# Check your pressure relief now!!



## B Mann (Feb 14, 2021)

I bought a used 60 gallon Sanborn compressor. I have been using it a couple years. I was having trouble with the pump. Posted below. It has some miles on it. I got it running, seemed fine. I turned it on earlier to work in the garage. Wife comes home a while ago and said is the compressor running in the garage??? I am thinking I did not want the compressor with the new gasket set running long because I wanted to retorque it. 

I step in the detached garage and check the running compressor. Pressure switch leaking air. I look at the tank gauge and it is pegged at 400+ PSI. OH CRAP.... Shut off doesn't work. I yank the cord. I go in the back garage and open a valve to release air. The place that had it before me took out the pressure relief and put in a gauge. I never noticed that. I thought the relief was under it. Diaphragm on pressure switch blew. It would not shut off motor.

*MAKE SURE YOU HAVE A PRESSURE RELIEF VALVE AND IT WORKS!!! *


----------



## iowagold (Jan 22, 2020)

most good compressor systems have at least 2 resetable spring loaded pressure relief valves...
and a fail safe one time disc valve is a great idea... but have extra disc's on hand.

a start box on any compressor is a great idea...
it will keep the current under control.
and for the ultimate fail safe good old fashion slow blow fuses.

tank inspection is a must...
if the tank is rusty... it can have pits on the inside to make it weak..
we always make a cage or enclosure like a room for the air compressor for noise as well as
protect persons from a bad tank just in case.

hard lines and bad fittings are also a thing that can become a pipe bomb or a projectile.

a lot of gloom and doom here..
but this is energy storage...
bad containment on energy makes for a bad day at best.

make sure to do annual inspections and PM's on tools, hoses , lines, fittings, valves, etc.


----------



## B Mann (Feb 14, 2021)

iowagold said:


> most good compressor systems have at least 2 resetable spring loaded pressure relief valves...
> and a fail safe one time disc valve is a great idea... but have extra disc's on hand.
> 
> hard lines and bad fittings are also a thing that can become a pipe bomb or a projectile.
> ...


Never heard or 2 spring loaded pressure reliefs. Always see one. 

Hard lines... Yes, especially PVC lines. They can shatter. 

Just like the electric cars. Storage of energy is great. But if a failure causes a quick release, bad things happen fast.


----------



## JohnNY (Apr 27, 2020)

B Mann said:


> I bought a used 60 gallon Sanborn compressor. I have been using it a couple years. I was having trouble with the pump. Posted below. It has some miles on it. I got it running, seemed fine. I turned it on earlier to work in the garage. Wife comes home a while ago and said is the compressor running in the garage??? I am thinking I did not want the compressor with the new gasket set running long because I wanted to retorque it.
> 
> I step in the detached garage and check the running compressor. Pressure switch leaking air. I look at the tank gauge and it is pegged at 400+ PSI. OH CRAP.... Shut off doesn't work. I yank the cord. I go in the back garage and open a valve to release air. The place that had it before me took out the pressure relief and put in a gauge. I never noticed that. I thought the relief was under it. Diaphragm on pressure switch blew. It would not shut off motor.
> 
> *MAKE SURE YOU HAVE A PRESSURE RELIEF VALVE AND IT WORKS!!! *


First off Thank God no one got hurt. 
Ive never seen a gauge that even read 400+ psi? But if that was truly an accurate psi im shocked that nothing else ruptured before even climbing that high? You have this compressor for 2 years, installed a new gasket set and didnt test run it? Why would the pressure switch all of the sudden fail just when you rebuilt the pump? 
The pressure relief is the one true safety measure to relieve excessive pressure in the tank, so you have 2 problems here so far, but at least easy fixes.
But if there was any good that you can take away from what could of been a horrific accident is that the tank is now pressure tested and you pump rebuild was a success. 

Edit: just read your other thread,


----------



## B Mann (Feb 14, 2021)

JohnNY said:


> First off Thank God no one got hurt.
> Ive never seen a gauge that even read 400+ psi? But if that was truly an accurate psi im shocked that nothing else ruptured before even climbing that high? You have this compressor for 2 years, installed a new gasket set and didnt test run it? Why would the pressure switch all of the sudden fail just when you rebuilt the pump?
> The pressure relief is the one true safety measure to relieve excessive pressure in the tank, so you have 2 problems here so far, but at least easy fixes.
> But if there was any good that you can take away from what could of been a horrific accident is that the tank is now pressure tested and you pump rebuild was a success.
> ...


