Okay I'll try to make this brief. I recently purchased a 220 volt 5hp 2-stage 60gal Eaton compressor. The company saidit needs to run on a 40amp breaker. So I had a 40 amp outlet and breaker installed However when the compressor arrived the mag stater where the wiring for the plug goes says not to exceed 10-14 ga wire. But a plug for a 40 amp receptacle needs at least 8ga. Eaton also ran 10 ga wire from the mag starter/pressure switch(they use a condor MDR3 which serves as both) to the motor. I am confused, it is my impression that 10 ga wire is only rated up to 30 amps, therefore, running this wire on a 40 amp breaker is a hazard as the wire would burn up before the breaker tripped if the motor pulled to much amperage??????
I.E. The motor is a Baldor single phase 23.5amps
Please help................Thanks

 

yeh yeh what do they know..

you could have done this on a 30 amp circuit.. you are ok..
5HP will never be over 30 amps.. better bigger wire than smaller.

Sam

 

Can you explain "had a 40 amp outlet and breaker installed" ? What is the source of power? Why use an outlet and plug? Usually they are wired direct or to junction box. Maybe ask an electrician?. T/M

 

I installed a plug on mine.. that way I can disconnect it easily to move or clean or whatever.

I ran 10ga for my compressor, and 6 ga for my large Miller Tig welder.
(wish I had thought ahead on the 10ga, as I almost had a 7.5hp compressor which would have required 8ga).

sam

 

I wired mine with a plug as well. Bought a pigtail with attached plug to match outlet (either a range or dryer pigtail ?) at my local DIY store. It had proper sized wire already attached.
Here's an aside suggestion: Buy new hockey pucks for under the feet. Drill and countersink (I used a spade bit to countersink, they drill as easily as wood) in center for appropriate sized bolt and bolt to feet. It will cut down on noise dramatically and the compressor will not "walk" from vibration.

 

By excedding they mean don't go smaller. The longer the distance of the wire the larger it needs to be due to resistance. That is why theres is only 10 ga. it is a short distance to motor. yours has to be larger because it is further from the motor.. Hope this helps explain it.

 

If the length of the run of the "wire" (more like cable at 8 AWG) was more than 30 feet then 8 gauge was correct for a 40 amp 220 Volt circuit. That is the same set up as an electric oven/range in the house. If it goes over 60 feet it should be 6 AWG. As a matter of fact the plug installed is probably the kind used on electric stoves - bottom tang verticle, two top tangs diagonal pointing outward at the top.

Whether it needed to be 30 or 40 amps is determined by the manufacturers requirements, but if 30 was all that is required, then 40 will be fine. That doesn't mean it will draw the full 40 amps, it just means your wiring, breaker and plug will handle 40 amps safely (and a certain margin) if it pulls that much.

And flamebuster is correct the higher the AWG the smaller the wire. So in exceeding 10-14 AWG you will be getting too small. And in my honest opinion, 14 is too small as well. The directions are oxymoronic..but you are ok.

If you need to find a chord and plug, an electric range chord and plug will work nicely - Home Depot - $12.95 - just put a new one in my house.

 

Sounds like a true electrician and better put than my description, well done.Julie...

 

You need to go by the manufacturers requirements for the circuit breaker. If it says 30 amps you need to go with a 30 amp breaker. The breaker safe guards against possibly doing damage to your compressor and electrical components. For instance if it is rated at 30 amp if you have bearing failure instead of amping up to 40 amps and triping out it will trip out at the 30 amp. With the additional 10 amps before it trips out you probably will be replacing the bearings and the motor.

 

Jack, that's not true at all. A rating is a requirement, and performance figure, not a destruction limit. When these components are built and tested, they are subjected to far more than the rated power, at a proof level of 125% and a burst level of 150-200%. That momentary 10 amp spike isn't going to destroy anything - especially on a 220 volt motor.

In this case the rating provides an indicator as to the MINIMUM circuitry required to support the motor. Going stronger will not hurt the compressor. It's gonna draw what it needs to operate.

