Stu's Shed

The ability to make, and harness fire was a defining moment in the history of man.  Being able to progress from utilising fire found in nature, to being able to produce it at will and use it for a variety of tasks, from cooking, hunting (herding animals), through to defense, lighting, heating and more.

Despite the original sources of fire often being electrical (lightning), it was a millenia before electricity itself was harnessed as a tool.

The modern man struggles to make fire to be honest – when was the last time you tried…..without a match or other commercial ignition source?  And it is even worse where it comes to electricity – what do you do when the grid goes down, or worse, you are nowhere near the grid at all?  Sure, solar power is becoming readily available, but unless you want to charge your laptop, portable solar power generation is still in its infancy.

So when you need to generate some serious power, you need a serious tool.  And as a bit of a twist, where fire was first produced with electricity, we need to turn that around, and use fire to produce electricity on demand.

There are a whole range of generators out there, but many would struggle to run a jigsaw, let alone anything serious.  Those that can really run up in price.

In (hopefully) the near future, the shed will be reestablished again, and there will be a time where power will not be available – I could run extension cords from the house, but they are not 15A supplies, so the tablesaw and thicknesser would be both out of action until the electrician can wire it all up.  And with 2HP of dust extractor, and 2400W tools to use alongside that, there is some serious power required.

To address these requirements (and a number of others), we have quite an extraordinary machine.  It comes from Promac – the team that has bought us the quality Flai U blade, the incredible Mustang blade, the exacting BMI range, and the Tormek wetstone sharpeners. I mention this range as it demonstrates the quality of the tools that Promac chooses to supply, and straight out of the box, the quality of this product starts to become apparent.

It is heavy – 88kg dry. Add to this 25L of fuel, and a litre (or so) of oil, and even as the fuel tank empties, you have around 110kg of serious machine.

So what do we have here? Under that 25L tank sits a 13HP electric start motor.  13HP!  I am so used to dealing with machines that top out at 3 1/4HP (the limit of power that can be produced with 2400W tools), 13HP is an impressive motor.  Compare that to your average lawnmower: 3 – 6HP.  Got to be happy it is electric start!  It still has a pull start as well – hope I never need that Output: twin 15A GPOs providing a combined 6.8kVA with 0.8PF (power factor), which in more understandable terms is 5000W, peak load 5500W.  There is also 12V DC if required.

You may wonder why a 6.8kVA machine doesn’t produce 6800W (after all, V x A = W), but there is another dimension here – the volts and amps can be out of phase with each other, and the amount they are is represented by a value between 0 and 1, called the power factor.  Machines that start under load (such as welders and air compressors) demand significant kVA to start.  A general rule of thumb is to work out what is 3x the HP, and this is around the kVA needed by the generator for soft-start motors that start under load.  So this generator can operate a 140A welder, or 10CFM compressor.  In the workshop, I’d be looking to start the dust extractor (which also starts under load), then devices such as tablesaws etc (who’s load increases with use).

The generator does not like being operated at too low a power – motors are not designed to simply idle for long periods.  If you need to operate low powered machines only (charging batteries for example), you need to create a load bank to artificially increase the power demand on the generator.  This can be something like a couple of 500W halogen lights.  This generator needs to operate with around 1600W of minimum load (over long periods) (a minimum of 30% of its maximum load). There are smaller (and one larger) generator available from Promac, so you can match the machine to your specific requirements.

This generator has a RCD onboard, so if used as a backup for mains power for the house, it needs to be wired in by an electrician, as you cannot have two RCDs on the same circuit.

The generator produces a pure sine wave of AC current.  This may seem like a no-brainer, but there are now many cheap generators out there that produce DC which is then modified to simulate AC, and result in a stepped waveform.

Why does that matter?  Well some basic electric machines won’t care – close enough is good enough.  Others however can be damaged very easily with a modified sine wave, such as computers and other electronic devices.  The voltage can also vary significantly, where 260V (and more) can be experienced, dramatically shortening the life of the transformer in the power supply.  So why do generators even exist that don’t produce a pure sine wave?  Cost.  People don’t want to pay for quality, and that is the result.

After unpacking the generator, and fitting the wheels and handles to the generator, next was to add the fluids.  It obviously does not ship with petrol, and the engine is also drained of oil.  There was a box in the package that I assumed was the oil, until I opened it.  Hang on – that is battery acid!  Not labeled though, which was surprising.  Each of the individual containers has a light plastic film covering it, but you don’t remove these.  Instead, the whole container is inverted and jammed on top of the battery (like adding printer ink to an inkjet printer).  The battery has a number of tubes that punch through the film, so in theory there is no chance of an acid leak.  In practice, the inside of the plastic bag that held the acid container was wet with drops of acid, but I couldn’t find any leak in the container.  Be careful, and wash up with plenty of water.

Next, oil, and there is a bit of a choice for what oil to get, depending on the expected temperature.  I chose 10W-30, for temperature ranges between -10 and 30C. (I wonder if there is a correlation between the temperature range, and the oil designation?!  Actually, is just coincidence!)  There is no quantity shown in the manual (that I could find), not on the engine, so I guessed at 1L.  Didn’t seem enough on the dip stick, so added some from a second bottle, and quickly created a puddle on the ground.  Bugger.  Actual amount from dry seems to be about 1100ml.

Fuel was easy – 25L of unleaded (and not one with ethanol), and it was ready to go.

Bit of choke, a turn of the key and the generator fired straight up.  Bring on the next power cut, I’m ready!  Didn’t have time to play with it more – job for another day.

No longer limited by where I can work, the ability to turn fire to electricity is now mine!  Have no fear, this topic won’t be ending here.

So whether you need power on the next job site, need to independently generate power when the grid is not available, or fearing an impending zombie apocalypse, this is serious power generation.

Filed under: Manufactures and Suppliers, Tools | Tagged: Electricity generation, Generator, Power factor, Promac, Volt-ampere | Leave a Comment »