Choosing a Hanging Stove

As you may know from my earlier post, I recently got myself a Primus ETA Lite. Now why did I wish for that particular stove? To tell you the truth it was a close race between some very specialised ones. I wanted one for alpine- and bigwall climbing, and that already narrowed the field down to gas stoves well suited for hanging. For 1-2 people, a useable volume of 0.5 L is sufficient when boiling water, and 1 L when melting snow. When backpacking or in a basecamp for any length of time I would prefer a bigger pot and a stove suitable for liquid feed. Anyway, here are the contenders:

Jetboil SOL-AL, Jetboil Flash, MSR Reactor 1.0 L – and Primus ETA Lite.

In order to be able to compare stoves, like now, I have begun developing a scoring system. For the purpose of this comparison I show relevant parts in the table below. 

Scoring System

Score	Weight	Packed Volume	Internal Volume	Wind	Simmer Control	Hanging Kit	Adaptor
*	<500 g	<2.0 L	>0.5 L	Fair	Fair	Fair	Fair
**	<400 g	<1.5 L	>1.0 L	Good	Good	Good	Good
***	<300 g	<1.0 L	>1.5 L	Excellent	Excellent	Excellent	Excellent

Whereas weight is important for obvious reasons, among manufacturers there is less focus on the packed volume. To me it is as important as I don’t want too much bulk in my backpack. Some of the parameters are entirely subjective and some are difficult to evaluate. For example there is no standard for comparing wind resistance. Until such has been developed we will have to depend on hearsay :-)

Comparing the Stoves

Below are shown the dimensions and weights of the stoves as specified by the manufacturers. The external volumes were calculated based on the specified dimensions, and the usable volume is the maximum level recommended by the manufacturer or the maximum level indicated on the pot.

Dimensions and Weights (including hanging kits)

	Weight	Diameter	Height	Packed Volume	Internal Volume	Usable Volume
	g	cm	cm	L	L	L
Primus ETA Lite	355	10	15	1,18	0,75	0,5
Jetboil SOL-AL	354	10,4	16,5	1,40	0,80	0.5
Jetboil Flash	454	10,4	18	1,53	1,00	0.7
MSR Reactor 1.0 L	445	12	15,5	1,75	1.00	0.7

Wind Resistance

While the reactor is said to be notoriously stable in even the harshest of winds, the other two are lass so without being sensitive to wind.

Simmer Control

Some have found a way to make the Reactor simmer, however some care is needed, and it gets a small star for that reason. The other two simmers easily and gets three stars.

Hanging Kits

The Primus hanging kit is very elegant, as you just have to flip over the handle and tie on the supplied string. The MSR hanging kit is also nice as it is made from thin wire, which fit inside the pot. The Jetboil hanging kit on the other hand is made from wires and three aluminium rods, which do not fit inside the pot.

Adaptor
Even as these stoves are designed with the particular scope of fast and light travel and cooking they may have an adaptor making them some kind of suitable for normal cooking.

Using my scoring system on the above data and assessments leads to the scores shown in the table below.

Scores

	Weight	Packed Volume	Internal Volume	Wind	Simmer Control	Hanging Kit	Adaptor	Score
ETA Lite	**	**	*	**	***	***	*	15
SOL-AL	**	**	*	*	***	*	*	12
Flash	*	**	**	*	***	*	*	11
Reactor	*	*	**	***	*	**	-	10

The Reactor scores one * less in the external volume department as the handle makes it a bit less unhandy when squeezing it down a backpack.

Fuel Consumption

Comparing fuel consumption based on manufacturer statements is impossible because of lack of detailed data. The burners and heat exchangers from Primus and Jetboil looks alike, so presumably they are in the same ballpark. The MSR proprietary heating system and heat exchanger differ from any other on the market. The system is said to be hugely wind resistant but at the same time something of a fuel hog. The other two are said to be of average to good wind resistance and more economical with regard to fuel.

Summing Up

When comparing the reviewed hanging stoves, the Primus ETA Lite fits my purpose best.

