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  1. #1
    Join Date
    Dec 2009
    Location
    Hotlanta GA.
    Posts
    214

    410A Need some help !! ???

    Have a trane 410A High eff. Cond, & Furnace, Cond md # 4TTX5036A1000AA, Didn't get the furnace and coil numbers today.............

    Any ways, I'm getting stumped a bit,

    O/A 98 deg.
    hp 485, liquid temp 100
    sp 125 suction temp 70
    air across coil rtrn 79 supply 67
    clean filter, cleaned cond, coil.
    pulled charge and recharged with new liquid 410A. after I saw hp of 510 with 95 deg liquid.

    Comp rated 15.4 a/ 14.8
    230 vac,
    Cond fan looks to be running high speed, didnp[t get into electronic today,

    Problem I feel is txv ???? Best super heat is 26-28 deg.
    adding freon raises hp, sp but does little to lower suction temp.

    Going back tomarrow,

    Pondering >>>>> is the txv holding open, unit froozed past weekend, filter was trashed bad, so I'm thinkin that caused the freeeze, with good air, why is the suction so warm, and the head so high ????

    Not much time under belt for this 410A stuff, added with the energy unit on top. I know I will need to get to the electronics and confirm speeds for the fans..............

    Indoor coil I rmember as the proper size for the cond, 3 ton >>..

  2. #2
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    [QUOTE=Mongo and me;7263022]
    Not much time under belt for this 410A stuff
    The refrigerant doesn't matter, the refrigeration cycle still works the same way, and the saturated temperatures are virtually the same.

    It really does help if you think in terms of temperature rather than pressure.

    Per your first set of numbers you are running a 40 evaporator, which is 39 lower than the return air temperature, and 29 of superheat.

    The saturated temp of the evap is low for a high efficiency system with the return conditions you stated, and the SH is high.

    The 131 condensing temperature is 33 over ambient, which is very high for a high efficiency system, and the SC is 31, which is also very high.

    So, you have low suction pressure, high SH, high head pressure and high SC.
    The diagnosis is the same regardless of the refrigerant used in the system.

    The system has a restriction, likely the TXV, and someone has previously misdiagnosed it and juiced it up with refrigerant, so it is grossly over charged.

    When you replace the TXV, recover all the refrigerant and remove the factory installed LL filter drier that is in the unit, don't just pump it down...
    If more government is the answer, then it's a really stupid question.

  3. #3
    Join Date
    Dec 2009
    Location
    Hotlanta GA.
    Posts
    214
    My idea on the bottom line for 410A:

    goal is 20deg. across evep coil, so with the suction temp. of 50 deg refrigerant > the super heat at say, 12 deg. would bring the refrig, to 62 deg. This should reflect in the dicharge air being close to that temp.

    suction presure would run 175 deg.

    for cond. figures, I go high eff. cond so O/A + 25 deg.
    so 93 O/A + 25 = 118 deg. or a presure of 405

    Now bear in mind, this is just a ball park formula to get me close, Iknwo the manuf. is listing thier charts for TXV, so all in all just let me knwo if I'm close on this thinking.

    Thanks for any imput !!

  4. #4
    Join Date
    Dec 2009
    Location
    Hotlanta GA.
    Posts
    214
    Right, I was thinkin the same, TXV trouble, this unit is only two years old, no one else has been on it (so I'm told).
    So pull the filter dryer, ok, then the TXV issue ??
    short of tearing into the coil box, IF the txv is corupt, would it show the low suction with high superheat, to me I see a starved coil, blockage at the filter dryer would releive that, allowing the txv to be satified given good working order. Past history says the unit cooled well before, so I'm not in a hurry to do a TXV exchange..........

    clean dryer = flow, flow = lower super heat = higher suction presure, & lower head presure given proper charge >>??? Temp drop across indoor coil should increase from the 10 degr. to a better performance of say 18 degr. >> ??

    What think thee ???

  5. #5
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    The expected temperature drop through the indoor coil is dependent on the return air dry bulb and wet bulb temperature conditions, so just looking for 20 every time isn't a good idea.

    Higher efficiency outdoor units will also typically run condensing temperatures lower than your stated 25+

    Trane includes a chart in the Service Facts that come with that unit, in the envelope on the inside of the corner access panel, that shows what the expected pressures are for the given conditions.

    For that particular unit, at 98 outdoor ambient, the unit would be expected to be running a condensing temperature of around 111(370 psig head pressure), which is just 13 over ambient.
    If more government is the answer, then it's a really stupid question.

  6. #6
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,914
    Quote Originally Posted by Mongo and me View Post
    Right, I was thinkin the same, TXV trouble, this unit is only two years old, no one else has been on it (so I'm told).
    So pull the filter dryer, ok, then the TXV issue ??
    short of tearing into the coil box, IF the txv is corupt, would it show the low suction with high superheat, to me I see a starved coil, blockage at the filter dryer would releive that, allowing the txv to be satified given good working order. Past history says the unit cooled well before, so I'm not in a hurry to do a TXV exchange..........

    clean dryer = flow, flow = lower super heat = higher suction presure, & lower head presure given proper charge >>??? Temp drop across indoor coil should increase from the 10 degr. to a better performance of say 18 degr. >> ??

