Generator

Thinking of getting one, 3-5kVA.

What does the team think of petrol vs diesel?

Diesel.

Petrol is far more volatile and evaporates away if the generator is not used for any length of time.
Petrol is more dangerous to store and transport.
Petrol engines have spark plugs and ignition systems which fail at the slightest sign of dampness.

A diesel generator is going to be some weight if its going to give 5kVA.....maybe difficult to hump in and out of the van!
Personally I'd be looking for a one with pull start, like a Yanmar or Lombardini unit. Many's the time the start up battery is found to be flat
The fuel in a petrol machine will last a year, no problem......much longer if you use Aspen fuel or a fuel preserver.
John

Diesel is slower to respond so does not work well with inverter generators so petrol is less noise, and more precise frequency and can be run in parallel with another unit, lighter and because it ticks over uses less fuel when driving an inverter generator. However without inverter technology the diesel has many advantages using less fuel and tends to be less droop than petrol (keeps better frequency) however tend to weigh more.

Speed is important at 1000 rpm the Lister would last 20 years, but at 6000 rpm tend to have a short life the petrol lasts longer.

Regulation is also varied for both units. Some of the old Listers would be spot on at no load and full load but between the two the voltage could really vary. Often only option due to weight is on a trailer.

There may be diesel inverter units but I have not seen them. Cost means the inverter petrol is expensive to buy, but not as expensive as external combustion engines as with the Wispergen. The sterling engine is the best option where sound is a problem they are often multi-fuel petrol. diesel or gas they are not really worried. With gas there is also the fuel cell no rotating parts.

I would guess it's down to what you want it for? There is a big difference in running all day with varying loads to starting up on the odd time when the battery SDS is just not man enough.

I have worked with generators most of my working life. From single cylinder Lister running traffic lights or lighting sets to 750 MW at Sizewell power station. Forgetting about the large units up to 60 kVA quality really varies. The little Lister diesel revving at 3000 rpm was a horror always going wrong, the Honda often had odd voltages 55 - 0 - 195 instead of 240 volt. For site work at T5 we used 35 kVA units simply at the small units were not reliable and since used for the aircraft warning lights could not afford failures.

Even low load only about 500W running 12 hours a day the small units did not last. This was 2004 and things have moved on and also I would guess the small hire units were high speed diesels talking to caravan owners the inverter petrol is very highly thought of.

If I was to decide to use cheap caravan sites without huck up I would go for an inverter petrol generator.

And when it gets old, will Diesel put out horrid black smoke like cars do?

mattylad said:

And when it gets old, will Diesel put out horrid black smoke like cars do?

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In the main cars put out black smoke because of the turbo charger. To gain the extra power offered by the turbo more fuel is injected which is all well and good when it gets the extra air pushed in by the turbo. Once the turbo starts to fail then you get black smoke as accelerating.

Although the larger generators are turbo charged you are looking at 500 kVA not 5 kVA. With the larger generators running light load causes carbon to build up so one has to connect up a load bank and slowly load up the generator and also slowly remove the load to clear the carbon build up. Small water cooled engines are not too bad but air cooled engines can also carbon up through running light load. With the old Lister we would blank off part of the flywheel to get it running hotter. There is no temperature regulation on the smaller air cooled diesel engines. Larger ones had oil driven cooling fans the speed was regulated similar to cooling fans on car radiators. However the unit still had problems meeting emission limits and I think all the air cooled and two stroke diesels have now gone. This is why we got the plumes of smoke from the Detroit diesel engine fitted to USA trucks.

We also had some two strokes the Forden and Commer the latter with two pistons per cylinder. The Yanmar looks very like the old Commer with horizontal barrels with the radiator bolted direct onto the engine back to thermosyphon cooling. But water cooling means weight and in the main that's a problem with small units. Once you decide on trailer mounted then weight is no longer a problem but in the main we want to lift generators of 5 kVA size in and out of a van.

We also have the noise problem a generator running all day will really upset neighbours. So to reduce fuel used, reduce noise, and reduce weight the inverter generator seems to be best option, these tick over until you place the load on it so the engine needs a fast response. This means diesel and turbo's simple are no good. Only option is petrol. Some models are even designed to work as pairs. It is the DC which is linked generator to generator so no need to synchronise one inverter handles both outputs.

