My Generator Study

I'm embarrassed to admit that I know very little about these tiny 1-phase petrol Jennies. :rolleyes:

Geoff.D said:
A carburettor jet! Of course all the millenials don't know what a carburettor is because no one has carburettor cars anymore!
And then we talk of progress!

Thanks BTW for finding a really useful reference that deals with the imprtant aspects.

The only issue not covered is the minimum load that a geni should be subjected to.
A petrol engine that runs too rich carbons up very quickly and then requires some serious servicing. The fuel to air ratio of a carburettor engine is determined by the jet or jets. The correct jet for the altitude prevents excessive carbon which is formed when the fuel does not get bruned properly when the engine runs. If a geni is lightly loaded, the exact same thing happens, hence why there is a minimum load required.
The added cost is as in the reference post you found --- you need to know what the load is and keep it below the rated value adjusted for altitude and above the minimum load figure (Typically one can work on a figure of 20% of rated power after being adjusted for altitude if no info is available from the manufacturers.
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Diesel Jennies especially are highly affected by low load. The carbon build up in the cylinders is known as glazing. We even have low load warnings and LDSS (Load-dependent-start-stopp) controls on our parallel configs to avoid low load scenarios. We even mention in our startup training that weekly start tests (no load) shouldn't be longer than 3mins or so.

If like us old timers you know a thing or two about carburettor engines you can fine tune the mixture without changing jets and adjusting the timing to ensure a perfect mixture and the least carbon build up.
You check this by looking at the exhaust of the engine. It should be running a grey colour not black. If the exhaust is running black, the mixture is too rich and or the load on the geni is not enough.
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Damn. now all these 10Deg before Top Dead Centre etc. stories come flying back. I was seeing a girl whose dad was a mechanic and she thought his timing gun was a broken torchlight because whenever she would hold it for him while he was working on the engine it would always flicker. :laugh:
 
Voicy said:
It's quite interesting to read all the replies in this thread.

How do you guys feed your appliances from your Jenny?
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Plug inside house, will finish off properly with conduit over the weekend. And yes, it's upside down for no apparent reason other than it will get corrected this weekend.
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And outside connection. Black extension leads is from generator, 16A each, white plugtops into the house through roof.
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And from generator.

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Voicy said:
I'm embarrassed to admit that I know very little about these tiny 1-phase petrol Jennies. :rolleyes:



Diesel Jennies especially are highly affected by low load. The carbon build up in the cylinders is known as glazing. We even have low load warnings and LDSS (Load-dependent-start-stopp) controls on our parallel configs to avoid low load scenarios. We even mention in our startup training that weekly start tests (no load) shouldn't be longer than 3mins or so.



Damn. now all these 10Deg before Top Dead Centre etc. stories come flying back. I was seeing a girl whose dad was a mechanic and she thought his timing gun was a broken torchlight because whenever she would hold it for him while he was working on the engine it would always flicker. :laugh:
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:D

The DIY'ers version! Still use this when I am confronted with a carburetter engine!

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Jaws677 said:
I'm just wondering what would the purpose of the earth spike be ?
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Surge protection and lightning protection! Absolutely essential if the geni is far from the load points.

EDIT/ As pointed out by @Düber in post #56, the earth spike is only of vaue IF you also have E/L in place.
 
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Geoff.D said:
Cringe! All those extensions and duble socket plugs! Shudder!
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Either that or run 30m of extension lead through steel-framed windows and multiple door frames that might cut the wires.

When I finish building the generator house I will run single continuous wires right through to the plug tops as things will be permanent then. I'm not a fan of multiple extension leads but had to make do with what I could at short notice.
 
Voicy said:
Diesel Jennies especially are highly affected by low load. The carbon build up in the cylinders is known as glazing. We even have low load warnings and LDSS (Load-dependent-start-stopp) controls on our parallel configs to avoid low load scenarios. We even mention in our startup training that weekly start tests (no load) shouldn't be longer than 3mins or so.
:laugh:
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The worst case we had to deal with in the prime mover days on microwave, was Groshertzhog ( hope I have the spelling right). Diesels ran at an efficiency of 27% below rated values.
Load balancing involved huge heater panels that had to be switched in with contactors linked to a load monitoring setup. As soon as the BMS system dropped charge, the heaters would kick in to keep the load on the generators constant.
The carbon build up was so serious that there was always a spare genset available, and another being serviced. The gensets were swopped out every two weeks. Two running constantly at a time. 5 sets all in all ( two working, one spare on site, one in transit and one in the workshop).
A mini power station with all the issues of phase synch and complex manual switch over gear. No fancy computers. All relays, contactors and blade switches.
 
