Craftsman Compressor Blows Breaker

Ken Christopherson

Well-known Member
Hey all,

I've recently acquired a 33 gallon Craftsman air compressor (vertical), that is supposed to have a 15 amp run. I plugged it into my 15 amp circuit in the garage, and it blew the breaker after kicking on initially. Today I was able to get around to wiring a new circuit (20 amp with 12/2 wire). Still am having the same issue. The compressor will kick on for about 5 seconds, and then kill the breaker.

Do I have to go to a 30 amp breaker with a minimum of 10 gauge wire? I'd like to be able to use this compressor for various jobs around the garage (including my JD A project that I have got going right now). Any help would be appreciated!
 
If the unloader is working properly then it's probably a bad motor. If you can switch it to 240V that would be all around better, but if the motor is defective it won't fix it!
 
Unloader valve working? Mine will do that if it gets shut down without the unloaded kicking in (blows out the air tube so no pressure on the compressor).

Also mine will do that on an extension cord.

Paul
 
Sounds like something is causing the motor to pull way too many amps.

Might look at the wire leads, be sure it's wired for 120v and not 220v.

Also, do you hear the centrifugal switch open when the motor comes up to speed? If you're not sure, open the start capacitor can, power up the motor and carefully unplug the start cap, see if it draws an arc. If it does, the switch did not open.

Other things, shorted motor windings can cause over amps, bad bearings in the motor or compressor can cause mechanical binding. Could also be a blocked line between the compressor and tank, carboned up valves, stuck closed check valve, etc.

Uping the breaker and wire size to 30a is not a solution, something is wrong or it would run on the 20a breaker easily.
 
About a month ago there was a similar discussion here about an oiless compressor that was tripping breakers larger than the rated current on the compressor's name plate. Some oiless compressors need slow blow breakers. I had a 25 gallon 4HP Craftsman oiless compressor that would trip 15 amp breakers since it was new.

Check the trouble shooting section of your owner's manual. Many Craftsman manuals are available to download from the Sears website if you need one.
 
I guess I should have probably said that I am not incredibly electrically savvy. This is y first air compressor (and got it for free from my future father in law as he purchased a new one). I have seen him use it in the past, but it has been a while since he used it, he said. Maybe something is bad in the motor and neither of us knew it?
 
You should check for voltage drop. When you say you upgraded the wiring, I assume that's the wiring inside the garage. But if the circuit feeding the garage is inadequate, heavier wiring in the garage won't help.
 
temperature and oil? had one that would blow fuse whenever the temp got below 30. called for 30 weight oil in crank case switched to synthetic compressor oil (0W50). end of problem
 
If it ran for five seconds before tripping a 20 amp breaker then something is wrong and wiring it to 30 amps is likely to burn it up. I think it's more likely the start capacitor was running it and when the start switch kicked off the run capacitor should have kicked in but there is something wrong with it.
 
Last post like this by Old there was alot of good answers which nobody wanted to hear. If you do all the mechanical checks already mentioned below then try an HACR circuit breaker in a 20 amp version. Order your panel makers type 20 amp single pole marked HACR on the side. Last time if you did the math the compressor was drawing 19 something amps which is too great for a 20 amp circuit.Square D will trip close to 20.
If there is a nameplate post that info too.
 
Should have stated HACR= Heating Refridgeration and Air Conditioning Breaker. Allows surge to not trip on initial start-ups.
Embossed into side of breaker .
 
Is it plugged directly into the outlet? Air compressors are very sensitive to extension cords.
 
Tell us all the nameplate data.
As previously stated you maybe connecting a 240 3HP motor to a 120V u-ground 15 amp receptacle .
I'll check the code book later but iirc a 15 amp 240V 3HP motor uses a 50amp breaker for short circuit protection. And thermal overloads set to 17.25 amp if the motor has a 1.15 service factor .
How old is this compressor? Is it something that somebody else was having trouble with and got rid of?
Lift the cover off the capacitors . Is there a wire burned off or a capacitor split?
 
I see all breakers are now rated as HACR and no designation is required . Allthough they were used for groups of refrigeration motors it is possible they are not differing in any way from a normal breaker [hence the dropping of marking requiremnets]. No new breakers sport such markings. On a sidnote I bet you are real annoying to work with at the jobsite. .
 
Here is the sticker that is on the tank that contains all of the information.
a152543.jpg
 
Plugged directly in, no extension cords. The outlet was installed right next to the breaker box in the garage. Only about 14-18" of 12/2 wire ran. The compressor is plugged directly into that.
 
