How to test a Generator?
 

Am heading to look at and maybe purchase a 125kW Genset tomorrow.
A big beast of a Gennie. 6cyl Turbo Dieseled Alice Chalmers/Onan...

It's mildly used and not hooked up to anything yet. I know that I can flip the breakers off and start it up to hear the motor but how can I test the Load on that powerful of a unit?

Thanks

Re: How to test a Generator?
 

Not sure how to load that beast up but I did locate an extra gas can for it.

Re: How to test a Generator?
 

Melbo,You need to take a few high amp electric power tools with you along with a few heavy guage 100 foot extention cords.You really want to have enough amperage load on the machine by using high amp items all at one time to see how it operates from idle to constant-load.You will definately see if the breakers need replacing(This is normal for a heavily used generator,but will allow you to knock the price down).
You will also want to make sure it runs for at least 30 min.watch for smoke,and leaks,as the leaks will not show until at full operating temp.

Re: How to test a Generator?
 

A set that size needs to be attached to a load bank. For the cost to have that done versus being wrong, meaning the gen end being defective, is small.

Parts for an older AC power unit are getting challenging.

The efficiency of the older sets like this one also needs to considered. Granted there are a lot of very low hour gensets around.

With that said, I have an old Cat gasser that came with a property I aquired that has 27,000 hours on it that runs and generates like it just was manufactured.

Re: How to test a Generator?
 

Its a "125 kw" guys, you could run every appliance, every light, including central air conditioning in 4 average homes.

I think it would take more that a few power tools to load it up ...

Re: How to test a Generator?
 

Melbo, what in the name of Sir Issac H. Newton are you going to need 125kW worth of electrical power? For most people about 20-30kW is more than plenty. I think you're gonna need two of Halophyte's gas cans.

Re: How to test a Generator?
 

Several advantages to one that size, if you can get them cheap enough.....and I've seen them in the 5-8,000 buck range with real low hours.......standby units that have never been worked to any amount.

One big advantage is that they usually crank out 3 phase power when you get up in that size. If you have any kind of shop, like I do, and can't EVEN GET 3 phase up to this neck of the woods, then a generator to run just for my equipment would be cheaper than going phase converter, for example.
You can buy all kinds of real nice used, industrial woodworking equipment, and get it cheap, but every single bit of it will have a 3 phase motor.

Re: How to test a Generator?
 

Yep.

The 125kW is on the 3 phase side.
At single phase, What would that be? Last one I had was 60 3 phase and 33.3 single... So I'm betting at single phase this thing would be around 70 to 75 kW.

It's not as large as you may think either. About 3 foot wide, (with Enclosure) and 5 feet long.

Last one I had came out of an Imax theatre. Had 207 hours on it and was 20 yrs old. I regretted selling that one the day it left the yard. But, I paid $2K and sold it for $6K so it had to go.

The Diesel motors that run these are pretty simple setups. A lot like a tractor motor. Was pretty easy to find parts for the last one which was powered by a J Deere.

As to why I need that much power? Well, It's for sale at $4000. I've seen the same gennie listed for sale at $13K so I know I could always turn it if I wanted. I'm looking for a house backup and a supplemental to the Hydro system that I'm planning to run off my waterfall. With that size, It won't even kick up in RPMs if the Stove, Dryer and well pump all kick at the same time.

I've been trying to break away all week to go check it out.

Maybe tomorrow. I may try to drag my Electrician with me.

Edit:
Andys right about the cost to bring 3 phase to a spot that doesn't have it. My m,ill just had to pay over $10,000 to have it brought in and they also had to put up a $5000 bond of some sort. At my house or Andy's? Forgetaboutit

Re: How to test a Generator?
 

"The 125kW is on the 3 phase side.
At single phase, What would that be? Last one I had was 60 3 phase and 33.3 single... So I'm betting at single phase this thing would be around 70 to 75 kW."

Nah....you're getting voltage, amperage and phase mixed up.....

If it's a 125kw generator, that's 125,000 watts. It will output most likely several voltages.....like 120, 240, and maybe 480.....and sometimes some wierder ones like 277 ( for lighting ballasts ).

Volts x amps = watts........or working it to figure your amps, watts/volts = amps.

125,000/ 120volts = 1041 amps

125,000/240volts = 520 amps

125,000/480 = 260 amps


When you double your voltage, you cut the availiable amps in half on a fixed watt generator.

The advantage of higher voltage is you can use smaller wire and control switch gear, since that is all dependent on the amperage you draw.....which is why in industrial, they go for higher voltages whenever possible......cheaper.

The advantage of 3 phase is you can run cheaper, more efficient motors.....3 phase motors don't require start capacitors to get running, which also limits most single phase motors to about the 10-15hp range.....so if you want to run a big ole hog of a planer/moulder like that guy we stopped by where you get your cabin logs, you GOTs to have 3 phase.....main motor on that hoss is probably 50-75hp.

So, you can get your full 125kw at any phase or voltage.....but your availiable amperage will vary based on the voltage you select.

Re: How to test a Generator?
 

Resister bank would do the job. Also a big electric welder, could do the "testing" job. But, it is a big sucker, with a very big tank.

Re: How to test a Generator?
 

You've been lying to us Andy, you're a fricken electrician wearing a carpenter's hat ...

What else do you do that you're not telling us ?

Re: How to test a Generator?
 

Been doing a little brain surgery on the side when I can find a willing volunteer that will let me practice..... :D

I'll let ya'll know when I'm ready to hang out a shingle.....GIM discount applies, of course.....PM bugs having so few brains to work with anyway....ahahahahaaaaaa

Re: How to test a Generator?
 

Sounds like a good deal for a nice genset. If possible, I'd sample the oil and have it analyzed at a lab. Blackstone Labs charges about $20 for this service. You would need the owner's cooperation but he shouldn't have a problem with it if he knows the engine is in good shape. Analysis can detect problems before they become obvious. Very cheap insurance.