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  1. #14
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    Jul 2005
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    5,576
    Quote Originally Posted by beshvac View Post
    The bristol I found like that had the same amps in either stage.
    It could be that instead there's a busted discharge valve on the second cylinder. Either way the second piston doesn't seem to be providing any refrigeration effect.

    If any of you pros don't have or have access to a psychrometric program or calculator, then you should think about locating one. It'll save a lot of head scratching. I have one posted in the educational forums, and there are several psychrometric apps available from itunes and the android market. You could also just use a wet bulb/enthalpy table and the total capacity formula

    btuh total = 4.5 x cfm x ΔH

  2. #15
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    I don't see a airflow problem. Even if it was the condenser fan not going to high speed, you're still get a significant increase in capacity, but high head pressures and high amp draw.

    IF inside airflow was a problem, you'd have low discharge air temps, not higher.

    It seems clear to me that it's not generating capacity.

  3. #16
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
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    14,915
    After all these service calls, if the intalling contractor hasn't figured out that the compressor is broken by now, Carrier should cut them off and not sell them anything more complicated than a single stage system until they get some remedial training for their technicians from an outside source...
    If more government is the answer, then it's a really stupid question.

  4. #17
    Join Date
    Jun 2005
    Location
    SW Wisconsin
    Posts
    5,035
    Quote Originally Posted by rogressem View Post
    Just an update on this, or lack of update. (Carrier Infinity supply air temp goes up from low to high stage, suction pressure goes up - good performance at low stage) Original thread:
    http://hvac-talk.com/vbb/showthread.php?t=1113821

    My original installer (from 2007) is waiting on a response from the local Carrier technical representative. In the meantime, I've been taking careful return/supply air temps at the air handler (return duct at air handler and a few feet downstream of evaporator). I've taken them almost every day, early morning and middle of these hot afternoons and the numbers are pretty consistent. BTU performance from low to high stage is essentially constant. This morning:

    LOW STAGE:
    Return Dry Bulb: 71.8
    Return Wet Bulb: 58.7
    Supply Dry Bulb: 48.7
    Supply Wet Bulb:47.4
    Following 3 readings from Infinity Controller
    CFM: 882
    Blower RPM: 599
    Static Pressure: .24


    HIGH STAGE:
    Return Dry Bulb: 71.5
    Return Web Bulb: 59
    Supply Dry Bulb: 55.4
    Supply Wet Bulb: 52.7
    Following 3 readings from Infinity Controller
    CFM: 1400
    Blower RPM: 960
    Static Pressure: .61
    Using the wet bulb temps & enthalpy chart I get 42,071.4-Btuh Low Stage &, 39,690-Btuh High Stage.

    Hope I didn't make an error...it's easy to do...4.5* CFM * enthalpy change. The Low Stage should not be higher than the High stage; maybe I made a mistake somewhere?

    If not; you got a real problem!
    Last edited by udarrell; 07-07-2012 at 04:48 PM. Reason: Low stage was a bit lower...

  5. #18
    Join Date
    Aug 2004
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    North Richland Hills, Texas
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    14,915
    Quote Originally Posted by udarrell View Post
    Using the wet bulb temps & enthalpy chart I get 42,071.4-Btuh Low Stage &, 39,690-Btuh High Stage.

    Hope I didn't make an error...it's easy to do...4.5* CFM * enthalpy change. The Low Stage should not be higher than the High stage; maybe I made a mistake somewhere?

    If not; you got a real problem!
    I think you got the enthalpy change to high.
    With the conditions listed, the first stage enthalpy change is 6.7 btu/lb, and 2nd stage is 3.927 btu/lb.

    Using that equation, 1st stage would be at 26,592 btu/hr, and 2nd stage would be at 24,740 btu/hr.

    The psychrometrics app I use is corrected for my local conditions, but the variation from standard should only be slight.

    The psychrometrics process calculator app I use, instead of that equation, gives slightly lower total capacity numbers, but they are within 1,500 btu/hr of the simplified equation.
    I like using the process calculator because it breaks out sensible and latent capacity.

    The way the system is operating now, it has higher total and latent capacity in 1st stage than in 2nd stage.
    In 2nd stage the sensible capacity is slightly higher, but there is almost no latent cooling being done.

    If there is a way to lock the system into only using 1st stage, I'd highly recommend doing so until the compressor is replaced.
    If more government is the answer, then it's a really stupid question.

  6. #19
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    95
    I got similar numbers (about 26,000 btu/hr) for both. I'm using that Psychometrics app for iphone/android (maybe the same one your using), which also seems to match the regular enthalpy charts that I see. I'm pretty much at sea level (+14 feet I think)

    I've been trying to figure out how to lock it in 1st stage until its fixed...not seeing a way to do that.

    Quote Originally Posted by mark beiser View Post
    I think you got the enthalpy change to high.
    With the conditions listed, the first stage enthalpy change is 6.7 btu/lb, and 2nd stage is 3.927 btu/lb.

    Using that equation, 1st stage would be at 26,592 btu/hr, and 2nd stage would be at 24,740 btu/hr.

    The psychrometrics app I use is corrected for my local conditions, but the variation from standard should only be slight.

    The psychrometrics process calculator app I use, instead of that equation, gives slightly lower total capacity numbers, but they are within 1,500 btu/hr of the simplified equation.
    I like using the process calculator because it breaks out sensible and latent capacity.

    The way the system is operating now, it has higher total and latent capacity in 1st stage than in 2nd stage.
    In 2nd stage the sensible capacity is slightly higher, but there is almost no latent cooling being done.

    If there is a way to lock the system into only using 1st stage, I'd highly recommend doing so until the compressor is replaced.

