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  1. #1

    Double check the HVAC advice I got please?

    Hi gang.. Went looking for help on the Internets and ended up here.. Thanks for any time put into reading this. My AC keeps running pretty constantly, so had a pro from dover come out to take a look. The house gets colder than the outside, but nothing amazing. Here's my stats:

    On the outside.. I've got a 2.5 ton Puron R410 by Carrier, about 5 years old.
    On the Inside, I've got an older R22 3 ton coil, from about the year 2000.
    The house is big enough to warrant a 3 ton unit, I have no idea why the outdoor unit got seemingly replaced, or replaced with a smaller unit.

    The air coming out of the outside fan isn't very hot, the air inside the vents gets down to about 65 degrees, though the outdoors are only about 10 degrees higher, so not hitting the 20 degree difference model.

    Haven't had the house that long, so treating everything as an unknown, even if it was done right. As part of that, had a recommended HVAC tech come out. Given they are two different freon types, just to make sure, the tech drained everything from the line, put new coolant in, and replaced the filter. He also removed a jacket wrapped around the fan motor (blew me away).

    He then checked out the indoor part, and recognized the 3 ton coil. He said it was a mismatch, and the coil wasn't getting as cool as it needed to because the outdoor unit can't keep up. He recommended I goto a 2.5 ton coil, or a 3 ton outdoor unit, to increase efficiency of the system.

    So, the AC doesn't do too bad, it does turn off eventually, but it's 22/24 hours on and pumping. From other posts I've read, it seems like you *can* have the mismatch in some situations? Seems like mixed posts about it.

    And I'm still trying to figure out what a Thermal Expansion Valve is, and if I have one. It seems recommended?

    Thanks fellas! I'm still learning and don't know what I don't know... Hoping you do

  2. #2
    Join Date
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    is all the "tech" did was pulled the refrigerant & recharge?

    personally, don't think you had much of a "tech"
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  3. #3
    Join Date
    May 2000
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    Indianapolis, IN, USA
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    It is very common, especially with Carrier, that the indoor unit is 1/2 ton larger than outside.

    A TXV is a variable refrigerant flow control that will adjust the flow of refrigerant through the indoor coil based on the load on the coil. It is more efficient than the fixed control likely in there now.

    I'm a little nervous about your tech too.

  4. #4
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    Jun 2001
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    Moore, Oklahoma, United States
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    The current fixed orifice/TXV could be sized for R22 @ 3 ton. You need a metering device for R410 @ 2.5ton.

  5. #5
    Join Date
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    didn't carrier use pistons for a few years when they first got in the 410 market?
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  6. #6
    Join Date
    Feb 2009
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    Portland OR
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    That tech seems a bit off to me to. As Loonie stated, most of the indoor coils are sized .5 up to 1 ton larger than the outdoor unit. This gives more surface area so that you get more airflow to remove more heat to become more efficient. Often times a matched coil is a bit larger to get this higher efficiency number.
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  7. #7
    Wow fellas thanks for the fast responses.

    Can someone tell me how I would know if a 2.5 ton hxv was installed? If it wasn't, would that help? (From reading other threads)

    So the consensus seems I need a new AC guy, and the "mismatch" is ok. Any advice on what I can point a new tech to for getting the system cooler and more efficient?

  8. #8
    Join Date
    Jun 2005
    Location
    SW Wisconsin
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    Quote Originally Posted by ecuguru View Post
    Wow fellas thanks for the fast responses.

    Can someone tell me how I would know if a 2.5 ton TXV was installed? If it wasn't, would that help? (From reading other threads)

    So the consensus seems I need a new AC guy, and the "mismatch" is ok. Any advice on what I can point a new tech to for getting the system cooler and more efficient?
    What is the model number of the evaporator coil?
    Then you'll also see the TXV, if it's there...

    There are ways to tell by covering portions of condenser's intake air & seeing what happens to pressures; but U don't have the Federal & state licenses U can't do that.
    Last edited by udarrell; 09-14-2011 at 01:14 PM. Reason: Look...

  9. #9
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    Quote Originally Posted by dandyme View Post
    didn't carrier use pistons for a few years when they first got in the 410 market?
    I believe carrier always had TXV's for the R410 line except for within the last 2 years or so with the FB "builder grade" airhandler.

  10. #10
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    Was the R-22 coil used with R-22?

    If not, it might be a good match provided that they put the right metering device in.

    Get the tech to open the plenum (or air handler if there's no furnace) and check the coil model number. If it's an approved match, there's no problem.
    General public's attitude towards our energy predicament: "I reject the reality of finite resource depletion and substitute it with my own; energy is infinite, we just need an alternative storage medium to run the cars on. The economy can grow indefinitely - we just need to "green" everything! Technology is energy! Peak what?"

  11. #11
    Join Date
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    Quote Originally Posted by dandyme View Post
    didn't carrier use pistons for a few years when they first got in the 410 market?
    The still use pistons on some units.

  12. #12
    Join Date
    Mar 2010
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    Manassas, VA
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    There could have been a jacket on the compressor - are you sure it was the fan motor and which one - indoor or outdoor?

  13. #13
    Join Date
    Jun 2011
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    Wake Forest, NC
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    An R-22 coil is not designed for the higher operating pressures of a R-410A system. If they replaced the TXV or piston you may be ok, but since you told us the supply air is 65 degrees unless it is close to 85 in your house I am going to guess they did not. It sounds like the TXV or piston is not properly matched to the condenser. That needs to be confirmed and then either a new R-410a coil installed with the proper metering device (preferred, but more expensive), or a new metering device installed onto the R-22 coil (not my recommendation).

    Have a pro come out and take superheat and subcooling measurements and determine if the metering device is appropriate for the condenser. If the metering device is not right then the SH and SC will not be right either. Then you will know you need to take corrective action.
    It's not rocket-science...

    It's electromechanical thermodynamic engineering

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