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Using a portable generator for saw/jointer

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Forum topic by Bill7255 posted 09-23-2013 11:26 AM 1403 views 0 times favorited 14 replies Add to Favorites Watch
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Bill7255

353 posts in 1746 days


09-23-2013 11:26 AM

I am building a new house and building my kitchen cabinets. I have built a new workshop. At this time the only source for electricity is a portable generator. I have a 11kw generator. I have 3hp saw and 3hp MM FS35 jointer I need to use. I set up the saw yesterday and it started with no problem. Starting amps was 49 and no load running amps was around 5. The jointer did not start on the first attempt and the meter showed 86 peak amps kicking out the generator breaker. The second attempt the jointer starter with 73 starting amps and about 6 no load running amps. It did seam to start slower (from memory as neither of these machines have been started for 4 months). The voltage from the generator I really only need to use the jointer for two starts to finish my cabinets. Is/what risk are there to using a portable generator? What should I look for?

Bill

-- Bill R


14 replies so far

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bigblockyeti

3666 posts in 1182 days


#1 posted 09-23-2013 12:43 PM

If neither the saw or the jointer has been started in 4 months, the belts will been a little reluctant to being bent (especially if the saw is a 3 drive belt model). The grease in the bearings will probably have to be churned out of the path of the balls and cages also. The inertia the jointer cutter head has would be substantial compared to the saw as well. I worked at a shop where the “yard” planer was outside under an overhang and when it was cold it was very reluctant to start, usually tripping the breaker 4-5 times gaining a little more speed each time before getting up to full speed. 11Kw is a lot for a generator and will have no problem running, and starting either tool (not at the same time!) once both have been run a bit. One other thing to check is to make sure your generator is putting out 60Hz (usually 3600rpm on a 2-pole generator) which will keep the voltage and current where they should be.

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firefighterontheside

13448 posts in 1317 days


#2 posted 09-23-2013 01:51 PM

11 kw should be plenty big for those tools, probably even at the same time, but you’re not likely to do that. I would think that generator has 20 amp circuits, but make sure. If it still trips the breaker, you may need a new breaker in the generator.

-- Bill M. "People change, walnut doesn't" by Gene.

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crank49

3980 posts in 2432 days


#3 posted 09-23-2013 02:22 PM

It’s fairly common for the starting amps to be 7 to 10 times the running amps.
On paper and in a perfect world that generator should be able to run about 14 to 15 horsepower.
But, of course, it couldn’t handle the starting inrush amps to get that 15 hp started.
However, once either of your machines are running it should have no problem keeping up.

As said earlier, it’s just got to get the belts and grease warm and loosened up a bit.
Heck, I’m the same way myself. Sometimes I wish I had a bigger breaker to get started in the morning.

The only danger I would be concerned about would be wear and tear on the generators breaker if it trips several times and keep an eye on the voltage. Low running voltage is harder on induction powered machines than slight over voltage.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

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Bill7255

353 posts in 1746 days


#4 posted 09-23-2013 02:42 PM

Thanks for the reply. The generator breaker is 30 amp. The jointer only tripped,the breaker twice, after that it started each time. I didn’t think about the belts being set from storage. So I should be good ro go.

Bill

-- Bill R

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MrRon

3926 posts in 2704 days


#5 posted 09-23-2013 04:51 PM

How big is your extension cord?

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bigblockyeti

3666 posts in 1182 days


#6 posted 09-23-2013 05:37 PM

The belt set I’ve noticed on my saw gets much worse in the winter. Before I break down and turn on the heat and if the saw has run in a couple of weeks it when I notice it the most. The belts are so reluctant to spin, the saw has a slight vibration for the first 30 or so seconds before smoothing out.

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firefighterontheside

13448 posts in 1317 days


#7 posted 09-23-2013 05:48 PM

I second that about the vibration. It’s the main reason that I want to get the link belt. I wonder if you would be better off, with the tool unplugged, turn the belt for half a turn before you turn it on. That way the motor wouldn’t have to overcome that bend that’s been formed in the belt.

-- Bill M. "People change, walnut doesn't" by Gene.

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Shawn Masterson

1297 posts in 1409 days


#8 posted 09-24-2013 02:17 AM

I was also wondering about the cord.

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bigblockyeti

3666 posts in 1182 days


#9 posted 09-24-2013 02:30 AM

Not sure about using three linked belts on my Unisaw, don’t know if it’s been done successfully by anyone. The reason for keeping the belts so short is to minimize the vibration that can be created by a long belt. Also, these belts are old, they still look decent, but I know they’ve never been changed and the saw is almost 20 years old. I know these were a matched set too.

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Bill7255

353 posts in 1746 days


#10 posted 09-24-2013 02:34 AM

Extension cord: I will have about 6 feet #12 from the generator that will connect to #10 for about 40 feet to receptacle plug. The cord from the saw that plugs into the receptacle is about 10 feet. Plug and receptacles are all rated 30 amp. For the test run I had about 16 feet of #12 cord.

-- Bill R

View Charlie's profile

Charlie

38 posts in 1173 days


#11 posted 09-24-2013 07:46 AM

The starting up slow overheats the motor windings and as inrush current goes up voltage goes down which is why they start slower. #10 wire all the way will help but I dont think the 11k gen is quite big enough to start the jointer without doing damage to the motor. Before others chime in saying that a 11k gen should start a 3hp motor. Take in the fact that you are driving a large heavy spindle on that jointer at start up. My jointer starts slower then my saw just because there is a lot more there to get moving.

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Bill7255

353 posts in 1746 days


#12 posted 09-24-2013 11:43 AM

Icsparks

I only need to do two more starts hours apart for the jointer. I can see doing multiple starts this would cause the motor to overheat, but running I don’t think the motor is overheating. Once I start it I will let it run for 5-10 minutes to stabilize. I guess I am asking is damage done over time or making multiple starts in short periods?

-- Bill R

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Charlie

38 posts in 1173 days


#13 posted 09-24-2013 11:28 PM

The damage is done during the short start up period. Once the motor is up to speed you will be fine. Motors are either on or off no need to stabilize once the motor is running at speed under normal conditions. there should be a code letter on the motor nameplate that will tell you the amount of current the motor draws at start up. If you only have two stars to do and its really inportant then use #10 wire and run it. Watch closely on how it starts. If you feel it is taking to long to get to speed then shut if off. You may want to rent a bigger generator for the day.

link to code letter
INRUSH AMPERES
= ((CODE LETTER VALUE) X HP X 1000)/(RATED VOLTAGE)
http://www.motorsanddrives.com/cowern/motorterms6.html

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Grandpa

3256 posts in 2136 days


#14 posted 09-25-2013 03:37 AM

I helped a fellow once. We were framing a shop and he was using a generator. He started his RAS and it did take some time to get up to speed. I remember thinking that this saw was not long for this life at this rate. Then when it got going he never turned it off until lunch time! I can’t say that is safe but with the 2 of us out in the country we got by with it. BTW he did use that saw for many more years.

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