should compressor cycle on and off during use?

It will run until it reaches a certain pressure then shut off.  The hose and regulator are acting like a mini tank and storing a little air pressure.  It's normal.

I take it you mean as you are using it. As you spray the pressure goes down and it should kick in to bring it back up and then shut down. You should notice if you crank the regulator up, it will kick in more often.

Yes, I mean when the AB is hooked up I hear (and see by the jiggling of the unit) the compressor going on and off. Seems like every 2-3 seconds at 30PSI. That's normal?

Mike

That does seem quite a lot even for that high a psi. But I guess it would depend on the size of the tank.

sachman

So I just received my first air compressor. I got this one:

http://www.amazon.ca/dp/B00FJDU42M/ref=pe_386430_30332290_TE_dp_1

When I use it, it cycles on and off. It is not automatically shutting off due to low or high pressure. It seems that the compressor is cycling on and off to maintain the presssure. Is that OK? I assumed I would here the compressor constantly while it was running.

Mike

sachman

Yes, I mean when the AB is hooked up I hear (and see by the jiggling of the unit) the compressor going on and off. Seems like every 2-3 seconds at 30PSI. That's normal?

Mike

This comparessor has auto-on-off and no airtank. You should expect it to start running when you pull on the airbrush trigger to let air flow. The motor should stop running when the air stops and remains silent. That's normal.

If the compressor cycles on and off every 2-3 seconds with no air flowing, it could indicate some leaks in your hookup. Use the soapy water trick to find it. If you are confident that there is no leak, the compressor is defective and should be returned for exchange ASAP.

Sorry. I guess I wasn't clear. While I spray, I hear the compressor go on and off every 2-3 seconds, a little less frequently at 20PSI, a little more frequently at 30PSI. It does not go on while I am not spraying, only as I spray. Is that normal?

Sounds like you have a leak in your hose fittings.  Check and tighten all of them, or use teflon tape on all of them for a better seal.

The situation you describe is why some modelers buy a compressor with a storage tank. The compressor will still cycle on and off but not as often. When you spray you are pulling air from the tank. When the compressor comes on it refills the tank. This gives a more constant even supply of air instead of fluctuating between high and low pressure.

In general I don't believe there is an economically reasonable way to add an air tank to an existing compressor.

keilau makes a good point. I hadn't spotted that it only has one tank. So yes, while your spraying, it will kick in more often to keep it topped up. As long as it stops running when your not spraying, which you say it does, that it sounds as though its working fine.

The switch that controls the on-off should have some hysteresis- that is, it should turn off at a certain pressure, then turn back on at a somewhat lover pressure. If the on and off pressures are too close, you will get what you are describing, a rapid cycling.  Some switches used in compressors have adequate hysteresis, some do not.

It's not the actual power that goes on and off, but the compressor. As Bish stated above, there is no tank on this model, so I guess there is no large area for the air to be "stored". But I wonder if this on/off cycling of the compressor is bad for its overall life expectancy. It is similar to the TCP TC-20 model (www.tcpglobal.com/ABD-TC-20-220.html). If anyone has that one, perhaps you can comment on whether yours does the same type of cycling. Cheers.

Mike

I don't have the one from TCP Global or the one linked by the OP but I do have the identical appearing one from Harbor Freight (same factory?) and it functions just as you describe. As Sachman says, I worried about 'cycle life' when I bought it but it worked (and still does) just fine after about 3 1/2 years of use. It's a nice little compressor and is great for our modeling use. As long as the frequent cycling doesn't bother you just have fun. The cycling is a result of the pressure switch doing its job - turning the compressor off at X pressure and back on at Y pressure (factory set) . The regulator is also doing its job of supplying air to the AB at the pressure you set. How frequent it cycles will depend a little on AB nozzle size - it will cycle a little less frequently with a 0.2 mm nozzle than with a 0.5 mm nozzle. The water trap and hose does act as a small reservoir so pulsing is not a problem. Mine often turns on when I depress the AB trigger then off when I release. If yours functions this way, don't sweat it, just enjoy.

It is very hard to image how the compressor motor cycling on and off every 2-3 seconds while the airbrush trigger is pushed down. It would be good if Sackman or Bick can post a YouTube video on how the compressor does it.

I had a TCP TC-20 equivalent from Northern Tools for a few weeks to test it out. The motor started running when I pushed on the airbrush trigger to let air flow. It continued to run as long as I push down on the airbrush trigger. It did not cycle on and off while air kept flowing. It is normal. The motor stopped when I let go of the trigger and the air stopped.

Typically, the compressor auto on-off pressures are about 20-30 psi apart. My regular compressor is a Passche DA-400 with an one-gallon airtank. The motor fills the tank to slightly above 90 psi and stops. It runs again when th tank pressure drop to 60 psi. With airtank, it is a much longer cycle for the motor to turn on and off. The DA-400 is a dual piston compressor. Most compressor with a single cylinder typically cycles on and off between 60 to 45 psi.

This airtank pressure is not the same as the pressure regulator setting. For most airbrush task, the regulator is set between 15-20 psi.

NO! Cycling every 2-3 seconds disregarding the airflow is NOT normal.

With the correct combination of nozzle size (small) & set pressure (low), cycling in a compressor without a receiver is not uncommon. As the airflow requirement is increased, either by increasing the set pressure or increasing the nozzle size, the compressor will be running more often & eventually cycling will reduce to the point where the pressure in the head falls constantly below the pressure switches upper/off limit & the compressor runs continuously.

The current combination of equipment isn't draining the compressor's head quickly enough to get it to the point of constant running. I also notice that the pressure switch has quite a narrow operating window (43>57psi = 14psi), add a little inaccuracy to that pressure switch & the upper / lower limits are very close.

