mycom unloaders - not loading
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  1. #1

    mycom unloaders - not loading

    Hi, new to the forum. We are running 3 mycom compressors with an ammonia chiller - critical charge system. suction pressure is okay, but only one compressor is running full load. the other two are unloaded down to about 25%. The solenoid switch seems to click on the loader arm but compressor doesn't load. Working here in an ice rink and our brine temp is holding , but barely. Any ideas?

  2. #2
    Join Date
    Dec 2010
    Location
    Savannah Ga.
    Posts
    36
    The Mycoms I am familiar with on Vogt ice machines use oil pressure to back the unloaders off. When the compressor is off, the unloaders have a spring that keeps them in the unloaded position holding the suction valve open. When you start the compressor, oil pressure opposes the spring pressure forcing the mechanism into the loaded position. The solenoid valves for the unloaders energize to force the compressor to unload by dumping the oil back into the crankcase before it reaches the unloder mechanism. (the solenoid when energized simply provides another path for the oil to go so it can't build pressure at the unloaders) Vogt ice machines must unload 2 of the 3 banks of cylinders to allow the suction to rise high enough to harvest the ice.... The system you have could possibly be set up differently than what I am familiar with.

  3. #3

    Be safe

    If these compressors are new or have been recently rebuilt it is possible that you have a problem with the unloader/loader system. like a push rod put in backwards or missing lift pin, etc. Go to Mycom's web site and you can download a manual for free.
    Please, unless you are totally familiar with how to safely depressurize and handle ammonia, DO NOT try to do it yourself. I used to be a shift supervisor in an ammonia production plant and a truck driver got soaked in ammonia. From what I heard, he doesn't have a sex life because his goodies were burnt off before they got him to an emergency shower. Imagine feeling your skin burning off and your eyeballs turning to goo and you can't scream because your lungs are filling with your blood plus any other liquids that your body can produce.
    I deliberately painted a gruesome picture because it is 100% true and I wouldn't want anybody to go through it. Please, please be safe.

  4. #4
    Join Date
    Nov 2012
    Posts
    13
    The Mycoms I am familiar with on Vogt ice machines use oil pressure to back the unloaders off. When the compressor is off, the unloaders have a spring that keeps them in the unloaded position holding the suction valve open. When you start the compressor, oil pressure opposes the spring pressure forcing the mechanism into the loaded position. The solenoid valves for the unloaders energize to force the compressor to unload by dumping the oil back into the crankcase before it reaches the unloder mechanism. (the solenoid when energized simply provides another path for the oil to go so it can't build pressure at the unloaders) Vogt ice machines must unload 2 of the 3 banks of cylinders to allow the suction to rise high enough to harvest the ice.... The system you have could possibly be set up differently than what I am familiar with.
    As well as this check your oil pressure guages the pressure may be still high enough not to trip the compressor but not high enough to overcome the unloader spring, also check the solenoid internals and external pipes for blockages.
    If this doesn't fix the problem it's time to get dirty and rip the heads off and investigate the unloader mechanisms.

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