Another Generator question

[BadtzBee]

Does anyone have experience in building (assembling) household generators? My plan is to couple an A.C. Synchronous Generator (10 kW, 50 Hz, 1 phase, 220 V) with a small diesel engine to supply standby power to my house during power outages.

I have an idea that the diesel motor needs to be rated higher than the generator, so I think I need about a 16 horsepower diesel (12 kW) to run the generator, does that sound right?

[Crossy]

Looking at a couple of commercial 10kVA diesel gensets they have engines like the Kubota D 722-E which is a 20HP unit.

Any reason you're not going to get a purpose built genset?

[BadtzBee]

I can't find anything bigger than a Panda 7.5 kW gasoline where I live (Sakon Nakhon), which a. isn't quite big enough and b. it's petrol (I prefer diesel) and c. who the hell are Panda?

I can pick up a Synch. Generator as described for around 17000 baht. The dealer wanted to match it with a Kubota RT 140 ES (about 14 HP 10kW) for 63000 Baht, which I think is too small. Welding up a rack for it all is simple enough, or the dealer will sell a purpose made rack for 3,500 baht. So, it seems a fair enough price for a large(ish) backup generator, and probably a lot cheaper than a genset of the same output (if i could even find one here!).

[Crossy]

I'd be wondering about the speed regulation of the single cylinder diesels, the D722 is the three cylinder and likely more responsive to load changes.

[BadtzBee]

Yes, something I hadn't considered. There's also the issue of RPM. The generator outputs 10kW at 1500 rpm - so I'm guessing the engine needs to do the same; if the engine outputs 10 kW at 2400 rpm, as does the RT140, this might be a problem. Unfortunately I'm not a full bottle on all of this, and trying to get reliable technical advice from the local suppliers seems to be an exercise in futility, even with the walking dictionary helping out.

Classic advice today - "You get car motor. Car Motor OK."

[Crossy]

Matching a generator and engine for most efficient operation is not a simple task, you could hit the jackpot and get it close first time, but ....

Actually the suggestion of a car (diesel) engine is not totally stupid although governing the speed could be interesting, car engines are designed to operate over a wide RPM range and it will certainly have adequate power at the required 1,500 RPM.

The generator speed of 1500 RPM is VITAL and needs to be maintained within a few %. It's that speed that determines the output frequency (50Hz), and, dependant upon the regulator technology (liable to be simple) the output voltage.

Note that if you have an inverter generator (unlikely from the farm shop) they are speed independent and allow the engine to run at or just above idle during times of low loading, great for fuel consumption and noise, not so great for the wallet initially.

If you get a generator with an AVR (Automatic Voltage Regulator) the output will be better controlled than the simple capacitor regulators.

Of course if it's just running lights the frequency is not critical, but for kit with motors it's important, running at too low a frequency will cause induction motors (your water pump and aircon) to run slow and overheat. Under or over voltage will also cause issues for motors.

Modern technology likes clean supplies, so if you have computers TVs etc. running off the beast I'd be looking at some form of external stabiliser and transient suppressor just for peace of mind that you're not going to fry the TV.

EDIT You may wish to re-think what you intend powering with the genset, we have a little KwaiThong 6kVA gasoline (converted to LPG) generator which happily runs everything except the water heaters, aircon and the 3HP irrigation pump, rarely getting above 50% load (it is most definitely NOT quiet mind). Right now our home with the lights, TV, my PC, fridge and a couple of fans is drawing a whole 5.3A (1,200W) from the mains. Obviously your comfort level and the duration of the anticipated power failures is important.

[IMHO]

EDIT You may wish to re-think what you intend powering with the genset, we have a little KwaiThong 6kVA gasoline (converted to LPG) generator which happily runs everything except the water heaters, aircon and the 3HP irrigation pump, rarely getting above 50% load (it is most definitely NOT quiet mind). Right now our home with the lights, TV, my PC, fridge and a couple of fans is drawing a whole 5.3A (1,200W) from the mains. Obviously your comfort level and the duration of the anticipated power failures is important.

Just curious, but assume it can't run the water heaters due to load presented, and the aircon/pump due to startup current required?

[Crossy]

EDIT You may wish to re-think what you intend powering with the genset, we have a little KwaiThong 6kVA gasoline (converted to LPG) generator which happily runs everything except the water heaters, aircon and the 3HP irrigation pump, rarely getting above 50% load (it is most definitely NOT quiet mind). Right now our home with the lights, TV, my PC, fridge and a couple of fans is drawing a whole 5.3A (1,200W) from the mains. Obviously your comfort level and the duration of the anticipated power failures is important.

