power tools and 2500 watt generator?

bobdog · July 2010

I have a Honda 2500 watt generator (old style, non inverter). I am planning on running tools that are 15 amps or less. For example a 15amp planer. I realize motors draw far more at start up but have no way of knowing how much. At 15 amps my generator will run this planar as it will only take 1800 watts. However, can anyone give me an idea how much a power tool, such as a planer, would use at start up? Thanks for your ideas.

Tim

Cariboocoot · July 2010

Re: power tools and 2500 watt generator?

There are probably very few things that generator won't run. If it will plug in to an ordinary outlet and work, it should work off a 2500 Watt gen.

How did you determine the power usage of your planer? 1800 Watts is about 2.5 HP and I doubt it develops that. A circular or table saw might, though. Also, the start-up surge of a motor is dependent on the motor's design and application; we frequently talk about the heavy draws of refrigerators which are trying to start against the load of the compressor. Free-running power tools will not use as much current, even though they may have a similar running power rating.

One caveat: make sure you use a heavy gauge extension cord. The Voltage drop through 50' or 25' of small wire can be significant. Many "outdoor" cords are only 16 gauge, which really isn't good enough.

bobdog · July 2010

Re: power tools and 2500 watt generator?

Cariboocoot wrote: »

There are probably very few things that generator won't run. If it will plug in to an ordinary outlet and work, it should work off a 2500 Watt gen.

How did you determine the power usage of your planer? 1800 Watts is about 2.5 HP and I doubt it develops that. A circular or table saw might, though. Also, the start-up surge of a motor is dependent on the motor's design and application; we frequently talk about the heavy draws of refrigerators which are trying to start against the load of the compressor. Free-running power tools will not use as much current, even though they may have a similar running power rating.

One caveat: make sure you use a heavy gauge extension cord. The Voltage drop through 50' or 25' of small wire can be significant. Many "outdoor" cords are only 16 gauge, which really isn't good enough.

Thanks Coot. I simply multiplied 120 volts X 15 amps and came up with 1800 watts. I think I did that right?

Cariboocoot · July 2010

Re: power tools and 2500 watt generator?

bobdog wrote: »

Thanks Coot. I simply multiplied 120 volts X 15 amps and came up with 1800 watts. I think I did that right?

Yes. But chances are the tools don't draw 15 Amps. Sometimes the tags they put on them are outlandishly inaccurate. The opposite end is a 2 HP circular saw I had which would pop fuses or at least dim the lights because it was way over 20 Amps on start-up. Piece of junk!

icarus · July 2010

Re: power tools and 2500 watt generator?

FYI,

I have a 1800 ex Honda and I run a 13 amp skill worm drive, makita 10" table saw and a Dewalt 16" surface planer off it just fine. (not all at once of course!)

A trick is to let the tool spool up before putting it under load. I also leave the tool running (except for the skill saw) unless it is unsafe while I do other prep work, so that the planer only has to start once.

Tony

bobdog · August 2010

Re: power tools and 2500 watt generator?

I thought I'd update this thread after using my generator this last week at the cabin. It ran the Skill saw fine, the drills fine and for a while the table saw fine. BUT, it wouldn't run the air compressor unless it was empty and the valve open. My guess is that like a refrigerator it had a hard time turning the compressor in addition to starting the 15 amp motor. This is a problem as all the siding and flooring will be installed using air guns.

In addition, after a while it appears as though it got too warm and just shut down (wouldn't even start the table saw).

So, we bit the bullet and bought a Generac 5000 watt portable genset. In looking around it seemed like a good product. We'll see how it fairs in a couple of weeks when we go back up to the cabin.

Tim

PS does anyone have any experience with Generac generators?

BB. · August 2010

Re: power tools and 2500 watt generator?

The little I know about Generac is that they are not built for long term use (but not many small gensets are).

Regarding the compressor--I have converted a couple before by purchasing an "unloader" type valve. Start the compressor with no air in the tank and then the unloader dumps air whenever the tank is full--No more heavy starting loads. Around $20 to $60 through www.grainger.com

I think this Search Link will work correctly (Graingers has lots of interesting parts so it is a nice one place shop and they are local to me--but they typically are charging retail+; Also, I believe you need a business license to purchase from Graingers--"Wholesale" only).

