low voltage effect on motors

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I do carpentry work out of a storage unit and run a generator to power my tools since the voltage drops too much to start the bigger capacitor start tools. There are a few people claiming to not have any problems, but I think they're also closer to the electrical box then me since I'm right in the middle. It will run a miter saw and drills and that sort of thing, but my air compressor barely did anything when I flipped the on switch. Even the miter saw lagged a bit compared to having a solid 120 volts. I didn't want to see what any of the other tools did cause it probably isn't good for the tool to do that. Do you think that's the reason it doesn't startup, just too far away from the breaker box? I'd say it's a good 250 feet, so I tested the voltage with a meter and it's 120 volts, but I can plug in a 2.5 amp fan and it drops to 114 volts. I'm assuming a fan shouldn't cause that much of a drop. They don't care that I run a generator, but I just do it after hours when nobody is around. What do you guys think? It's really only capacitor start tools that won't startup.
 
I know in the winter my "2hp" hf air compressor wouldnt start with a 100ft 14 gauge cord. Started just fine at the outlet or with a 25ft 12gauge cord.

And by no means was that a 15amp tool.

has to do with startup current and to long a wiring run.


somewhat similar ..why you dont want to use a 100ft garden hose with a power washer.
 
Yeah sounds like you're too far away from box, a 6v drop for only a 2.5A load is major, voltage probably sags to less than 100v with a 20A startup load... I dunno the specs but with that far of a run you probably need something like a 6 or 8 gauge wire...

Originally Posted By: Rand

somewhat similar ..why you dont want to use a 100ft garden hose with a power washer.


I have no problem running mine on a 100ft, 5/8" hose(well 97' I've cut off approx three feet)... As long as you have volume along with pressure there is no issue... Comparing the electrical issue to a pressure washer would be like using a 1/4" hose...
 
Does the generator ROM drop when you try to start moto?. If so it's a bit undersized. Motors draw MORE current as the voltage drops because of something called "BacK EMF".
 
Framing crew I worked on had 2 compressors. A gasser and an electric. Sites sometimes had gotten a temporary meter yet. Plus a 7.5 KW generator. Generator would run 3 saws and a radial arm saw Cords were at probably 14 AWG , Maybe a 12 AWG 50 footer with a quad of 120 VAC outlets.
 
Originally Posted By: HerrStig
Does the generator ROM drop when you try to start moto?. If so it's a bit undersized. Motors draw MORE current as the voltage drops because of something called "BacK EMF".


The generator runs everything fine. I was talking about the wiring of the storage facility is probably too far away from where I'm located compared to where the breaker box is causing the 6 volt drop.
 
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Originally Posted By: JetStar
And if you do happen to sag the generator with that long of a wire run, it will drop frequency, which compounds the problem.


The other guys that run tools are much closer to each end of the row of storage units and I think they have the electrical meters on the side. I'm right in the middle which is a good 200ft run, so I think this is why they don't have a problem.
 
Voltage drop should be limited to 3-5% per best practices in the NEC. Higher voltage drop creates problems, especially in induction motors.

Heavier conductors should handle most of it. Do it right with real SOO type 10/3 cable, and quality terminations. I've made multiple extension cords myself and they do great for stuff like this.
 
Originally Posted By: JHZR2
Voltage drop should be limited to 3-5% per best practices in the NEC. Higher voltage drop creates problems, especially in induction motors.

Heavier conductors should handle most of it. Do it right with real SOO type 10/3 cable, and quality terminations. I've made multiple extension cords myself and they do great for stuff like this.


except its the facility wiring that is lacking not his wiring.
so he cant really fix it.. hence the generator.
 
If a 2.5 amp load causes the voltage to drop 6 volts, a 15 amp load will cause a 36 volt drop.

Some types of motor designs will draw less current at lower voltages, but a typical tool motor will draw more current. So you might be looking at a 40-50V drop.

The problem might be in a junction box along the way, rather than the wiring. A dirty way to identify the problem is to plug in increasing numbers of heavy loads such as space heaters. (You might also be testing the smoke detectors and insurance policy at the same time -- triple score!)
 
14 ga copper has resistance of 2.575 milliohms per foot. 500 ft (250 line + 250 neutral) has 1.288 ohms of resistance. At 2.5 amps, it will drop 1.288 x 2.5 = 3.22 volts.

When the facility was originally built, the electrical inspector should not have passed a run of 250 ft with only 14 ga cable, he should have required 10 ga cable, which would only drop 1.25 volts at 2.5 amps, 6 volts at 12 amps
 
Originally Posted By: Rand
Originally Posted By: JHZR2
Voltage drop should be limited to 3-5% per best practices in the NEC. Higher voltage drop creates problems, especially in induction motors.

Heavier conductors should handle most of it. Do it right with real SOO type 10/3 cable, and quality terminations. I've made multiple extension cords myself and they do great for stuff like this.


except its the facility wiring that is lacking not his wiring.
so he cant really fix it.. hence the generator.


Exactly. I should have just kept the question simple.
 
Get a smaller compressor, preferably a cheap one with a universal motor instead of an induction motor. Ordinarily an induction motor is preferable for more efficiency and longer life. But the really can't handle lowered voltage. Universal motors tend to just slow down.

The extra time waiting for air may be worth it compared to the hassle of the generator.
 
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