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Using bandsaw on a generator

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Forum topic by DW833 posted 03-28-2020 02:02 AM 356 views 0 times favorited 13 replies Add to Favorites Watch
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DW833

228 posts in 2614 days


03-28-2020 02:02 AM

Topic tags/keywords: bandsaw generator

I have a craftsman bandsaw model 119.224010. It has a 1hp motor and the motor label states that it uses 11 amps when using 120v. I think that is running amps, but not sure. I don’t see anything about start up amps.

The workshop I have doesn’t have power, so I need to run the bandsaw off a generator.
The generator has outlets for 120v / 20 amp. And a RV outlet for 120v 30 amp.

Whenever I start the bandsaw on either outlet, it runs for just a second and then the circuit breaker on the generator shuts the generator down. I’m not sure if it is the starting or running amps that is causing it. I thought it would be the starting amps since it only runs for a second.

I have an adapter that plugs into the RV outlet and the other end has a plug for a three prong 120v plug.
Same thing happens when using the RV outlet. The adapter I have supports 15-20 amps.

Not sure what to do at this point. Since the motor states 11 amps and that is running amps, I think it has to be the starting amps that is the problem. For a motor with 1hp/11 amps, how do I determine how much starting amps it needs. Online research I found points to no more than 20 amps.


13 replies so far

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Aj2

2951 posts in 2529 days


#1 posted 03-28-2020 04:13 AM

My guess is the starting surge is just too much. The two hardest starting machines in my shop are Air compressor then bandsaw.
You could try taking the blade off and see if it will start one wheel.
Keep your extension cord as short as possible. Not sure what R V adapters means.

Good Luck

-- Aj

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MrUnix

7991 posts in 2930 days


#2 posted 03-28-2020 04:54 AM

You should be able to run that saw on any suitable sized generator… I used to run 1.5hp contractor saws all day long on a 5000 watt generator without any issue. Heck, I run a 1hp ~100 foot deep submerged well pump off a similar (5000W Coleman Powermate) generator when we have power outages, and it barely hickups when the pump kicks on. The amperage on the motor data plate should be FLA (Full Load), so it should never get anywhere near that under normal operating conditions. For startup (inrush) current, look at the “Code” rating on the data plate and let us know what it is. Also, what size is your generator? Does the bandsaw run fine when using a normal household outlet?

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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CaptainKlutz

2993 posts in 2225 days


#3 posted 03-28-2020 08:59 AM

Have seen this kind of issue before. Couple of things:
1) How long is extension cord and what size is used?
2) Is generator running properly at full RPM when you start the saw, or is it demand based and increases RPM for load?

If cord is long, or using a standard 14AWG extension cord one might (improperly) use for 1HP motor; then the startup current spike requires more power (watts) and most importantly lasts longer. Best analogy: It is just like trying to drink a thick milkshake through a skinny straw! Takes 3x times as long, and in case of generator – breaker trips.
Try using a short 5-10 ft 12AWG cord on 20A circuit and check for breaker trip. Should be using a larger size 10AWG extension cord of length is over 25 ft with generator connected to motor (inductive) load. Should always be using 10AWG minimum if using the 30A receptacle, or the resistance of wire prevents the extra power from reaching the tool.

Another challenge with older generators is failing breakers. Thermal breakers are typically rated for couple hundred cycles max, and are not intended to be used as a switch. If a generator has history of being pushed too hard, and breaker trips often; they become more sensitive over time and fail sooner. Have seen 20A breakers tripping with ~10A lighting loads on cheap camping generator abused only one season. :-(

Last but not least, if you generator has on-demand RPM control; it might not be responding fast enough to your motor load. This causes voltage droop, and with lower voltage the motor draws more current;
and ‘poof’ it trips the breaker. For on-demand generator, set it to run at full power all time when starting motor loads.

PS – Not going to ask what kind of generator, as any generator that has a 30A RV plug, should be able to start up an RV AC unit? AC unit requires about same start up load as 1HP saw motor. But still check your documentation and verify the total wattage output and that is supports your motor.

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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tvrgeek

941 posts in 2380 days


#4 posted 03-28-2020 10:50 AM

Klutz covered it mostly. Eliminate the extension cord question by plugging it in directly.
GFI issue?

