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  1. #1
    Join Date
    Jul 2004
    Posts
    8
    wuts up guys... i have a question that no one at my trade school seems to have the time to answer, but ok i know that when i charge an air conditioning unit that its best to cover the condensing unit to simulate a 95 degree day plus 30 because thats when the system will be at its highest head pressure,but what i want to know is that should the same be done for commercial refrigeration??? say walk in coolers in restaurants and reach ins?? ive seen reach ins that have the condenser coil right there in the kitchen above the unit and ive seen walk ins with the condenser coil on the roof. it just doesnt make sense to me to simulate a a 95 degree day on a condenser thats right there in the kitchen because i doubt itll get to 95 degrees indoors, but it does make sense to me to do that for walk ins that have condensers on the roof becuase it can get that hot outside... any info would be appreciated...thanx

  2. #2
    Join Date
    May 2004
    Posts
    11,967
    ,but what i want to know is that should the same be done for commercial refrigeration???
    Absolutely not!

    Only in a very cold climate and only when there is no other way to bring up the head should you block the condenser and this should be only a temporary solution to solve a problem and find a fix.

  3. #3
    Join Date
    Jun 2004
    Posts
    160
    Originally posted by chillout
    when i charge an air conditioning unit its best to cover the condensing unit to simulate a 95 degree day plus 30
    I never cover the condensor when charging a r-22 air conditioning system,

    I do add 30, 25 or 20 degrees based on the seer rating of the unit to my outside air temperature

    to get me in the ballpark for a high side charging temperature

    then I go to subcool or superheat to finish charging.

    I have read threads on this site that suggested blocking the condensor on a refrigeration system when charging to prevent floodback.

  4. #4
    Join Date
    Jul 2004
    Posts
    8
    thnx fellas

  5. #5
    Join Date
    Nov 2001
    Location
    California
    Posts
    559
    Originally posted by chillout
    ... i have a question that no one at my trade school seems to have the time to answer, but ok i know that when i charge an air conditioning unit that its best to cover the condensing unit to simulate a 95 degree day plus 30 because thats when the system will be at its highest head pressure... any info would be appreciated...thanx
    OK, don't get me wrong here, I'm not really being a smart aleck; however, I just want to say, seriously, I'm really sorry to hear that you're learning in a trade school to charge a condensing unit this way.

    If you doubt what I say, phone up any equipment manufacturer you choose, ask for tech support, and hear it from them. Most of them have a toll free number. I think it'll be worth your time.

    Hopefully you'll learn enough in tech school about other topics to get you by, but please don't think you're learning the correct way to charge a system if that's what your instructor is teaching. It used to be a rule of thumb to charge that way...maybe a couple of decades ago. Actually, it's been longer than that.

  6. #6
    Join Date
    May 2000
    Location
    Monmouth Junction-NJ-USA
    Posts
    5,996
    [QUOTE]Originally posted by Learner
    Originally posted by chillout
    . It used to be a rule of thumb to charge that way...maybe a couple of decades ago. Actually, it's been longer than that.
    Im from a few decades ago and it really was not a rule of thumb then either. I did however in late fall, winter, and early spring (working on tract houses start ups) when necessary only, block off condensers on systems and get in the ball park. Butttttt u have to make sure there is a load on the evap or it is pretty useless. Did this cause the first hot day start ups usually brought 500 calls or more and this lightened the load considerably. Worked mayb 85% effective, but the systems were so oversized then how could we tell. Would not think of attempting it today.
    If you really know how it works, you have an execellent chance of fixin' er up!

    Tomorrow is promised to no one...

  7. #7
    Join Date
    Jul 2004
    Posts
    8
    yea its pretty much officlial that the instructors at my school suck. other guys are starting to complain because the instructors just send us to the shop and let us mess with the systems while theyre out handling personal matters... and if we ask them a question about a unit they respond to us with a question. gets pretty frustrating

  8. #8
    Join Date
    May 2004
    Posts
    11,967
    Sorry dude,

    Don't kick them all, they too had to learn this business and pay their dues. Some are just better than others so you may just try to take things with a grain-of-salt.

    One of the best ways to learn is being asked questions before you get answers. If you look at this site and read several of the post you will see this;

    • Post gives a short situation
      Post asks a question for help
      Reply asks for more detailed information
      Post gives more information that brings up more questions
      Reply gives answers and asks more questions
      More reply with more questions and more possibilities.
      Post investigates and finds his repair


    You might say it is the way things are. I can't vouch for leaving school to take care of personal business but you paid for your schooling so hang in there. Transfer but don’t quit, we need more young men in this business.

  9. #9
    Lerner, you sound like your walking on egg shells. Whats up?

    You need to spend some time with James and let your hair down.

    I dont mean to go insulting people, needlessly.

