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  1. #1
    Join Date
    Mar 2005
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    Pneumatic issues

    I have a building with a pace hot deck/ cold deck system and a panooomatic control system. it'
    s a direct acting 2 pipe setup and I recently had a service call for a thermostat hissing when the stat is turned up. I calibrated the thermostat and then retested and noted that when the start is turned up and pressure is bleeding off it drops to about 2 psi and then continues to hiss. at first I incorrectly assumed I had a bad thermostat and replaced it only to fond exactly the same issue. I removed the branch line and found the air that was causing the hissing was coming from the branch line and was backfeeding through the thermostat causing the stat to hiss. I checked the actuator at the airhandler to see of I was getting the feedback from there but it doesn't appear to be the case.. there is no air line schematic and none of the lines are labeled. what am I missing here?? I have attached pics of the pneumatic controls
    Attached Images Attached Images     
    you will attract more flies with honey than with vinegar, but you can attract the most with a dead cat

  2. #2
    Join Date
    Feb 2008
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    It appears that (perhaps) the branch lines from the thermostats are fed into the (C-2220) Hi/Lo signal selector. As such it may defective and the source of the 'back feed".

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  4. #3
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    Feb 2008
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    Back in the day, (1980) the attached diagrams were widely used to control Multi-Zone systems.
    Attached Images Attached Images

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  6. #4
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    Thread Starter
    Thank you, this helps greatly
    you will attract more flies with honey than with vinegar, but you can attract the most with a dead cat

  7. #5
    Join Date
    Sep 2006
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    As in all systems isolate and verify each component. We use to utilize the blue rubber hosing so we could pinch the lines to verify problems. I will always start with my main air and verify that I do indeed have the correct main pressure. Then I would check each component separately to find the issues. I have seen the low high pressure selectors leak really bad. I guess what I'm saying there is no short cut to troubleshooting.
    Law Of The Thermostat: He who has the thermostat wins!!!!!

  8. #6
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    May 2014
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    Bay Area California
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    I should post a pic of my garage regulated 'air station' I built decades ago to better learn pneumatics. I could even dump a box of 'old' pneumatic controls on the floor that I used to use as training aids. LOL, I love pneumatics.
    A skilled Tech would solder a relay on that board and call it good to go.

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  10. #7
    Join Date
    Jan 2003
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    Quote Originally Posted by simux View Post
    As in all systems isolate and verify each component. We use to utilize the blue rubber hosing so we could pinch the lines to verify problems. I will always start with my main air and verify that I do indeed have the correct main pressure. Then I would check each component separately to find the issues. I have seen the low high pressure selectors leak really bad. I guess what I'm saying there is no short cut to troubleshooting.
    Can do the same with poly, just might need to replace a section if you get carried away. Just squeeze it with needle nose and with moderate pressure it will seal off fairly well. Can make quick work of finding something like this.
    Propagating the formula. http://www.noagendashow.com/

  11. #8
    Join Date
    Nov 2001
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    You could also have the main and branch air connections on the thermostat reversed. You would not be the first person to do this. It's also easy to connect to a spare damper motor, valve top of some kind of extra controlled device to see if the same bled happens. If not then it most likely is what ever the branch line is attached to. Try it on the next selector that you know is working to see if the problem goes away.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

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