# Old Compressor and GFI



## Hondaman56

I was given a very old Craftsman compressor. Its in excellent condition. The issue with it is that you will plug it in and it will start right up. I runs for a short period then trips the receptical GFI. This model is old enough that it has no ground although when I replaced the main cord I attached the ground to the control box frame. I'm not sure if its dirty contacts in the pressure switch, or the old motor. Its a simple set up with a 10 gallon take, a single cylinder cast iron pump and a simple pressure switch. It has an in line check valve. Any ideas on what exactly this may me and how to rectify it if its just that its an older unit running on a newer technology circuit?

Thanks


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## rhenning

It is not a GFI problem but your compressor is drawing to high a amperage load for the circuit it is plugged into. If it was GFI problem it would pop quickly not after it runs for a while. You are popping the circuit breaking part of the GFI. If the current GFI is rated at 15 amps you may need one that is 25 amps or more to run the load of a compressor. Roger


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## 89yt12

after my GFI in my garage triped on my compressor and killed the power to my deep freezer, ruining $500 worth of food, I TOOK IT OUT AND CHUNKED IT


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## Hondaman56

Well, chucking a perfectly good compressor is a waste provided I can solve the problem cheaply. I appreciate the info on the load, but.... On that same circuit was a freezer and a mini-fridge. Why would they not trip the GFI if it was only 15 amp? The first time I ran the compressor it ran for about a minute and a half and got to 80 pounds pressure then cut off. I originally though it was the cut off switch was mal-adjusted, but found that it had tripped the GFI. Every other time I tried to run it it tripped within 5 to 10 seconds. I did unplug the freezer and mini-fridge thinking it was too much of a load, but as I said it tripped within 5 to 10 seconds. Why the change from the first try to the others? Motor getting warmed up, issues in the motor? Can it be fixed without swapping the whole motor? Thanks....


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## rhenning

My 20 gallon Sanborn 3 HP compressor says it use 25 amps at 120 volts AC. Read the label on the motor and it will tell amperage circuit needed to run. Mine will work for a time on a 15 amp circuit but will eventually pop the breaker. On my garages 25 amp circuits it will run all day long. Roger


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## tractornut

i would change the outlet to a non gfi outlet or plug it in somewhere else as was said before the compressor is drawing too much power under load and the gfi can't handle it


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## 89yt12

its the "shock load" of the compressor that will trip it since it can pull alot real quick at start up, alot more than his mini fridge or freezer at startup


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## Hondaman56

*Problem Solved*



tractornut said:


> i would change the outlet to a non gfi outlet or plug it in somewhere else as was said before the compressor is drawing too much power under load and the gfi can't handle it


Tractor gets the greasy bolt award. I used a 15 foot 12 gauge extension cord to plug it into the non-GFCI receptacle to the garage door openers. It ran perfectly. While running I tested it for voltage leaks and found none. Its just an older motor that is inefficient, and the GFCI doesn't like its higher current draw. I ran that machine for 3 hours straight sandblasting an antique milk can for my wife. Never tripped the breaker or got overly hot out of normal temp rise range due to normal operation on a hot Saturday.


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## 89yt12

i should of looked at your post better you thought i chunked my compressor, HECK NO!!!!! it was my GFCI i chunked


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