    What think thee ???
    The factory installed filter is piped before the liquid line service port, where you are getting the high head pressure and SC readings. If the LL filter drier was restricted enough to starve the TXV, you would be getting VERY differrent pressure and SC readings at the LL service port than you are getting now.
    If more government is the answer, then it's a really stupid question.

  7. #7
    Join Date
    Jun 2009
    Location
    NYC
    Posts
    423
    Looks like a partial refrigerant restriction and dirty filters/coil cause the ice-up. Now the high head or higher head is from an overcharge system note that your subcooling is high. So coupled with a restriction and an overcharge to overcome a restriction under a high heat load is a high head with high superheats.
    Replace your filter driers, and check TXV strainers, if necessary replace TXV.

  8. #8
    Join Date
    Dec 2009
    Location
    Hotlanta GA.
    Posts
    214
    so we drop the ll fitler dryer, as I am hooked up after it, and still showing High Very high head condition, and a lower then normall suction presure. This is my stump that I ponder on........... Over sharge would reflect a higher head, but also a higher suction.

    TXV trouble would be a better call, I'm pakin in tooo much freon, and the evap coil is starved for freon as indicated by the higher super heat..............

    dirty coil would only confirm itself by the super heat being lower then normall, fan speed is good as best I can tell............

    I saw the Trane chart, didnpt knwo the normall Super heat for this unit, I am shooting off a rule of thumb on that one, I saw mostly a 12-9 deg sh for this unit.... Sucks when the chart is at the unit and not here on my desk !!!

    any ways, I see your point on the head presure, I KNWO i have a problem and its showing up as head high presure, just need to work out the causes for this and eliminate them.......

    Thanks for the help, I don;t have too many ears to bounch this stuff off of at work, always starts to coem clearer when I have another person to talk out load to.....

  9. #9
    Join Date
    Dec 2009
    Location
    Hotlanta GA.
    Posts
    214
    OK, lets walk the TXV strainer point and see how it goes, over charge backs up and gives high head, I open the cabnet and read the temp goin into the txv, and then get a close temp reading on the coil exit, this would indicate the restriction given the strainer. Next is to paly with the txv bulb, see what responce I get heating and coolin it..... I could always do a quick fan off while running and see the frost line, how close to the txv and so on.......... I have found distibution tubes stopped that way !!!

    in any case, I have a good list to go over in the morning.............

    Its all about the heat, can I get it to be absorbed into the evap. coil, and then can I get ride of it in the cond........

  10. #10
    Join Date
    Dec 2009
    Location
    Hotlanta GA.
    Posts
    214
    Well not to leave this hangin, I did the tear apart job on the TVX, back flushed sepratly and then put it all back together. Vac, charg, ect . ect.

    Worked !!! Presured can into line, and the unit settled out OK. Did learn a good thing, the TXV did not have adjustment on it, so what ever the fatory eng. then that was it. DId get to see the modulation of it from start up, as house cooled off the suction dropped and I could actually see the fan speed change's on the blower. Love it when a pan comes together.........

    Thanks all for the bouncing board, I get hooked on commerctial and and it takes me awhile to get back into the resd. I knwo its all the same, kind of !!! Must be the heat of the attic takin it toll on me !!!

  11. #11
    Join Date
    Aug 2013
    Posts
    22

    Hmm

    Quote Originally Posted by Mongo and me View Post
    Well not to leave this hangin, I did the tear apart job on the TVX, back flushed sepratly and then put it all back together. Vac, charg, ect . ect.

    Worked !!! Presured can into line, and the unit settled out OK. Did learn a good thing, the TXV did not have adjustment on it, so what ever the fatory eng. then that was it. DId get to see the modulation of it from start up, as house cooled off the suction dropped and I could actually see the fan speed change's on the blower. Love it when a pan comes together.........

    Thanks all for the bouncing board, I get hooked on commerctial and and it takes me awhile to get back into the resd. I knwo its all the same, kind of !!! Must be the heat of the attic takin it toll on me !!!

    So the Big problem was the TXV?

  12. #12
    Join Date
    Nov 2006
    Location
    Southeastern Pa
    Posts
    18,236
    Quote Originally Posted by samasasam View Post
    So the Big problem was the TXV?
    Apparently.

    More study of the refrigerant cycle needed.
    [Avatar photo from a Florida training accident. Everyone walked away.]
    2 Tim 3:16-17

    RSES CMS, HVAC Electrical Specialist

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  13. #13
    Join Date
    Aug 2013
    Location
    Tulsa, OK.
    Posts
    4
    More than likely the TXV. Installers usually don't remove the bulb off of the suction line just inside the coil box causing it to heat up and damage the TXV. Simple fix, this coil has a bolt on TXV in it.

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