There are units designed to use the prime mover engine, popular with narrow boats, these are also inverter units does not matter what speed the prime mover engine is running at you still get 230 volt 50 Hz out. However it requires a new front pulley which would be a problem with a van and also you need the safety system as used with Ambulances so the vehicle can be left with the engine running. Fitting to narrow boat with a 100 year life span OK, but a van with 7 years just not worth it.

Thanks to all.

It's not to go into a van, as long as it has decent wheels so I can drag it about it will be fine. It's for emergency domestic use, so probably 3kVA would do, or even less - lights and boiler are the real priority loads, but then one inevitably starts adding the "and it would be nice to also.." loads. And TBH one thing which makes me prefer a large one is the difficulty of stealing it.

Noise would be an issue, but I could build something around it as long as the exhaust wasn't too noisy.

Fuel storage - petrol could be rotated through the lawnmower and the car, so would be OK. Storage safety is a matter of degree - I've already got petrol in a plastic container in the same shed (50-odd m from the house) as a 15kg propane cylinder, so moving to a 20l metal one, for example, wouldn't cause me sleepless nights.

Diesel appealed to me, particularly with a low-tech engine, because of the possibilities of using a wide range of fuels - diesel (of any colour), kerosene, heating oil..., but realistically the emergency I'm guarding against is power outages, not a breakdown in society leading me to need to forage for opportunistic fuels.

Haven't thought about getting a propane one...

You can get petrol engines to run on 28 sec gas oil once they are hot. Honda did one I seem to remember Tractors ran in this a lot it was called TVO tractor vaporising oil basic idea was rap TVO fuel line around exhaust to pre-heat start and stop on petrol but run on TVO.

However home use life you describe means cheap as only used once in blue moon so noise and even fuel consumption is not really a worry wait until Aldi or Lidi do them again and get one then.

28 days later.... BAS will be there with his lights on at least

Don't forget the fridge\freezer in the equation.

I've a cheap petrol genny. Think it's 2.2kW. It won't run our fridge as the inrush for the motor is too great for the genny.

Also if it's been sat for any length of time it's next to impossible to start. Not ideal for emergency use.

ericmark said:

You can get petrol engines to run on 28 sec gas oil once they are hot. Honda did one I seem to remember Tractors ran in this a lot it was called TVO tractor vaporising oil basic idea was rap TVO fuel line around exhaust to pre-heat start and stop on petrol but run on TVO.

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Sounds a bit like my dad's old paraffin blowlamp. Seeing start attempts used to frighten the bejesus out of me when I was a kid.

ban-all-sheds said:

Sounds a bit like my dad's old paraffin blowlamp. Seeing start attempts used to frighten the bejesus out of me when I was a kid.

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.. but we (at least, most of us!!) used meths to get them started, not petrol - which is an awful lot safer (and I still have at least one in the cellar!).

Kind Regards, John

I got a new Honda EU20i a couple of yeares ago which was already converted to propane. Each 47Kg tank of propane will run the gen for a couple of weeks or so, and does not go stale, and is safe to store.

The gen is electronics friendly and variable throttle, which means it is quiet. I have a transfer switch on the house, and it runs everything except for major kitchen appliances.

I only use it for power cuts. Before this gen I had a 3kW site generator, which was embarassingly loud, and wasn't very friendly to the electronics.

If I wanted more power, I could get another identical EU20i and parallel it up for 3.6kW to run more appliances. This would also be cheaper than the 3kVA Honda.

JohnW2 said:

ban-all-sheds said:

Sounds a bit like my dad's old paraffin blowlamp. Seeing start attempts used to frighten the bejesus out of me when I was a kid.

Click to expand...

.. but we (at least, most of us!!) used meths to get them started, not petrol - which is an awful lot safer (and I still have at least one in the cellar!).

Kind Regards, John

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I remember using meths to get paraffin lamps hot before lighting them when I was in the scouts

DaftPunk said:

I remember using meths to get paraffin lamps hot before lighting them when I was in the scouts

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Indeed. I have, and regularly use, a paraffin-fuelled weed burner (aka flame-thrower!) which has to be fired up in the same sort of fashion.

Kind Regards, John