Who's the electric guru here?

[uncledj]

  I recently changed an air compressor at a facility and the one I removed was too nice to scrap.   I know that it runs as I started it for a few seconds while it was still in place, before disconnecting for the changeout.   It started and ran well for the 2 seconds I ran it.   It had no oil showing in the sight glass so I didn't want to run it any longer.   The maintenance guy at the facility condemned it because he saw oil film around the compressor end and thought that meant it was bad.   So, I strapped it to my bike trailer and brought it home.   The issue is that it's 3 phase and I'll need to get a converter to run it.   It has a 200 v ?  10 hp motor.   I typically see 208-230 for a 3 phase or 220-240 for single phase.   So I don't know what the 200 v on the nameplate is about.   

My question is, should I get a 10hp or a 15hp converter.   My tendency is to go larger, but I read that an oversized converter can cause the motor to run hot.

Whaddya think....1o run a 10hp air compressor....a 10hp drive or a 15hp drive?

[RDawson]

I’ve never dealt with converters so it may be a dumb question, How does the converter price compare to changing the motor to a single phase?

[Freebird]

I was an industrial electrician for 20 years and have to say that I’ve never seen a 200 volt motor.   In fact, the lowest voltage I ever dealt with on 3 phase was 480 Volt.   Also higher ones 4160 and 6900 volt.  All the smaller ones were 480 volts though either with each leg being 277 volts.   I’ve never dealt with commercial a/c though.  

[Freebird]

Just did some quick research and apparently 200 volt motors are not unusual on A/C systems.   I think, if I read it correctly, they are sometimes used on 208 Volt line systems. That being the case, I would go with the 10 HP drive.   I think if the line voltage is within 10% of the rated motor voltage you will be fine.  Wow, I haven’t been an electrician for about 35 years.   I’ve forgotten a lot. 

[RDawson]

There’s my “duh” moment for the day. I was reading it as an air compressor 🤷‍♂️

[uncledj]

  It IS an air compressor.    A 10hp drive is just over $200, a `15hp drive $300.    A used 10hp motor would be around $700 + shipping, a new motor would be around $1200 +.

  I'd like to go the cheap route since, although I ran it for a couple of seconds, I don't know for sure that the compressor itself is healthy.  If the compressor ends up without any major damage, this will make one hell of a shop compressor.   

  I guess the question would be whether an air compressor motor would be a "Heavy start load" or a "Rated start load".

 

I'll be retiring in a couple of years and will be looking to move back to the Youngstown area.   I'll be looking for a place with a large detached garage, or with enough land to put up a pole barn to use as my "Tinkering space".

  This would be a hell of a compressor for such a shop.

Edited Saturday at 12:06 PM by uncledj

[Marcarl]

Just my thoughts. An AC compressor is built different than an air compressor, but I suppose your know that. There are reasons for this and in some cases things like this might work. One thing I think of is that the AC compressor sends oil into a closed system, so what are you going to do with the oil in a one-way system and you will need to supply the compressor with new oil on time.

JMT

[uncledj]

Well, I seem to have created some cornfusion with the A/C description of the motor.   It's an air compressor, not an air conditioning motor.

Yes, in most air conditioning compressors, if they're hermetic or semi hermetic, the oil travels through the system and returns to the compressor.  There are large systems, designated as having "open" compressors that have a separate motor that typically drives the compressor using a Woods style coupler.  These systems do not flow oil with the refrigerant.

With an air compressor, I don't think they're supposed to discharge any oil, but only in a perfect world.   I think they all  leak a little oil and let a little oil into the airstream, but should be negligible on a healthy compressor.     My suspicion is that this compressor, while never worked hard, has not had good / any service over it's 14 year life.   I think the oil leaked out or was pumped out (slowly over the years)   Still has the original oil filter on it.    The question there will be how long did it run with low / no oil, and if / how much damage was done.    I'll need the power converter to run it off of single phase.    Since originally posting I ordered a 10 hp converter and will be able to determine compressor condition once I can run it.

 

[RDawson]

My big question would be what I plan to use it for. I’ve  had a 60gallon-150psi upright like those found in local stores, probably China origin for around 30 years. I’ve run impact guns, paint guns, etc for years. A commercial compressor like that would be way overkill for my use, the upside being it would never have to work very hard and should outlast me and my kids. 
Now that you’ve mentioned maintenance I started thinking, I’ve changed the oil maybe 2-3 times in 30 years and truth to be told it gets the condensate drained a couple times a year. It’s a wonder the tank hasn’t rusted through, good thing I don’t treat my bike like my tools. 
It is a great find though and a very expensive compressor to replace. 

[uncledj]

About the only thing that I'd use it for that requires a large compressor would be sandblasting or soda blasting.    To do either effectively takes a lot of air and a lot of pressure.   I've done it with a 5 horse compressor that I have and find that as pressure drops I waste more sand "cause I don't have the discipline to stop and wait for pressure to build.   This compressor is rated 175 psi so it should work well for the sandblaster or the sandblast cabinet.

It'll come in handy if I ever need to use a jackhammer too.  lol.

I'll post to let everyone know if a 10hp drive starts this 10hp motor.

Edited yesterday at 12:58 PM by uncledj

[Woody]

Have you changed the oil in the compressor yet? hopefully it was just low and not out of oil. site glasses are notorius for leaking oil so after cleaning the area around the site glass keep an eye on it. Hopefully you have great find.

[luvmy40]

Most air compressors start in an unloaded state. It should be close to "Rated" with some inrush possible. If the 10hp converter doesn't manage the inrush, you might think about adding a soft start or going with one of the newer 3 phase drives that converts single phase 208 to 3 phase. I have no idea what they cost though.

 

Edited yesterday at 01:14 PM by luvmy40