Compressor issue

[chim]

The company I worked for had a project for the Army COE on which there were drawings AND specifications that both had to be met. Although the drawings indicated wire sizes that appeared to be "normal" for the circuit ratings, there was a spec that called for a certain maximum allowed voltage drop, and that the wire sizes may need to be adjusted. Due to distances, there were many 20A circuits that had to be wired with #8. One of the guys who worked on the project claimed there were a few circuits that needed #6. They physically tested the circuits with something like this:

SureTest® Circuit Analyzer | IDEAL Electrical

circuit-analyzer.com

 

[5030]

When I had my shop wired (from the drop box), I used cable thick as your wrist.

 

[Williy]

It's kinda funny to see someone with two 100 ft 16 gauge
wire extension cords complaining their drills don't work
trying to use power from their neighbors

willy

 

[etpm]

Many others posted here that the main problem is voltage drop from the too long and too small gauge extension cord. Believe them. In your first post you diagnosed the problem yourself. It will start fine when plugged into the outlet but will not start when plugged into the extension cord. There may be another problem, that being the unloader not working properly. But your main problem is the extension cord. When an extension cord of too light gauge is used there will be a voltage drop that exceeds the amount of voltage drop the motor can experience and still start to rotate. The motor doesn't care though, it still wants to rotate. Since there is not enough voltage it will instead start to draw more current , more amps, in an attempt to start rotating. Furthermore, when the motor is rotating it acts as a a generator. This generator action limits the amount of current the motor can draw. When the motor is not rotating there is no generator action and the motor will attempt to draw as much current as it can. This is why your breaker pops. The previous statements apply to induction motors, which is no doubt what your compressor has.
Eric

 

[3Ts]

It would be nice to see an amp rating on the motor sticker

There is one in your picture of the motor. The FLA is Full Load Amps. Sometimes you'll see a LRA (locked rotor amps) which is how much it will draw if the motor is not turning. Keep in mind that the starting of the motor will draw more than the running current.

 

[1930]

Many others posted here that the main problem is voltage drop from the too long and too small gauge extension cord. Believe them. In your first post you diagnosed the problem yourself. It will start fine when plugged into the outlet but will not start when plugged into the extension cord. There may be another problem, that being the unloader not working properly. But your main problem is the extension cord. When an extension cord of too light gauge is used there will be a voltage drop that exceeds the amount of voltage drop the motor can experience and still start to rotate. The motor doesn't care though, it still wants to rotate. Since there is not enough voltage it will instead start to draw more current , more amps, in an attempt to start rotating. Furthermore, when the motor is rotating it acts as a a generator. This generator action limits the amount of current the motor can draw. When the motor is not rotating there is no generator action and the motor will attempt to draw as much current as it can. This is why your breaker pops. The previous statements apply to induction motors, which is no doubt what your compressor has.
Eric

Post 16 identifies a probable problem that needs correction

 

[Arctic Taco]

Upsize your extension cord to at least 10 AWG, as well as your pigtail for starters.
Of course double checking the check valve(if equipped) is also a good idea.
A lot of electric motors used to have an FLA on the data plate- some don’t anymore. It should have an RLA(regular load amps) value at least, a compressor will pull at least 4-6 times RLA to start. Put an amp clamp on the line wire( usually black)and read that value while starting that will give the info you need.
Good luck

 

[Gord Baker]

My money is on voltage drop with the long cord and needing greater amperage on startup. Suggest larger conductor extension cord to fix the problem. Should be at least 12 gauge per the attached chart for 15amp continuous.

What Peter mentioned above about the check valve could also be contributing

FIRST check the dates for destruction on the tank if there are any. Used compressors which may have never been drained are a bomb.
Unless your extension cord is #12 or 10 BWG there is too much voltage loss at 100'.Move it closeer to the shop and try it with a much shorter extension cord.

 

[Gord Baker]

FIRST check the dates for destruction on the tank if there are any. Used compressors which may have never been drained are a bomb.
Unless your extension cord is #12 or 10 BWG there is too much voltage loss at 100'.Move it closeer to the shop and try it with a much shorter extension cord.

Quote Reply

 

[LouNY]

FIRST check the dates for destruction on the tank if there are any. Used compressors which may have never been drained are a bomb.
Unless your extension cord is #12 or 10 BWG there is too much voltage loss at 100'.Move it closeer to the shop and try it with a much shorter extension cord.

Quote Reply

Most air compressor tanks that fail just start leaking nothing "explosive" or dramatic.

 

[dcarman]

I picked up a couple of compressors, one is electric the other gas. The electric starts up fine from my temporary power source a hundred feet away with a 100 ft 15 amp extension cord but as soon as it needs to automatically re start itself cause the air pressure drops it will not start, it just sits there making an unhappy noise until it blows a fuse or damages the outlet it’s plugged into.
What might be the problem?
It operates fine when plugged directly into the same outlet.

