Air compressor learning experience redux
 

I mentioned in a thread couple-three weeks ago "Learning Experience"
that a compressor kept running owing to relief valve failure that I'd
had the one here not cut off at pressure...

So, finally got new pressure switch and it acts same way...anybody think
of a reason the switch doesn't drop out at cutout pressure?

This is brand new switch as I just figured the old one had konked and
the contacts didn't look great and had 30+ yr service so hadn't done any
real looking at the switch itself.

The inlet pipe is not plugged, the air pressure drops and it will kick
in in synch with the gauge but just keeps on climbing past 125 cutout
when running...

Got me baffled...

--

Air compressor learning experience redux
 

On Fri, 1 May 2020 19:09:30 -0500, dpb wrote:

I mentioned in a thread couple-three weeks ago "Learning Experience"
that a compressor kept running owing to relief valve failure that I'd
had the one here not cut off at pressure...

So, finally got new pressure switch and it acts same way...anybody think
of a reason the switch doesn't drop out at cutout pressure?

This is brand new switch as I just figured the old one had konked and
the contacts didn't look great and had 30+ yr service so hadn't done any
real looking at the switch itself.

The inlet pipe is not plugged, the air pressure drops and it will kick
in in synch with the gauge but just keeps on climbing past 125 cutout
when running...

Got me baffled...
Mabee it's set to 126 - or 150 -
Try resetting the pressure (or check your gauge - it may be reading
low)

Air compressor learning experience redux
 

On 5/1/2020 8:24 PM, Clare Snyder wrote:
On Fri, 1 May 2020 19:09:30 -0500, dpb wrote:

I mentioned in a thread couple-three weeks ago "Learning Experience"
that a compressor kept running owing to relief valve failure that I'd
had the one here not cut off at pressure...

So, finally got new pressure switch and it acts same way...anybody think
of a reason the switch doesn't drop out at cutout pressure?

This is brand new switch as I just figured the old one had konked and
the contacts didn't look great and had 30+ yr service so hadn't done any
real looking at the switch itself.

The inlet pipe is not plugged, the air pressure drops and it will kick
in in synch with the gauge but just keeps on climbing past 125 cutout
when running...

Got me baffled...
Mabee it's set to 126 - or 150 -
Try resetting the pressure (or check your gauge - it may be reading
low)

Actually, if it is the gauge it's reading high when supposed to cut off
and dead on at cut in...switch says is 95-125 and it's well past 130 and
still running when on but will cut back on when drop pressure to
indicated 95 (within a couple w/ resolution of gauge).

But, the baffling isn't quite so baffling -- after supper went back out
and adjusted the cutoff back a little--and it now cuts out where should...

Will have to get another gauge to check whether the present gauge is
really off or not altho didn't take much adjustment so I'm guessing it's
pretty close and the switch just has a little more than nominal
hysteresis between close and open points. This one is a little
different than others I've seen -- has a screw supposed to only change
cutout and the normal one that changes both. I'd not seen the former
before...then again, first one I've had to swap out in almost 30
years...they generally last the life of a tank or compressor in my
experience.

--

Air compressor learning experience redux
 

On Sat, 2 May 2020 00:03:12 -0500, dpb wrote:

On 5/1/2020 8:24 PM, Clare Snyder wrote:
On Fri, 1 May 2020 19:09:30 -0500, dpb wrote:

I mentioned in a thread couple-three weeks ago "Learning Experience"
that a compressor kept running owing to relief valve failure that I'd
had the one here not cut off at pressure...

So, finally got new pressure switch and it acts same way...anybody think
of a reason the switch doesn't drop out at cutout pressure?

This is brand new switch as I just figured the old one had konked and
the contacts didn't look great and had 30+ yr service so hadn't done any
real looking at the switch itself.

The inlet pipe is not plugged, the air pressure drops and it will kick
in in synch with the gauge but just keeps on climbing past 125 cutout
when running...

Got me baffled...
Mabee it's set to 126 - or 150 -
Try resetting the pressure (or check your gauge - it may be reading
low)

Actually, if it is the gauge it's reading high when supposed to cut off
and dead on at cut in...switch says is 95-125 and it's well past 130 and
still running when on but will cut back on when drop pressure to
indicated 95 (within a couple w/ resolution of gauge).

But, the baffling isn't quite so baffling -- after supper went back out
and adjusted the cutoff back a little--and it now cuts out where should...

Will have to get another gauge to check whether the present gauge is
really off or not altho didn't take much adjustment so I'm guessing it's
pretty close and the switch just has a little more than nominal
hysteresis between close and open points. This one is a little
different than others I've seen -- has a screw supposed to only change
cutout and the normal one that changes both. I'd not seen the former
before...then again, first one I've had to swap out in almost 30
years...they generally last the life of a tank or compressor in my
experience.
Every one I've had to work with since about 1969 had dual adjustment
- one screw for low pressure cut-in and one for high pressure
shut-down. Set wrong you can have a compressor that sounds something
like a machine gun------ At the shop we usually had them set at 95-150
so they weren't cutting in and out so often - and at 150 an old CP734
impact had some SERIOUS power.