I did test run it several times for a few days. Let it cycle while I was there quite a few times. 

Only thing I can come up with, was when I took the motor apart to see what let loose in it. The points in the starter winding switch were quite pitted. Maybe the switch was too?? Or maybe the diaphragm in the pressure switch blew out and the contacts would not open. One thing for sure, the switched is getting destroyed. No use anyone else getting a hold of it. 

I have seen gauges run higher... But this one was a 300 PSI and it was pegged all the way around.


----------



## JohnNY (Apr 27, 2020)

Maybe the motor brushes failing drew to many amps on the switch welding the contacts together? Take a look at it before you smash it, curious to know why it didnt shutoff.


----------



## stevon (Mar 5, 2019)

B Mann,

without a magnetic starter it is common for the pressure regulator contacts to weld shut and be stuck on. When compressor first starts the LRA is up to 10 times the listed Full load amps. So a motor that has FLA listed as 20 amps, is uses up to 200 amps to turn the motor rotor from 0 rpm up to the listed rpm of the motor. That's one of the reasons a pressure safety valve is needed. I'm glad no one was injured and you were able to figure this out or.......









Stephen



B Mann said:


> I bought a used 60 gallon Sanborn compressor. I have been using it a couple years. I was having trouble with the pump. Posted below. It has some miles on it. I got it running, seemed fine. I turned it on earlier to work in the garage. Wife comes home a while ago and said is the compressor running in the garage??? I am thinking I did not want the compressor with the new gasket set running long because I wanted to retorque it.
> 
> I step in the detached garage and check the running compressor. Pressure switch leaking air. I look at the tank gauge and it is pegged at 400+ PSI. OH CRAP.... Shut off doesn't work. I yank the cord. I go in the back garage and open a valve to release air. The place that had it before me took out the pressure relief and put in a gauge. I never noticed that. I thought the relief was under it. Diaphragm on pressure switch blew. It would not shut off motor.
> 
> *MAKE SURE YOU HAVE A PRESSURE RELIEF VALVE AND IT WORKS!!! *


----------



## B Mann (Feb 14, 2021)

JohnNY said:


> Maybe the motor brushes failing drew to many amps on the switch welding the contacts together? Take a look at it before you smash it, curious to know why it didnt shutoff.


No brushes... It is an induction motor 5HP. The switch had no resistance to shut off.... Thinking stuck contacts. 220 switch using lines, it would have to have both contacts stuck. After the pressure dropped under 100 PSI the switch felt normal... But power was off at that point.


----------



## JohnNY (Apr 27, 2020)

B Mann said:


> No brushes... It is an induction motor 5HP. The switch had no resistance to shut off.... Thinking stuck contacts. 220 switch using lines, it would have to have both contacts stuck. After the pressure dropped under 100 PSI the switch felt normal... But power was off at that point.


Im sorry, i meant the points in the starter winding you referenced.


----------



## stevon (Mar 5, 2019)

B Mann,

In modern electric motors the startup "clutch" only adds more capacitance to the circuit providing more initial torque. If the contacts there were stuck closed there, the motor would overheat and trip the thermal overload. OPs problem is related to the LRA current welding the pressure switch contacts closed in the on position. The contacts or entire pressure switch must be replaced and because this is a 5HP motor a magnetic starter (they are relatively cheap) it is highly recommended to prevent the destruction of the replacement pressure switch, at 200+ startup amps, welding easily occurs....









5 HP Single 1 Phase Magnetic Starter Motor Control 220-240 Volt 22-34 Amps | eBay


Find many great new & used options and get the best deals for 5 HP Single 1 Phase Magnetic Starter Motor Control 220-240 Volt 22-34 Amps at the best online prices at eBay! Free shipping for many products!



www.ebay.com













JohnNY said:


> Im sorry, i meant the points in the starter winding you referenced.


