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Igor! I need mor VOLTAGE!

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TheClaw

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Wow! It's been a long time since I've been on the forum. I hope somebody may be able to help. We downsized temporarily. I went from cozy heated garage with abou1 100amp of 120V and one 240 outlet. The dinky garage I'm in now might have 20 amps of 120V to power the outlet a couple of lights and the openers. I have been having a hell of time getting my generator to power the compressor.

The compressor has a large tank, probably a 3hp motor and twin cylinder pump. I rewired the motor for 240V, connected a 240V plug. Started the generator, flip the switch to 240V and turned on the generator. All i got was a strained have of revolution of the motor before a breaker popped.

Checked all the breakers and tried again. The generator is about 10 years old, runs ok but not enough juice to fire up the Compressor. Do all I need to do is get a bigger generator? If so, what size and what would you recommend. Here are pics:

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PCustoms

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Double check your wiring, you only need about 1800w running.

Was the generator already up and running when you flipped the breaker?
 
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nadogail

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Your 4KW generator should be able to run that motor, based on the motor name plate information. Maybe the 4000 watts is an exaggeration.
 
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Milton Shaw

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You might try loosing the belt and let the motor start and then slowly let the belt slip until the compressor is at full speed. If that works then the start up requirements is too much for that generator. Cheapest thing to do is probably to get an electrician to get you more power.
 
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PoorUB

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I sold generators for some time. For motor starting we took a minimum of 2-1/2 times, 3 times preferably of running watts of the generator.
That generator is rated for 3,500 watts running. That was the number we used, not the peak watts which is like old compressor rating of 6 or 7 HP on a 15 amp motor!

That 4,000 watt generator will not start that compressor. It might start it if the outlet pipe was disconnected and run free, but compressors are hard starting as they are pretty much under full load right now. You will need a minimum of 4,500 watts to start it unless you find a way to unload the compressor on start up and I am not even certain it will start it then. Disconnect the outlet pipe and try it.

7.5 amps x 230 volts = 1725 watts

1725 watts x 2.5 = 4312 running watts.

You are about 800 watts short.

Also, that motor is 1-1/2 HP, maybe 1-3/4 HP
 
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TheClaw

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@PCucstoms

Generator and compressor were fine before the move. I've triple cheked the motor wiring. Ive gone back and forth before. Starting sequence

Plug it all in.
Start generator
Flip the 120/240 switch to the 240 position.
That's when shuts down.

@Milton Shaw

I'm leasing a downside house. Quotes for running new juice to the garage ranged from $3000-8000.

@PoorUB

Very helpful info. I'm also running it to an empty tank so there is nothing pushing against it. I like @Miltoidea about loosing the belt. Heck ill just take it off for a test.
 
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TheClaw

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@PoorUB

How did you figure the hp of the motor? Somebody else looking at the data plate said more like 5hp. Something in the math?
 
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PoorUB

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TheClaw said:
@PoorUB

How did you figure the hp of the motor? Somebody else looking at the data plate said more like 5hp. Something in the math?
Click to expand...
5HP? :ROFLMAO: Sorry, I couldn't help it!

On 1 phase power, 1 HP on 115 volts will be a bit less than 10 amps. 230 volts a bit less than 5 amps.

I have a 5 HP motor on my compressor and it is right around 25 amps at 230 volts. I want to say 27 amps, but I forget, and I am not walking out to find out right now!

Some motors are a tiny bit higher in efficiency, some lower. Older less efficient motors might draw over 10 amps per HP on 115 volts and a bit over 5 amps at 230 volt. This is just a guesstimate, but close enough for a decent estimation.

I did HVAC work for years so I got used to the 10 amp and 5 amp numbers.
 
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PoorUB

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Leasing a home? Do you have a 4 prong stove or dryer outlet handy? Buy 25 feet, (or what ever length you need), of 10/3 or 8/3 cable and a 230 volt breaker panel and make a temporary power supply box. Size the cable for what ever size the breaker feeding that outlet on the house breaker panel.
 
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kengoff

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Running about the same compressor as yours, different badge but size and motor the same. On a 5kw continues generator it wouldn't start the compressor. A 5.5kw would, ran the compressor off the generator like that for 3 years.
 
