Reverse & Direct Acting Pressure Switches

[Justinw]

I'm told that Low gas pressure switches are Reverse Acting in that they open if Gas pressure falls below the setpoint of the appliance pressure regulator and that High gas pressure switches are Direct Acting in that they open when gas pressure exceeds the outlet pressure of the appliance pressure regulator.

My question is how does one define Reverse and Direct acting as they pertain to the above explanation?

Many thanks for any help on this.

Justin

[Cagey57]

Using old Pneumatics lingo they would be defined as MOPR (make on presure rise) or MOPF/MOPD (make on pressure fall/drop).

Another reference would be Open Low (Make on Rise), the switch opens on Low Pressure and Open High (Make on Fall) , switch opens on High presure.

Now that you mention it I can't recall them being refered to Direct or Reverse Acting before you ask the question.

You might post in the Boiler/Hydronic forum for additional responses.

Very good question though.