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  1. #1
    Join Date
    Apr 2007
    Posts
    49

    Register Temps ????

    If any of you remember, I was having all sorts of issues with my zoning system and ductboard:

    http://www.hvac-talk.com/vbb/showthread.php?t=138281

    http://www.hvac-talk.com/vbb/showthread.php?t=137046

    To make a long story as short as possible, the HVAC company came out today and installed a new VS airhandler and a 2-stage compressor. In addition, the raised the level of the AH and installed Wyes in place of the bullhead T's.

    Since it was late when they got the system running, they said they would be back tomorrow. I took some register temp readings with a Fluke 561 HVACPro IR Thermometer. The average temp at the stats was 74-75, but the registers were at around 62. The old system that I replaced could get the register temps in the mid 50's before the freeze stat kicked in.

    So I went up to look at the Arzel and noticed that the Y2 2nd stage connectors from the stats were not hooked up. So 30 minutes later, all the stats were connected properly and the Arzel indicator light showed it was now calling for the 2nd stage.

    But my register temps are still in the 59-61 range. Like I said, the old unit got them in the 54-57 range. The Arzel LAT (leaving air temperature) sensor is set at 48, so that should not be the problem.

    Am I missing something? I am barely getting an 11-12 degree drop from room to register. The air just does not feel cold.

    Thanks.

  2. #2
    Join Date
    May 2006
    Location
    Enfield, CT
    Posts
    37

    Shouldn't you wait until they return to finish the hookup!

    Seems to me that you are jumping the gun. They are to return tommorrow and they probably left the y2 disconnected for a reason. I'm glad I didn't have to get involved with this project. You have to give them a chance to get it set up before you start undermining the operation. You seem to have a problem with your system that they are addressing. The idea of two stage is just that. Why cool to sub zero if your only going to the tropics. Good luck and give your contractor a chance.

    Rich

  3. #3
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    IR thermometers are not accurate when pointed at light colored material. If you aim the IR thermometer at a register boot behind a register, the IR thermometer will lie to you. If you are not right on top of the item who's temperature you are measuring, then you are measuring the average temperature of the object and the area around it. If your IR has an 8 to 1 ratio and you are 8 feet away from the object, you are measuring the average temperature of a 1 foot diameter circle. Again, your IR thermometer may lie to you. If you understand the limits of an IR thermometer, it can be a good tool. If you don't understand those limitations, you will lead yourself down the proverbial garden path.

    By the way, don't mess with the system during the installation. You might screw something up you don't understand. I am glad you are not my customer.
    Remember, Air Conditioning begins with AIR.

  4. #4
    Join Date
    Jun 2004
    Location
    4H: Hot, Humid Houston H.O.
    Posts
    3,304
    I have been using an IR thermometer, blissfully forgetful of what Kevin O'Neill said. Now that he mentions it, I am reminded that the IR thermometer is only supposed to give correct readings for low emissivity (e.g. black) surfaces. However I also have a Logtag data recorder stuck in the supply vent, each seems to tell me that my system gives cooling air around 62F at the register. Maybe the error is small enough to be lost in the noise, I cannot explain why they agree. As far as I can tell my system is working fine, it has passed the spring checkup and I have no comfort complaints. It is a Trane XE1200 running 350 cfm/ton, plus a dehumidistat sometimes slows the airflow down further.

    I will second the opinion that you would benefit from letting the installers get to where they say they are finished, and only then critiquing the results. It is way too easy to get unintended consequences when you make changes, you want these guys to act professional so give them the room to do so.

    Hope this helps -- Pstu

  5. #5
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Quote Originally Posted by ferrismech View Post
    Seems to me that you are jumping the gun. They are to return tommorrow and they probably left the y2 disconnected for a reason. I'm glad I didn't have to get involved with this project. You have to give them a chance to get it set up before you start undermining the operation. You seem to have a problem with your system that they are addressing. The idea of two stage is just that. Why cool to sub zero if your only going to the tropics. Good luck and give your contractor a chance.

    Rich
    First stage should be a greater temp drop then that,but yes wait till they come back.

  6. #6
    Join Date
    Apr 2007
    Posts
    49
    Quote Originally Posted by ferrismech View Post
    Seems to me that you are jumping the gun. They are to return tommorrow and they probably left the y2 disconnected for a reason.
    No. He went around and hooked Y2 up at the stats so I would have the 2nd stage. He must not have known they were no hooked up at the Arzel. He meant for me to have stage 2 before he left.

  7. #7
    Join Date
    Apr 2007
    Posts
    49
    Quote Originally Posted by Kevin O'Neill View Post
    IR thermometers are not accurate when pointed at light colored material. .......the IR thermometer will lie to you.

    I am glad you are not my customer.
    But shouldn't they be comparable? If I measured the register with system A and got X reading, should I not be able to compare it to system B and Y reading? They may not be accurate, but the difference should be the same.

    In terms of being a good or bad customer, instead of them having to eat the original system they improperly installed, I am paying for the new one and donating the original to Habitat.

    So I hope when you mess up a job, and no body's perfect, that you get a "bad" customer like me who bends over backwards so you don't have to eat a system.

  8. #8
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,316
    If I recall correctly your freeze-up problems were caused by poor airflow. Today your installer came out and made an effort to correct the airflow problems. To what degree can be discerned over the internet, looks like he met with a degree of success, since you're no longer freezing up.

    What you haven't disclosed is if these changes have now made your house uncomfortable.