Just curious, but assume it can't run the water heaters due to load presented, and the aircon/pump due to startup current required?

Correct, our little genset will actually start and run our Samsung inverter A/C, but it stands no chance of starting the conventional units on the spare beds. The way the house is wired makes it easier just to not run water heaters and A/C.

[IMHO]

EDIT You may wish to re-think what you intend powering with the genset, we have a little KwaiThong 6kVA gasoline (converted to LPG) generator which happily runs everything except the water heaters, aircon and the 3HP irrigation pump, rarely getting above 50% load (it is most definitely NOT quiet mind). Right now our home with the lights, TV, my PC, fridge and a couple of fans is drawing a whole 5.3A (1,200W) from the mains. Obviously your comfort level and the duration of the anticipated power failures is important.

Just curious, but assume it can't run the water heaters due to load presented, and the aircon/pump due to startup current required?

Correct, our little genset will actually start and run our Samsung inverter A/C, but it stands no chance of starting the conventional units on the spare beds. The way the house is wired makes it easier just to not run water heaters and A/C.

One more thing - care to share more detail on how you converted your Kwai Thong to LPG and the parts used?

Not long after Songkhran we have the boat festival, and I was thinking of putting a couple of those 6kW key start Kwai Thongs on the back of a pickup to run 9000W RMS of JBL Pro/Crown powered speakers I've got laying about

[BadtzBee]

Thanks to all for the advice. The air-con and water pump are the two items I really want to run, so the smaller gen sets aren't going to do it for me. I was speaking to a friend who has a fair bit of industrial generator experience, and it seems a 14 HP unit will do fine - it's just a matter of initially loading up the generator to max. output and adjusting the throttle to turn the motor at 1500 rpm. After that the governor in the diesel will take care of the revs. As long as the diesel engine has enough torque to turn the generator shaft then no problem (14 HP should be plenty).

[Crossy]

One more thing - care to share more detail on how you converted your Kwai Thong to LPG and the parts used?

The KwaiThong EP6500 we have is powered by a Chinese clone of the Honda GX390 13HP petrol engine.

Having failed to find the necessary bits in Thailand, I bought one of these kits http://www.ebay.co.uk/itm/NEW-Generator-LPG-conversion-kit-for-propane-gas-bottle/320332914025?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222003%26algo%3DSIC.FIT%26ao%3D1%26asc%3D20203%26meid%3D5752865430144912346%26pid%3D100005%26prg%3D9063%26rk%3D5%26rkt%3D6%26sd%3D110907049531&rt=nc although I don't recall it costing quite that much.

You need to be a bit handy with the Dremel (or a rat-tail file) to ensure the adaptor ring doesn't obstruct any of the carb passages and the air filter mount needs 'adjustment', but it only took me a couple of hours to get the beast running on LPG.

You can get the Garretson regulator (the heart of the conversion) and adaptor ring on their own from other sellers and the other bits are readily available here.

I just wish I bought a Garretson regulator with a solenoid primer rather than a push button.

EDIT As noted earlier these little gensets are definitely NOT quiet, not the ideal power source for a sound system

[IMHO]

One more thing - care to share more detail on how you converted your Kwai Thong to LPG and the parts used?

The KwaiThong EP6500 we have is powered by a Chinese clone of the Honda GX390 13HP petrol engine.

Having failed to find the necessary bits in Thailand, I bought one of these kits http://www.ebay.co.uk/itm/NEW-Generator-LPG-conversion-kit-for-propane-gas-bottle/320332914025?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222003%26algo%3DSIC.FIT%26ao%3D1%26asc%3D20203%26meid%3D5752865430144912346%26pid%3D100005%26prg%3D9063%26rk%3D5%26rkt%3D6%26sd%3D110907049531&rt=nc although I don't recall it costing quite that much.

You need to be a bit handy with the Dremel (or a rat-tail file) to ensure the adaptor ring doesn't obstruct any of the carb passages and the air filter mount needs 'adjustment', but it only took me a couple of hours to get the beast running on LPG.

You can get the Garretson regulator (the heart of the conversion) and adaptor ring on their own from other sellers and the other bits are readily available here.

I just wish I bought a Garretson regulator with a solenoid primer rather than a push button.