  7. #20
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    95
    Beginning to wonder that myself. I know this company has had some turnover lately, so I'm not sure how good their Carrier expertise is anymore (not a big company, so I know that must be a challenge).

    I've already been looking at the other factory authorized Carrier dealers in my area, but I was hesitant with starting over with somebody new. I've also been giving them a break during this heat wave - at least I have some cooling!

    Quote Originally Posted by mark beiser View Post
    After all these service calls, if the intalling contractor hasn't figured out that the compressor is broken by now, Carrier should cut them off and not sell them anything more complicated than a single stage system until they get some remedial training for their technicians from an outside source...

  8. #21
    Join Date
    Jun 2005
    Location
    SW Wisconsin
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    5,035
    Quote Originally Posted by mark beiser View Post
    I think you got the enthalpy change to high.
    With the conditions listed, the first stage enthalpy change is 6.7 btu/lb, and 2nd stage is 3.927 btu/lb.

    Using that equation, 1st stage would be at 26,592 btu/hr, and 2nd stage would be at 24,740 btu/hr.

    The psychrometrics app I use is corrected for my local conditions, but the variation from standard should only be slight.

    The psychrometrics process calculator app I use, instead of that equation, gives slightly lower total capacity numbers, but they are within 1,500 btu/hr of the simplified equation.
    I like using the process calculator because it breaks out sensible and latent capacity.

    The way the system is operating now, it has higher total and latent capacity in 1st stage than in 2nd stage.
    In 2nd stage the sensible capacity is slightly higher, but there is almost no latent cooling being done.

    If there is a way to lock the system into only using 1st stage, I'd highly recommend doing so until the compressor is replaced.
    Well, re-figuring the Low Stage I get enthalpy change of 6.69 which gets 26,553-Btuh; discovered switching back & forth to get WB #s; I ended up reading WB #s from the wrong stages.

    Now I get 1400-cfm * 4.5 is 6300*3.86 enthalpy change is 24,318-Btuh.

    Well,I read the 47.4-F off the Low stage & then subtracted it from the High stage wet bulb of 59-F which gave me a false 6.69 enthalpy change on the chart which gave me the false high of 39,696 figure, looked okay for a sick 4-ton system.

    Well, I believe it's supposed to be a 4-Ton system.
    Is it a heat pump or straight A/C system?

    It is simple if you get the right WB numbers...I was switching back & forth & somehow ended up reading the wrong WB#'s from different stages, WOW.
    Had some distractions here too...

  9. #22
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    I agree, that locking it into 1st stage would be best. I'd also set airflow to maximum. This way you'll get the most capacity. On my newer controller,you can select low stage only form the advanced menus. I think it's in the system staging in under the lockout settings.

  10. #23
    Join Date
    Jul 2007
    Location
    Virginia
    Posts
    95
    OK, here is the latest on this issue. Based on the info my local HVAC contractor passed to Carrier, Carrier concluded the TXV was bad. It was just in the 5 year parts warranty, so Carrier paid the cost of the TXV (I actually paid the difference and had the entire evaporator replaced with a newer aluminum Carrier N coil). No need going through all that and then have the evaporator leak in a year or so.

    At any rate, made no difference at all, and I knew 10 minutes after they fired it back up. Same symptons:

    1) Supply air temp goes up 5-10F from low to high stage

    2) Delta T, measured at the evap is 10-14F in high stage, good 20 or so in low stage

    3) Suction pressure always goes up about 10psig from low to high stage, head pressure essentially doesn't change. Local tech says Carrier told him this was OK, although the Carrier application and service guide for the 24ANA7 reads: "Suction pressure should be reduced by 5--10% when switching from low to high capacity. There should be a 10--20% increase in liquid pressure when switching from low to high capacity."

    4) When I take careful and repeated wet bulb/dry bulb return/supply temps at the appropriate locations near the evaporator BTU calculations are essentially unchanged from low to high stage. (I've posted figures here before - no need to post them again - they didn't change)

    Now, before Carrier agreed to replace the TXV, they did have the local tech come back out an check compressor amp draw (because he neglected to do that on the first visit). On a super hot day it was 6A low stage and just over 9A hi stage. Again, the Carrier service guide reads: "Compressor current should increase 100--250% when switching from low to high stage.", but this apparently didn't throw any red flags for the Carrier service rep, so they went with a TXV replacement

    At this point, I'm waiting the local HVAC company to get a response from Carrier on the next step. I figure I probably have a good case. Carrier didn't agree to do an in-warranty TXV replacement if they didn't think something was wrong, and since the symptons have not changed, I wouldn't think that they could now say everything is OK. I still think its that Bristol TS compressor.

    Here is my question: If I hit a dead end here, can I go directly to Carrier Mid Atlantic and start working this issue myself? Does Carrier have service reps that respond to things like this, rather than going through a local HVAC contractor?

    No major complaints with the company I'm using - they are Carrier factory authorized, but I have the feeling they aren't the most experienced with these types of issues (they only have two techs). In most cases, I actually like dealing with a small company, but I think they may be in over their head on this one.

  11. #24
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
    Posts
    14,915
    There is not one single thing about the readings you have passed on to us that would even hint that the problem was related to the TXV.

    The compressor is clearly not functioning properly in 2nd stage.

    It is ridiculous that this fiasco has continued this long.

    The preemptive move to the all aluminum coil was a good call though, so there is that.
    If more government is the answer, then it's a really stupid question.

  12. #25
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
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    I wonder what part about a bad compressor there not understanding ,also i would refuse to pay for the coil replacement .

  13. #26
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
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    14,915
    This is sad.
    I just realized that you posted about the poor performance of this system just over 2 years ago, and it still isn't fixed...

    For the record, I said the compressor wasn't working at full capacity in 2nd stage 2 years ago when you first posted about it.
    If more government is the answer, then it's a really stupid question.

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