-Bill

Cariboocoot · August 2010

Re: power tools and 2500 watt generator?

Yep: air compressor = very hard to start. Like refrigerators or water pumps; trying to start against a load means more start-up current, and induction motors use quite a lot even when there's no load.
Unless you get an unloader valve as Bill suggested, or rig a diverter/check valve (more complicated) or some other such rig-a-ma-role.
Or get a smaller compressor. You'd be amazed at how little you actually need to run air guns. I actually run mine with this: http://www.princessauto.com/air/compressors/electric/8260713-3_4-gallon-pancake-air-compressor
2 HP, 12 Amps so it might have trouble on a small gen too. Never tried it on the Honda. Maybe soon.
I'm sure the Generac will last at least long enough to finish the project. I've got a cheap old B&S 5kW unit that's been going for 10 years now. Don't use it much anymore, but it's too heavy & not valuable enough to bother getting rid of.

monoloco · August 2010

Re: power tools and 2500 watt generator?

I have a nice little lightweight compact compressor from Senco that is super quiet and works really well with finish guns. Some times if you are nailing rapidly you will have to stop to let it catch up. I haven't tried it with a framing gun.

dmiller · August 2010

Re: power tools and 2500 watt generator?

If only one person is using tools I would always go with a 1600W Honda or Yamaha inverter generator. Much nicer in all ways than a non-inverter "contractors" generators. But more expensive to purchase, of course.

As a former builder I only expected to have a contractor generator for a year or two (at the outside) before it was destroyed or stolen. As a homeowner/traveler I want a very different tool.

bobdog · August 2010

Re: power tools and 2500 watt generator?

BB. wrote: »

The little I know about Generac is that they are not built for long term use (but not many small gensets are).

Regarding the compressor--I have converted a couple before by purchasing an "unloader" type valve. Start the compressor with no air in the tank and then the unloader dumps air whenever the tank is full--No more heavy starting loads. Around $20 to $60 through www.grainger.com

I think this Search Link will work correctly (Graingers has lots of interesting parts so it is a nice one place shop and they are local to me--but they typically are charging retail+; Also, I believe you need a business license to purchase from Graingers--"Wholesale" only).

-Bill

Where do you install the unloader valve?

BB. · August 2010

Re: power tools and 2500 watt generator?

The unloader goes between the compressor and the tank. When the tank is full, the valve opens and dumps air from the compressor directly to the open air.

There are lots of unloader styles (including unloaders that dump air pressure when the electrical switch turns off--so the first few revolutions are not against 100 psi pressure).

The most generic unloader is probably this one. It is designed to convert any start/stop compressor (with 1/2" tubing) to a continuous run (bypass the electrical pressure switch or set above unloader pressure setting).

Here is a several page PDF with a bit more information and physical dimensions.

I used one of these with a 1/2 horse air compressor (all most enough CFM enough to run a standard size paint sprayer for painting cars and such without pausing for tank to repressurize). I ran it on an old 1,800 watt B&S genset (1970's vintage). I even made it so the electric motor could get to speed, then pivot the electric motor down on a hinge to slip the belt and get the air pump up to speed (yea, the generator could not even start an unloaded pump). Worked really well.

-Bill

dwh · August 2010

Re: power tools and 2500 watt generator?

BB. wrote: »

Also, I believe you need a business license to purchase from Graingers--"Wholesale" only).

-Bill

In California (might be different if you are buying from out of state) Grainger's requires a "Seller's Permit". It allows you to buy without paying sales tax, and to charge sales tax when you sell. (And naturally, to forward any collected taxes to the state.)

They are easy to get (and there are temporary permits as well), but the state is VERY picky about getting paid any taxes you collected. If you screw up, they'll still give you another permit, but they'll make you pay a deposit equal to however much taxes THEY think you'll end up owing.

I never got stuck having to pay a deposit, as I kept a separate bank account just for state taxes and the only time they got nasty with me, I was able to easily prove that I had handled the state's money with due diligence. After that they never bothered me again.

http://www.taxes.ca.gov/Sales_and_Use_Tax/SellersPermit.shtml

EDIT: Just remembered another detail about that deposit. When you fill out the application, you have guesstimate how much you think you'll collect in sales taxes - if that amount is high enough, they'll hit you for a deposit even if you've never screwed up.

power tools and 2500 watt generator?

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