Air compressor woes, household electrical newbie here

2282 Views 19 Replies 7 Participants Last post by Silk, May 18, 2009

gasteffens

Discussion Starter · May 16, 2009

Well pretty much as the title says. I purchased this compressor...

http://www.homedepot.com/webapp/wcs...nktype=product&storeId=10051&ddkey=THDSiteMap

I plugged it into my garage outlet, which is a 14 gauge 20 amp circuit. I opened all the valves and allowed it to run to break in the compressor motor itself. When I was done with that, I closed the valves and turned it back on. It ran fine up to pressure when it shuts off. I used some air and when it went to kick back on, it just tried to turn about 1.5 revolutions and then the motor buzzed.

Its as if it cannot start back up under load. We had this plugged directly into an outlet that had two plugs in it. We checked the voltage on the other plug while turning the compressor on, and it drops from around 120v down to about 75.

If I have left out any crucial information I apologize as I am COMPLETELY new to working with electrical on the household. (Fairly experienced with automotive systems.)

I had read many many reviews of people using this unit on a 15 amp circuit (as the motor is marked) without issue. I figure we have 20 amp, so it SHOULD work fine. Also mind you that we turned everything in the garage off at the time of trying this and that made no difference.

What more information do you need to give me some ideas of what to do next. My dad knows a little bit about electrical from my mom's dad when he used to be an electrician. But we do not want to get too in over our heads. A fellow member of the fire department is also an electrician by trade so I will enlist his help next, but I wanted to see what I can research before then.

Thanks in advance for any help!

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Yoyizit

· #2 · May 16, 2009

gasteffens said:
I plugged it into my garage outlet, which is a 14 gauge 20 amp circuit.
???

Its as if it cannot start back up under load.

We checked the voltage on the other plug while turning the compressor on, and it drops from around 120v down to about 75.

Almost certainly you have a high resistance connection upstream of the compressor. It could be a bad house neutral connection at your panel.
If you plug in a 10A hair dryer into this outlet the voltage should drop no more than 4vac when the dryer is switched on.

gasteffens

Discussion Starter · #3 · May 16, 2009

Yoyizit said:
Almost certainly you have a high resistance connection upstream of the compressor. It could be a bad house neutral connection at your panel.
If you plug in a 10A hair dryer into this outlet the voltage should drop no more than 4vac when the dryer is switched on.

I was honestly thinking that there would be something with resistance, because that is what causes the voltage to drop. Now you say a bad house neutral connection at the panel.

Now that you say that, I remember to mention we have one primary panel in the house, and it looks like one big wire running out to the barn where there is another panel. The garage runs off this panel.

That's good to know. Is this something I can find easy or should I have my electrician buddy help me do the more detailed diagnosis?

THANKS for the quick reply!!! :thumbsup::thumbsup:

Yoyizit

· #4 · May 16, 2009

gasteffens said:
Is this something I can find easy or should I have my electrician buddy help me do the more detailed diagnosis?

If one side of your house is at 75vac and the other side is at 240-75 = 165 then your neutral will have 165-120 = 45vac across it, instead of less than a volt.
Sometimes the bad connection is on the PoCo side of your meter.

gasteffens

Discussion Starter · #5 · May 16, 2009

Yoyizit said:
If one side of your house is at 75vac and the other side is at 240-75 = 165 then your neutral will have 165-120 = 45vac across it, instead of less than a volt.
Sometimes the bad connection is on the PoCo side of your meter.

I see... I'm not sure if I described the situation correctly... with nothing on at the plug it is 120, but as soon as I load it down with turning the compressor on it drops to around 75... but it still sounds like a neutral issue with the way you are explaining it... I think I will have to have my friend come help, but at least I know maybe this can be fixed?

gasteffens

Discussion Starter · #6 · May 16, 2009

Quote:
Originally Posted by gasteffens

I plugged it into my garage outlet, which is a 14 gauge 20 amp circuit.
???

Its as if it cannot start back up under load.

We checked the voltage on the other plug while turning the compressor on, and it drops from around 120v down to about 75.

Almost certainly you have a high resistance connection upstream of the compressor. It could be a bad house neutral connection at your panel.
If you plug in a 10A hair dryer into this outlet the voltage should drop no more than 4vac when the dryer is switched on. Today 10:36 AM

What I had meant was the wiring in the garage is 14 gauge with a 20 amp breaker on the circuit.

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Bigplanz

· #7 · May 16, 2009

gasteffens said:
Quote:What I had meant was the wiring in the garage is 14 gauge with a 20 amp breaker on the circuit.

Somebody put the wrong breaker on that circuit. It should have a maximum 15A breaker. That probably has nothing to do with your problem, but if you run 20A through 14 gauge wire, you are creating a dangerous situation. Change the breaker to 15A.

gasteffens

Discussion Starter · #8 · May 16, 2009

Bigplanz said:
Somebody put the wrong breaker on that circuit. It should have a maximum 15A breaker. That probably has nothing to do with your problem, but if you run 20A through 14 gauge wire, you are creating a dangerous situation. Change the breaker to 15A.

Will do. My dad and I have been chasing odds and ends wiring issues with the house since we moved here... we will add this project to the list... thank you... any ideas on why it won't run the compressor? Any ways to check for the bad connection/wire that could cause the voltage drop?

