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  1. #14
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    Quote Originally Posted by rogressem View Post
    Yea, good catch, I typo'd that. RPM was 1036
    Are you saying that the controller was reading 1036 cfm?

  2. #15
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    No, that was blower RPM
    CFM always reads 1400CFM, except when running 1st stage (can't remember that off the top of my head)

    Quote Originally Posted by second opinion View Post
    Are you saying that the controller was reading 1036 cfm?

  3. #16
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    Aug 2004
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    North Richland Hills, Texas
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    In 2nd stage, with the return air conditions you posted, the temperature drop through the system should be right about 20ºF, give or take a couple of degrees, for a system moving 400 cfm/ton.
    According to your controller, the system is moving 350 cfm/ton, nominal airflow for a 4 ton system being 1600 cfm.
    At that airflow, I'd expect the temperature drop to be more in the range of 20 to 22ºF with the return air conditions given.

    Assuming all of the readings are correct, your system is operating way under capacity.
    Has it been determined beyond any doubt that the compressor is actually running in 2nd stage?
    The suction pressure is significantly higher than I'd expect to find in 2nd stage, it is more in line with what you would get with first stage compressor operation, and 2nd stage airflow.
    The head pressure seems a tad low for the outdoor temperature, another indication that the compressor may not be operating in 2nd stage.

    Is this one of the units with the Bristol TS compressor, or does it have the Copeland 2 step compressor?
    If more government is the answer, then it's a really stupid question.

  4. #17
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    Nov 2004
    Location
    Austin, TX
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    888
    The Infinity system is capable of giving you a temp drop of approximately 27 degrees when operating in comfort mode. It seems high but I've observed in on multiple occasions. The 1400cfm indicates it is operating in comfort mode. (350cfm per ton).
    360psi indicates a 107-108 p/t. With a 96 deg liquid line temp the subcooling = 11-12 deg.
    The report stated 15 degrees.

    You may be a little low on refrigerant since the data plate specifies 15 degrees.

    I'm not trusting his numbers. I've taken measurements at different points at the duct work and had a large variation. Eddies in the airflow near the evaporator coil can create cold spots. I've found checking supply air further downstream will sometimes point out a cold spot and thus an erroneous supply temp.
    I'd recheck the return temperature at the furnace and at the return grill. You could be drawing in air from leaking return duct. The relative humidity drop of only 2%? Hmm,

    A leak in the supply duct work can dump air outside of the conditioned space. To make up for the air loss the building will draw outside air into the structure. This will increase the load on the system and your ac will not hold setpoint on hotter days.
    This could explain a relative humidity drop of only 2 degrees.
    “I am for doing good to the poor, but...I think the best way of doing good to the poor, is not making them easy in poverty, but leading or driving them out of it. I observed...that the more public provisions were made for the poor, the less they provided for themselves, and of course became poorer. And, on the contrary, the less was done for them, the more they did for themselves, and became richer.”
    ― Benjamin Franklin

  5. #18
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    Quote Originally Posted by mark beiser View Post
    In 2nd stage, with the return air conditions you posted, the temperature drop through the system should be right about 20ºF, give or take a couple of degrees, for a system moving 400 cfm/ton.
    According to your controller, the system is moving 350 cfm/ton, nominal airflow for a 4 ton system being 1600 cfm.
    At that airflow, I'd expect the temperature drop to be more in the range of 20 to 22ºF with the return air conditions given.

    Assuming all of the readings are correct, your system is operating way under capacity.
    Has it been determined beyond any doubt that the compressor is actually running in 2nd stage?
    The suction pressure is significantly higher than I'd expect to find in 2nd stage, it is more in line with what you would get with first stage compressor operation, and 2nd stage airflow.
    The head pressure seems a tad low for the outdoor temperature, another indication that the compressor may not be operating in 2nd stage.

    Is this one of the units with the Bristol TS compressor, or does it have the Copeland 2 step compressor?
    It's the Bristol. A psychrometric calculation puts his capacity at somewhat less than 2 tons. I agree, it's running in first stage.

  6. #19
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    Quote Originally Posted by hvacrmedic View Post
    It's the Bristol. A psychrometric calculation puts his capacity at somewhat less than 2 tons. I agree, it's running in first stage.
    Yeah, I was thinking either a Bristol TS in 1st stage, or a 2 step scroll with a borked unloader.
    I'm not a Carrier guy, so don't know by the model numbers what they came with.

