Air Compressor PSI drop

[Chattah]

I recently picked up a used compressor. It's a harbor freight model 21 gallon 3hp 125PSI unit. I have noticed however when using it the regulated air pressure set at 100PSI drops about 40-50 PSI when I use an impact, air hammer ect. It's running through a 50 foot hose though my other compressor doesn't have this issue using the same hose.

I have replaced the HF regulator and gauges with known good units but still get the same issue. I did notice that the outlet for the regulator is attached to the pressure switch and not directly to the out pipe on the tank like on my other compressor. Could this be what is causing the issue?

 

[metaleltr]

Yes, the small restriction through the pressure switch is what is making the pressure drop apparent. If you had a gauge at the tool you would notice a similar pressure drop when you operate the tool.

 

[Chattah]

Yes, the small restriction through the pressure switch is what is making the pressure drop apparent. If you had a gauge at the tool you would notice a similar pressure drop when you operate the tool.

Thanks, I'm going to try bypassing that tonight.

*Edit - When I say bypassing it I don't mean disabling it that would create a bomb. I'm referring to hooking up an output for the tools off of a separate T before the air hits the pressure switch.

 

[algee]

Thanks, I'm going to try bypassing that tonight.

*Edit - When I say bypassing it I don't mean disabling it that would create a bomb. I'm referring to hooking up an output for the tools off of a separate T before the air hits the pressure switch.

Forgive me for bringing up an old thread, but did installing a tee and attaching the regulator off the the branch instead of the outlet of the pressure switch fix the pressure drop? I'm having the same issue. Thanks for your time.

 

[pepi]

I see the problem it is laying on it's side

 

[pepi]

I see the problem it is laying on its side.

 

[Chattah]

I see the problem it is laying on its side.

Haha, you nailed it.

 

[Chattah]

Forgive me for bringing up an old thread, but did installing a tee and attaching the regulator off the the branch instead of the outlet of the pressure switch fix the pressure drop? I'm having the same issue. Thanks for your time.

No it didn't fix anything. One thing I did notice was the tube that comes out of the tank where you attach the regulator is extremely tiny. It's my guess that the tiny tube is the cause of the problems. I pretty much gave up on that compressor and will probably end up listing it for sale. I was able to repair my other compressor which doesn't suffer from this problem.

Sorry I couldn't have been more of a help. One thing I didn't try was to install a T on the hole where the pump fills the tank as that hole is larger. That might help but I lost my motivation lol.

 

[algee]

No it didn't fix anything. One thing I did notice was the tube that comes out of the tank where you attach the regulator is extremely tiny. It's my guess that the tiny tube is the cause of the problems. I pretty much gave up on that compressor and will probably end up listing it for sale. I was able to repair my other compressor which doesn't suffer from this problem.

Sorry I couldn't have been more of a help. One thing I didn't try was to install a T on the hole where the pump fills the tank as that hole is larger. That might help but I lost my motivation lol.

Chattah, thanks for the response. There is a fellow who had a similar problem as ours in a different forum with the pressure drop. It turned out to be his regulator. I can't remember if he bought a 3/8 or 1/2 regulator, but after upgrading to that and setting the pressure to 90-95 psi, he stated that it remained there without drop with tool operating.

I too, lost motivation and just removed the regulator altogether using the tank pressure.

 

[Fixnair]

That compressor probably puts out maybe 8 CFM. The manufacturer sizes his fittings to pass only that amount of air. The manufacturer cares not that you are going to use an impact wrench that uses 15 CFM or a D/A sander that uses 20 CFM .