View DW833's profile

DW833

228 posts in 2614 days


#5 posted 03-28-2020 07:37 PM

Thanks for all the replies. I’ll answer as many of the questions as I can.

Bandsaw works fine when plugged into a wall outlet.
The generator is 3400 running watts and 4000 starting watts.
I think I tried it without a blade, but not sure. I’ll try that again.
Tested it without a cord. Plugged in directly to generator. Same result.

Brad, I don’t see a “code” rating. May be inside the motor.
The generator has an option to use full load all the time or manage the load. Same result on full load at all times.
This is a new generator with no problems running anything else. The only other large tool I’ve run on it is a shop vac. No problems with it.

Looking at the motor cover, it must have a large starting capacitor. I haven’t opened the cover yet, so I’m not sure. Is it possible to check the capacitor to see if it is working or should be replaced?
I’ll research on youtube to find out how to do that.

See image below.

Thanks again. Any other suggestions are appreciated.

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tvrgeek

941 posts in 2380 days


#6 posted 03-28-2020 08:15 PM

So you have 28 Amps full load if it actually supplies what it says it does. I guess it is just marginal for how long it takes for a bandsaw to reach speed for the start winding to drop out. It takes at least a full second for my BS to come to speed, where my shop vac is less than a quarter that time. They are brush motors without starter windings.

Try some other heavy loads. A circular saw for instance.

View MrUnix's profile

MrUnix

7991 posts in 2930 days


#7 posted 03-28-2020 09:04 PM

Brad, I don t see a “code” rating. May be inside the motor.
- DW833

It would be on the motor data plate, same place where you find the FLA, RPM, etc…
Most newer motors have it (NEMA requirement)... but not all.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

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DW833

228 posts in 2614 days


#8 posted 03-28-2020 09:14 PM

There is not a code rating on the data plate. Is that the same as class? It is a class B.

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CaptainKlutz

2993 posts in 2225 days


#9 posted 03-28-2020 11:08 PM

Guessing the generator does not have enough power?
Measuring the voltage/current curves with a fast meter or an oscilloscope would verify.
Could be capacitor is failing or wrong size. Could be simple issue of low motor efficiency. Without data, every thing is just a guess.

Might be able to cheat, but a stern warning up front – it is dangerous:
open the lower door of band saw, with palm of hand get lower wheel spinning in proper direction, turn on switch and make sure you fingers/hand are not inside the wheel or touching the blade as it starts – or you get hurt.

If generator is running at full power, having the mass already moving at low speed can reduce the start up load and also reduce the amount of time the start capacitor is engaged, occasionally this is enough to avoid tripping breaker. Did this in past on a 1.5HP compressor, using a wimpy generator in the field a few times.

Best Luck.

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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MrUnix

7991 posts in 2930 days


#10 posted 03-28-2020 11:48 PM

There is not a code rating on the data plate. Is that the same as class? It is a class B.
- DW833

No, that should be the insulation class. Class B indicates it can run at a maximum ambient temperature of 40ºC, and can handle up to 80ºC temperature rise.

Cheers,
Brad

-- Brad in FL - In Dog I trust... everything else is questionable

View JohnMcClure's profile (online now)

JohnMcClure

991 posts in 1371 days


#11 posted 03-29-2020 12:06 AM


If generator is running at full power, having the mass already moving at low speed can reduce the start up load and also reduce the amount of time the start capacitor is engaged, occasionally this is enough to avoid tripping breaker.

This should work. Be careful! Hand-spin the saw, then (with your hands clear) start it while still coasting. I bet it doesn’t trip the breaker.

-- I'd rather be a hammer than a nail

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DW833

228 posts in 2614 days


#12 posted 03-30-2020 12:59 AM

Thanks for the suggestion. I’ll try that in the next couple of days and let you know.

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therealSteveN

5545 posts in 1305 days


#13 posted 03-30-2020 03:16 AM

You said

“Bandsaw works fine when plugged into a wall outlet.
The generator is 3400 running watts and 4000 starting watts.”

That is on the small size for a generator. If you jumped to running 6500 watts, you would be good provided you had an ample sized extension for whatever distance. Plugged directly to the generator, you would be golden.

-- Think safe, be safe

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