Testing a rotary screw compressor Gunner style

Not yet.

Are you planning on keeping it or selling. Around 20 years ago a company I worked for a company that had a screw compressor and it kept needing seals replacing. In the end the guy doing the maintenance looked at the air requirements which was largely a race fab shop so air tools and some blowing, and a small sand blaster, intermittent use basically and he said they had been sold the wrong type of compressor. He said the screw compressor was great for constant use but for the intermittent use it was seeing it would wear the seals as it was doing. It was exchanged for a piston compressor and no further problems.

Selling, for sure. I have a 10 HP Quincy.

First off, have you got a 75 KVA transformer minimum to kick your 240V

Then you'll have to turn Everything Else off and have a 200A shop service and go straight to the mains, or a full 200A disconnect on a

Might be easier to rent or borrow (or buy) a portable generator with

Unless you want to install a 480V power service to do it - it'll run you a bloody fortune, but might be worth it in the long run - at a minimum, it makes the building a lot more desirable for resale.

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For Testing Purposes:

Make sure the starter contacts can handle the amps for 230V. If that's OK, you can wire around the overload heaters, I'm hoping you have an amp clamp meter so if there is a problem you can shut it off before burning up the motor. Start it up and check amps on each phase to make sure they are within spec.

RogerN

(...)

Perhaps the concrete contractor next door would like to donate some land and some 460 V power for a short test? Tell him you only need to test for a month and then watch his body language. :)

--Winston

Take it to a motor shop and test it there.

Ig, just temporarily re-wire the motor (only) for 230, then hook it up and push in the motor starter armature by hand. There's almost always a manual engagement bar you can push to energize the relay... and that's all a motor starter is... A big relay with thermal over-current cutouts.

LLoyd

Lloyd, what I am afraid, is that in this rotary screw compressor there may be some auxiliary valves, gizmos or some such, that need to be properly sequenced for the compressor to work.

And so, my thinking goes, if I just dumbly run the main motor, I may ruin the compressor.

IOW, I am afraid that this is not like a regular compressor, where a motor does everything.

Gunner Asch fired this volley in news: snipped-for-privacy@4ax.com:

That's only pesky if you're not wearing goggles and gloves, or don't have the mains to handle it.

(but it could be "pesky"... there will be a few milliamps flowing)

Lloyd

HEY! He Can Be Taught!!! YES!!!!!! ;-)

Lloyd, I'll bet Iggy's right on this one - Screw Compressors have circulating oil running around in them for the screw assembly, and it wouldn't shock me if there's a separate scavenge pump. And an active sequence circuit where a solenoid relief valve holds open till the screws are up to speed.

If nothing else, you want to have the overloads in the circuit in case you single-phase the power or something else goes wrong, at least you have a chance that the safeties will save the motor. When something that big blows up, it goes with style. Big Boom.

And that's NOT the time you want your hands inside the control box pushing the main contactor in by hand. That's a real good way to pull back a stump, and for your friends to start calling you Lefty (when you were born a Righty...) or "The Claw". Get the point?

You can pull that trick on a HVAC condensing unit that you know works normally ("I got the new fuses in OK, right?") BUT even then you use a stick or a screwdriver to do the contactor pushing to keep your hands out of the 120/240V arc and spark zone.

That is not so good with 480V or higher Mystery Gear you are testing for the first time with no expectations of normal running.

You might get away with a "Here, Hold my Beer and Watch This!!"move once or twice before Darwin's Law bites you in the ass HARD, but eventually it will. You want to be the one pointing and laughing, not the one going to the Emergency Room.

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"Bruce L. Bergman (munged human readable)" fired this volley in news: snipped-for-privacy@4ax.com:

I won't argue the presence of accessories that might need to run, too,

But I was NOT talking about reaching into the contactor with a GD screwdriver! Didn't you read my post, first?

I said, "There's almost always an actuator bar ..."... It's _designed_ for manual actuation of the motor starter -- for testing purposes.

Geesh!

On the other stuff, you may well be right, but don't condemn me for what you didn't even read!

Lloyd

More like wearing a full on Arc Fault Suit with a full hood, gloves and boots - there's a Whoooooooooooooooooooooole Lotta Milliamps flowing when you "Pull the Lever, Kronk!" on a 50-Horse Motor.

If it's130A Running current for 50 HP at 240V 3Ph, the Locked Rotor Current is going to be north of 1,000 Amps. And it will be drawing that much or more every time you take a screwdriver and shove that contactor closed... Be scared. And do it the regular way, with the doors closed.

And I wasn't kidding about that "turn everything else off" remark if the shop only has a 200A 240V 3Ph service - even with a 400A or 600A service you'd better have a spare set of main fuses, too. Doesn't take much to pop one when you're starting something that big.

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My shop has 800 amps.

An old experimental electolytic cell I worked on used 200V 18000A DC or 10 Hz AC (to reduce inductive losses) for heatup or maintenance. Very expensive custom Fuji recti-former, 15KV feeds.

Pete Keillor