EDIT As noted earlier these little gensets are definitely NOT quiet, not the ideal power source for a sound system

My primary interest in the LPG conversion would be achieving longer runtime between refuelling (nothing worse than stopping a parade vehicle to refuel, or trying to put more fuel into a running genset on the back of a moving pickup, with half drunken people smoking 2 feet away) - however at that price it's hard to justify for gensets that will be at most used 2-3 times/year...

I'm familiar with the noise these gensets make - they are the power source of choice for most parade vehicles No problems with sound - the JBL/Crown system they'll be powering does well over 140dB @ 1M - you'll only hear the gensets if you're next to them, and given how loud the sound system is, no-one gets too close to it

The only next challenge is what to power off what genset... there are 4 subwoofers each with it's own 1000W RMS Crown amp (4000W total), 2 front of house speakers, each with 3x500W RMS (3000W total), and another 2 monitors with 2x500W RMS each (2000W total). I guess it'll take a little trial and error to determine the best way to load each genset..

Edit: The Crown amps are all D-Class, achieving better than 90% efficiency at full load, so actual genset loads +10% of power rating.

[Crossy]

The EP6500 has a pretty big tank, good for several hours at full load, during the floods ours was running 11 hours (not at full load mind) without running dry.

How long do these parades last?

[cdmtdm]

crossy why did u chose the kwai thong over the other popular unit i see Tuffy ? ( looks like a honda) i am about to buy one tomorrow ....

[Crossy]

crossy why did u chose the kwai thong over the other popular unit i see Tuffy ? ( looks like a honda) i am about to buy one tomorrow ....

It was what was in stock at the farm shop and we we're desperate. During the flooding our little Honda had died and I wasn't going another night without power.

In the end we were without mains for 6 months

[bankruatsteve]

Just FWI: I've been very happy with my 2KVA Kwai Thong. I have it set up (now with a DPDT panel that I got from the states) and it takes care of all the lights, water pump, and my 9K BTU A/C. That's all I need and it starts first time every time (with choke).

[IMHO]

The EP6500 has a pretty big tank, good for several hours at full load, during the floods ours was running 11 hours (not at full load mind) without running dry.

How long do these parades last?

They day usually starts around 4AM, sound checks and final tuning around 5AM, and the music starts around sunrise - In my wife's hometown there are a lot of Moo Bans participating, and while the judging normally ends by about 4-5 PM, the party can go on well into the night.

Last year my wife's Moo Ban lost points on sound and were pipped into 3rd place - then using a typical Isaan sound system with cheap copies of JBL EON's some homemade subs, and only about 2000W RMS of actual power - hence why I'm transporting my JBL & Crown (genuine) gear up there this year. Our system won't look as big as some of the trucks in the parade, but it will be louder and sound a million times better

If you're ever upcountry around May-June, you should try to visit one, they're pretty cool

[Crossy]

I'll be sure to bring my ear-defenders

Do you intend running the gensets in parallel? Could be a solution to deciding which one drives what.

These simple gensets synchronise easily, the required synchroscope can be made from two 15W lamps in series.

Procedure here http://yarchive.net/car/rv/generator_synchronization.html

[IMHO]

I'll be sure to bring my ear-defenders

Do you intend running the gensets in parallel? Could be a solution to deciding which one drives what.

These simple gensets synchronise easily, the required synchroscope can be made from two 15W lamps in series.

Procedure here http://yarchive.net/car/rv/generator_synchronization.html

After a quick read of that, and seeing the possibility that voltage could double, it sounds too risky when the damage could be 450K Baht worth of gear

My thoughts were to just split the load 50/50 (i.e. 2 subs, 1 main and 1 monitor) per genset and see how that goes - then try one genset running all 4 subs, and the other running all mains and see how that compares.. The load is very much dynamic of course, so I'm imagining either way could have a benefit.

[Crossy]

Actually it's only the voltage across the lamps that could be double, you close the switch at 0^o phase difference (lamp out) and the gensets then remain locked in sync.

Sync them up first then apply the load if you're worried.

I have actually done this, long ago and with 3-phase generators (you need 3 lamps), once you've done it once it's not that difficult.

[cdmtdm]

got my Kwai thong , runs like a charm , ready for the first of many rolling powerouts once the wet starts .... i was a bit surprised it only has a 3 month warranty or is that not correct .... the tuffy brand had zero warranty ...