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Geoff.D said:
The worst case we had to deal with in the prime mover days on microwave, was Groshertzhog ( hope I have the spelling right). Diesels ran at an efficiency of 27% below rated values.
Load balancing involved huge heater panels that had to be switched in with contactors linked to a load monitoring setup! As soon as the BMS system dropped charge, the heaters would kick in to keep the load on the generators constant.
The carbon build up was so serious that there was always a spare genset available, and another being serviced. The gensets were swopped out every two weeks! Two running constantly at a time.
A mini power sation with all the issues of phase synch and complex manual switch over gear. No fancy computers. All relays, contactors and blade switches.
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Eugh. Those relays and contactors did their part well, but it's been a ball ache for us to rebuild panels with new automation, while trying to work around old iffy contactors and coils inside switchgear.

To avoid load issues on sites that are on permanent gen power, we often run 3 Gensets on different schedules. During peak hours, we'll have say 2x200kVA or such running on LDSS (2nd gen kicks in as load surpasses 80%) and then after 6pm, it switches over to a single 60/100kVA Jenny to "keep the lights on" until 6am.

Biggest single genset that I've comissioned so far was a 2.5MVA beast that ran parallel with 2x 1600kVA mains transformers.

Haven't had much issues with them at altitude or temperatures, but I've started regulating the motorheaters with the engine temp sensors to make sure they don't cook hoses or run too cold. The motorheater alone on my last generator was 9kW. Just to keep the engine block warm.

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Very interesting thread.
My 2c worth, mostly from experience, reading up and asking. I also love to learn so feel free to criticise.:)

I hear and read alot about a UPS cleaning or fixing the electricity going through it.
That might be true for the really, really expensive ones, but not your normal ones. They just have a relay that is just a pass through.
This is only switched when running off the battery.
They do monitor the power all the time but have fairly loose tolerances, so something has to be very weird before they change over, otherwise what you are getting out is exactly the same as what you are putting in. No magic scrubbing happening.

My generator is a older Honda without an AVR, at 50% to 75% load the frequency runs between 49.1 Hz to 51.1 Hz with the voltage between 216 v to 224 v,
This is when the load changes ie. switching lights on and off, washing machine etc. When the load is stable then it is a perfect 50.1 Hz with 219 v. The reason obviously being, the mechanical governor is slower to react than the meter reading, due to the frequency being decided by the RPM. My electronics have been happy with this for a number of years, in fact what I have lost was due to Eskom's fluctuations.

Geoff.D said:
You check this by looking at the exhaust of the engine. It should be running a grey colour not black. If the exhaust is running black, the mixture is too rich and or the load on the geni is not enough.
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Yes unfortunately unleaded petrol has robbed us of this valuable indicator so check your spark plugs for a nice brown colour(some say pinkish) to let you know what is happening, and please don't spend the next month trying to get the exhaust grey

Jaws677 said:
I'm just wondering what would the purpose of the earth spike be ?
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Geoff.D said:
Surge protection and lightning protection! Absolutely essential if the geni is far from the load points.
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cbrunsdonza said:
Generators need to be earthed. Electricity has to go somewhere when you touch those bare wires and I prefer to the ground and not through me.
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Jaws677 said:
I must do a write up but if you think a single copper spike in the ground is going to help anyone in you case you are badly mistaken.
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@Jaws677 beat me to it. Bashing an earth spike in the ground next to your generator with nothing else is only going to give you some exercise and possibly create a very dangerous condition if thing go wrong.
My generator goes to its own DB board with display of Amp's and volts, a circuit breaker feeding an earth leakage. It then goes through a contactor for disconnecting, run by a relay.The earth is common to all power sources through out. The earth can only help or work if it is connected to an earth leakage and the surge arrestors.

Just a point on servicing, cars and other engines have an oil filter which most generator engines don't. It is therefore imperative that they run with clean oil. If you think it needs a service, or if you are not sure or if it is just a day of the week, then service it !!
It will last a long time if you look after it.
 
Yup quite right! We have been robbed of the easy check with unleaded petrol! Thanks for the reminder. Will update my post accordingly. Thanks @Düber.

A setup running a geni without EL, quite correct. Another reason why it is not a good idea to go anywhere near the existing DB board unless the complete installation has been done with a geni as back up power in mind.

A neighbour of ours placed his geni in the bottom corner of his yard ----- away from his home. A long extension cord multiple double sockets etc. What he did in his home I have no idea. But as luck would have it a surge induced by alightning strike close by, sorted out the geni, and vaporised that extension. The geni was replaced and an earth spike provided. This time a proper armoured cable was installed, presumably to a separate DB board. Needless to say we all mutter when he start sthe geni and keeps it running for hours on end at night, he does not hear but we certainly do.
 