Yoyizit

· #9 · May 17, 2009

gasteffens said:
Any ways to check for the bad connection/wire that could cause the voltage drop?

If you have 75vac at one end of a cable and 120vac at the panel, the fault is between the two points.
Work your way back along each outlet until you see a big voltage change; that's where the problem is.

Bigplanz

· #10 · May 17, 2009

gasteffens said:
Will do. My dad and I have been chasing odds and ends wiring issues with the house since we moved here... we will add this project to the list... thank you... any ideas on why it won't run the compressor? Any ways to check for the bad connection/wire that could cause the voltage drop?

Is this the first time you have had a problem in the garage? You might want to plug the compressor into another circuit and see if it works correctly.

gasteffens

Discussion Starter · #11 · May 17, 2009

Yes this is the first time we have had a problem... however this is the first time we have had an electrical load as large as this put on the circuit. I happened to run into my electrician friend while I was running errands tonight and he is going to take a look Monday afternoon. I will report with my findings as for right now, the way it behaves is odd.

He suggested we try plugging the compressor in at the house directly and bypass the barn and garage systems and see if it's a problem with the whole house or just the extensions.

Magnettica

· #12 · May 17, 2009

It's a wild guess but it could likely be because voltage lags current when starting an inductive load, and your compressor certainly is an inductive load. But that's just a guess. If I get slammed for the next pages it'll be because I am wrong.

micromind

· #13 · May 17, 2009

How far away from the electric meter is the compressor? It sounds like there is a main panel at the house, and a sub-panel at the garage. If so, how far is the garage panel from the house panel? And what size is the breaker that feeds the garage panel? How far from the garage panel is the outlet for the compressor?

If long wires are involved here, this compressor might not work at all in the garage. Dropping down to 75 volts is quite a bit, it might be because of a problem somewhere in the system, or it might be a design problem.

Rob

frenchelectrican

· #14 · May 17, 2009

I don't know if you knew this or not did you check the unloader valve on the compressor ? for that model you should hear the popping sound when it cut off { when it get to the max pressure or pressure switch kick out }

The other thing that other guys did ask you the question how far is your breaker box to the compressor location?

Also double check the motor connection to see if you are really on 120 volt connection inside the motor junction box { some case the factory can get this on wrong voltage hook up and it do happend once a while so look at the connections }

Merci,Marc

Yoyizit

· #15 · May 17, 2009

To drop 120-75 = 45v with 15A being pulled through #14 copper you'd need 580' of Romex.

micromind

· #16 · May 17, 2009

The starting current of the motor is a bit more than 15 amps. More like 90. But at 75 volts, it'll be around 60.

It doesn't take very much #14 to prevent a 15 amp motor from starting at 120 volts. At 240, it can be MUCH longer.

Rob

gasteffens

Discussion Starter · #17 · May 17, 2009

micromind said:
How far away from the electric meter is the compressor? It sounds like there is a main panel at the house, and a sub-panel at the garage. If so, how far is the garage panel from the house panel? And what size is the breaker that feeds the garage panel? How far from the garage panel is the outlet for the compressor?

If long wires are involved here, this compressor might not work at all in the garage. Dropping down to 75 volts is quite a bit, it might be because of a problem somewhere in the system, or it might be a design problem.

Rob

I would say it is about 50-60 feet from the house to the barn where the sub panel is. We tried the compressor 10 feet from the panel at the outlet right off the panel, with the same result. The garage is another 10 feet over from the barn, which gets its power from the barn.

I still have to try the compressor on the house itself to see if that has an issue or not.

Yoyizit

· #18 · May 17, 2009

gasteffens said:
I would say it is about 50-60 feet from the house to the barn where the sub panel is.

With working circuitry you'd need to pull 150A for this distance to get this drop,
but the breaker didn't trip,
so it's high-resistance/non-working circuitry.

gasteffens

Discussion Starter · #19 · May 17, 2009

Yoyizit said:
With working circuitry you'd need to pull 150A for this distance to get this drop,
but the breaker didn't trip,
so it's high-resistance/non-working circuitry.

All right well my buddy has a bunch of testing equipment (and a lot more knowledge) he is going to bring Monday afternoon. I will report our findings which will hopefully be something we can fix. I need to use that compressor!

Thanks everyone for the help!!!!

Silk

· #20 · May 18, 2009

Magnettica said:
It's a wild guess but it could likely be because voltage lags current when starting an inductive load, and your compressor certainly is an inductive load. But that's just a guess. If I get slammed for the next pages it'll be because I am wrong.

Voltage does not lag current in an inductive circuit. It's exactly the opposite.

Voltage leads current in an inductive circuit.

Voltage lags current in a capacitive circuit. This still has nothing to do with the voltage drop to 75 volts. Motors all run at less than unity power factor, because of the need to set up a magnetic field in the windings. The effect of this will be increased costs to the POCO for the current that is just circulating at a phase shift and is not capable of doing any work, but that still doesn't affect the consumer (residential that is) because he is charged by watts not VA.
In other words, the PF of the motor is a known and calculated variable in the design of the motor, the FLA of the motor with less than unity PF has been calculated. Voltage drop has nothing to do with the results of induction in a motor (except by the increase in amperage due to the poor PF).

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