    One more thing...changes in airflow warrant a rechecking of refrigerant charge.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  9. #9
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    You may want to put several objects in the oven and the refrigerator, some dark, some light, some in between. Make them large enough to read up close with an IR thermometer, ie several inches across. Put one of each in the fridge, and leave them there for a half hour. Open the refrigerator door and read them one right after another.

    Then move them to an oven set for about 150 degrees. Leave them there for a half hour to allow the temperatures to stableize. Open the oven door and read their temperatures, one right after another.

    I did this several times and found differences in read temperatures as much as 20 degrees.

    Then I put the IR thermometer on the shelf and stopped using it. Just because it is digital, does not mean it is accurate. I am sorry to say I spent 250.00 on it. You live and learn......
    Remember, Air Conditioning begins with AIR.

  10. #10
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Quote Originally Posted by Herdfan View Post
    But shouldn't they be comparable? If I measured the register with system A and got X reading, should I not be able to compare it to system B and Y reading? They may not be accurate, but the difference should be the same.

    In terms of being a good or bad customer, instead of them having to eat the original system they improperly installed, I am paying for the new one and donating the original to Habitat.

    So I hope when you mess up a job, and no body's perfect, that you get a "bad" customer like me who bends over backwards so you don't have to eat a system.
    When we finish a job, we measure the freon, subcooling and superheat. We measure the air flow with accurate instruments. We check to see that it operates properly. If it is very hot or very cold in the house, we go back the next day to verify proper operation. Then we go back in six months and check again. Then we go back in another six months and check one more time.

    I do not believe in turning it on and leaving without checking for proper operation. That is not a startup, that is a guess up. When we do a startup, if we messed up, we catch it before it screws up the whole thing.

    If my customer knows how to install and service a system, what am I doing there? He/she may as well do it themself.
    Remember, Air Conditioning begins with AIR.

  11. #11
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,316
    Well said, Kevin.

    I use an IR thermometer in the plant mainly to look for trouble. Shoot it at the bearing housings on a cooling tower motor, and compare it to an identical tower next to it running at the same speed and see if there's a wide variance in surface temperatures, for instance. Or open a disconnect and shoot the lugs to see if one is running warmer than the other. Or aim it way up at a hot water valve to get a quick read if any hot water is actually going through the valve. Just some quick ways to help focus what I'm after, but I don't depend on the thing for more accurate readings required to do, say, a capacity check on a system.

    Which whether Herdfan realizes it or not is what he's trying to do. Only problem, not enough information. Without wet bulb and known airflow he's just scattershooting each time he aims that gun at his supply grills. Not to mention that registers are not a good place to take a supply air temperature reading. It's handy for knowing how much cooling is being lost via duct heat gain, but even that requires a discharge air temperature reading right at the supply plenum, which is where his other readings should be obtained. I don't recommend he go drill into his plenum, however, to do it! Might be followed by PPPPSSSSSHHHHHHHH!!!!!!!
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

  12. #12
    Join Date
    Mar 2007
    Location
    Myrtle Beach, SC
    Posts
    2,919
    Quote Originally Posted by shophound View Post
    Well said, Kevin.

    I use an IR thermometer in the plant mainly to look for trouble. Shoot it at the bearing housings on a cooling tower motor, and compare it to an identical tower next to it running at the same speed and see if there's a wide variance in surface temperatures, for instance. Or open a disconnect and shoot the lugs to see if one is running warmer than the other. Or aim it way up at a hot water valve to get a quick read if any hot water is actually going through the valve. Just some quick ways to help focus what I'm after, but I don't depend on the thing for more accurate readings required to do, say, a capacity check on a system.

    Which whether Herdfan realizes it or not is what he's trying to do. Only problem, not enough information. Without wet bulb and known airflow he's just scattershooting each time he aims that gun at his supply grills. Not to mention that registers are not a good place to take a supply air temperature reading. It's handy for knowing how much cooling is being lost via duct heat gain, but even that requires a discharge air temperature reading right at the supply plenum, which is where his other readings should be obtained. I don't recommend he go drill into his plenum, however, to do it! Might be followed by PPPPSSSSSHHHHHHHH!!!!!!!
    Shophound,

    That is a great use for those instruments! Using them to compare readings from two or more of the same device can be used to see what equipment requires further troubleshooting. Great example!
    Remember, Air Conditioning begins with AIR.

  13. #13
    Join Date
    Aug 2003
    Location
    Fort Worth, TX
    Posts
    11,316
    Quote Originally Posted by Kevin O'Neill View Post
    Shophound,

    That is a great use for those instruments! Using them to compare readings from two or more of the same device can be used to see what equipment requires further troubleshooting. Great example!
    The cooling tower example was for real. I had one tower motor that would consistently pull higher amps than two others next to it, and was puzzled as to why. Identical towers with identical motors running at 60 Hz on identical VFD's...one motor bearings much warmer than other two. Even after the bearings were changed, the problem of both hot bearings and higher amps did not go away. GPM through all three towers not an issue.

    It turned out to be misalignment between motor and blower sheaves. It wasn't much, but it was enough to smoke the original motor and set the replacement up to do the same had I not finally caught on to the cause. The IR instrument had a good part in leading me in the right direction.
    • Electricity makes refrigeration happen.
    • Refrigeration makes the HVAC psychrometric process happen.
    • HVAC pyschrometrics is what makes indoor human comfort happen...IF the ducts AND the building envelope cooperate.


    A building is NOT beautiful unless it is also comfortable.

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