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Jaws677 said:
I must do a write up but if you think a single copper spike in the ground is going to help anyone in you case you are badly mistaken.

There is no earth leakage protection.

Infact a floating system without the earth spike will be safer if you don't have an earth leakage device. By adding the earth spike you are actually creating a path for fault current to flow ie if you touch the live conductor through your body into the earth back up through the earth spike completing the circuit back the alternator.


I'm not even sure if the neutral is bonded to the Frame on these generators - I'll check it out.

A long way to say don't stuff around get a professional to tie this into your DB with a change over switch.

And not a dude you pick up from the corner of builders warehouse

Electricity kills. Get an electrician who can issue a COC . Your insurance will ask for this should something go wrong and your house burns down.

Loadshedding is here to stay might as well get is done right now.
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A very useful idea. that write up of yours. I cringe at what some are up to.
 
Trust|Nobody said:
I guess this method was followed:
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That video looks sketchy.

The dude calls it a 5.5KiloVolt generator. He also calls it a "DB Board" (the B in DB stand for Board already, but I'm just clutching at straws with that one. :P ).

His mains isolator is a single pole, which means you still have a municipal neutral connected to your system. This should be isolated with a 2P switch to make it safe.

His video also doesn't go through the proper steps of removing the double-plug-end chord safely. If you unplug it before switching off your generator the prongs can zap you. Also "plug it into any outlet" is also a recipe for disaster as you're loading a 5.5kW (23Amps) supply onto wire rated for a 10A or 16A socket. Not to mention the rating/limitations of your extension chord.

Last but probably most noteworthy is that @Jaws677 is entirely correct. If you're going to spend money on a gen, best you do it safely.

Some years ago I drew up a sketch for a mate on how to install a simple 2-way selector switch so you can select between "mains" and "gen" without plugging anything in or out, nor do you run the risk of feeding one into the other. The design also includes a "Mains-return" alarm, which gives you an indication of when your mains is back up and running so that you can switch back to it after a few minutes of it running stable. (Without having to stick a multimeter into anything.)

Be safe out there kids.
 
Voicy said:
That video looks sketchy.
AGREED!

Some years ago I drew up a sketch for a mate on how to install a simple 2-way selector switch so you can select between "mains" and "gen" without plugging anything in or out, nor do you run the risk of feeding one into the other. The design also includes a "Mains-return" alarm, which gives you an indication of when your mains is back up and running so that you can switch back to it after a few minutes of it running stable. (Without having to stick a multimeter into anything.)

Be safe out there kids.
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I would appreciate if you will share the change-over diagram. It will save me the trouble if I have a good starting point for my planned system.
 
I dont like looking at youtube videos. Very few of them are ever credible solutions. Mostly are just incredibly stupid.
But, This one I could not resist, up to the point where he plugs the geni into a wall socket. That was it for me, I stopped viewing right there and then. The worst possible idea ever.
 
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dennis.se.foon said:
I would appreciate if you will share the change-over diagram. It will save me the trouble if I have a good starting point for my planned system.
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Please excuse the terrible drawing, but it equates to something like this:

2.JPG

Your "3 position selector switch" can be something like this:

3.JPG

The 3 position is so that you have:
1 - Mains
0 - OFF
2 - Gen

The OFF position allows safe switching in order to avoid spikes on any equipment - and to avoid any possibily of mains and gen ever coming into contact. This sometimes happens on 2-position switches.

Keep in mind that this selector must be rated to take your full mains capacity as it will be a permanent fixture.

The "Mains ON" / "Gen ON" indicators can either be a 230V buzzer or a lamp, or both in one like this:

4.JPG

I added protection circuit breakers for it - which comes in handy if you want to switch off a noisy buzzer. But the buzzer / lamp helps you see when you have mains or gen power at the inputs of your selector switch. If you don't go for a buzzer (or maybe even a buzzer that you can silence) you can leave the lamps on.

You can choose to have a permanent cable running to your Gen's output, or a dedicated socket that leads from the selector switch to your gen and nowhere else.

So if Eskom loadsheds you, you:

1) Start the Gen.
2) Check the status lamp to see that you have gen power.
3) Switch the selector from 1 "Mains" to 0 "OFF".
4) Wait a few seconds to allow fridge motors etc to stop completely.
5) Switch the selector from 0 "OFF" to 2 "Gen".

When you see the "Mains ON" lamp or buzzer activate, you can use the selector to switch back to Mains. Keep in mind that it's worth waiting a few minutes to see that the mains is stable...also allow a few seconds "OFF" to allow motors and such to stop completely before activating the mains.

EDIT: I forgot to change the title of SW4 to whatever your main circuit breaker in your DB is called. SW5 and SW6 are 2Amp circuit breakers - not used for anything other than monitoring the availability of each supply.
 
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