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Jbullfrog

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Start hunting for a Miller Bobcat or Trailblazer. Big enough to run the essentials in your house as a back-up and weld too! They can be had for under $2k if you hunt.
 
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nadogail

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I bought a 10 KW Peak Alternator from Harbor Freight. I spin it with a 13 Horse Chonda engine made by Lifan, it can run my stick welder when I am burning rods at the 100 Amp setting. It can also run my compressor and other stuff.

I plug the welder into the 30 amp outlet.
 
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Captain Spaulding

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You are close to locked rotor amps to get that motor spinning, and that generator doesn’t have that much current to give. Starting a motor, especially a loaded motor, takes a big slug of power.
 
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PoorUB

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pattenp said:
(230Vx7.5A) / 746W = 2.31HP, not knowing the power factor it's probably 2HP at best.
Click to expand...
Power factor will be roughly 75% so 2.31 HP x .75 = 1.7 HP.
Even a .80 power factor comes in at 1.8 HP.

These compressor motors are not built to high standards. They are built to a price point.

I seriously doubt it is 2 HP.
 
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talonboy

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I have had the exact same issue. New garage no electric yet. Tried to run my Ingersol Rand 5hp 60 Gal compressor off my old Coleman 5000w generator. Compressor started, but sounded funny and started smoking after a few seconds, then tripped the breaker on the compressor. Borrowed a 6500w Ryobi generator and had much the same issue. Generator started, sounded funny, then kicked the breaker on the compressor motor after 30 seconds or so. Hooked up my voltmeter and tried again. Noticed the generator was putting out 240v, which dropped to about 190v when the compressor was switched on. Clearly a bigger generator is needed.
 
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mike93lx

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talonboy said:
I have had the exact same issue. New garage no electric yet. Tried to run my Ingersol Rand 5hp 60 Gal compressor off my old Coleman 5000w generator. Compressor started, but sounded funny and started smoking after a few seconds, then tripped the breaker on the compressor. Borrowed a 6500w Ryobi generator and had much the same issue. Generator started, sounded funny, then kicked the breaker on the compressor motor after 30 seconds or so. Hooked up my voltmeter and tried again. Noticed the generator was putting out 240v, which dropped to about 190v when the compressor was switched on. Clearly a bigger generator is needed.
Click to expand...
A 15kw might be enough. Possibly not
 
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CGT80

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That motor is small, but start up can be very high. My baldor 5hp 213 frame (1-3/8" shaft and 108 pounds for entire Motor) is an older motor and has a nameplate of 28.5 amps and 1.15 service factor. It is 27+ amps while pumping but at start up it will show 169 amps on one leg for a half second with my clamp on meter. That is more than 5x nameplate and I have read it can be up to 8x. My brother had a hobart 230 amp engine drive stick welder and he runs his miller 220 multiprocess machine from it. I think the generator in the unit is rated At 10,000 watts. Starting motors and running welders are tough tasks for smallish generators
 
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cruzer75

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So I don't have 240v run to my garage. What I do is have a heavy gauge (6gauge) extension cord that I run from a 30amp switch (on/off/on).

I can turn the Water heater on or I can turn the garage 240 on.

I could have also used the dryer plug but previously we used the dryer more than the electric hot water heater (used the boiler for hot water primarily)

Maybe this is a better solution than the generator for now?

Stewart
 
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TheClaw

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So i got a big honkin' DuroMax 13000,10000 generator. My motor has three lines coming from it, Black, Red and Green. I know that the the Blk and Red are hot, Grn is ground. If i wire it to the 4 prong L14-30P plug, how do I know I'm getting all of the 240 volts going to the motor? What do I do with the spare lead on the plug?

The motor will turn if I attach a L6-30R plug to it and wire the motor for 120V but when I wire the motor for 240 but if I then use a L14-30P to L6-30R conversion plug it won't spin up.

I know there is enough juice coming out of this generator but I don't know if I'm using the right plugs onto the right reptecals. and how do I know i'm getting 240 from the receptacle labled 120/240?

The generator labels the 4 prong receptacle as 120V/240V 30Amps


receptacle.pngconversion chord.png
 
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