When it is empty the startup current draw is low enough to get through your little cord. When the pressure is higher at restart the current draw is a lot more causing your issue. Not only are you using to light a cord, it is way to long for this application. The solution is more power at the compressor - in other words a shorter and/or heavier cord.

 

[Gord Baker]

Most air compressor tanks that fail just start leaking nothing "explosive" or dramatic.

Most perhaps but not All. Check Google and You Tube for exploding tanks.

 

[bgr]

Your problem is the too long extension cord. Not check valves or anything else. Buy a long air hose and keep the compressor by the power source to avoid the voltage drop. A long air hose is much cheaper than a 100 foot 12 gauge extension cord

 

[Dpm708]

Most perhaps but not All. Check Google and You Tube for exploding tanks.

I picked up a couple of compressors, one is electric the other gas. The electric starts up fine from my temporary power source a hundred feet away with a 100 ft 15 amp extension cord but as soon as it needs to automatically re start itself cause the air pressure drops it will not start, it just sits there making an unhappy noise until it blows a fuse or damages the outlet it’s plugged into.
What might be the problem?
It operates fine when plugged directly into the same outlet.

Heavier extension cord gauge good idea. However how about this for my 2 cents. Plug compressor in power at source. Get 100 ft 3/8 ID air hose. Get small air only tank. (Auto supply etc.) or heavy duty (like Hatachi) booster storage tank. Run 3/8 hose to secondary tank. Add manifold or tee to tank with some quick connects. Use short 25 ft. +- 1/4 inch air hose connected to your workpiece.(s) Depending on your CFM usage the compressor should maintain psi in both tanks. For what you would spend for 100 ft #10 HD outdoor extension cord. Of course I would still go over your compressor for any issues that can be corrected if possible. Just another thought. Good luck.

 

[Bentrim]

1 As already mentions you need a bigger cord for 100' or a bigger shorter cord and longer hose. There is too much voltage drop in an extension cord and you will burn up the motor if you continue to use with a too small cord.
2 You indicate air is leaking out the compressor inlet, this indicates your chack valve is bad, Note the "fitting" where the compressor output line goes into the tank, the one with the small line that goes to the pressure switch. That is your check valve. It is supposed to close when the compressor stops and any trapped air between the compressor and tank is supposed to be released at the switch. Oh yes be sure that is working too.
When the switch shuts off you should hear a psssst of air escaping at the end of the small tube at the switch. The purpose of this is to give the compressor a "clean" easy start and reduce the load on the motor.
So you may have two problems 1 check valve bad 2 the switch release bad and not releaseing pressure between the compressor and tank

 

[boatmoter]

I picked up a couple of compressors, one is electric the other gas. The electric starts up fine from my temporary power source a hundred feet away with a 100 ft 15 amp extension cord but as soon as it needs to automatically re start itself cause the air pressure drops it will not start, it just sits there making an unhappy noise until it blows a fuse or damages the outlet it’s plugged into.
What might be the problem?
It operates fine when plugged directly into the same outlet.

your power cord amps is under rated for what you need. 100 ft and only 15 amp. I would only use that to run a drill or a light ot weedwacker. your losing the amps to power your compressor because of the length of the cord. at 15 amp I would not use any longer then 25 ft at 15 amp. you will burn your motor up on the compressor with the long cord

 

[I Piddle]

I picked up a couple of compressors, one is electric the other gas. The electric starts up fine from my temporary power source a hundred feet away with a 100 ft 15 amp extension cord but as soon as it needs to automatically re start itself cause the air pressure drops it will not start, it just sits there making an unhappy noise until it blows a fuse or damages the outlet it’s plugged into.
What might be the problem?
It operates fine when plugged directly into the same outlet.

 

[1930]

Thanks to everyone here, the unloader valve was frozen open, I unstuck it and it operates flawlessly now.
I will get a new valve cause I noticed that it could potentially get cocked a little sideways and get stuck again.
I will not run the compressor any longer without an 8 gauge power cord because I do not want to damage the motor.
I really appreciate everyone’s input

 

[kayco53]

Think I would plug it in without the long cord and see if it works. if it does like in my case I put the compressor by the plug and ran a long airline to get around voltage drop.

 

[Gord Baker]

Your problem is the too long extension cord. Not check valves or anything else. Buy a long air hose and keep the compressor by the power source to avoid the voltage drop. A long air hose is much cheaper than a 100 foot 12 gauge extension cord

Right. My air 'Pig' has destruction date (20 years after mfg.) stamped on one leg.