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  1. #1
    Join Date
    Apr 2005
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    Virginia
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    176
    I just installed a ductless split system today and the ref. connections were flare fittings (which I am never to fond of) and would be behind the unit hung on the wall which could be a pain if there was a leak. So I decided to pressure test just the lineset and flare connection with 200 psi of nitrogen and left the pressure til I return Tuesday to set outside unit and finish up. Do you think that this is to much pressure to leave on the system for that much time or should I go back and relieve pressure?

  2. #2
    Join Date
    Aug 2001
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    1,936
    no

  3. #3
    Join Date
    Feb 2004
    Location
    New Mexico
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    5,473
    You can find a leak with a lot less nitro than that.
    Tracers work both ways.

  4. #4
    Join Date
    Dec 2003
    Location
    Nevada
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    1,815
    Systems can tolerate higher test presures. About 350 PSI usually check the unit for test pressure info.
    Quote
    “Engineers like to solve problems. If there are no problems handily available, they will create their own." Scott Adams

    "We can't solve problems by using the same kind of thinking we used when we created them."
    Albert Einstein

  5. #5
    igwt777 is offline Professional Member - T&B bad email address
    Join Date
    Jul 2005
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    172
    I always cut both flare fittings and then braze using couplings. I dont think 200 psi of nitro will hurt that coil, but always follow manufacturers instructions.

  6. #6
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,155
    Originally posted by lmtd
    Originally posted by hvac7
    I just installed a ductless split system today and the ref. connections were flare fittings (which I am never to fond of) and would be behind the unit hung on the wall which could be a pain if there was a leak. So I decided to pressure test just the lineset and flare connection with 200 psi of nitrogen and left the pressure til I return Tuesday to set outside unit and finish up. Do you think that this is to much pressure to leave on the system for that much time or should I go back and relieve pressure?
    There is a maximum rating for each coil. Most r-22 evaps are rated for 150 or less.
    Don't you mean 150# or MORE? Manufacturer's do their leak tests at 450#. Carrier's minimum recommended N2 leak test for installation leak test is 150#. I seem to remember similar numbers when I was at Trane.

  7. #7
    Join Date
    Sep 2002
    Location
    South Dakota
    Posts
    6,579
    Originally posted by jrbenny
    Originally posted by lmtd
    Originally posted by hvac7
    I just installed a ductless split system today and the ref. connections were flare fittings (which I am never to fond of) and would be behind the unit hung on the wall which could be a pain if there was a leak. So I decided to pressure test just the lineset and flare connection with 200 psi of nitrogen and left the pressure til I return Tuesday to set outside unit and finish up. Do you think that this is to much pressure to leave on the system for that much time or should I go back and relieve pressure?
    There is a maximum rating for each coil. Most r-22 evaps are rated for 150 or less.
    Don't you mean 150# or MORE? Manufacturer's do their leak tests at 450#. Carrier's minimum recommended N2 leak test for installation leak test is 150#. I seem to remember similar numbers when I was at Trane.

    The reason for the 150 psig maximum pressure test is so you don't harm the low pressure control. Many systems actually list different pressure test maximums for each side of the system.

    Lots of people read those listed test pressures which were on the condenser data plate and thought those were the normal operating pressures. Therefore, manufacturers quit putting them on the plate.


  8. #8
    Join Date
    Apr 2005
    Location
    NE PA
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    698
    EPA recommendations are test pressure no higher than the max low side pressure that is listed on the label of the unit.

    paul

  9. #9
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,155
    However, he's testing evap side with (presumption) service valves closed. N2 test pressure is allowed to be higher. It is limited by differential across the suction service valve. As the d/p approaches 150-200 psid, the ball valve may roll.

    In my original post, I was questioning the rated EVAP pressure stated.

  10. #10
    Join Date
    Jan 2001
    Posts
    18

    Thumbs up Nitrogen pressure testing

    If system holds 100 psi over night it is tight.
    we use 150 to 200 psi when using an ultrasonic leak
    detector,never had a problem yet!

    Remmember to use your micron gauge when you evacuate!

    alway's Remember to add trip charge to your invoice.

  11. #11
    I went to school with a man who actually tried to charge a Taylor soft serve machine to the printed pressures on the data plate!
    350 over 150!


    The reason I have never gone that high ... is I have been doing service for awhile and I know where leaks occur at.
    I have torn apart stuff to see where it's broke at.

    Some coils are made of paper thin copper or aluminum and simply wont hold the pressure you are using.

    Another big issue is the end plates where the return bends are pressed thru the plate.
    If you use excessive pressure and those copper bends expand .... you will be over stressing the joints and cause a premature failure of the coil.


    besides that ... 100PSIG of nitrogen is suffecient when usinng an ultra sonic leak detector.


    It has already been discussed that N2 can change pressure .. even when no leak is present. There is a formula for this.

    Most people dont know it, but it's true nonetheless.


    but hey ... at least your one of the good folks who does use nitrogen.
    So many never do. And yet they consider themselves experienced people.


    NOT!!!

  12. #12
    Join Date
    Sep 2002
    Location
    South Dakota
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    Those of you who are thinking that the maximum test pressures listed on the unit are somehow related to some burst pressures of the coils and piping are thinking incorrectly.

    As I posted earlier in this thread the posted test pressures are related to the protection of the controls that may be attached to the system.

    Most of the materials used in the construction of R-410A systems are either the same as or only slightly stronger than those used for R-22 systems. The brazing materials and assembly methods at the factory are the same for both. Yet, the operating pressures for 410 systems are much higher than those of 22 systems.

    The actual burst pressures for HVAC copper, coils and brazed fittings is very, very high. Much higher than the 150 psig nitrogen pressure being bantered about in this thread.

    That said, it is not necessary to leak test with anything higher than 100 to 125 psig.


  13. #13
    Join Date
    Jun 2001
    Location
    Louisville, KY
    Posts
    12,155
    Not confused at all with burst pressure of copper coils which is around 2300 psig.

    Since late 90's, Trane does their leak testing at 450 psig in the Trenton coil plant. Is it necessary for your joints in the field to be tested at that pressure? Pretty close.

    From the 2TWR2 installer's guide:
    After the brazing operation of refrigerant lines to both the outdoor and indoor unit is completed, the field brazed connections must be checked for leaks. Pressurize through the service valve ports, the indoor unit and field refrigerant lines with dry nitrogen to 350-400 psi. Use soap bubbles or other leak-checking methods to see that all field joints are leak-free! If not, release pressure; then repair!
    Note that this is a R-22 machine. R-410a machines have the same requirements.

    The source document for these leak checks is the Uniform Mechanical Code. I don't have the reference at my home. However, I have had this conversation with Trane factory engineers. I too questioned the high numbers. I had the UMC page copied into their reply with the explanation. Unfortunately, I didn't get to keep my email when I changed jobs.

    Carrier's service manual for R-22 recommends a minimum of 150 psig.

    Here's a copy of Carrier's R-410a service manual:
    New installations should be checked for leaks prior to complete charging.

    If a system has lost all or most of its charge, system must be pressurized again to approximately 150 psi minimum and 375 psi maximum. This can be done by adding refrigerant using normal charging procedures or by pressurizing system with nitrogen (less expensive than refrigerant). Nitrogen also leaks faster than Puron. Nitrogen cannot, however, be detected by an electronic leak detector.
    Bottom line: 100 to 125 psig is below the factory recommended pressures for leak testing your field fabricated joints. (As Norm pointed, you don't want N2 greater the low side pressure controls rating with the service valves open IF there are low pressure side controls.)

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