Help with compressor setup! (Doesn't turn off)

[luvmyglockfou]

So, just as the title says..

I bought an 80 gallon "Black Max" 220v compressor with 6.7hp motor yesterday. It's got a new motor and a new compressor on it, which I think may be contributing to my issue (incorrectly setup by previous owner). Anyways, I got it for $325 so I wasn't too disappointed. It works great and is dead silent.

So when I got it all plumbed in today I am facing an issue. The overpressure relief valve (safety relief valve set to 115psi) popped before the compressor turned off. I am not sure how to set up this compressor, as all the compressors I have had before this were of the tiny, oilless design. Here is a picture of the switch plunger when the switch is in the "ON" position:

Switch in the "OFF" position:

There is also a couple of what look like adjustment screws WITHIN the plastic case that houses the wire connections. I haven't done anything with them, but maybe they could use adjustment? I don't know..

I could REALLY use some help getting this thing set up to run well and safe! Thanks!

 

[Jim Johnstone]

Well a few issues. The pump is single stage where the tank says 2 stage. What that says to me is the previous owner installed the single stage pump but left the pressure switch set for 2 stage but must have installed the correct OPRV.

Is there any diagrams in the inside of the pressure switch cover? Or a name on the cover so you could go online and look up a manual?

Sent from my SGH-I727R using Tapatalk 2

 

[luvmyglockfou]

Well, now I feel dumb. I didn't even look at the back of the cover.

 

[fury9]

It's a two stage pump, one cylinder is smaller than the other

 

[luvmyglockfou]

Yeah its gotta be a two-stage pump...15.2 SCFM @ 90PSI.

 

[luvmyglockfou]

I can't find a manual for this thing...but the back of the switch plate is obvious. What's an effective way to set the cut-in and out?

 

[Fixnair]

What pressure relief valve is going off? Is it on the tank or on the compressor head?

How many cylinders does it have? 2 or 4. If only two it appears it is a single stage. Both cylinders being the same size. 115 PSI is about max for this thing.

To set the pressure switch, screw the center screw down a few turns. Then run the compressor 'till the desired cut out pressure is reached. Turn off the compressor by some means other than the lever on the pressure switch. Make sure there is no air being used so the pressure in the tank remains constant. Now slowly back off on the center screw 'till you hear or see the contacts open. Now adjust the other screw out as far as it will go. Do not force it past the stop. That should be the minimum differential setting for the switch. ( difference between cut in and cut out ) Now you're done. Test it with the compressor running normally to be sure.

 

[luvmyglockfou]

What pressure relief valve is going off? Is it on the tank or on the compressor head?

On the main line out of the tank

 

[kams1973]

An intake air filter on each cylinder definately indicates it is a single stage pump.

 

[Skin]

Someone added that pressure relief valve after the fact. It should say the rating on it. If it really is 115psi that's your problem since the sticker on the compressor clearly states 125PSI off which it would of been preset to from the factory. If the valve is opening before the switch hits its shut down pressure...well there you go.

Also just because its a single stage doesn't mean you're 'limited to 115psi'. My antique home compressor is a 1HP single stage and its set to shut down at 150. Works fine. Reason being your line pressure is going to drop so you don't want only ~100PSI at the tank otherwise the compressor runs more and your tools have no balls.

 

[luvmyglockfou]

Someone added that pressure relief valve after the fact. It should say the rating on it. If it really is 115psi that's your problem since the sticker on the compressor clearly states 125PSI off which it would of been preset to from the factory. If the valve is opening before the switch hits its shut down pressure...well there you go.

Also just because its a single stage doesn't mean you're 'limited to 115psi'. My antique home compressor is a 1HP single stage and its set to shut down at 150. Works fine. Reason being your line pressure is going to drop so you don't want only ~100PSI at the tank otherwise the compressor runs more and your tools have no balls.

Yeah I added the pressure relief valve because there wasn't one on there...the last guy just didn't have one. The package said 115 psi but it religiously pops at 100...annoying and will be taking it back to lowes tomorrow. That being said, I have to get another one somewhere!

 

[p0lar]

An intake air filter on each cylinder definately indicates it is a single stage pump.

Precisely.

OP, you may be able to adjust that pressure switch down to the 115 range, if you wanted, but I'd buy a safety relief valve rated at 135 PSI, a new gauge, and try to adjust the current pressure switch down to that rating.

If you can't adjust the pressure switch down to 135 PSI, or it's not reliably cycling, just replace it. LeFoo pressure switches are very cheap (and inexpensive) - buy one that's pre-set at 130 or 135 and you'll have range either way.

 

[luvmyglockfou]

I got the compressor to reliably turn off before the 105psi emergency relief valve and kick on as designed, 30 psi lower. All I'm waiting on is a new relief valve so I can turn it up where it needs to be! Thanks for all the suggestions !

 

[larry_g]

Some where on that tank should be a tag that says the max and working pressure of the tank. Being a 2 stage tank it will be in the 200 psi range. You want to have your pressure relief valve in that range. The PR valve is there to protect the tank from over pressuring. Once the PR valve is correct then your pressure switch should work correctly. I am not a believer in running a single stage system much above 125 psi cutoff. Running to 150psi is like running your car at WOT all the time. You'll find it lasts longer if run below the max it will do.

lg
no neat sig line

 

[luvmyglockfou]

Just ordered a 175 psi relief valve. I won't be running this past 125 on a habitual basis.

 

[TwoInch]

i have noticed that the relief valves tend to blow under the rated PSI. i had a 125psi max tank that came equipped with a 145 or 155 relief valve from the factory, and it would blow off at 120psi. i bought a replacement, a 135, and it blows at 128 on the dot.

are they designed as a max blow off at *** psi? so that anything within the last 15psi or so is acceptable? pain in the ***.

 

[luvmyglockfou]

i have noticed that the relief valves tend to blow under the rated PSI. i had a 125psi max tank that came equipped with a 145 or 155 relief valve from the factory, and it would blow off at 120psi. i bought a replacement, a 135, and it blows at 128 on the dot.

are they designed as a max blow off at *** psi? so that anything within the last 15psi or so is acceptable? pain in the ***.

I don't know...but it does ****! I hate to see a 115 psi valve go back to lowes because it blows at 101 psi...but I didn't buy a 101psi valve! I ordered the 175psi to have a buffer

 

[WhoWhatNow]

Just ordered a 175 psi relief valve. I won't be running this past 125 on a habitual basis.

Check the plate on the tank. Make sure it is rated to at least 175psi. Some tanks are only rated to 155psi.

 

[luvmyglockfou]

It is rated to 175. I won't ever have it above 125

 

[Skin]

Check the plate on the tank. Make sure it is rated to at least 175psi. Some tanks are only rated to 155psi.

rated pressure is well below the failure point of the tank.