Why is my air compressor drawing too many amps?

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I have an old air compressor (1970s/1980s vintage) that has recently started tripping the circuit breaker that it is on. I hooked up a clamp meter and found that when the compressor motor is running with no load (belt removed) it is drawing 12 amps and when the belt is in place it is drawing 27 amps.

The motor is a 1hp unit with a listed FLA of just over 17 amps @ 120v. I've checked for any loose connections as well as looked it over with a thermal camera while it's running and see nothing that stands out as obviously abnormal.

The motor can be wired for either 120 or 240 volts, and is currently wired for 120 volts. There are four wires inside of the connection box on the end of the motor.

What would cause such a high current draw and what should I check...

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Why is My Air Conditioner Compressor Not Working?

Why is my AC unit not working?

The condenser unit, a big box that sits outside of the house, is oftentimes referred to as the compressor. It is responsible for half of the heating and air conditioning process, filled with different capacitors, motors, fans and the beginning stages of the refrigeration process. When the compressor is not working, air conditioning of any kind comes to a stop.

Though it is unusual for a compressor to stop working, there can be several common reasons why it would. Check to see if one of these top five most common reasons could be yours.

The thermostat is not in the “cool” position.

Many times, we find that the thermostat is not actually calling for cool air. Whether it is a new thermostat installation or a forgotten moment, the thermostat has not been programmed to condition the air. To ensure that you receive cooled air, make sure that the desired air is set to a...

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We have listened to lots of compressor FAQs over the years and we’ve put together a guide to help you understand what you are buying and how it works. We hope it will help you make sense of the terms we use in our product descriptions and help you choose your new compressor.

Compressed air is a source of energy that can be stored in a vessel (tank) and in distribution pipe work. The air compressor draws air from the atmosphere and then compresses this air to between eight and ten times it’s normal pressure. During compression the molecules in the air speed up and this creates our energy source, which is then stored in the tank or pipe work ready for use. Our FAQ helps to explain this in more detail.

Q. What is pressure?

Q. Why are compressors sometimes fitted to a tank?

Q. How do I know which power supply to choose?

Q. What does the “capacity” of a compressor mean and how do I choose?

What is pressure?

Pressure is a...

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Here is a question to ponder: What should the amperage draw be of a compressor in which the nameplate says the RLA (rated load amperage) is 59.6, but the compressor is only pulling 45 amps? Is there a problem here? Do we need to change the compressor?

These are questions commonly raised during Copeland Compressor Operation and Service Seminars (COSS).

The running or operating amperage of a refrigeration or air conditioning compressor is directly related to the load put on the compressor motor.

Various Motor Loads

One method of motor loading would be the mechanical load. Think of the relatively small amount of friction created by the matched components of the compressor, such as the crankshaft to bearings, connecting rods to the crankshaft, pistons to cylinders, etc.

Another method of motor loading would be the pressures entering and exiting the compression chamber, basically the suction and discharge pressures.

Of these two loads, the...

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As the person stated before, there's usually a pressure switch that stops you at a predetermined pressure. If that fails, then there is supposed to be a safety (pressure relief valve) on the tank. The pressure relief valve is supposed to be sized for a flow greater than the compressor, so it will not allow the pressure to get above the max pressure of the tank.

Let's say the safety and the pressure switch fail.....then either the pressure in the tank will cause the tank or a fitting to fail, or the motor driving the compressor will draw too many amps and shut down. I've only seen this situation twice, and both times the motor overloaded. I've seen tank failures, but only because they were old or not maintained (allowed to...

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Did your A/C suddenly shut off? Has your circuit breaker tripped?

If that just happened for the first time, reset the breaker and see if it trips again when you run your A/C. If it doesn’t trip again, everything's probably fine.

But if the breaker does trip after you reset it, something’s not right. In this case, don’t try resetting it again—read this article instead...

