I have been using my brand new compressor (Hitachi EC119 – 2 1/2 hp, 15 amp) plugged directly into a 15 amp outlet with no problems, however, today I ran a 50′ extension cord (12 guage) and plugged in my compressor. It ran okay for a while (although it seemed to recycle too often even when not in use) and then I unplugged it. When I plugged it back in there was a mini light show and a pop. One of the prongs was black. I then tried using the cord with my Skilsaw and it worked fine. I then plugged the unit directly into the outlet and it worked. Any ideas? Could it be that the extension cord was too long? Why the pop? Could this have damaged the compressor?
I looked at this unit on Amazon for reviews and it seems that there may be a problem with the 15amp rating.
Replies
Turn it off before plugging it in.
I have had the same problems with a Porter Cable compressor. I had to go to larger gage wire and shorter run. Also found out it doesn't do well in GFI circuit.
Semper Fi
Semper Fi, Devildog.
What MarkH said.
happy?
I have a 2.5 hp Emglow that is supposed to draw 14 amps. It doesn't work on a 12 GA cord. Either use 10 Ga extention cord, or plug directly into the T-pole.
Sounds like it was running when you unplugged it. Compressors don't like to be run through extension cords unless they're heavier gauge.
I always turn the compressor off before I unplug it and I make sure it's off when I turn it back on. Also in this case it's not on a GFI circuit. The outlet is the only power source off the meter (everything else has been removed for the remodel).
Is the compressor trying to draw too much power through the wire? If the extension cord is #12 then how is this different to #12 romex in the wall? After all trying to run this compressor (supposedly rated at 15amps) off a 50' run of #12 romex shouldn't be a problem. In the past when I have had the compressor plugged directly into the outlet and another tool is also drawing power from that outlet the breaker would just trip. Why isn't that happening? Why am I getting the sparks?
If you got the sparks as the compressor was being plugged in then either the compressor was NOT turned off or there was something causing a short -- either a defect in compressor or cord ends or possibly a small fragment of metal (did you have any metal shavings in the area?).If you got sparks once the compressor was plugged in and you turned it on then probably the plug and socket were not mating well. This could be caused by some sawdust in the socket, eg, or a bad socket.If the cord is too small two things will happen: 1) The cord will get rather warm, and 2) when the compressor stops it will have difficulty restarting. Sparks would not be a sign of a too-small cord.
If ignorance is bliss why aren't more people
happy?
In New Mexico, where I live, one of the state's changes to the NEC is that runs of Romex longer than 75 or 100' (depends on whether its a 15 or 20 amp circuit) have to be sized up (12 awg rather than 14 awg for example) to avoid excessive voltage drop. So if you had an already long run of romex and then plugged in a 50' cord, you could definitely see a difference in performance at your compressor.John
Is the compressor trying to draw too much power through the wire? If the extension cord is #12 then how is this different to #12 romex in the wall? After all trying to run this compressor (supposedly rated at 15amps) off a 50' run of #12 romex shouldn't be a problem. In the past when I have had the compressor plugged directly into the outlet and another tool is also drawing power from that outlet the breaker would just trip. Why isn't that happening? Why am I getting the sparks? Normally, a 50' 12 gauge cord will deliver the necessary running and surge currents for a 15 amp load with little or no voltage loss. If you are plugging in your compressor without the switch turned off you will most likely see sparks. The compressors surge load (starting load) could be as much as 2 or more times the motors rated amps and will settle down to the normal running current after a second or two unless the motor is in a bind. If the compressor motor is cycling excessively, each time it starts it draws a surge load which in turn can heat up the cord as well as the wire in the wall.
Since the pressure switch controls the compressor, you may want to check for air leaks, and if there are none, the switch could be defective. But if the compressor checks out OK and is cycling too frequently during normal use, its probably too small for the required tasks.
BTW, as a length of a wire gets longer, the resistance in the wire adds up and impedes the current flow. The voltage, in effect, pushes the current. This resistance basically eats up voltage. Since a motor requires a certain amount of power (watts) to run, if the voltage drops the current will have to increase in order to 'satisfy' the load. Using Ohms law, volts x amps = watts. A 15 amp load x 120 volts = 1800 watts. If the voltage were to drop 10% to 108 then 1800/108= 16.66 amps. The increase in current causes everything to heat up and any wire, switch, plug, etc. rated lower could possibly fail (fry). To reduce the voltage loss to an acceptable level, the resistance of the wire has to be reduced and therefore a larger gauge must be used.
I hope I've been a little bit of help. Good luck.
There is a loss of power when you use extension cords, I think the amps is what falls off, but I'm sure some electrician will jump up and say it's some other thing. In contrast, a lot of compressors may RUN at 15 amp, but the initail start-up sucks much more than that, which is why you pop breakers in older houses. The longer the cord you are running, the less power is actually getting to the unit.
