For some years now the MSR Reactor has been unchallenged as the king of high performance windproof water boilers. The Primus Ulti seeks to change this, with a compact, remote format catalytic stove for boiling water in the worst weather.
Vital Statistics
Weight: 600g (1litre size)
Boil time: 3.5minutes (1 litre)
Price: £285 RRP
Short Summary
| Pros | Cons |
| Boils water quickly | Heavy |
| Stable | Expensive |
| Supports canister inversion | |
| Sturdy |
Transparency Statement
This stove was purchased from Varuste.net during a promotional sale for £183.50. This review is not sponsored by Primus Equipment or any other party.
What is a catalytic stove?
Where an ordinary gas stove will burn with an open flame, which is highly susceptible to the wind, stoves with a catalytic burner do not have an open flame and direct a lot of radiant heat into the pot/pan. Combined with a pot that encloses the burner head, this type of stove design is highly resistant to the wind, often working well in scenarios where a traditional backpacking stove will fail to boil water.
Above you can see the Ulti burner glowing red – with no sign of the usual blue flame.
One thing worth noting about these types of stove – water boiling is pretty much their sole purpose. Simmering, frying etc – save that for your multi fuel stove. Catalytic burner stoves are designed to do one thing and do it well – boil water quickly.
Thoughts From The Trail
I’ve taken the Ulti on every trip I’ve been on since I purchased it, to get a feel for how it performs in real world usage. The Ulti’s main competition is the MSR Reactor – and you’ll see a lot of comparisons made with it in this review. I’ve owned an MSR Reactor for over 13 years, so it’s a stove I know very well.
One immediately noticeable difference is weight. The 1 litre Ulti is 600g vs the 416g reactor. For trips where you’re counting every gram, this does give the reactor the edge.
The Ulti feels sturdier for its extra weight. The pot’s handle has a reassuring side-to-lock feature that keeps it from folding back down unexpectedly. The handle feels reliable. Compare this to the MSR Reactor handle, which is held on by a hinge – which had to be recalled previously due to failure.
The lid is held on with a snug fitting rubber loop on the end of the handle, which secures to a stud on the side wall of the pot. This is easy to use with gloved or cold hands, and holds everything together neatly without rattle.
After over a decade of listening to the reactor rattle inside my pack, this is a subtle, but welcome difference.
The Ulti also boils water fast. It is only ever so slightly slower to boil than the reactor – a difference that isn’t particularly noticeable or burdensome.
The Ulti has a remote design rather than an on-canister design. Simply put, this means that the stove is connected to the gas canister via a short braided hose, rather than screwing directly on to the top of the gas can. This accounts for some of the additional weight vs the reactor. In fact – if you add the weight of MSR’s “Low down” remote adaptor to the reactor – the weight slightly exceeds the Ulti. Given the more robust feel of the Ulti’s burner and pot – this makes the weight a welcome trade-off in all but the most intensive gram-counting trips.
The remote design has three principal benefits:
Stability
Having a lower centre of gravity, the Ulti is much less likely to tip over on uneven ground, or if someone brushes past it at camp. It also has four sturdy plastic feet at the bottom, which help keep it in place.
Lower Profile – For Porch Cooking
Because the Ulti sits closer to the ground than the Reactor, it’s safer to use for tent porch cooking. Remember to always open the doors of your tent when cooking! Some of my tents have doors that roll to the side, but not all the way up. With the Reactor, I’d find myself nervously holding the pot over the burner head as I lit it, to protect the fragile flysheet from any rising heat. I’ve been less concerned when using the Ulti, due to it sitting much lower (the height difference essentially being the height of your gas canister)
Gas Canister Inversion
As the gas connection is remote, the Ulti supports inverting the canister, for use in extreme cold where gas flow / pressure is inadequate. This results in the gas leaving the canister as liquid, and a preheat loop vaporises the liquid back into gas before burning. Primus recommend always starting the stove with the canister upright – and only inverting the canister when required. I have not yet had cause to use this feature, but will update the review if/when I do.
The fuel hose tucks neatly into the underside of the burner head, where it is secured by the plastic feet.
The pot has a slight lip, making it easier to pour the water after boiling.
The 1 Litre pot has room for the stove burner, but not for a gas canister. The larger pot sizes have space to also hold the gas.
Safety Cutoff / Durability
One issue with the Ulti’s competitor, the MSR Reactor is the presence of a safety cutoff device that cannot be reset in the field. The Reactor has a safety device, believed to be a piece of lead, that melts and blocks the fuel supply in the event of overheating. I encountered this failure myself – admittedly only once after 13 years of use. I reached out to Primus Support to clarify if they employ a similar device – they confirmed that they do not.
For many, the reassurance that your stove isn’t going to pack in while you’re out in the wild will be worth the weight penalty.
Summary
The Primus Ulti is a sturdy, high performing water boiling stove. It boils water quickly in a range of conditions from calm to gale force winds. It’s heavier than the competition, but feels reassuringly solid for it. It’s expensive, but can sometimes be found on sale at certain retailers.
The Ulti is available directly from Primus (click here) and from a variety of worldwide outdoor retailers.
