Help me choose an air compressor for sandblasting and shop.
Posted March 05, 2011 - 04:11 PM
Posted March 05, 2011 - 04:45 PM
Posted March 05, 2011 - 06:08 PM
Posted March 05, 2011 - 06:15 PM
Well Done My Friend! Glad it's working.
Posted March 05, 2011 - 06:50 PM
Have you had a chance to check the amp draw when the presure is near max?
At 32 amps your right at the max load for that motor. You might want to slow it down just a bit, just to be safe. If you slow it down, the amp draw will drop, & your starter protection will probably hold. At a minimum, I'd check the motor temp when under heavy use. I realise that you're not sure how much air you need, but I'd at least consider slowing it down at a later date to be safe.
Posted March 05, 2011 - 07:22 PM
Glad all came together. Like Railman said, check the amps near shutdown.
Posted March 05, 2011 - 07:36 PM
I can remember what the next size pulley down was.
Posted March 07, 2011 - 08:14 AM
Posted March 07, 2011 - 09:44 AM
Posted March 07, 2011 - 09:48 AM
Your motor should have a thermal overload protector built in, which will protect it from prolonged overload. Should be a reset button on the motor.
I am almost positive there is no reset switch on the motor. I will double check it when I get home though.
Posted March 07, 2011 - 09:52 AM
Posted March 07, 2011 - 12:29 PM
- NUTNDUN said thank you
Posted March 07, 2011 - 12:38 PM
Overall, I think going to a smaller drive pulley is the right thing to do. I've smoked motors on material blowers running right at their max amps, & it's just not worth the risk. If your planning on doing blasting, you'll probably come near continuous running, & have a good chance of motor overheating. By dropping from the 7 3/4 to 6 3/4 you'll drop about 100 pump rpm, & about 3 cfm. You'll still be around somewhere around 21 cfm rating at 175psi, & have a little margin of safety. If you listen to the video closely, you can hear the motor slowing a bit near the end. With a service factor of 1.15 x 31 amps = 35.65 amps right where your top reading was. The key here is that you plan on running it near continous for periods, & need a margin of safety.
I definitely don't want to have to replace the motor anytime soon. Once I get the smaller pulley on I will probably need help figuring out how to wire the overload relay back in to the circuit. The guy that came over and did the wiring did it so fast I didn't really have a chance to see what he even did when we first tried the overload.
I originally plumbed the auxiliary unloader in with the unloader from the pressure switch but I don't think the auxiliary unloader valve is any good anymore. Once I took that out of the plumbing and ran the compressor till it kicked out I tried spinning the motor by hand to see if the pressure switch's unloader was working and it seemed like it wasn't as there was a lot of compression on the compressor.
I don't know when the unloader on the pressure switch kicks in. I don't know if it kicks in right after it hits the cut out or if it kicks in right before the cut in. I would like to have a continuous run unloader setup on it that way if I am using enough air during sandblasting to where the compressor is basically running non stop anyway it would be easier on the motor instead of starting and stopping all the time.
Posted March 07, 2011 - 12:45 PM
with a motor like yours you want to keep the start and stop to less than 5x per hr
so you will want a constant run feature of some sort, I am glad mine has 1 its more like a screw compressor and its easier on the electric motor
my 10hp doesnt have a reset button either and its a baldor,but the 3hp on my spray booth does
Posted March 07, 2011 - 01:27 PM
On my screw compressor, It would operate either in continuous, or start stop mode. When the pump shut down, it did three things.
#1 was the one way valve shut to hold tank pressure away from the pump.
#2 was the unloader valve opened, releasing the screw from start up pressure.
#3 was the intake butterfly/throttle plate closed up.
The intake butterfly is exactly like a carbruator throttle plate.
If any of the three items malfuntioned, the pump would try to start under load.
I've had all three malfunction at different times!