----------



## stevon (Mar 5, 2019)

B Mann, sorry my responce was to JohnNY and should have been replied to him

JohnNY said:
Im sorry, i meant the points in the starter winding you referenced.


----------



## iowagold (Jan 22, 2020)

magnetic start box is an requirement for a 5hp compressor in my area of the country by code.
i would run a proper magnetic starter on any air compressor that is 208-240vac single phase and 3 phase.
it is just smart to run one period.
that safety thing.

and depending on your system pressure always run a 25 psi over your run rating pop off valve set.
we run one at the compressor and the second after the tank.
so if your house pressure is 175 psi do the safety pop off at 200 psi.
the tank, pipes and hoses should be rated at a min rating of 300 psi working.

and run surge protection for the electric box...
lightning can make for a bad day welding breakers and start contacts.


----------



## JohnNY (Apr 27, 2020)

stevon said:


> B Mann, sorry my responce was to JohnNY and should have been replied to him
> 
> JohnNY said:
> Im sorry, i meant the points in the starter winding you referenced.


im sure those starting amps occur fairly quick? But if they can create enough heat to weld contacts closed, when that occurs are they in turn buffering the amp load from tripping the main breaker?
(Im not an electrician, or electrical engineer)

And the mag switch, is that a system that, when call for air it energizes a magnet pulling the high amp rated contacts closed making the switch?


----------



## stevon (Mar 5, 2019)

JohnNY,

Here is a good article describing LRA or "inrush current"









Understanding Motor Starting (Inrush) Currents, & NEC Article 430.52 – JADE Learning


Inrush current, also referred to as “locked rotor current,” is the excessive current flow experienced within a motor and its conductors during the first few moments following the energizing (switching on) of the motor. This current draw is sometimes referred to as “locked rotor current” because...



www.jadelearning.com





Stephen



JohnNY said:


> im sure those starting amps occur fairly quick? But if they can create enough heat to weld contacts closed, when that occurs are they in turn buffering the amp load from tripping the main breaker?
> (Im not an electrician, or electrical engineer)
> 
> And the mag switch, is that a system that, when call for air it energizes a magnet pulling the high amp rated contacts closed making the switch?


----------



## stevon (Mar 5, 2019)

JohnNY,

Here is another useful article about:

"All About Magnetic Motor Starters - What They Are and How They Work"









All About Magnetic Motor Starters - What They Are and How They Work


his article looks at magnetic motor starters and explains how they work, their applications, and some considerations for choosing a motor starter.




www.thomasnet.com




.

Stephen



stevon said:


> JohnNY,
> 
> Here is a good article describing LRA or "inrush current"
> 
> ...


----------



## JohnNY (Apr 27, 2020)

stevon said:


> JohnNY,
> 
> Here is another useful article about:
> 
> ...


Thanks Stephon,

So below is a picture of my motor. I now see how it states the L.R amps are 93 when the motor is rated at 15. 
Now this is a smaller motor then the OPs and it has Starter Capacitors on it, so dont they provide the LR or assist in buffering it to the switch? Why wouldnt a larger motor have start Caps? Or do they and if not, can you add them?


----------



## stevon (Mar 5, 2019)

JohnNY,

The start and run capacitors do help marginally but when an electric motor is turned on under load at 0 degrees rotation, it's like a crow bar across the mains for the first 0-90 degrees of motor rotation (usually for miliseconds). This causes extreme load on the pressure switch contacts that will eventually destroy any contacts with time. I see you have a Furnas brand pressure switch which is a lower cost one. I would recommend the Square D version that is rated for a 3 HP electric motor. 3 HP is what your motor actually produces according to the chart below under Single Phase 220 Volt, never mind the _*marketed*_ "5HP special" or even more HP advertised on some model compressors...









Square D 9013FHG32J39M1X Pumptrol Pressure Switch,40 to 150 psi,1/4" FNPS | Zoro.com


Order Square D Pressure Switch, (1) Port, 1/4 in FNPS, DPST, 40 to 150 psi, Standard Action, 9013FHG32J39M1X at Zoro.com. Great prices & free shipping on orders over $50 when you sign in or sign up for an account.




www.zoro.com





Stephen


----------



## stevon (Mar 5, 2019)

JohnNY,

15 amps at 220 to 240 volts in an efficient modern electric motor equates to 3HP actual shaft output of the motor. The 17 amps is listed for older less efficient motors. The old motor designs didn't care so much about efficiency when energy was cheap and there were few environmental laws.