Later I will post a detailed review of the Primus ETA Lite and possibly the MSR Reactor 1.0 L.

Cheers!

Electrical and Gas Powered Water Boilers

The other day I got two water boilers as birthday presents. The Braun Multiquick 3 is an electrical powered water kettle for kitchen use and the Primus ETA Lite is a backpacking stove running on canister gas. The manufacturers state their water boilers abilities to boil water “fast”: 200 mL in 45 sec and 0,5 L in 2 min 45 sec respectively. Additionally, Primus states their ETA technology to achieve efficiencies close to 80%.

Now, which one is the fastest, and what are their efficiencies?

To find out I ran a series of tests[i] measuring the time to boil various volumes of tap water. Then I calculated the energy spent by the water boilers based on effect data submitted by the manufacturers, and the energy absorbed by the water based on the water volumes and the temperature gain.

Braun Multuquick 3

Volume	Time to Boil	Energy Spent	Energy Absorbed	Efficiency
(mL)	(s)	(J)	(J)	(%)
200	51	112200	71400	64
500	98	215600	178500	83
1000	197	433400	357000	82
1700	337	741400	606900	82

The time to boil 200 ml water by the electrical powered water kettle from Braun was measured to be 6 seconds  (13%) slower than stated and the mean efficiency was calculated to be 78%.

Primus ETA Lite

Volume	Time to Boil	Energy Spent	Energy Absorbed	Efficiency
(L)	(s)	(J)	(J)	(%)
100	34	51000	35700	70
200	64	96000	71400	74
300	97	145500	107100	74
400	134	201000	142800	71
500	171	256500	178500	70

The time to boil 500 ml water by the gas powered backpacking stove from Primus was measured to be 6 seconds  (3.6%) slower than stated and the mean efficiency was calculated to be 72% which is ballyard “close to 80%” as stated by Primus.

Comparing the two beasts at the two common data points, 200 mL and 500 mL, the electrical device proved to be faster than the gas device by 13 seconds and 73 seconds respectively. Similarly, the electrical device was the more efficient overall.

To sum up, the water boilers appear to live up to manufacturer claims and they are both very energy efficient.

Calculations

The energy spent was calculated from the stated effects multiplied by the time to boil:
Energy (Joule) = Effect (Watt) x Time (s)

The energy absorbed was calculated from the water volume converted to weight multiplied by the rise in temperature multiplied by calories converted to Joule:
Energy (Joule) = Volume (ml) x 1 g/ml x 85 (K) x 4.2 Joule/calorie.
The rise in water temperature was calculated from the boiling point of water minus the tap water temperature: 373K - 288K = 85K.

Technical Data:

	Braun Multuquick 3	Primus ETA Lite
Maximum capacity	1,7 L	0,5 L
Effect	2200 W	1500 W

Additional Data (stated for reference):

Room temperature: 295K (22 °C)

Tap water temperature: 278K (15 °C)

Atmospheric pressure[ii]: 1020.4 hPa

Humidity[ii]: 80%

Elevation: 50 m

Gas: 20% Isobutane, 80% Propane mixture from MSR.

Endnotes

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[i] In order to cool down the water boilers between each boil they were filled with cold tap water three times and left to stand at least one minute each time.

[ii] Source: Danish Meteorological Institute

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2014-11-10

Additional test

I visited my brother, Kåre the other day celebrating the birthday of his oldest son, Rasmus. Kåre has a MSR Reactor 1.0 L, a reversible vacuum cleaner and an anemometer. So we did a few boils while his guests were entertained otherwise:

The Reactor boiled 0.5 L of 12 C cold water in a bit less than 2 minutes at zero wind. Using a stated of 2750 Watt we calculated its efficiency to be 56%. Bear in mind the uncertainty of a one-point measurement and a stated value found on the Internet. However it is a bit low when compared to the 72% of the Primus ETA Lite. On wind stability: We found the Reactor stable up to at least 17 m/s when the anemometer maxed out. In comparison the Primus ETA Lite blew out at that wind speed, while it was ok at 5-6 m/s. These initial results call for a more thorough study. Will return.

Cheers!