Primus Stove; Parasene England: Lighting And Ignition Accessory: Simple, Effective Electric Pre-Heater Add-On, Homemade Construction July 2018.

By Dorian Stonehouse

PREHEATING the Primus stove involves filling up the fuel crucible with alcohol, methylated spirits or kerosene (paraffin) and lighting it up. 

Soot produced by preheating with kerosene especially can build up in the burner, causing dangerous blockage .

The Primus (Parasene) stove being preheated

Primus Stove; Parasene England: Lighting And Ignition Accessory: Simple, Effective Electric Pre-Heater Add-On, Homemade Construction July 2018

The flames then heat up the riser pipes and burner.

The hand-pump is now operated, and with an additional flame quickly applied to the burner, ignition occurs of the pressurised (then atomised) fuel.

Pumping up the pressure and causing soot to build up

The Primus Parasene stove with flames

The whole thing is self-sustaining: fuel burns, keeps the riser pipes and burner hot, which in turn keeps the atomised fuel burning.

Not realising that the burner is not hot enough he/she keeps on pumping

The Primus (Parasene) stove burning fuel fast!

If the hand-pump is operated, before the fuel has reached the correct combustion temperature, due to soot blockage or bad timing, the stove behaves like a flame-thrower.

Now panic sets in as flames engulf the stove and covering the place in soot – call the fire brigade !The Primus (Parasene) stove - call the fire brigade!

Primus Stove; Parasene England: Lighting And Ignition Accessory: Simple, Effective Electric Pre-Heater Add-On, Homemade Construction July 2018

It is possible to completely discard preheating methods using fuel; and instead wind a simple nichrome electrical heating element on to the riser pipes; with a simple electronic circuit operating in conjuction with it.

It works on the principle, that if the burner is not hot enough, an indicator lamp stays on, and the electric spark igniter and buzzer stays off.

Outline of the simple Primus electric heating element circuit – that works!

The Primus (Parasene) stove Schematic of heating circuit

The circuit works as follows: when S1 (right) is switched on, the nichrome heating element (left), which is wound around the riser pipes , gets red hot.

The chip is a simple timer circuit (right) controlled by a handful of components, and thermistor (left).

The semiautomatic electric Primus stove

The Primus (Parasene) stove, showing wiring of element

Primus Stove; Parasene England: Lighting And Ignition Accessory: Simple, Effective Electric Pre-Heater Add-On, Homemade Construction July 2018

If the environmental temperature is cold, the thermistor will take a longer time to charge the capacitor (not shown) in the timer circuit, and the heating element remains on for a longer period; thereby ensuring the correct ignition temperature.

Conversely, at high temperatures the heating time is reduced.

About 5 minutes gone, so almost at the required ignition temperature

The Primus (Parasene) stove with electrical heating element alight

Under cold conditions, the pre-heating period is typically about 5 minutes.

Then the spark igniter and buzzer are (together) automatically triggered.

This alerts the operator to start pumping.

I can almost taste those lovely

chicken burgers and chips!

The Primus (Parasene) stove, with heating element fully alight

The riser pipes are first given several coats of heat resistant rope adhesive, otherwise the heating elements will short out on the copper pipes.

In the meantime, let’s have a look up top

The Primus (Parasene) stove, showing spark gap for high voltage starter

The high voltage insulators are made out of 13 amp ceramic cartridge fuse links, and they last for a good few months (thinking of this hack did take some time). 

The Primus (Parasene) stove top side, close-up of spark gap

Primus Stove; Parasene England: Lighting And Ignition Accessory: Simple, Effective Electric Pre-Heater Add-On, Homemade Construction July 2018

The ceramic tubes are held in position by tempered springs from large (high quality) clothes-pegs!

The high voltage contacts can be cut from good quality steel wire.

We have soot-free ignition!

The Primus (Parasene) stove, showing ignition spark

The hot element remains energised as the buzzer and spark persists.

The operator then switches the (very noisy) circuit off, resetting the timer for next time.

Don’t know about you, but I love to watch electrical arcing – beautiful!

The Primus (Parasene) stove, showing spark in uv close-up

Lighting up is smooth and successful- every time

The Primus (Parasene) stove, now alight smoothly

Should my Parasene (Primus Stove) burner get partly blocked by soot during electric preheating; the burner dome gets red hot instead of spewing flames everywhere! 

The stove makes a loud whooshing noise, telling me to depressurise and repair the fault.

Of course, for every upside there must be corresponding downside, and the Primus semiautomatic Electric Stove is no exception. 

The Primus (Parasene) stove, burning bright and okay

The current requirement of the nichrome heating element is quite high at around 15 amps for about 5 minutes.  However, current reduction can be achieved by experimentation.

Cheap switch mode power-supply for CCTV cameras – does the job

Power-supply for the heater element and circuit

One obvious method of reducing the current is to try different lengths and diameters of nichrome wire; thereby aiming for an optimum (rather than a maximum) current figure.

Also, don’t forget that in hot climates a lithium ion battery pack and a cheap solar charging array should easily do the trick.

Some more information on Primus Stoves that you may like:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3415938/

A reminder to all visitors

I hope that you have enjoyed this article on the Primus semi-automatic stove.

Please may I ask all visitors to post links on their social media accounts directing visitors to electrosparkles.com so that more people can enjoy the website, and join in to present their technical ideas for featuring.

Heartfelt thanks

Dorian.

 

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