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.