Generator for sawmill

Bert · April 05, 2011, 07:32:46 AM

Hi all.

Who knows about diesel generators? I need to run a 125 HP motor on the headsaw, 75 hp on the hydraulics, and 50 hp on the edger. Power from the utility company, phase converters etc are not an option. I've run into difficulty sizing gensets. Best response Ive gotten so far is I'll need at 170KW set. Doe this sound right? Everything runs on 480 volt.

pineywoods · April 05, 2011, 09:26:38 AM

Theoretical load is .78 kw per hp. That's in theory. the hp ratings would total out pretty close to 170 kw, BUT that's for running loads. Electric motors may pull twice that during startup. I'd look for at least 250 kw.

Ron Wenrich · April 05, 2011, 05:03:41 PM

Buy something big enough to expand. We have a 350 kW (I think), and its maxed out. We have a chipper with 75 hp, a vertical edger with 60 hp, 10 hp for a blower, 20 hp for the vibrating conveyor and 15 hp for the live deck, along with what you have.

SPIKER · April 05, 2011, 08:31:23 PM

Pineywoods & Ron are right, You need to size a generator about 110% above FLA of the 3 largest loads to avoid starting lag/pull down of the genset. Something several people suggested I was nuts until they had to buy the generator I suggested that they balked at & the one they bought first was too small...

Mark

Ron Wenrich · April 05, 2011, 09:56:01 PM

We have a protocol for starting our equipment. First to start is the chipper. We have a ramp on it, so it doesn't stall out the gen set. After the chipper is up, then we start the headsaw, then the edger, and work on down to the smaller motors.

We can still dim the lights by putting a big hickory chunk into the chipper.

Gary_C · April 06, 2011, 02:29:07 AM

Quote from: Ron Wenrich on April 05, 2011, 05:03:41 PM
We have a 350 kW (I think), and its maxed out.

Ron, how much fuel does that generator drink?

Ron Wenrich · April 06, 2011, 05:56:31 AM

About 7-8 gal/hr. When we compared prices between that and the electric installation, fuel was a lot cheaper. But, the electric company wanted $100k to install.

Our neighbor put up a solar array to power his metal fabrication shop. Apparently, that was cheaper than industrial electricity. His array covers about 1 1/2 acres.

scsmith42 · April 06, 2011, 07:26:08 AM

Re fuel consumption, I have a 225KW Kohler genset with a 400 Big Cam Cummins driving it; it consumes about 5 gallons per hour with about 50KW of loading on it.

Once you get past the basic amount of fuel required to run the generator, the rest is simply demand (within reason). Thus, a 400KW generator with a 100KW load usually won't consume much more fuel than a 200KW unit with a similar load.

Ron Wenrich · April 06, 2011, 05:05:00 PM

Checked today, and ours is a 275 kW generator. There is a constant load between the saw and the chipper.

Bert · April 14, 2011, 09:58:24 AM

Ron,

When you say you have ramp on the chipper, is that a soft start? Are all the other motors direct started?

Ron Wenrich · April 14, 2011, 04:52:02 PM

I guess you call it a soft start. I'm not much of an electrician. The one that is calls it a ramp. The chipper starts slowly, than picks up speed after the momentum has started. If you try a direct start, sometimes it will stall out the gen set.

All other motors are direct start. The chipper gets started first. After that goes up, we start our motors from the biggest to the smallest. If we have to shut the chipper down, before we start up again, we turn off all the motors, and start from chipper on up. Other motors we can start with the other motors running.

Bert · April 15, 2011, 07:13:16 AM

I'm not an electrician either, just trying to gain some knowledge on what all i need for this project. You get so many different answers on things on how it should be done. Even from electricians the answers vary, sometimes wildly. I'd rather just know someone who is doing it and what works for them. If i can direct start these motors i can save some coin on soft starters. I'm thinking i can avoid a soft starter on the headsaw based on your response and the fact the saw really starts with very little load since its not in the wood on start up.

timerover51 · April 16, 2011, 12:52:45 AM

My converter tables give 1.34 horsepower per kilowatt, or 0.746 kilowatt per horsepower. You have 250 horsepower base load, so 186.5 kilowatts. You want some room to expand, and also do not want to continuously run the generator at max load. Figuring that you might want to run the Diesel at about 60% power output for a constant load, that would make for a generator of about 300 kilowatts. You would not want to run much lower than 60% with the Diesel. I would recommend a 300 kilowatt generator.

Properly tuned, you should be burning about 0.5 pounds of Diesel per One horsepower-hour of output, allowing for a little bit of losses between the generator and electric motors. Diesel goes about 7 pounds per gallon, so at 125 pounds of Diesel an hour, you should figure on between 17.5 and 18 gallons of Diesel an hour fuel consumption. That is being conservative, and you might to a bit better, but I would say your minimum is going to be 14 gallons an hour.