The circuit breaker is used to prevent an overdraw of specified amps through a given gauge of wire and is installed solely as a safety device for the house wiring - not the appliance. The compressor motor will have a separate breaker on it that will prevent damage to it if it sees an amperage overload or overheat, and is that sensative to current or heat.

Under normal operation, the motor is going to draw well below 40 or even 30 amps - with a good 220 volts. But if that voltage (in the summer - air on) slips down to say 205, then the extra wire thickness and higher rated breaker will actually prevent damage to the motor or compressor mechanism from poor quality power, or shutting down frequently in the middle of running.

At 220 Volts, if the compressor motor has a failure that causes it to clamp up and draw 40 amps, the physical damage to the machine has already occured. If it is such that it causes a high draw, it will be instantaneous, and it will trip the breaker in a millisecond. In your scenario, the purpose of the distribution panel circuit breaker is to prevent damage or fire in the house wiring given too high a draw not protect the compressor.

And if you have that catastrophic a circumstance, you are going to be replacing parts anyway, and not because of electricity.

 

Yeah. I wired my compressor into my house 240 myself (they're 240, not 220). There is a overload breaker on the compressor. I don't think there are any 240 Volt compressors that don't have an overload breaker. Mine has 12 ga from the switch box to the motor, it's factory. Mine has a pig tail cord that I installed from the switch box to my 240 Volt extension cord (it's the really heavy 6 ga type for my welder and stuff). I plug into the end of that, and that heavy cord is hard wired right to a 40 amp breaker in my house panel. And no Julie, it's not a smoker...haha. I did a lot of searching the web and didfferent electrical sites before I installed mine. I had an electrician that was gonna do it, but he never showed, so I said screw it. It's not hard at all to do. Mine is actually wired in with a regular extension cord (the 3 prong grounded type plugs for 120 stuff) but it's a super heavy 8ga industrial type, so it works just fine, since my compressor has the two hots and a ground, instead of two hots, ground, and common. I had to do mine this way, because the house we're renting didn't have any 240 outlets in the garage (guess I'll get dinged on my deposit for the hole I cut in the drywall for shoving the heavy cord through), and I needed to be able to move my welder around, and wanted enough mobility to have my equipment usable at all times. Heck, (close your eyes Julie, don't read this part) I can be welding, and have the compressor running, and the wife inside cooking in the oven all at the same time, on the same 40 amp breaker, so I don't think you'll ever use 40 amps running a compressor.

 

The heaviest draw of an electric motor is at the moment of startup, after that it takes many less amps to keep running. That's why it sometimes calls for a "slow blow" type breaker, to allow for that short duration heavy current surge without tripping.

 

Sure Joe no problem with the welding and cooking on the 40 amp circuit. Remember, just because something is rated at a given amperage, doesn't mean it's going to use every bit of it. And unless you do, your breaker won't trip, and the circuit is safe.

Your machine requirements said to use a 40 amp breaker, then use a 40 amp breaker. Use it with 8 ga wire for up to 30 feet of run and 6 ga wire for over 30 ft of run. Use a 40 amp plug. From th eplug to the compressor you can use a 12 ga appliance cord rated for a 40 amp appliance - like an oven.

Remember folks amperage again is an inaccurate term. The electrical draw is actually measured in watts (and billed in Killowatt hours). Amperage being a function or wattage is what is used because it indicated volume not heat (work). And, remember also that electricity is drawn through the working appliance not forced to it. If the work the appliance is trying to do it will require more amps to supply the needed watts and the breaker will trip. The wiring will not experience the higher wattage in the circuit (heat) and will be kept safe from overheating.

It sounds lie a good set up Joe. The 12 Ga wire for the final short distance is perfectly acceptable (though 12 guage would not be for the long run - in the house - from the box - distance being a key factor). The appliance cord I suggested is only 12 ga. - but more than sufficient with a 5 foot run.

 

Good info Julie, only exception is that "common" and "Neutral" are different terms for the same wire, also known as the "identified conductor" or "grounded conductor" which is identified by the color white or slate grey.

 

I stand corrected! Thanks!