30amp 120V adapter?

[Theodore]

Planning ahead. I want to use a 120V 3200W electric concrete saw (i.e. VEVOR Electric Concrete Saw, 16 in, 3200 W Motor). Many reviews say it could bog down and then will trip even a 20amp breaker. I don’t want to set the house on fire, so I figure I can run it from my portable generator (5500 running watts/8250 surge). But I’ll even have to avoid using the 20amp breaker-protected outlets on the generator. I figure I can convert the 120-240/30amp generator output via a nema L14 30 to 3 prong 120v adapter (i.e. MECMO NEMA L14-30P to 5-15R 5-20R Generator Adapter, 4 Prong Twist Lock Generator L14-30P to 110V 5-15/20R T-Blade). I agree it is possible I might overload this adapter, but I figure safer to do that than potentially and repeatedly tripping the house breaker.

Your advice on this approach is welcome.

 

[Bannerman]

3200W / 120 volts = 26.66 amps.

The adaptor shown, is suitable for up to only 20 amps ( 2,400 watts) @ 120 volts.

The saw's info is somewhat conflicted as the initial heading specifies 3200 W motor, but one of the images shows "Max. 2800w power".

The description specifies:

• Note: It is recommended to perform cutting operations at 32A current. (When the current is 15A, the single cutting depth should not exceed 50mm (2"). If a cut of greater than 50 mm (2") is required make several passes)

If you supply power from your generator's 20a/120v outlets, the breaker will be less likely to become tripped while continuing to limit the cutting depth to 2" per pass.

 

[Sponsor]

 

[Breplum]

I have witnessed many hardwood floor refinishers use their home made clamp-on heavy duty extension cords with spring loaded clamps connected directly to the house main panel as the only way to run without trouble.

 

[Reach4]

Planning ahead. I want to use a 120V 3200W electric concrete saw (i.e. VEVOR Electric Concrete Saw, 16 in, 3200 W Motor). Many reviews say it could bog down and then will trip even a 20amp breaker. I don’t want to set the house on fire, so I figure I can run it from my portable generator (5500 running watts/8250 surge). But I’ll even have to avoid using the 20amp breaker-protected outlets on the generator. I figure I can convert the 120-240/30amp generator output via a nema L14 30 to 3 prong 120v adapter (i.e. MECMO NEMA L14-30P to 5-15R 5-20R Generator Adapter, 4 Prong Twist Lock Generator L14-30P to 110V 5-15/20R T-Blade). I agree it is possible I might overload this adapter, but I figure safer to do that than potentially and repeatedly tripping the house breaker.

Your advice on this approach is welcome.

What plug comes on the power cord for that saw? If that comes with a NEMA 5-15 or NEMA 5-20 plug, I would not go to the extent you are. I suspect a Vevor to exaggerate specification.

To me, bogging down indicates you are feeding the saw too fast, or the motor is under-powered.

Tripping a breaker will not burn the house down. Running 30 amps thru 12 AWG copper will not burn the house down. There is a lot of margin built into the house wiring standards. In a car, they can run 30 amps continuously thru 4.9 ft of #12.

 

[bigb56]

There are a lot of different rules for motor loads that take into consideration things like inrush and duty cycle. They don't apply to your portable saw but the principles are the same. A higher rated breaker on a smaller wire is often used on motors although the motor is protected against over current at the load by time delayed "heaters". A higher rated breaker is also used on smaller wire for certain equipment where the duty cycle of that equipment is not high enough to overheat the wiring.

That said I wouldn't hesitate at all to run that saw on a 30 amp circuit as a temporary setup. I would run a cable right out of the electric panel to a box with a receptacle just for that saw, nothing else. This is kind of a gray area that code doesn't address. Code tells you what you can and cannot do for permanent building wiring but does not go beyond that.

The fact that it uses 3,200 watts means it uses 27 amps but if they only supply it with a 15 amp plug and tell you it works "best" on a 30 amp circuit you will need to make the temporary setup with a 15 amp configuration (ordinary duplexes are rated to 20 amps even if 15 amp configuration) or change the plug on the machine to a 30 amp and use a 30 amp receptacle configuration.

 

[bigb56]

I have witnessed many hardwood floor refinishers use their home made clamp-on heavy duty extension cords with spring loaded clamps connected directly to the house main panel as the only way to run without trouble.

Yep I've connected a floor sander to one side of a 50 amp breaker! I also have a welder receptacle mounted in a box with a pigtail that I can temporarily wire into any 240V panel.

 

[Fitter30]

3200W / 120 volts = 26.66 amps.

The adaptor shown, is suitable for up to only 20 amps ( 2,400 watts) @ 120 volts.

The saw's info is somewhat conflicted as the initial heading specifies 3200 W motor, but one of the images shows "Max. 2800w power".

The description specifies:

• Note: It is recommended to perform cutting operations at 32A current. (When the current is 15A, the single cutting depth should not exceed 50mm (2"). If a cut of greater than 50 mm (2") is required make several passes)

If you supply power from your generator's 20a/120v outlets, the breaker will be less likely to become tripped while continuing to limit the cutting depth to 2" per pass.

10 gauge extension cord and a 30 amp breaker. 30 amp should be a twist lock
L5 30 R reciprocal.

 

[Bannerman]

Fitter30, the adaptor that Theodore enquired about initially, shows a L14 30P Twist lock for the 30 amp 4-prong generator outlet, and a 5-15/20R on the outlet side of the adaptor.

For a saw rated to consume >25 amps @ 120 volts, it should have been equipped with a plug designed for >30 amps, but since the seller's web page specifies operating from a 15-amp source when cutting is limited to a depth of 2" or less, I suspect the saw is equipped with only a standard 2 vertical blade plug + ground, to fit standard 15 amp outlets.

 

[Theodore]

So I wired a spare dryer cord directly into a stand-alone 15AMP/125V outlet (using only the ground, the neutral, and one of the two hot wires) in an all metal junction box (to avoid risk of plastic box overheating). That should do fine as a strictly temporary condition. I'll just keep a wary eye on it to make sure the outlet itself isn't overheating while in use, and I'll keep the assembly free-and-clear of anything flammable in case it does want to overheat and start melting the outlet. And I'm using a 12gage-100ft extension cord from that outlet to the saw. Definitely not a permanent fixture, but sounds like this is in keeping with the measured risks you all described.

 

[bigb56]

I don't think you'll have any issues. What is your duty cycle, in other words how many consecutive minutes out of each hour do you figure the saw will be working each time it is started? Intermittent duty cycles are far less demanding on the supply side equipment than continuous loads.