View Full Version : Pneumatics
02-11-2007, 01:47 PM
My Journeyman, who has been in the business for 40 years is about to retire and there are maybe a select other few at our company that are good on pneumatics, but also close to retiring + i never work with them, my journeyman has shown me as much as he could at the buildings that have pneumatics.
Is there a website or literature on the operation of all the different parts of pneumatics. I know the basics, but that isnt going to get me anywhere when i have to troubleshoot some of the more advanced systems i have seen around.
02-11-2007, 02:49 PM
Some tech/mech's will have a book with the manufacturer's control documentation. I would get a copy of these Journeyman's books. The Honeywell Grey Manual is also a good reference. (Posted somewhere in this site) Then I would get a calculator and learn how to do the pneumatic control formulas. Here's some basic control terms from the day!
Pneumatic Control Terms
Controller A device that receives an input from a sensor and outputs the appropriate signal.
Controlled Variable The substance that your trying to maintain, temperature, humidity, air flow etc
Controlled Device Normally an actuator which operates a valve or damper. Could be an input to another controller.
Throttling Range The total change of the controlled variable required to move the controlled device fully.
Sensor (Transmitter) A device that measures the controlled medium, air , water, humidity, etc
and sends it's pressure signal to the controller. Majority work on 3 to 15 psi standard or 12 psi change.
Range The actual parameters of a sensor or transmitter, 0 to 100 F,
0.5 to 1.5 Wc, 5% to 95% RH.
Span The difference between the low and high ranges of the sensor
Sensitivity Change in pressure per unit change. Example 0 to 100 sensor, 12divided by 100 = .12 Psi change per degree
Thermostat Built in sensor combined with controller.
Single Input Controller A controller with one remote sensor or transmitter.
Dual Input Controller A controller with two remote sensors or transmitters.
Proportional Band The percentage of the sensor span used to generate a change in the output equal to the controllers P-Man. Example 10% setting on a Honeywell controller means 10% of 12 Psi = 1.2 psi change input to change the output by 10 psi. Powers or Siemens would be 1.2 psi input change to change the output by 5 psi.
Gain Johnson Control term to equate the comparison of a 1 PSI input change to output relationship. Example a Gain of 8.33 means that a 1 psi input change would change the output by 8.33 psi.
P-Man Pressure of the manufacturer, Powers 5 PSI, Honeywell 10 PSI, Robertshaw 13 PSI.
Authority The amount of control the reset controller has on a dual input controller expressed in percentage.
Ratio Johnson Control term to express the control the reset loop has on the primary loop in percentage.
02-11-2007, 05:18 PM
now that your controls guys are retiring maybe nows the time to retire your bldg.'s controls and upgrade to ddc only makes sense with todays energy costs if you can't sell an upgrade at least go for the central plant portion
vav's and stats can come later.
02-12-2007, 06:02 AM
Take a look at 'HVAC Control Systems' www.go2atp.com. It has 8 chapters of hands on pneumatics.
02-14-2007, 03:58 PM
Most of the controls manufacturers give classes on their controls. You might get your company to spring for sending you to class. I took mine at Honeywell and Powers (Siemens). They usually consist of three or four days of class and lab time and normally have classes for both basics and advanced levels. Fortunately pneumatic controls is one of those things where if you know one manufacturer you can figure out the others.
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