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Union Electrician
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Discussion Starter #1
A customer with a tire shop has two very nice compressors. A 25 horse and a 15 horse.
Both compressors are pretty new, but run on the very old high leg 3 phase 240 volt system. The shop is currently in the old part of SLC and they're moving just 3 blocks over to a property they have which is mixed zoned (sort of a forgotten part of the city by city planners).

Anyway the new location has single phase 240V.
I looked on Grainger at phase converters. The solid state type on their site only go up to 12HP. The rotary type go beyond 25HP, but the price is prohibitive at over $6k!

Two questions; am i looking in the wrong place? I was stunned when i saw the $6125.00 price tag for the 25HP converter.
The owner has two very large air storage tanks, perhaps a standard single phase 240v piston driven compressor could fill the tanks and the guy will have enough air for the day?

Thanks,
Joe
 

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For a load like an air compressor you will need to go bigger than a 25 hp phase converter. Check out americanrotary.com. We bought a 20 hp phase converter from them for our shop and it has worked great.
 

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Head Grunt
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3,270 Posts
Might better just replace the compressors with a new single phase screw compressor like this for the money :http://www.aircompressorsdirect.com/Ingersoll-Rand-UP6-7.5-125.230-1-Air-Compressor/p2409.html

He can sell the others and regain some money back. The psi should be adjustable if he prefers to run at 150psi but 28cfm at 90psi should be more than enough to run a good size shop, especially if he has storage tanks already. But, he wants to put this thing in its own room somewhere as they are a constant drone. The motor stays running all the time and a clutch engages the screw to make air when psi goes down. I have worked around one of these SOB's when i turned wrench and always wore ear protection because of it but it fed the air for 14 auto techs and 6 auto body techs at the dealership where i worked with no issue at all.
 

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Wood Craftsman
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Yes they get pricey as you go up the HP ladder. I would look into what woodchuck suggested.....

Either that or see if the owners of the building would consider having the electric co run 3ph to the shop.That is going to be pricey but you never know......

B,
 

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Head Grunt
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your customer may tell you he needs huge big HP compressors but it reality it comes down to what puts out the most CFM. Those big HP compressors are huge money and of course trying to get 3 phase or an inverter is big money. IMO he may be better off going to a couple smaller 80gallon single phase 240v piston compressors with high cfm output if he doesnt want to go with a screw compressor. You can even pick up a cheaper 80 gallon IR single phase putting out 20-24cfm each for $1200-$1500 each. Couple of these together will really put out some air. Tire shops may claim they need a lot of air but look at what large body shops are running, a da-sander will consume far more air than any other air tool with the exception of an open hose. You can operate both compressors off one pressure switch using a relay.
 

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The expense for the POCO to convert to three phase service depends on the facilities they have at the location. If the transformer that presently serves the new location is on an open-wye or three phase line, it could be as simple as adding one transformer to obtain 120/240 4-wire three phase service along with changing out the service drop. Not sure what the environment for that sort of thing is in SLC, but where I am, there would likely to be no charge (from the POCO) for the work and the only expense would be for an electrician to change out the meter base and panel.
 
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Union Electrician
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Discussion Starter #7
Sorry, I apparently typed this reply last weekend but for some reason did not post it. Thanks for everyone's responses, knowledge is worth more than gold!

The customer is a friend of a friend, so I want to save the friend money, but as an installer I don't know much about air compressors. These two I mentioned are big square boxes (about 4' cube) on casters. My only knowledge that they are nice is from what ive seen on TV.
The 15horse was given to the friends husband for payment of a debt and if I could simply change the motor I would gladly accept it as trade as well.
More to the point now, and i really appreciate everyone's input, it's a small tire shop, but they do semi truck/trailer tires.
There's a pole just 50yards down the road with 3phase (voltage unknown) and the pole with the service attached to it on the customers property is leaning at nearly 60degrees. I suggested to the friend that she have the poco come out to fix their leaning pole and as retribution for their lack of maintenance to extend the 3 phase from down the street. Not likely but worth a try, and I haven't heard yet how well that conversation went.
The guy could sell the two compressors for good money and buy a nice single phase one that could do nearly the same work?
Or even just get a cheap 120v compressor in combination with one or both of his 100 gallon (i work in a refinery where gallons is easier to visualize than cubic feet) storage tanks?
I don't know, but it seems to me with the storage tanks the power or sophistication of the compressor shouldn't matter?

Thanks,
Joe
 

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You can use the smaller motor to act as an idler to help start the larger motor. Done all the time in small home machine shops with no three phase. All you need is a phase converter from http://www.phase-a-matic.com/

Problem with compressors is the large starting current.

I've used the phase a matic before and it works well, read the site PDF on static converters. Call the guy and see what he says. Nice guy.
 
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