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Thread: headmasters

  1. #1
    I know how the headmasters work,by flooding condensor on the low ambiant. But say say you find a leak on one, how do you go about charging it after your leak has been repaired? Do you need to pull the rest of charge and weigh in acording to nameplate or can you top up? If you can top up how does that work in summer when your using less of the charge? Just a general question from a greenie, thanks for all responses.

  2. #2
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    I usually just clear sight glass and add a little more after that.

    The amount I charge after clearing the sight glass depends on size of the equipment.

    The receiver will store that extra refregerant in the summer time.











  3. #3
    press1 is offline Professional Member BM -bad email address
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    I agree, clear the glass, push a bit more in and make sure the leak is fixed.

  4. #4
    The scientific method is to follow directions writen by others, Sporlan, Alco, as well as the manufacturers of the condensing units themselves. Copeland, Tecumseh, HeatCraft, Bohn.

    I read here somewhere that some use a rule of thumb like, clear the glass and add 2 pounds extra per horsepower of compressor.

    But it all depeds upon the system. Some can stand a little extra and some can not.

    Something you CA do is find it, fix the leak then charge it up clearing the sight glass. Then be ready to add more refrigerant, but first .. to simulate low ambient, begin hosing down the condensor with water nozel.

    Take your time, watch your head drop s l o w l y. Do not try to drop the head rapidly, or else you will foil your efforts.

    As the head goes slowly down, watch your sightglass. As it bubbles, add more refrigerant.
    But use your weight scale so you can label the condensing unit with the total charge amount once your finished.

    This is not a fool proof method. It is just one way of dropping the head in order to simulate low ambient conditions, "momentarily", so you can watch your headmaster absord/ feed more freon into the condensor and yet maintain your even temp to the liquid line.

    It is a balancing act, at best.


    If someone has a better method, let's hear it.

  5. #5
    To keep this brief, search for Andy Schoen's comments on this topic.

    Also, as R-12 comments, read the manufacturers literature on this subject http://www.sporlan.com/90-30-1.htm.

    Most importantly, remember if you charge only to a full sight glass, the system will be short at any ambient temperature lower than what it was when you charged to a clear glass.

    Doing it right is important unless you want a call back. Imagine someone else in your company showing up at the job and seeing a flshing sight glass because you didn't add enough extra charge. Poor guy will be looking for a leak that may not exist-that sucks.

    This can easily happen if you charge to a full sight glass at say a +50 ambient, but the system is short again (not enough charge added in) at +25.

  6. #6
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    When recharging after installing a new or repairing a HM, you should be very careful not to overfill. The receiver may not hold what you think.

    I assume you are working with light commercial?

    During your refill charge just enough for the sight glass to flow a river. Your HM will be in bypass with the cold weather. Check your HM pressure setting and bring your head just below that point. Let the system run for a while until the TXV begins to pinch. This will slow the flow of refrigerant and begin to back up the sight glass as normal. Block off your condenser airflow enough for the head to rise and take the HM out of bypass. Be careful not to overheat the cond motors.

    Doing this will simulate summer conditions and you can adjust your charge to bubble (less with a blend) and you can continue with your superheat settings on the TXV.

    After and only after your superheat setting are proven can finish your refill. Remove your device that blocks the cond airflow and let your HM operate normally. Recheck your operating pressures and do a final check of superheat.


  7. #7
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    Headmasters

    I have a chart from Heatcraft which shows additional weigh-in amounts listed by ambient temp at time of start-up. They no longer include it in their manuals, but it might be handy for you. It is for R-22 & R404A only.

    Let me know a fax number.

  8. #8
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    Charging systems with headmasters......

    Whenever you're charging a system with a flooding type head pressure control such as a headmaster you have to establish a baseline reference point which roughly simulates a 90ºF summer day. For a typical system this may equate to a 110-120ºF condensing temperature.......convert that to pressure and that's where you want to start. The primary point here is as Lusker pointed out, you want to get the head pressures up high enough by blocking condenser airflow to be above the throttling range of the headmaster control.....like 180# for R22/R404A and 100# for R134A. If you already have a summer day you're already there at your baseline.

    Charge the system to just barely clear the glass and at that point you have for all practical purposes an empty receiver. From this point you can charge by what the manufacturer's literature gives you (which most don't anymore), you can go to Sporlan's longhand version of calculating condenser flooding charge at: http://www.sporlan.com/90-30-1.pdf , you can wing it with my 2#/HP rule of thumb that R12Rules alluded to or you can try another technique.

    Lusker made a point that you're limited by receiver capacity when dealing with seasonal changes, meaning if you don't have sufficient receiver capacity to handle this "transient" charge you could potentially overcharge the system to the point where it'll be kicking out on high head come spring.

    In an attempt to come up with a better rule of thumb based on receiver capacity, I started crunching some numbers using Standard Refrigeration's receivers sizes and published pumpdown capacities. I came up with a fairly consistent relationship between a quick calulation of receiver volume and refrigerant holding capacity.

    Here goes: All you need is the nominal receiver diameter and length. Calculate the receiver volume in cubic inches and divide by 34. This will give you the receiver's pumpdown capacity to with 5-10% on anything 5" diameter and above. (The little guys don't follow the rule too well).

    V = (D x D x 3.14)/4 x L cu in, divide that result by 34 and you have what you need to charge to get the maximum low ambient control that your system will muster.

    Try it, it might even work.

    [Edited by icemeister on 12-14-2004 at 07:42 PM]

  9. #9
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  10. #10
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    Hussman has a chart for their units. It ask you to clear sight glass, then you would check ambient temp and follow curve that tells how much to add.

    If you want to make sure its not overcharge, Then simulate a 90 degrees day like lusker and ice mention above then run the unit into a pumpdown.

    If you are overcharge it would kick out on high pressure real quick

  11. #11

    Re: Headmasters

    Originally posted by forged alloy
    I have a chart from Heatcraft which shows additional weigh-in amounts listed by ambient temp at time of start-up. They no longer include it in their manuals, but it might be handy for you. It is for R-22 & R404A only.

    Let me know a fax number.

    Welcome to the forum community Alloy Man.

    Hope ya like it here.


    You got a real good name, so the goat herder probably wont be bothering you, as he usually does the new guys.

    Have you considered posting to his thread; 9mm ?

    Before ya post ... ya gotta read it all the way thru FIRST!

    Then you can post.... knowing just where the thread is at at that particular point....




  12. #12
    Thanks all responses, am currently checkin out that sporlan site. Sorry Forged Alloy I got no fax # ta give ya! I do greatly appreciate the offer !

  13. #13
    Join Date
    Jul 2004
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    A clear sight glass don't mean nothing. At low ambients alot of the refrigerant is sitting in the reciever. I've worked on some Hussmans that required 4 lbs. more after a clear sight glass. Simulate a higher head by blocking flow over the cond. coil. I recently had to gas up a remote Kairak at 35 ambient w/110 lbs of 404a. Second time I've did it on this unit. Bubbles came and went after I was done. Older Sweet Tomatoes restaurant. This monster kicked thru the summer. The first time I gassed it up was in the winter time as well and I had bubbles then too. Head press. matters most. This system has 2 W/Ins, a bath chiller and 13 R/Ins. 15 TXV's and 10 EPR valves. Leaks are a pain to find.

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