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Thread: New to service

  1. #14
    Join Date
    Nov 2011
    Location
    St. Louis
    Posts
    3,210
    Quote Originally Posted by phase24 View Post
    So for resi maintenance every year you guys hook up gauges?? I always believed why risk contamination or messing with the psi, if there is no problem. Take a temp split at the ahu and move on.
    No. Absolutely not. I only hook up if I see an issue, mainly a weak TD, customer complaint or something else that spooks me. We were just reminded yet again by an energy auditing guy with 40 something years in that hooking up without good reason is a bad practice; even if done with utmost care.

  2. #15
    Join Date
    Dec 2011
    Location
    Grass Lake, MI
    Posts
    251
    I'll be honest, I don't agree. Relying on Delta T as the only determining factor doesn't show the whole picture. It seems lazy to me. If you want to do the job correctly you need to know superheat and subcooling measured against the proper methods. Does a 20 degree Delta T really tell you anything if the outdoor temp is 40? You have no load on the system and no way of knowing if the system has a proper charge. The guy with 40 years seems to be taking a very old school approach. Like holding your hand on the suction line to check for beer can cold. If you are worried about contamination, purge you gauges with nitrogen. If you won't do it right, why are you doing it at all?

  3. #16
    Join Date
    Jan 2009
    Location
    IRELAND
    Posts
    42
    these house type units not really in use here ,do they not come factory charged ,most ac here comes charged with specific weight of charge to be added for extra lineset lenghts ,makes life easy

  4. #17
    Join Date
    Nov 2011
    Location
    St. Louis
    Posts
    3,210
    Quote Originally Posted by jpbhvac View Post
    I'll be honest, I don't agree. Relying on Delta T as the only determining factor doesn't show the whole picture. It seems lazy to me. If you want to do the job correctly you need to know superheat and subcooling measured against the proper methods. Does a 20 degree Delta T really tell you anything if the outdoor temp is 40? You have no load on the system and no way of knowing if the system has a proper charge. The guy with 40 years seems to be taking a very old school approach. Like holding your hand on the suction line to check for beer can cold. If you are worried about contamination, purge you gauges with nitrogen. If you won't do it right, why are you doing it at all?
    The guy with the 40 years is on the cutting edge and a psychrometric wiz.

    You have no genuine load on the system when it's cool, period.

    Regardless of how careful you are, or how often you purge your lines, you run the risk of contaminants and you will certainly take a bit of gas with you.

    If you want to do the job correctly you would calculate the actual capacity on a psychrometirc chart. And you would not like what you find, and the customer would certainly not like it either, especially as the chances are good your company installed it. Very few systems run anywhere near what they are rated at.

    I habitually grab the lines when I walk up to a system inside and out. They speak volumes, while not actually announcing the actual subcooling and superheat.

    I do it because my boss tells me to, and with the knowledge that if that small percentage of customers who had PMs in cool weather experience refrigerant issues later on in the season; we will take care of them.

  5. #18
    Join Date
    Nov 2009
    Location
    Kansas City
    Posts
    124
    I agree with you. No point in doing it unless you can do it right. The customer is paying for a service and which you cannot provide accurate readings unless the temp is above 55. Some say to use a trash bag or cardboard to block off outdoor coil to drive your pressures up. I'm glad my company will not make us do PM unless it is 55.

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