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Thread: Lots of Questions on Coils with EEVs

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    Lots of Questions on Coils with EEVs

    Are EEVs only used in multi-stage high SEER systems or are there benefits to using them on single stage lower SEER systems?
    Is the controller for the EEV the system controller located in the Furnace or is there an independent controller that comes with the coil.
    When installing a coil with an EEV, are the pressure and temp sensors pre-installed on the coil or are they sourced and placed elsewhere on the system?
    If the EVV is controlled from the furnace's control board, am I correct to assume the Furnace has to be a model that supports the use of an EEV or can any furnace control an EEV?
    Are EVVs more reliable or less reliable than a TXV?

    Maybe my question can be simplified like this:
    Can you use an EEV model coil on a single stage system? Is there any situation where you would want to?

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    Comfort cooling?
    Process?
    Makes a difference.

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    Quote Originally Posted by ehsx View Post
    Comfort cooling?
    I'd say comfort is the primary purpose of an HVAC system.
    Does an EEV provide a significant advantage over TXV?

    Quote Originally Posted by ehsx View Post
    Process?
    I'm not sure what you mean by "Process".
    Are you saying the choice of which valve to use depends on whether I value cooling comfort or value how each type of valve goes about metering the flow of refrigerant? From what I can tell, the system would have more control over the metering with an EEV because it has real time pressure and temperature data where a TXV operates independently in the system relying on its own internal pressure differential system to control the flow.

    Quote Originally Posted by ehsx View Post
    Makes a difference.
    I would choose comfort over process until the added cost produced very little noticeable comfort advantages.

    With all that said, can you run an EEV in a single stage system and even if you could, what would it get you?

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    Quote Originally Posted by geobrick View Post
    I'd say comfort is the primary purpose of an HVAC system.
    Does an EEV provide a significant advantage over TXV?

    *At ahri design conditions, single stage system, there would be little or no benefit and 10%+ additional cost. *

    I'm not sure what you mean by "Process".
    Are you saying the choice of which valve to use depends on whether I value cooling comfort or value how each type of valve goes about metering the flow of refrigerant? From what I can tell, the system would have more control over the metering with an EEV because it has real time pressure and temperature data where a TXV operates independently in the system relying on its own internal pressure differential system to control the flow.

    *Process applications are considered operations where outdoor air is not used for cooling by opening windows or ecomizer operations.*

    I would choose comfort over process until the added cost produced very little noticeable comfort advantages.

    With all that said, can you run an EEV in a single stage system and even if you could, what would it get you?
    Additional cost.

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    geobrick, I moved this thread out of the "AOP Residential HVAC" forum, because that is where homeowners ask their questions.

    As a contractor, you should ask your questions in this "Tech to Tech Chat - Residential" forum.

    Please take note of this new location, as the "Moved" icon in the other forum will only last a day.
    Instead of learning the tricks of the trade, learn the trade.

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    Quote Originally Posted by ehsx View Post
    Additional cost.
    Ha! You meant 'prices' and got auto corrected and I went on and on trying to interpret 'process'.

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    Quote Originally Posted by rundawg View Post
    geobrick, I moved this thread out of the "AOP Residential HVAC" forum, because that is where homeowners ask their questions.

    As a contractor, you should ask your questions in this "Tech to Tech Chat - Residential" forum.

    Please take note of this new location, as the "Moved" icon in the other forum will only last a day.
    Rundawg, I'm not a contractor. I'm just a retired engineer with an unhealthy compulsion to understand how things work. As evidence, look at how I wrote a full paragraph above trying to interpret a typo.

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    This is a great question. I do not perform much residential A/C so no answer from me, but I will be waiting to see if someone comes along to answer

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    Trane is a firm believer in their residential TAM air handler series. They use eev on their evaporator and heat pumps. They claim to be much more reliable. They work great on full variable speed high efficiency systems and as well when paired with an old 8 seer r22 system with the flip of a dip switch.

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    Quote Originally Posted by geobrick View Post
    Rundawg, I'm not a contractor. I'm just a retired engineer with an unhealthy compulsion to understand how things work. As evidence, look at how I wrote a full paragraph above trying to interpret a typo.
    An EEV can increase the efficiency of even a single-stage unit.

    As the Differential pressure required for the EEV to work can be lower, this means lower head pressure making the compressor more efficient.

    Also, this would require a dedicated controller or a board design to control the specific Valve installed.