The poster notes notes that as pressure increases from 20>30psi that the cycling is less frequent - if the pressure were to be increased to 40psi (or a larger nozzle used), the chances are that cycling would stop & that the compressor would run continuously. 

Sachman - are you using a small nozzle, or is it possible that airflow through your airbrush is partially blocked? 

Hello!

It might be an issue of overheating or malfunctioning overheating protection. In such case the cycling is not due to pressure (how could such a compressor build up enough pressure to shut down with an open airbrush at the end of the line?) but due to the thermal switch cutting off. A way to test it would be to make sure theair output is open - disconnect the airbrush at the end of the line or something like that, and check the regulator setting (fully open). Then turn the compressor on. It should run at least 10 minutes without switching off. If it switches off, it's either overheating, or the thermal protection is defective.

Hope it helps, have a nice day

Paweł

I planned on posting a video. Thanks for the remindr. Here it is:

http://youtu.be/Q9Xbr6frpoM

Someone else asked about the nozzle. The Iwata Neo has a 0.3mm nozzle. The compressor cycled like in the video witha brand new AB so I don't believe there is an AB blockage issue. And the paint comes out nicely. Any comments on what you see in the video would be appreciated.

Hello!

I looked at your video and it is the pressure switch operating, not the termal switch, so that's a good thing. Now we need a wild theory explaining, why the pressure is going DOWN while the compressor is operating. I suspect it has something to do with the regulator. I would like to ask you to try and run the system without the airbrush, with the air flowing freely, and also to check if and how the cycling times change while you set other pressures on the regulator

In a similar compressor I bought for the friend, the pressure switch was set to turn on at about 2 bar and turn off at about 3bar, and the regulator needed about 0,5bar pressure drop to operate. That meant the only range where you coud get stable pressure out of the regulator was 1 - 1,5 bar - not much of a range. If you set your pressure at - say - 2 bar - this is what happens: first the pressure at the switch is zero. The compressor starts pumping. It quickly reaches 3 bar and the pressure switch cuts off. The regulator regulates the pressure to your 2 bar that you set. Then you open up the airbrush and start drawing air from the system. The pressure at the compressor starts dropping. At about 2,5 bar at the compressor the regulator stops regulating (it needs a pressure at the compressor at least 0,5 bar higher than preset). So you see a pressure drop at the manometer. Then the pressure at the compressor drops a little bit lower and the switch turns the compressor on. Until it starts spinning you still see the pressure dropping, then it quickly raises and turns the compressor off by the pressure switch. Not a very good arrangement - ideally we would like a steady pressure all of the time.

Two ways that I see, in which you could improve the operation of the system would be to install another pressure switch (that might be complicated), or to install a kind of tank between the compressor and the regulator. That "kinda tank" could be a few feet of an air line - it would store air and help cool it down to get the moisture out better. That would also decrease the number of cycles the compressor does - and is easier to do than messing with the switch, although it is some plumbing. Essentially it would require unscrewing the regulator from the fitting, installation of two hose nipples and clamping a length of hose in between.

Wow - that was a long writing. Sorry about that! Hope it helps you and good luck with your setup, have a nice day

Paweł

Hello!

You would have been better off, purchasing a compressor with a storage tank from the get go.

sachman

I planned on posting a video. Thanks for the remindr. Here it is:

http://youtu.be/Q9Xbr6frpoM

Someone else asked about the nozzle. The Iwata Neo has a 0.3mm nozzle. The compressor cycled like in the video witha brand new AB so I don't believe there is an AB blockage issue. And the paint comes out nicely. Any comments on what you see in the video would be appreciated.

Mike, thank you for posting the video. I have never seen anything like that before. And of course, my airbrush compressor experience are all based on products that were from 3 or more years ago.

The reason of this weird behavior of the compressor was explained by MilairJunkie well. He is an airbrush dealer and should see enough brands and quality of compressors to know. Based on yours, Bick's and the MilairJunkie's experience, the conclusion should be to avoid cheap compressors from China. The frequent start up will hasten the wear of the motor and the piston seal. Bick has said that it did not hurt his Harbor Freight compressor too much yet in 3.5 years. But there is no reason to design a auto-on-off switch with a narrow pressure range like this.

As the compressor manufacturers proliferate in China, there are more and more evidence that some of the cheap brands are designed by people with no engineering background. And the quality control varies a lot.

I have a H.F air brush compressor. set at 20 psi I turn on the power  switch, press the air brush  button air comes out od AB , take my finger off airbrush and then it stops , but then tries to go back on by itself  ?  If I intall a tank on this would it help? please help   

I guess the first question would be, is that a problem?

Leaks?

OK...I watched the video and i think the reason your getting PSI drop is that it takes time for the PSI to build back up and your flowing air through the AB while it is doing that.  Thats why it appears to show a PSI drop. But the compressor shuts off after the PSI comes back to 20.  

I have a very similar compressor to the one in the video. Mine is the Iwata version and it is constantly on.  I set my PSI to 18 while the AB is being used but if im not using the AB it will bump up to 22 PSI and when i pull the trigger it drops back down but mine never shuts off.  This is mine https://merriartist.com/products/is-800?utm_medium=cpc&utm_source=google&utm_campaign=Google%20Shopping&gclid=CjwKCAjw3-bzBRBhEiwAgnnLCgL6KlmTFutqd70R3LG2i8AipmAMCOT4P3jI2fn0oA6vG2J1IksM6BoC6FsQAvD_BwE

Mine does not shut off but constantly runs. I wonder now if mine is SUPPOSED to shut off...hmmm

lowfly, I don't know if you're aware of this but the post you're replying to is nearly 6 years old.

I taped up all connections  very well ... do you think its leaking from mositure trap on the regulator or something else ?Thank you G morrison