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what do you guys think?

If the orfice was missing or if the refrigerant was bypassing the orfice you would have low suction and low head.If that the case then there is no need of checking superheat or subcool temps at this time.

Most time if the orfice is missing or the refrigerant is bypassing you will have flashing at the liquid line.
The liquid line will sweat.

Hope this helps.

Comments

  • bill_71
    bill_71 Member Posts: 46
    got a question

    one of our techs went for a routine cleaning for a new customer and the compressor was rattling and locking up. the main reason why the customer wanted a cleaning done. he shut it down. the customer went with replacing the compressor. its a 2 ton system. i went there, recovered 11# of refrigerant on a condenser that was factory charged with 3# 10 oz (r-22) and had about 60-80 ft of line. gee, i wonder why the comp crapped out. anyways, replaced the comp, evacced, cleaned cond coil. evap, fan and filter are all fine, fan is on high speed per factory specs. it is only a 6 y/o rheem unit. recharged, ended up putting in 6#. sub was "ehh" but suction p/t were way low. 50psig and a 28 deg line. orifice system.
    idwb-71 db 83 6deg split with 0deg superheat. called the local rheem dealer and they confirmed that the ahu and cond are both 2 ton and the orifice size that was stamped on the distributor is proper but does this sound like there was no orifice ever put in the line?? i'm going back on tuesday to check, but as usual, the customer claims its been working just fine until we showed up, which makes me question how the comp has lasted 6 years with a gross overcharge and no orifice. questions and disbelief and an angry customer oh my
  • Tony_23
    Tony_23 Member Posts: 1,033
    ???

    What's your liquid line pressure ?
  • Darin(in Michigan)_3
    Darin(in Michigan)_3 Member Posts: 28
    subcooling??

    I would use subcooling to determine if charge is approximately where it should be. Then I would look to air flow. Next I would check line set sizing charts for proper sizing based on lengths. Oil leaves the compressor and get stuck in lineset droops and runs dry then siezes the compressor from what I've heard.
  • Empire_2
    Empire_2 Member Posts: 2,343
    WOW....:-)

    Just a suggestion?....Next time when they call for a routine maintenance, and there is a problem,....It is NOW a service call and we charge more for that for obvious reasons like the stuff the customer is giving you now.:-) Anyways..How long was the new compressor running before you came to you final conclusion? As far as factory specs go,...It can only ring true depending on how the system was installed with duct and other factors. 2 ton is generally 800 cfm, but what if there are other variables like only 4 6"runs, or 12 6" runs.....:-) it's irrelevant.
    If you did not have an orifice in the Evap coil, you would, (depending on it's design), Almost immediately slug back to the compressor and you pressures would be Low head and slightly lower suction which isn't good, but very recognisable. Sub cooling as much as we all like to say it bears no significance in a system that uses a restrictor..... This system works on pressure Differential Period!...:-)
    Let me run this by you. Maybe the last person charging this unit added and added more Ref. to get that darn suction pressure up and possibly overcharged it??? I have seen it before and it's actually kind of funny, "but if it's Lo Give er More Gas". We need to look at Return duct/ Supply, Temps and pressures/ Squirrel cage condition/ Etc...
    Also, just thinking out loud here....If the syste4m was possibly overcharged, and I say that with caution, is the Ref. circuit contaminated with crap?

    I feel for you and I know you will do it right, but don't let this customer run you around. He will have questions and you better have the answers..... I hope I wasn't coming off as an **** Bill. If I did I am sorry, but I don't want to see you get burned on this one.

    Peace..... Hey Don...:-)

    Mike T.
  • Techman
    Techman Member Posts: 2,144
    How much?

    Good Morning All! Hi Bill,that factory # of r-22 is good for 15-25' and each extra foot of 3/8 liquid line has .6 oz more ,5/16 has .4 oz .So for an extra LL length of between 35-55' that adds up to a few extra #'s. .I'm using 32 fluid oz per #. I think the system recharge is a little low. What is the outdoor ambient?What is the head? And is there a sight glass or an electronic sight glass on this unit?
  • bill_71
    bill_71 Member Posts: 46


    3/4-3/8 suc/dis i installed liq and suc dryer along with the comp. i didn't record any numbers for subcooling. i do recall, however, that at one point i almost had textbook sub readings but suction was still in the toilet. i checked the airflow side of things and all were fine. if there was an air restriction then i would have a better then 6 deg td. i started with 5# r-22 because the long line and factory charge in the cond. i put more in, i took some out, all through this process sub went up and down, temp drop stayed the same, suc and sup were always at the readings i gave earlier, never really moved.
  • lee_7
    lee_7 Member Posts: 458


    With most dryers, you will need to add 1 pound of refrigerant to system. As you stated, you added to dryers, so you should be at least 2 pounds higher then factory plus extra for lineset.
  • Tony_23
    Tony_23 Member Posts: 1,033
    Huh ?

    32 oz per lb ? Refrigerant is weighed in, no ? 16 oz/lb dry weight, not fluid oz.

    Did I miss the head pressure somewhere ? I haven't seen that number yet, either.
  • Tony_23
    Tony_23 Member Posts: 1,033
    Air restriction

    Won't an air restriction will give you less TD ? Less airflow, less heat being exchanged, colder coil, lower superheat. Just like a plugged air filter with an iced up coil.
  • Techman
    Techman Member Posts: 2,144
    Wait-Weight

    Thanks Tony!
  • don_185
    don_185 Member Posts: 312
    Why????

    Why does all text books say that with a overfeeding meterting device that the suction pressure will be high?

    When I've come across them in the field everything is low.

    Low suction,lowhead,low superheat and,low subcooling.

    Hows ya doing Mike?
  • Check...

    and make sure all the supply registers are open. Check for a plugged evap coil too. Make sure you can see light through it. If that's all good look for undersized ductwork. It DOES sound like an air restriction/low air flow problem.
  • bill_71
    bill_71 Member Posts: 46


    i ended up going back today.....took out the orifice and the damn thing was in backwards!!! i brought a txv with me and decided to just throw it on and be done with it.........air restriction will give you a higher td with low suction and low superheat. what i had was low suction, no superheat and only a 6-7 td. there was no "squeeze" happening in the orifice so in essence no cold coil( well not cold enough to pick up sufficient heat anyways). i couldn't give any accurate high side pressures because there was no way of knowing how close i was to having a properly charged system.
    total charge was 6# 4 oz 7 sup 12 sub and a td of 12 but my god it was humid in that space..... 82 db and 73wb
    thanks for the input guys.............
  • Techman
    Techman Member Posts: 2,144
    bill

    Congrat's to you for your dogged determination!
  • GREG LAUER
    GREG LAUER Member Posts: 103
    check with rep

    3/8 liquid line size doesn't sound correct for a Rheem they size diferently than every one else. check with rep on proper line sizing. or send me m# and S# of indoor and out and I'll check there site for you
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