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  1. #1
    Join Date
    Oct 2007
    Location
    south of boston
    Posts
    174

    No Access To Determine Txv Or Md

    hello new to doing residential, and i have a herd time figuring out if a coil is txv or md when it is on top of a furnace which has no access panal, and there is nothing marked on casing of coil. i have been guessing MD , should i guess txv if condenser list sc temp, the a/h i do remove cover to look but its the enclosed ones i cant see which i hate guessing at, any help is appriciated

  2. #2
    Join Date
    Mar 2001
    Location
    North Carolina
    Posts
    428
    no access panel....no numbers?...have snips??..charge customer to find out, if they wish to have it repaired properly, If you cant access it that means it has never been checked and probaby can use a cleaning.
    Last edited by obxtech; 07-24-2008 at 11:52 PM.

  3. #3
    Join Date
    Apr 2007
    Posts
    623
    I am assuming you dont run into this very often, as most evaporators have removable panels. But it shouldnt be that tough, make a hole and take a peak. be sure to mark it on outside once you have determined what its got. Dont ever assume that you have a txv just because there is a sc chart in the outdoor unit.

  4. #4
    Join Date
    Oct 2007
    Location
    south of boston
    Posts
    174
    obxtech

    there is no #s on it i have tried to see, but no markings, i have opened the ones with access panal, i will see what i can figure out next time thanks

    antitfun

    i do run into this often, unfortunately, it sucks on p/m cuase i cant get to coil makes me wonder how any one checked coil, is it wrong to think if its a brass fitting its md and if its brazed its txv or is that just not true, well thanks

  5. #5
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,753
    A TXV is a MD.
    MD= metering device.
    FD= fixed bore metering device, such as an orfice, cap tube, or piston.

    If you "assume" your doing the custmer a disfavor.

    Some times you have to cut an access to see for sure.
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  6. #6
    Join Date
    Aug 2007
    Location
    MN
    Posts
    2,680
    carry some 10x10 patches and cut a hole above the coil and look down with a mirror and flashlight or a camera like the rigid seesnake.
    You can't fix stupid

  7. #7
    Join Date
    Aug 2003
    Location
    Lincoln, Nebraska
    Posts
    1,051
    Around here there are many evap coils installed with no door on them. They are pitsburged shut. There are still companies doing them that way to save over the cost of a cased coil. I hate how they do it as its very time consuming to check the coil. There ought to be a law!

    I also agree that you need to cut a hole to find out which devise you have.
    Its a good Life!

  8. #8
    Join Date
    Apr 2007
    Posts
    623
    Quote Originally Posted by zombietech66 View Post
    obxtech

    there is no #s on it i have tried to see, but no markings, i have opened the ones with access panal, i will see what i can figure out next time thanks

    antitfun

    i do run into this often, unfortunately, it sucks on p/m cuase i cant get to coil makes me wonder how any one checked coil, is it wrong to think if its a brass fitting its md and if its brazed its txv or is that just not true, well thanks
    What is preventing you access to them. I see very few built into the duct, guess Im glad I work in my area and not yours, And yes some coils do have piston assmblies exterior of the coil case, I assume these are the brass fittings you are talking about.

  9. #9
    Join Date
    Aug 2007
    Location
    East central Indiana
    Posts
    75
    Quote Originally Posted by zombietech66 View Post
    hello new to doing residential, and i have a herd time figuring out if a coil is txv or md when it is on top of a furnace which has no access panal, and there is nothing marked on casing of coil. i have been guessing MD , should i guess txv if condenser list sc temp, the a/h i do remove cover to look but its the enclosed ones i cant see which i hate guessing at, any help is appriciated
    I run into the same problem around here.

    I'm retired but work during the busy season for my old boss doing PM's. When I come up against this I'm stuck between a rock and a hard place.

    On the one hand, I hate to take the extra time to cut and patch a hole large enough to clean the coil and check the MD. After all, the boss is making very little if anything on these calls.

    On the other hand, I feel like I'm shortchanging the customer by not seeing if the coil needs cleaning and by not knowing what the MD is so that I know how to properly charge the system.

    What to do, what to do?

  10. #10
    Join Date
    Mar 2001
    Location
    North Carolina
    Posts
    428
    Quote Originally Posted by mldncx1 View Post
    I run into the same problem around here.

    I'm retired but work during the busy season for my old boss doing PM's. When I come up against this I'm stuck between a rock and a hard place.

    On the one hand, I hate to take the extra time to cut and patch a hole large enough to clean the coil and check the MD. After all, the boss is making very little if anything on these calls.
    Which is why you find repairs needed and upgrades.

    On the other hand, I feel like I'm shortchanging the customer by not seeing if the coil needs cleaning and by not knowing what the MD is so that I know how to properly charge the system.
    You are.if you are doing a preventive maintenance and you overlook the obvious thats not very preventive now is it?

    What to do, what to do?
    Perform your maintenance as normal. note all work home owner needs done, like accessing coil, any upgrades that they could benefit from, quote them a price and let them decide if they want to short change themselves.
    Maintenance agreements are a good thing!

  11. #11
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,861
    you can pull the blower and look up at the coil to see if it is clean , as for knowing if it is a piston or txv might as well make a access hole

  12. #12
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,753
    Doesn't work on 90% furnaces.
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  13. #13
    Join Date
    Jul 2006
    Location
    Virginia
    Posts
    4,861
    Quote Originally Posted by beenthere View Post
    Doesn't work on 90% furnaces.
    in your part of the country im sure there are many 90%furnaces in South Texas they are few and far between. As the price of gas goes up im sure they will be come more popular . back to the topic it is bs to install a coil with no access so i will have to agree with obxtech charge them extra to access the coil or check it the best you can without knowing

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