Re: Calibrate Pressure Switch?
 

I do this too for the Nason SM model but apparently the SM model is not marketed as field adjustable. Only the CJ model is marketed as field adjustable.
http://www.nasonptc.com/pdfs/Switches_Catalog.pdf

I could not find a source indicating the SM model is ok for field adjustments. As far as I can tell, the manufacture never intended for the SM model to be adjusted by the user.

So would this be an illegal modification to a pneumatic component? Luckily I have a pair of factory set SM models as replacements.

Re: Calibrate Pressure Switch?
 

You may not modify pneumatic parts.

Re: Calibrate Pressure Switch?
 

Is calibrating really modifying?

As you are well aware the inspection checklist explicitly requires this switch to be checked that it shuts off the compressor at the appropriate pressure. I see no harm in allowing teams to adjust these rather than forcing them to purchase new ones when a small adjustment will fix the issue. It seems wasteful.

Re: Calibrate Pressure Switch?
 

I think that depends on the switch. As pointed out before, the old Nason pressure switch is not meant to be user set.

Re: Calibrate Pressure Switch?
 

The gap in my spark plugs isn't meant to be user set either. They are a certified technician only job. But I adjust them every time I install new plugs and my car keeps running.

If you are saying I can't adjust a set screw that is designed to be turned with a screw driver because it is modifying a pneumatic component, then we all have to stop using NPT fittings because they deform when threaded together. And push to connect fittings as well because the o-ring and barbs change shape every time a piece of hose passes through them.

Re: Calibrate Pressure Switch?
 

No, you're putting words in my mouth. I was only referring to the Nason pressure switch that had been previously provided in the KOP. This switch was not designed to have the set screw to be adjusted which is why the setscrew was sealed with silicone. Additionally it is ordered with a specific set pressure at which it opens so adjusting the set screw is definitely a illegal modification.

Re: Calibrate Pressure Switch?
 

You could just order a CJ-2C3-70J/HM directly from Nason and be done with it. No problem about modification because it is adjustable.

Re: Calibrate Pressure Switch?
 

Not putting words in your mouth, I said if...

Also, if the manufacturer didn't want it adjusted, they would manufacture it in such a way that it couldn't be adjusted. I would venture to say the set screw is sealed with silicone to prevent it from loosening under vibration commonly associated with compressors, not to keep me from adjusting it. That being said, we never have and probably never will adjust ours. 112-115 psi has worked for two years so far. I think the 114 we have right now will do just fine.

Re: Calibrate Pressure Switch?
 

The product catalog seems to disagree with that assertion as it seems to have purposely left out the set screw in the drawing for the SM switch but not the CJ/CM model. It also includes a adjustment knob and instructions.

Re: Calibrate Pressure Switch?
 

I emailed Nason and got a straight answer on the SM calibration switch. It can be adjusted but only a couple PSI. Unlike the CJ the SM only as 0.030" of contact with the switch so there is a risk of of over turning causing the sensor to always stay on or completely turn off. They said this roughly translate one turn of the sensor relative to the brass hex.

I did not want to copy their email without their permission, but if you PM me I can forward it to you.


Lastly, I already made preparations for my un-adjusted SM sensor. I don't really want go back to the adjusted one which has a unknown number of turns. It could be right at the edge where the sensor does not work and I want to avoid having that potential risk.

So far the level of adjustment that teams are suggesting they need, they are way outside the +/-2PSI of adjustment Nason is recommending. While i think adjusting this sensor is legal, for me personally, +/-2 PSI is too much work for me to care for. The risk of disabling your sensor by going beyond 1 turn of rotation, I would not recommend the adjustment to any team. it would be far simpler to order a SJ sensor, and not worry about that risk.

thoughts?

Re: Calibrate Pressure Switch?
 

To quote Big Al "You may not modify pneumatic parts."

Re: Calibrate Pressure Switch?
 

If you seal your pneumatic system and calibrate your pressure release valve correctly then you can always jump your pressure switch to 120 psi before the match starts. Yes, you would not get 120 the whole match but you would get an extra 20 psi in storage at the start.

Re: Calibrate Pressure Switch?
 

Is it modification if it is a manufacture allowed change? According to Mark, the email from the manufacture states it can be calibrated, while it is only a slight change.

Re: Calibrate Pressure Switch?
 

Ask the question from FIRST in the Q&A and see what they say.

Re: Calibrate Pressure Switch?
 

Mark showed me the response from Nasson and it appears to be more of a calibration of the switch actuator than actual pressure calibration. If you move to far in one direction the switch will turn off and too far in the other direction and it will never turn on. The effect is the pressure on the actuator caused by the spring in the switch I am guessing. The manufacturer states that this is only 2 psi. If you want your switch to operate reliably, I would not recommend any adjustment in addition to my previous statements.
Thanks to Mark for this in depth research.