Your circuit breaker is tripping because of these 2 reasons:

Circuit/wiring issues

Your A/C is using too much power

We’ll go into more detail about both of these causes and what you can do to stop your air conditioner from tripping the circuit breaker.

Let’s start with circuit/wiring issues...

Cause #1: Circuit/wiring issues

The reason why your circuit breaker keeps tripping may not have anything to do with your A/C at all. The problem could be with your circuit breaker and home wiring.

Loose electrical connections

Your breaker box has...

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Originally Posted by

Solo Inventor

Compressors can be a PITA to power because once the tank is up to pressure, the motor pretty much has to run at full load whenever it is running. The problem might be that they designed the motor to run close to it's torque limit and at 208 volts it just can't quite produce enough torque. Once the motor speed starts to dip a little, your amperage draw will start to rise, your voltage drop will increase, you will have even less torque and you will have a vicious cycle that will quickly trip your overload relays.

One test you can do is to drain your tank pressure down a bit and then watch your amp meter as the tank fills. You will probably see a rapid rise in current once the tank hits a certain pressure. If you can live with a pressure below this threshold, then just adjust your pressure switch.

A boost/buck transformer will probably make a world of difference in your compressor's performance. When a motor needs to run at close...

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During the more hmid times of the year, my dad says he actually lets the drain of the compressor "leak" a little all the time. The hiss can be annoying, and you'd need a compressor that's well more than capable of handling whatever demands you put on it, but it can be an option.

Another thing that I have seen done that works real well is to run a hose from your compressor to the wall, hooking that to a hard line that goes up to where your wall meets the ceiling. Then run your horizontal line down the wall, but letting go kinda down hill... dropping a few inches every 10 feet or so. Then tee off this line to go back down the wall to your connection for the lead hose & tools.

But... here's the important part: point your tee up, then use a couple elbows so the drop to your "outlet" goes up, makes a u-turn then down the wall.

Then at the end of the "almost horizontal" run, turn 90 degrees down toward the floor. At the end of this, put a ball valve or gate valve to drain...

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The computer that contors the AC is not responding. Lucky for you this part is no longer in circulation. Take it to a professional electricle repair shop and have them by pass the computer that controlls the AC completly. In other words wire dirctly to the dash controls. I just had this process done to my 95 olds after repacing my compressor twice in less that 3 years and having the system rebuilt behind the dash board because of leaks due to the system being overfilled by previous shops that had preformed work on my ac system because it would not blow cold air. What a head ache and pain in the wallet. 4u2peep@excite.com

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Low Pressure

One of the most common problems experienced in a compressed air system is low pressure or perceived low pressure. Symptoms can include machinery faults, inability of air cylinders to apply necessary force, or inadequate torque on an air tool.

Too often one of the following methods is chosen as a solution:

Increase compressor pressure Add compressor capacity

Often, these actions may solve only some symptoms of an underlying problem. In order to effectively solve a low pressure problem, some analysis is required.

Attempt to observe a low pressure event from the point affected as well as from the compressor itself.

Say a machine is shutting down on low air pressure at 80 PSIG, and pressure at the machine is drawing below this level. However, the compressor is observed to be lightly loaded and maintaining 100 to 110 PSIG. In this case, we can determine that compressor capacity is certainly not the issue, and that there is significant...

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How to choose an air compressor

There is a lot of confusion out there about selecting the right size air compressor to run your air tools. Basically, there are several factors to look at when choosing the proper air compressor for your shop or garage. You should understand these factors enough to be able to talk to your local salesman and select the right compressor.
The first criteria to consider is horse power rating. Many people assume the higher the horsepower rating on the box, the better the air compressor. However, these ratings are not a true representation of the power the compressor has. You will need to look at the power the compressor draws in electricity. For example, a 5HP unit may need around 15 amps from a normal 110 volt circuit. This rating will only give you approximately 2HP. The 5HP rating the manufacturer is toting is inflated.

In order to really get 5HP you will need at least 24 amps from a 220 volt circuit. If you power tools say that you...

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