Replacing Air Compressor Pressure Switch - New Switch has Different Turn on/Turn off pressures

[inline6]

My trusty compressor developed a problem with its pressure switch.  The contact started sticking and the compressor kept running even when the tank pressure exceeded the cut off pressure.  I've had it for about 27 years, and used it a fair amount given I am just a hobbyist.  I am too lazy to get a picture of it, but it is this same model - though I think it was branded under Campbell Hausfeld:

 

So the switch - I went online looking for replacements.  The original switch had the model "DAC-278-1"  with number 140 and 175 which apparently indicate the turn off psi and turn off psi.  Since I bought it new... for 27 years, it turned on around 120 psi and turned off at 155 psi.  Tonight, the $18.95 replacement arrived and I installed it.  Here is the one I bought:

https://www.amazon.com/dp/B00273R6KU?psc=1&ref=ppx_pop_dt_b_product_details

Interestingly, this switch kicks the compressor motor on at about 145 psi and turns it off at about 175 psi.  And this one, has screws to allow adjustment to the turn on and turn off points.  

My question is this, is it harder on the compressor to utilize 145/175 instead of 120/155?  It seems logical that to get to 175, it has to run longer than to get to 155.  But, if it kicks in at a higher pressure also, maybe it ends up running the same amount of time when air is not being used?  And then, there is reality - I consume air while it is running quite often, like for sand blasting or glass bead blasting.  And pretty much all of my tools are limited to 90 psi...  So, is it wasteful or unnecessary to run 145/175?

For what its worth, my lines are cast iron pipe and the water separator and regulator are rated for 200 psi max, the hose is rated sufficiently high enough, etc.   

Edited April 6, 2023 by inline6

[dutchzcarguy]

9 hours ago, inline6 said:

is it harder on the compressor to utilize 145/175 instead of 120/155?

Offcourse it's harder to go to a higher pressure and it's unneccessary.. in europe these compressors go max 8 ato/bar some rarely go to 10 ato/bar  ( 120psi/150psi)  

It's better to use bigger diameter pipes/hoses as there is more liters/min. going to your tools.  Going over 8 ato. is always a pain for any compressor.. Always means more waer and maintenance on internal parts.

For as far i worked on compressors, they have always adjustable pressure switches.

(offcourse sandblasting is a job for very powerfull compressors. exeding 10+ Hp easely.. you need 500 ltr/min and more.  You can do this with smaller compressors but it will take a lot of time.)

Edited April 6, 2023 by dutchzcarguy

[dutchzcarguy]

9 hours ago, inline6 said:

the compressor kept running even when the tank pressure exceeded the cut off pressure.

And i sure hope there is a Pres.Max sensor/outlet (of 150psi/10bar or so) on the tank.. as a explosion is not something you want in your workarea!

What's the limit of your tank?

[Patcon]

I wouldn't run the higher set points. My first concern is the integrity of the tank. My tank gets drained but not like it should. A ruptured tank is a bomb that you don't want to be around. Also I would expect the higher pressures are harder to achieve. I suspect the compressor efficiency is not a linear function

[dutchzcarguy]

7 hours ago, Patcon said:

I suspect the compressor efficiency is not a linear function

I'm sure it is not.. That also why there are stage-compressors. It says so on your tank (inline6) but i don't recognize it as such.. staged compressors have cylinders in cascade on your compressor i see only 1 cylinder?  Often stage compr. have 3 cylinders were 2 feed 1 to go to extra high pressure.. It also needs cooling as those high pressures get you a lot of heat you don't want (expansion) .

Are you sure the compressor is as old as the tank because the tank says stage but i see a 1 cylinder.. or is it a 2 parallel pistons? But anyway, i would not go over 8 bar as it saves you the cylinder(s) and piston(s).