Young, poor, and eager to learn
Yes, there's a loss of power, but it's the voltage that falls off -- amps actually INCREASE to compensate, within the capabilities of the wires and motor.
If ignorance is bliss why aren't more people
happy?
It's voltage drop.
Give me the wire size, the length of run and the amps of load and I will pull out my EletricCalc 96 and run the numbers for you.
If you wanted to see it in action - last winter I repaired a circuit that ran 400' to power a 10a sump pump load. This was a critical application - the infamous Tasman Sump - the pump had to work.
They ran it in 12g wire back when. Now the maint. dept. wondered why the voltage at the pump end was 2.2v. The conductors had gotten hot enough they had actually melted into the P40 conduit at the sump. I had to chunk out a sweep in 3" sections. We won't talk about the use of common wire nuts underground (underwater) and a few other issues such as finding orange extension cord buried in the mud.
The moral - a 10g cord will buy you a lot of slack. HD had a 100er for about $65 - a good price. The ToolBear
"Never met a man who couldn't teach me something." Anon.
sometimes, not always, the ends on extension cords are just plain junk...cut the end off and replace with a Hubbell, or P&S 20a body and the problem will be minimized,but not eliminated..
..like others have said...turn the thing off
MarkH is correct. Turn it off before plugging it back in.
It has nothing to do with the brand.
Same thing happened to me. Nice fire in my hands. Ex-BIL the electrician said it's because of the tremendous draw of the unit as it's being plugged in.
Wish I knew that before.
I've worked with the same compressor for a while.
I found myself one day with a proper extension, so I used a household one.
After a few minutes I could smell burning. The cord was actually melting.
Moral; get a better heavy duty cord @ 50'
A 50 foot, 12 gauge extension cord is a pretty heavy duty cord. It shouldn't cause very much voltage drop at all; you can use an online voltage drop calculator such as this one to figure out how much: http://www.electrician.com/vd_calculator.html. Plugging in your numbers I got only a 1.3% drop, which is pretty good. As others have said, replace the cord ends if they are suspect.
However, if the compressor really has a 2 1/2 hp motor at 230 volts, it's probably running at around 14 amps all the time, which is marginal on a 15 amp circuit.
Edited 12/28/2005 1:54 pm ET by Stuart
Could it be that the extension cord was too long?"
Yes. I make up a lot of heavy gauge cords myself, as shorties don't seem readily available. So if all you need is a ten foot 12 gauge, buy a 25' and cut it into three pieces. or if you need a 40' er, buy a 100' 10 gauge and cut it up.
As a side note, I hooked my 1.5 HP dust collector up to a 14 gauge 25' cord recently, and it took at least 4 times as long to spool up, compared to being plugged directly into a 30 amp 10 gauge circuit.
WSJ
Two thoughts occured to me about your situation.
Not always considered but it's somewhat easy to step out of rating with your average extension cord, especially one used at capacity. Most all would assume that all recepticle electric are equal. This is not always the case, where are you plugged in on the elec. circut reletive to your main? Choosing to plug in as close to your main panel as possible might be of benefit.
Second thought; seems as though your at the pratical limits for all appliances concerned. Now, the issue at hand manifested itself upon restart/startup of a COMPRESSOR UNIT. The results you expect from the unit- compressed air. duh. but, in order to get this result the unit must cycle many times...suction, compression, suction, comp.....etc. The easy part of the cycle is the suction phase and then compression phase, with most energy demands occurring here.
Now, if your unit can be stopped(turned off) midway into compression a subsequent restart under this circumstance coupled with long extyension, plug location and even the overall distance from your tx power poll. Possible result=> not enough electric juice to complete compression from previous shut-off and iniatiate re-start and possible momentarily direct shorting the motor.
Might not have to take the unit back right away. Ask the service tech. for the unit if it has a bleed-off after shutdown.
good luck.
KC - No hill too steep No sand too deep.
Most compressors like to be next to the power plant, or, failing that, the job power drop. They don't like voltage drop one bit and most carpenters know 0 about voltage drop.
Run more hose. I had to switch to a PC pancake model rated for life at the end of a 100' 12g cord because my double hot dog would blow most breakers in remodel situations. I also bought a 100' of 10g cord, split it in half and use one part as the start of my cord layout. Chop saw and compressor can go on that if needed.
We have a big $700 Emglo wheelbarrow model that came without a switch. It would burn the tips off the plug as you plugged it in. Nice arcs and black smoke and such. Try to get the boys to find and kill the correct breaker, then plug it in. We were on the plug a week plan.
Solution: I put 10' of 10g cord on it and a RT switch mounted on the belt shroud. This has worked for three years thus far.
One job the idiots had it hooked up at the end of 200' of 12g cord. They wondered why the plug melted off. I wonder why the compressor still works.
The ToolBear
"Never met a man who couldn't teach me something." Anon.