    The only 2 Infinity systems I've delt with were well after the customer gave up on the installing contractor. In both cases it was just minor stupid installation/setup details that were giving the system fits.
    If more government is the answer, then it's a really stupid question.

  7. #20
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    Northern VA 38 degrees N by 76 degrees W
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    Quote Originally Posted by mark beiser View Post
    Yeah, I was thinking either a Bristol TS in 1st stage, or a 2 step scroll with a borked unloader.
    I'm not a Carrier guy, so don't know by the model numbers what they came with.

    The only 2 Infinity systems I've delt with were well after the customer gave up on the installing contractor. In both cases it was just minor stupid installation/setup details that were giving the system fits.
    It is the Bristol TS

  8. #21
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    Quote Originally Posted by mark beiser View Post
    Yeah, I was thinking either a Bristol TS in 1st stage, or a 2 step scroll with a borked unloader.
    I'm not a Carrier guy, so don't know by the model numbers what they came with.

    The only 2 Infinity systems I've delt with were well after the customer gave up on the installing contractor. In both cases it was just minor stupid installation/setup details that were giving the system fits.
    I'm a Carrier guy and I don't have them memorized either. There are too many to keep up with.

  9. #22
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    Quote Originally Posted by hvacrmedic View Post
    I'm a Carrier guy and I don't have them memorized either. There are too many to keep up with.
    So the sub-cooling is 15 no matter the conditions?
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  10. #23
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    Quote Originally Posted by rogressem View Post
    Yea, thats what he told me, and I see it here (attached)
    Here is a charging chart for your system. Check out Step 13, it shows the required subcooling does vary depending on conditioins.(I have no idea what that name plate means by 15 degrees subcooling). The charging chart shows subcooling can go from 8 to 18.
    http://www.xpedio.carrier.com/idc/gr.../24ana-3si.pdf
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  11. #24
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    Jul 2007
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    Virginia
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    Original installer is coming out today since I agreed to a year on the maintenance contract. As part of today's maintenance he agreed to check all those temps that the other guy checked Thursday. I'll get his interpretation on that.


    Quote Originally Posted by tipsrfine View Post
    Here is a charging chart for your system. Check out Step 13, it shows the required subcooling does vary depending on conditioins.(I have no idea what that name plate means by 15 degrees subcooling). The charging chart shows subcooling can go from 8 to 18.
    http://www.xpedio.carrier.com/idc/gr.../24ana-3si.pdf

  12. #25
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    Jul 2004
    Location
    Massachusetts
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    Quote Originally Posted by tipsrfine View Post
    Here is a charging chart for your system. Check out Step 13, it shows the required subcooling does vary depending on conditioins.(I have no idea what that name plate means by 15 degrees subcooling). The charging chart shows subcooling can go from 8 to 18.
    http://www.xpedio.carrier.com/idc/gr.../24ana-3si.pdf
    That charging chart is on the unit but you have to pull the cover to see it. It's all right there for one who seeks the info. The User Interface can tell you only whether the outdoor unit has been commanded to run at first or second stage but not whether it's actually achieved that speed.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

  13. #26
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    Quote Originally Posted by tipsrfine View Post
    Here is a charging chart for your system. Check out Step 13, it shows the required subcooling does vary depending on conditioins.(I have no idea what that name plate means by 15 degrees subcooling). The charging chart shows subcooling can go from 8 to 18.
    http://www.xpedio.carrier.com/idc/gr.../24ana-3si.pdf
    It helps to know what you're looking at. The SC that you select at the top of the chart is the "required subcooling" and that would be what is listed on the nameplate, and that differs fom one model to another, and even from one size to another of the same model. The chart is for use across the entire product line, it's generic, thus the reason for the range from 8 to 18. In this case the required subcooling is 15°. You use the column below 15° and ignore the other columns. HTH. That chart is only for those who don't know how to subtract LLT from SCT. Ironically there is no 15° column, so you're expected to interpolate. I don't know how a tech who can't subtract is going to manage that, but there you go. That's how you use the chart.

    There are also a range of favorable conditions under which that SC value is valid. Instructions are to weigh in the charge when conditions aren't favorable and come back later when they ARE favorable to trim the charge.

    Oops, just relaized this is in the AOP forum. I hope this doesn't qualify as DIY info.
    Last edited by hvacrmedic; 06-23-2012 at 03:07 PM.

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