    Peter

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    Quote Originally Posted by geobrick View Post
    Rundawg, I'm not a contractor. I'm just a retired engineer with an unhealthy compulsion to understand how things work.
    Can you please change your profile then so it does not state that you are a contractor - thanks.
    Instead of learning the tricks of the trade, learn the trade.

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    Quote Originally Posted by geobrick View Post
    Ha! You meant 'prices' and got auto corrected and I went on and on trying to interpret 'process'.
    Process would be cooling manufacturing processes like rocket propellant or chemical manufacturing.
    "Is this before or after you fired the parts cannon at it?" - senior tech
    I'm tired of these mediocre "semi flammable" refrigerants. If we're going to do it let's do it right.
    Unless we change direction we are likely to end up where we are going.
    "It's not new, it's better than new!" Maru.

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    Quote Originally Posted by rundawg View Post
    Can you please change your profile then so it does not state that you are a contractor - thanks.
    I just checked my profile and it's all messed up. I don't remember filling out a profile and there's nothing right in there (except where it says "man" under biography).
    It says my interests are "JuliusNiPJD". I'm not at all interested in that because I don't know what it is.
    The email address is wrong (not anything close to what I'd use).

    Anyway, all fixed now.

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    Every single "refrigeration" type machine would benefit by an EEV. They work quicker, control better and increase the efficiency of every refrigeration producing machine. If you want a study go back to Carrier A/C, as one example as an early demonstration of what an EEV can do, and study Carrier's early machines with EEV.

    Their soul purpose is to react to temperature/pressure changes quickly unlike a mechanical TXV which eventually moves a needed to get control of the refrigerant. The EEV moves instantly to changes which allows less chance of liquid flood back to the compressor(s) and more refrigerant in the evaporator(s) which means more cooling with less energy used.

    I wish I could remember the name of the Carrier Chillers made in the 80's - 90's and they would control with a superheat of around 3 degrees.
    "The American Republic will endure until the day Congress discovers it can bribe the public with the public's own money.
    - Alexis de Toqueville, 1835

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    Some Questions Answered

    I'm now, accidently(?), the proud owner of a 14 SEER residential HVAC system with an EXV.

    The contractor's proposal included a coil option where the model# had an 'E' where you'd expect a 'T'. I told him that it would have an EXV because that's what the manufacturer's spec sheet says but he insisted it would be a TXV (I think his contact at the distributer told him that). When they delivered it, and he saw it was an EXV, he was willing to bring me a different model coil but I decided I'd like to see an EXV in action, so I kept it.

    It helped me understand more about how the EXV is controlled in the system. The coil comes with a control board for the EXV motor. There's a factory installed pressure sensor on the vapor line and a temperature sensor that clips to the vapor line of the coil. It's all self-contained within the coil. The control board can optionally be located outside of the coil case to have access to the DIP switches and diagnostic LEDs. The installer chose to mount it outside the case. The EXV controller taps off the thermostat line for the R, C (24vac) and Y lines. For a heat pump situation, it would also use the BL line, so it knows when heat is being called.

    The EXV comes from the factory with the DIP switches set for 10 deg Super-Heat (options are 6, 8, 10, and 12). I don't know what the installer bases that setting on, but he left it set at the factory default of 10. The manual shows '6' is the recommended setting for several higher SEER condensers it lists but also says, "Although the above superheat set point is considered to be the most efficient set point for each coil, installation conditions can drastically effect the measurement of superheat by the EXV control. For this reason, the following DIP switch settings have been provided to enable flexibility for various installation conditions." That's where it shows how to set the DIP switches for the other SH set points (6, 8, 10, or 12).

    The contractor did all the final setup at the condenser using subcooling levels.

    So far, it's all working fine. I'll report back here if anything unusual happens over time (or if there's an early failure).

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  22. #16
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    Not trying to hijack this thread, but are there generic EEV kits available that can be used to replace existing TXV/orifice type systems?

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    Sporlan has a controller for exv’s

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    Quote Originally Posted by DeltaT View Post

    I wish I could remember the name of the Carrier Chillers made in the 80's - 90's and they would control with a superheat of around 3 degrees.
    Some current chillers will run the ssh from 5-8 *f , based on load & dsh sh.

    I’ve yet to see a dx evap that could run below ~5* ssh without liquid carry over. Refrigerant cooled motors and suction accumulators can make a difference. Flooded evaps can run near 0* ssh without carryover.

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    Why is low superheat a desired thingy?

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    In a dx evap, increases efficiency & capacity

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