Air Compressor Recommendation - PeachParts Mercedes-Benz Forum

shertex · #1 04-03-2017, 04:59 PM

Bought a 20 gallon. 3.5 hp Craftsman air compressor off of Craigslist a couple of years ago. More than I needed...but kind of got used to it. Motor just gave up the ghost.

Any recommendations for a replacement? Would need to be 120v.

If I'm honest with myself, I mainly use it for tire inflation. But after getting used to a decent compressor, there's no going back to those inflators that take forever.

Thanks.

ah-kay · #2 04-03-2017, 05:22 PM

What makes you think it is the motor? Burning smell? My experience is the starting capacitor if the motor fails to start. Check the cap, normally it is 100uF 120V or higher.

shertex · #3 04-03-2017, 05:24 PM

Circuit breaker tripped, smoke coming from motor. Also was running weakly for a few moments very briefly when I plugged back in, then died altogether.

I also think I did something dumb...it was connected to a power strip so I'm wondering if the current draw was too high.

ah-kay · #4 04-03-2017, 05:47 PM

Motor probably is done for. I would still take a look at the motor winding. You cannot mistaken for a burn motor, some winding will be blackened. Check the cap for bulging. Good luck.

shertex · #5 04-03-2017, 06:05 PM

Weird...working again. I guess it had some sort of internal protection circuit.

jay_bob · #6 04-03-2017, 06:34 PM

The cap is starting to fail. Replace the cap before it fries the motor...

Diseasel300 · #7 04-03-2017, 06:39 PM

x3 on the cap being bad. Continuing to operate as is will cause excessive current draw and eventual motor failure. Correct the problem now and you'll likely save it.

97 SL320 · #8 04-03-2017, 07:27 PM

Pretty much ignore HP ratings unless the compressor is from the mid 80's or older. There was a 2004 law suit against consumer air compressor makers for overstating HP and output.

The short story is you aren't going to get more than 2 HP from a 120V 15 A wall outlet.

Don't shy away from a 220 V compressor, adding an 220 outlet isn't voodo. It uses the same type of wire as 110 V and you install a 2 pole breaker rather than a 1 pole. A real 2 or 3 HP 220 compressor on a 20 ish gas tank that you can roll around would be fine.

Have a look here for more info. Evaluating True Horsepower and CFM Ratings of Air Compressors

shertex · #9 04-04-2017, 10:29 AM

For the electrical novice....how do I locate the cap?

Diseasel300 · #10 04-04-2017, 11:12 AM

The cap will usually be under a cover on the side of the motor. It will be very obvious as it mounds up out of the side case where it would normally be round.

Some motors have 2 caps. If yours does, you'll usually see 2 cap covers on the side of the motor. Some have the "run" cap tucked in the end bell of the motor. There will usually be a couple of screws that hold the end plate on. If the cap is hidden in there, it'll be the round variety.

barry12345 · #11 04-04-2017, 12:23 PM

If you have or can borrow a meter with a capacitor checking function. Quite common these days. You can check them before buying new ones. Also if you re capacitor say a cruise control you can check them as you remove them. Even check the new ones before installation. Usually a waste though as new are usually good in the vast amount of cases.

As for compressors. Just staying with the cheapies that are pretty much designed to fail for simple applications. Only piston pump types really go the distance usually anyways.

I was present when they selling of and rating of compressors became pretty much total lies. A neighbor that knew I know a little about electrical called me then.

He asked what size wire to apply to a seven and a half horsepower compressor motor. I told him you really should have a magnetic starter as well. Anyways I did the calculations for his unit and length of cable run.

A few months later I was visiting him and saw the compressor. Stated 7.5hp but looked and ran like a three horsepower unit. A craftsman product.

I did not take my clamp on amp meter over to check. I did feel bad about the cost of the wire he was stuck with though. I did check and heard it was a new way to rate electrical motors. A scam to me as there was nothing wrong with the old motor rating standards.

On the other hand today anybody can own a small compressor. As long as they are aware that for any real work they need a good piston pump design. Other than say for driving shingle nails as a maximum use limit a small diaphragm type pump seems to work.

Many companies that at one time built only decent compressors went and joined the junk league for much of their product lines. Still a little portable 110 volt compressor is very portable and convienient.

As long as you treat them like the toys they are.

97 SL320 · #12 04-04-2017, 06:55 PM

Quote:

Originally Posted by barry12345

As for compressors. Just staying with the cheapies that are pretty much designed to fail for simple applications. Only piston pump types really go the distance usually anyways.

To be more exact, an oil lubricated piston compressor as there are piston compressors that use a rocking piston with a teflon ring.

For a consumer that uses it to fill tires or other small tasks every other month, the low end stuff works well enough.

An even better compressor is a rotary screw though it is more suited for a full time repair shop. Prices have fallen in recent years, Atlas Copco for one sells a true 5 HP GX4 unit with tank for $ 4,500. Super quiet no bang bang of a piston compressor, just a pleasant whir.

Quote:

Originally Posted by barry12345

A few months later I was visiting him and saw the compressor. Stated 7.5hp but looked and ran like a three horsepower unit. A craftsman product.

I wouldn't expect any consumer grade compressor to be rated any different.

Quote:

Originally Posted by barry12345

I did not take my clamp on amp meter over to check. I did feel bad about the cost of the wire he was stuck with though. I did check and heard it was a new way to rate electrical motors. A scam to me as there was nothing wrong with the old motor rating standards.

I don't see it as any new NEMA approved rating.

Quote:

Originally Posted by barry12345

Other than say for driving shingle nails as a maximum use limit a small diaphragm type pump seems to work.

And they are light too, no use dragging around something heavy.

[/QUOTE]

shertex · #13 04-04-2017, 07:10 PM

Do you all think it's likely that plugging it into a power strip resulted in a current draw that was too high? I know extension cord can do that...not sure about power strip.

dude99 · #14 04-04-2017, 07:24 PM

Depends on how cheap the power strip is, its probably not helping things....

97 SL320 · #15 04-04-2017, 07:35 PM

What is the power strip rated at? What is the gauge of wire of the cord? I've seen 15 Amp power strips and very light duty ones for a computer and a few power blocks.