Nope, no extension cord. Plugged directly into the outlet that is wired only for the purpose of the air compressor. Only about 14-18" of 12/2 wire from the circuit breaker to the outlet, as well.
 

Only way 2.0HP is going to happen is if the Power Factor is 1.0 and the motor efficiency is 83%. Not impossible but highly unlikely.
My code books shows a typical 2.0HP 120V motor drawing 24.0Amp.
That would require a 30 amp 10 gauge cable. A 45 amp time delay fuse or a 60amp breaker.
As previously requested. What is the info on the motor it's self?
The 2 HP on the label and 6.4 cfm at 90psi is consistent with the 3HP and 9.8cfm at 90psi on my compressor.
 
Doesn't particularly matter.
After the boss gets tired of the other guys not getting anywhere while trouble shooting a problem. They call me in to figure it out.
 
I'll have to pull the motor casing off and look maybe tomorrow afternoon. I don't have time to get to it tonight before I head in to work.

I'm guessing I'll be wiring a 30 amp in with 10/2 wire.
 
The amperage draw should be listed on the inside of the cover on the end of the motors where the wires connect.

Are you running 110 or 220 volts to the motor? Check to make sure the motor is connected for the voltage that you are using to power it.
 
I had the same problem with, more than likely, the same air compressor. If you Google your problem you will find lots of others with the same problem. I ended up pulling the motor and using the tank as a volume tank on my portable setup. That was $100 down the drain for me (bought the compressor used)!
 
Heres the deal and how we designed a motor branch circuit wayyyyyyyy back when I practiced HOWEVER that's been several years and codes have since changed so NO WARRANTY.

First we computed the maximum sustained full load

Second we sized the conductors to have a minimum
ampacity of at least 125% of the full load

(IE if the motors FLA were 15, 80% of 20, or 16, meant a 12 gauge 20 amp rated wire would suffice HOWEVER to reduce voltage drop subject to wire length since it was that close Id probably specify 30 amp or 10 gauge wires)

Third we sized our overcurrent protection device
(Fuse or Circuit Breaker) to protect the feeders
(If I used 10 gauge wire that meant Id use 30
amp overcurrent protection)

NOTE HOWEVER since a motor can draw 5 or 6 times the FLA when starting and that could trip a standard thermal magnetic breaker, ifffff the motor had thermal overload protection, THE CODE ALLOWED USE OF A BIGGER STANDARD BREAKER TO ALLOW THE MOTOR TO START

NOTE HOWEVER in many cases where a disconnect or combination starter was used, Id specify a fuse instead of a circuit breaker and use Dual Element Time Delay Class 5 (if I recall correctly) fuses which would allow the initial high current start up surge allowing the motor to start yayyyyyyyyyyyyyyyyyyy

NOTE ALSO it sounds like the HCAR breakers dr sportster suggested serve the same purpose !!!!!!

SUMMARY:

1) The nameplate looks like its ONLY 120 volts so 240 is out of the question UNLESS the motor is actually dual voltage 120/240 and if so Id definitely run it at 240 instead. Without taking the time to look it up (NO WARRANTY) 15 amps looks low for 2 HP???????????????????

2) Your going to have to use an ammeter to determine the actual FLA

3) Once FLA is established, size the conductors and then the overcurrent protection device

4) Id use dual element time delay fuses or that HCAR dr sportster mentioned or else oversize a standard thermal magnetic circuit breaker as permitted by code that allows the motor to start

5) Sure there isn't a problem in the motor or its start winding causing excess current????????? Sure the available voltage isn't too low??????????Sure the mechanical pressure relief unloader valve system is working???????

SOMETHING JUST ISNT SOUNDING CORRECT IN THIS WHOLE STORY BE IT VOLTAGE OR CURRENT OR HP???

Nuff said, John T too dern long retired EE so no warranty
 
(quoted from post at 20:38:30 04/01/14) So everyone in the local is stuoid?. Maybe you should run the apprenticeship program!

I got out of the IBEW local shortly after getting my Interprovincial Red Seal. Too many guys with a license with no idea how to use "Holmes Law".
I've been working in the nuclear industry for the past 24 years on protection, control, low and high voltage power.
 
If they are anything like the KOBALTS,I was given for the tanks,the motors are not marked and are an intricately part of the compressor head.Just the label on the tank to go on.The motors don't look tobe over 1/3-1/2 HP in sizewise.
 

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