Edited April 7, 2023 by dutchzcarguy

[inline6]

Thanks for the info guys.  I will take a picture of my compressor today and put it here - that pic above was the same model, but a picture I found online. 
It/mine is a two cylinder compressor.  I bought the compressor when it was new.  The switch I replaced was the original one.  I don't think it was adjustable, so I found it odd that both had 140/175 specs, but that the original worked at 120/155.  Good point about adding more heat.  Yeah, agree, it doesn't look like any benefit to keeping the higher points.  I will adjust them both down today.

Edited April 8, 2023 by inline6

[dutchzcarguy]

And.. you can always temporarely set the max pressure higher for the occasional sandblasting.. IF all your equipment can stand the pressure ofcourse!  But best is to make FATTER lines tubes and pipes!  More air is best. (And a tip to others that look for a compressor, get yourself a small tank and big diameter pipes (They can even be made with PVC high pressure piping and glued together these days.)  The pipes deliver a lot of air and are also the tank!)

[inline6]

Pictures of my compressor:

    55

 

I was able to adjust the new switch to kick in around 120 and turn of at about 155, just as before.  

[dutchzcarguy]

Nice big compressor!  Psi i do understand as it is pounds per square inch.. something like we have kg/cm2. But what is: lb-po2 ????  I googled it but i get some explanation about oxigen in blood? 

So what does lb-po2 mean? anyone?  

Another question would be, how can a compressor say it's a 2 stage, when it has only .. appears to have only 1 cylinder?  

 

 

Most 2 stage compressors have more cylinders yours could have 2 cylinders parallel i don't know.. here a example of a 2 stage compressor. 2 cyl. pump into a third and make some high compressed air..

 

The top and right cylinder pump into the left cylinder. Also.. to cool the compressed air the lines are ribbed to cool.

[inline6]

Good questions.  I see the label has "deux temps".  I think that is French.  A Google search seems to indicate the french use lb-po^2.  It is equivalent to psi.

My compressor pump is an "inline 2", with the cylinders side by side. One is smaller than the other.  The larger one is the low pressure part of the pump, and the smaller one is the high pressure part.  Looking at the paperwork I have for it, I see I bought it on 11/01/1997 for $709.77.  🙂  I bought my glass bead cabinet at the same time - just after I bought my first garage (with a house attached hahaha).  It was my first expensive tool purchase.  I was 28... 

It will be a sad day when/if this compressor wears out.  But we are both getting old!

Edited April 8, 2023 by inline6

[dutchzcarguy]

18 hours ago, inline6 said:

the french use lb-po^2.

I think that's the french word for Psi. They USE..  kg/cm2 ..  Maybe it's standing there for the canadians that speak french?  France  is europe.. and europe is Metric 🙂 

I believe in Metric pressure is in kilo-pascal ..  I'm prefering (as many) Bar or Ato or kg/cm2 (also kgf/cm2 .. f stands for force.)

Google says/comes with:

The bar is a metric unit of pressure, but not part of the International System of Units (SI). It is defined as exactly equal to 100,000 Pa (100 kPa), or slightly less than the current average atmospheric pressure on Earth at sea level (approximately 1.013 bar). By the barometric formula, 1 bar is roughly the atmospheric pressure on Earth at an altitude of 111 metres at 15 °C.

 

19 hours ago, inline6 said:

the cylinders side by side.

YEAH!  I thought i see 1 cylinder but there are 2 cylinders in the " cylindrical" shape..  the first big cyl. feeding the second smaller one.. good system! 

19 hours ago, inline6 said:

It will be a sad day when/if this compressor wears out.  But we are both getting old!

Yes.. After some calc.. hihi so your also a 60's born? i'm from '61 you are stil young from '69 haha..  My compressor is also from the later '90's but a much smaller on of just 2 horsepowersss.. 😉  Enough for some airtools.

[Racer X]

On 4/7/2023 at 8:00 PM, inline6 said:

Pictures of my compressor:

    55

 

I was able to adjust the new switch to kick in around 120 and turn of at about 155, just as before.  

So in 27 years, have you ever changed the oil in the compressor?