    Just look at how Dice insults me. It's not meant to get my goat.... oops .... sorry Dice ..... didnt mean it THAT way!
    He just pokes fun at me and me right back at him.


    If your as old and your experience makes you.... then you should feel free to let your hair down a little bit.


    Chillout .... what school do you attend? Do they need someone qualified to teach over there?

  10. #10
    Join Date
    Jul 2004
    Posts
    8
    Originally posted by R12rules

    Chillout .... what school do you attend? Do they need someone qualified to teach over there?
    i go to IBT in Santa Clara , Ca. ... i mean i guess the guys teaching there are qualified cuz they got all these certifications to back them up but i dunno.... just doesnt seem like they wanna teach....almost like the hate their jobs and dont wanna be there.

  11. #11
    Forget the certs! A cert dont mean jack in my book!

    Show me the scars! A guy who has been in this industry for a long time has some war wounds from the field.

    Show me the scars. And THEN I'll listen to their stories about what they have done and where they have been.


    A guy who has been thru several business startups will know things about business that an MBA would not even know. Not unless they had been "in the trenches" themselves!

    It all boils down to experience.

    Plus, not everyone who has the knowledge of this industry is qualified or gifted to impart that knowledge to other people.
    Oh sure, someone can stand in front of a classroom and lecture all they like.
    But that doesnt mean they are "teaching" their students!


    And where is their passion? If they lack passion, they are sunk.


    How about your teachers? Tell us about them.

  12. #12
    Join Date
    Nov 2001
    Location
    California
    Posts
    559

    Cool

    Originally posted by R12rules
    Lerner, you sound like your walking on egg shells. Whats up?

    You need to spend some time with James and let your hair down.

    I dont mean to go insulting people, needlessly.

    Just look at how Dice insults me. It's not meant to get my goat.... oops .... sorry Dice ..... didnt mean it THAT way!
    He just pokes fun at me and me right back at him.

    If your as old and your experience makes you.... then you should feel free to let your hair down a little bit.
    Whew!!! I just let my hair down and scraped the eggshells off the bottom of my feet. I feel better already. Thanks for the insult R12, since you felt I needed to hear it!!! Do you always go around looking for old guys to insult, or was it really that obvious I needed it?

    I just wanted to make sure the young tech asking questions knew I was serious about not believing everything these teachers are teaching him in school, regardless of how authoritative they may sound.

    If my post would have resembled a Dicelike attitude, chillout may have continued believing his teachers instead of me, even if I am almost as old as my experience indicates, and he may have began a career of going around overcharging everything.

    But if I'm ever in Pennsylvania after dark, I'll be walking on eggshells again, not knowin' for sure if Dice may be around the corner with his 9 mm. http://hvac-talk.com/vbb/showthread.php?threadid=2858

  13. #13
    Originally posted by Learner
    Originally posted by R12rules
    Lerner, you sound like your walking on egg shells. Whats up?

    You need to spend some time with James and let your hair down.

    I dont mean to go insulting people, needlessly.

    Just look at how Dice insults me. It's not meant to get my goat.... oops .... sorry Dice ..... didnt mean it THAT way!
    He just pokes fun at me and me right back at him.

    If your as old and your experience makes you.... then you should feel free to let your hair down a little bit.
    Whew!!! I just let my hair down and scraped the eggshells off the bottom of my feet. I feel better already. Thanks for the insult R12, since you felt I needed to hear it!!! Do you always go around looking for old guys to insult, or was it really that obvious I needed it?

    I just wanted to make sure the young tech asking questions knew I was serious about not believing everything these teachers are teaching him in school, regardless of how authoritative they may sound.

    If my post would have resembled a Dicelike attitude, chillout may have continued believing his teachers instead of me, even if I am almost as old as my experience indicates, and he may have began a career of going around overcharging everything.

    But if I'm ever in Pennsylvania after dark, I'll be walking on eggshells again, not knowin' for sure if Dice may be around the corner with his 9 mm. http://hvac-talk.com/vbb/showthread.php?threadid=2858
    Hate to be an antagonist but I thought your response was right on. If you had not said it that way I probably would have. I have known quite a few guys that have spent the thousands to go to tech schools, and then when they get into the trade they realize they have been duped. These trade schools teach these guys at best how to spell refrigeration and define the basic meaning of HVAC. And that is it..........

    If you live in the Santa Clara Valley (as I do) get on down to one of the many local unions, take the entry test and get a real education in the trade. This area is still one of the strong union areas and the work here is good.

    OK enough soap box talk.....

    With regaurds to charging package A/C units you can get the charging curves from the local wholesale house for the unit and charge the unit to the ambient from the curve. If you are charging a unit that is empty and evacuated, weigh the charge in per the manufacture tag on the unit. That is the simplest way.

    Finaly.... do not ever be afraid to ask a question if you are not certain. The only dumb question is the one you do not ask.

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