -- all but the coldest weather.

However, one can shed quite a bit of weight in fair weather by going with an upright canister stove, so I wouldn't say the upright canister stove should be counted out just yet.

For "fast and light" fair weather trips, I tend to to take and upright canister stove.

For trips where I anticipate temperatures between 0F/-18C and 40F/5C, I'll either take a liquid fuel or remote canister (with pre-heat loop) set up. If there's a possibility I'll need to cook in my tent, I'll generally go with gas.

If temps are going to be below 0F/18C, I start looking at a liquid fueled stove burning kerosene (kerosene being a bit safer to burn in a tent if need be).

On short trips where weight isn't at a premium, I tend to go with liquid fuel simply because liquid fuel is so cheap. A 110g canister of gas (four ounces by weight) costs $5.49 (tax included) versus $0.38 for the same amount of liquid fuel. Gas is about fourteen times more expensive than white gasoline if bought in four ounce canisters.

HJ