View Full Version : Air Compressor Help for Dynatorch w/ Hypertherm PowerMax 1250

09-21-2010, 07:58 PM
Hey all,

For the past few months, we've been running a Hypertherm PowerMax 1250 on a Dynatorch CNC table with an Ingersoll-Rand SS5 air compressor (60 gal, 5 hp, 230 V) and a Harbor Freight compressed air dryer. Online forums seem to indicate that this compressor is sufficient and the CFM ratings all check out, but after several hours of cutting, the air compressor motor has been shutting off from over-heating (it's VERY hot to the touch at the point).

Our air compressor cycles between 100 and 125 psi and the motor turns on about 20 times/hr, which I've been told is roughly 4 times the recommended amount. For the past few weeks, we set a shop fan up right next to the motor, which must have provided enough cooling, because it worked perfectly, but today even it's not doing the trick.

When the motor shuts off, we usually wait 45 min - 1 hour before resetting it. That usually buys us another 2 hours of cutting, but today, it's only been about 20-30 minutes.

Are we using the wrong air compressor, is there just something wrong with this one, or is there something else we need to fix with our system?

Any advice or suggestions would be much appreciated!


09-21-2010, 09:32 PM

What is the CFM on your AC? I am running a IR AC that sounds like yours, It is a 17CFM. It runs great with our 1650 and we can run die grinder at the same time. It sounds like you may have a motor or pump problem. does the pump spin easily when it shuts down? That might indicate a motor problem, if the pump is tight then it might be a pump. Another thing to consider is the unloader, does overload trip when it tries to start or when it is running? If the unloader is not dumping the line pressure then the motor will have to overcome the hi-PSI to start, which puts a lot of stress on the start capacitors.

Hope this helps, good luck!


09-22-2010, 11:35 AM
if you haven't already done it might also want to check your voltage to the compressor, adequate wire size for the length of run etc..

big iron
09-23-2010, 02:26 AM
You need to check the nomaclature plate on the motor it will display the amperage for your supplied voltage. You will need to use a clamp on AC amp meter on one of the "hot" Powered input wires to the motor.
When your motor starts under load untill up to the rated RPM the current draw will spike for a seconed and then if all is working correct the current draw will drop and be very close to the amperage rating on the nomaclature plate when the motor is running at it's rated speed (RPM).
On single phase motors you only need to check one input leg, on 3 phase motors you will need to check all 3 inputs.
Be sure and check your input voltage when the motor is running to be sure you don't have a voltage drop problem, also be sure that you have the correct voltage for the motor.I think you have a voltage drop problem and /or a higher then normal amperage draw. Both will over heat the motor.
Voltage drop could be due to long wire runs and incorrect wire size or bad connections.
High amp draw could be too small of motor for the load or a mechanical problem with your pump/pump unloader etc. hope this helps

09-23-2010, 10:42 AM
Thanks for all the feedback, everyone. I've spent a bunch of time on the phone with Ingersoll-Rand and been able to eliminate the pump as an issue because with nothing else on, the pump wheel spins freely and the pump up times closely match the proper values from IR.

I'm going to continue to look into wiring potential voltage/amperage issues, but my gut tells me that even if that's not to spec, the bigger issue is that the motor is just having to turn on too frequently.

Tommy - how often does your IR AC cycle when you have everything running off of it? With my 30 psi range, I get 2 minutes or slightly less from the top set point to the bottom one where the motor kicks on, and my cycles/hour are about twice the recommended limit recommended by IR.

I did find a few small air leaks in my system, but patching them didn't make a noticeable difference.

If anyone has any recommendations about ways to reduce my cycles/hr with my current set-up, it would be much appreciated. I'm starting to think that I'll need to purchase a second air compressor, or at the very least, a second tank.

Thanks - I really appreciate the feedback so far!

09-23-2010, 11:12 AM

Sometimes ours will run non-stop four an hour or two. This particular unit is rated for 100% duty cycle. It does get hot but nothing that shuts it down. I will check the model number and specs and post it later. I run 70 to 80 psi output on our 1650 and usually a die grinder, which seems to take the most air. If there are no nozzle plugs or hang ups anywhere, then it will run for an hour straight. The torch cooling cycle (when the torch finishes a cut) rarely has time to expire before the next pierce starts, so it is a constant flow of air.

It sounds like you are narrowing it to a electrical issue.

Good luck!


11-28-2010, 06:30 AM
I've got an IR 5HP with an 80 gal tank which runs a Hypertherm PM 1250 G3 plasma generator through an IR refrigerated air dryer.

The machine says 15 CFM on the name plate and is ~20 yrs old.

We have another 80 gal pressure tank (a salvaged vessel from a defunct compressor of the same size/make/etc) plumbed inline as well.

Our compressor will kick on about three to five minutes after the plasma machine makes its first cut, and will run for about ten or so minutes before it stops. Then there's another five mins or so where it's off, then back on again for ten minutes or so. Rinse, repeat, until the sheet is cut.

The longest I've had the machine run continuously was about 55 mins doing a very tightly nested 4x8 sheet of 11 gage steel. That was with a finecut nozzle and the plasma machine set at 75 PSI. The air compressor never skipped a beat.

If the problem really is that your compressor is running too often, you'll either have to buy a higher capacity machine, or add volume down stream of the compressor to buy your motor some breathing time to cool off. Our setup basically has double the supply volume of the standard model, so it takes longer to bleed the pressure down to the motor start point.

I've never had my compressor trip its heat overload before. I've popped the breaker that feeds it a time or two when really going to town with an air die grinder for a long time, but that took nearly two hours of solid use with no rest at all for the compressor before it happened.

I'd be worried about the motor on the compressor if it is kicking out due to heat overload. If the motor on the pump is giving up before the breaker in the load center is tripping, your wiring is fine.

It may be time to dig out the multimeter and figure out what's crapped up with your pump motor.