Stephen 



stevon said:


> JohnNY,
> 
> The start and run capacitors do help marginally but when an electric motor is turned on under load at 0 degrees rotation, it's like a crow bar across the mains for the first 0-90 degrees of motor rotation (usually for miliseconds). This causes extreme load on the pressure switch contacts that will eventually destroy any contacts with time. I see you have a Furnas brand pressure switch which is a lower cost one. I would recommend the Square D version that is rated for a 3 HP electric motor. 3 HP is what your motor actually produces according to the chart below under Single Phase 220 Volt, never mind the _*marketed*_ "5HP special" or even more HP advertised on some model compressors...
> 
> ...


----------



## JohnNY (Apr 27, 2020)

stevon said:


> JohnNY,
> 
> The start and run capacitors do help marginally but when an electric motor is turned on under load at 0 degrees rotation, it's like a crow bar across the mains for the first 0-90 degrees of motor rotation (usually for miliseconds). This causes extreme load on the pressure switch contacts that will eventually destroy any contacts with time. I see you have a Furnas brand pressure switch which is a lower cost one. I would recommend the Square D version that is rated for a 3 HP electric motor. 3 HP is what your motor actually produces according to the chart below under Single Phase 220 Volt, never mind the _*marketed*_ "5HP special" or even more HP advertised on some model compressors...
> 
> ...


@stevon ,Thats why I love this site, the amount of information and learning and helping each other is priceless. (Hope that didn't sound corny). But in all seriousness with the OP's origonal post, sharing his experience, it could prevent some catastrophic occurrence to someone else. Thank you for recognizing the cheap pressure switch and that link to the square D. Im gonna look into that and order one.


----------



## stevon (Mar 5, 2019)

JohnNY, 

Thanks for the kudos, the square D pressure switch is a better quality brand but it's contacts will weld too, eventually. The fact that they advertise a HP rating up to 3 HP indicates that they are confident in their design and that it will work for many years without problems, I think you can order parts for the switch too.

Stephen


----------



## JohnNY (Apr 27, 2020)

stevon said:


> JohnNY,
> 
> Thanks for the kudos, the square D pressure switch is a better quality brand but it's contacts will weld too, eventually. The fact that they advertise a HP rating up to 3 HP indicates that they are confident in their design and that it will work for many years without problems, I think you can order parts for the switch too.
> 
> Stephen


I also have this switch that I happened to grab at at Tractor supply clearance shelf a while back. This one any better or just as cheap? 
Edit: after a guick google seach seams like a cheapo?
Lefco LF19-4H


----------



## stevon (Mar 5, 2019)

JohnNY, 

You could get by with this for a while and with a working tested safety release valve you will be OK, and I might use it. But this is a Chinese switch and I don't trust their rated LRA listed on the side of it, what I want to see is the published max *HP* rating of this switch, which isn't listed anywhere I searched on the internet. My experience is that the Chinese tend to exaggerate specs on almost everything they market and sell. If I had it for free, and new, I would install a new safety release valve (USA version preferred) and use this switch and be done with my repair on a 3 HP or less compressor. I would *not use* this with any motor that draws more than 15 amps @ 220-240 volts. This looks like its a cheap, mass marketed 1.5 HP compressor use design

Stephen


----------



## stevon (Mar 5, 2019)

JohnNY, 

This switch is set for a water pump. I don't know if it has the spring and/or settable range to use in a compressor application.

Stephen


----------



## stevon (Mar 5, 2019)

My bad, yes you can use it


----------



## JohnNY (Apr 27, 2020)

stevon said:


> My bad, yes you can use it


LOL np. I appreciate all your help. I went into the gargae and opened the one that is on there and cycled it ilon and off and boy did it soark at the contacts. Reminded me of the old trains I used to play with. The contact terninals are very small and have some build up on them like the points had in my old camaro. I cleaned them up for now. Will order the new switch and release valve for good measure.


----------



## B Mann (Feb 14, 2021)

I appreciate all the info... I may not be posting, but reading along.


----------

