Results 1 to 9 of 9
  1. #1
    Join Date
    Aug 2018
    Posts
    3
    Post Likes

    Refrigerant contaminated?

    Hi, its my first post so hi everybody and thanks for reading.

    Installing a 4-zone mini split air + heat, 36K BTU inverter type by Midea for residential customer.

    Specs:
    • Pre-charged with refrigerant for up to 100' linesets, R-410A.
    • As usual, there is a set of king valves, and a low/high service valve on each zone
    • 4 EXVs, one for each zone, located directly past each high side svc valve.
    • Low side - all zones common. Pre-charged refrigerant floods a lineset from the low side when each low side valve is opened.
    • System has never been powered up - brand new.
    • We have the refrig schematic but I can't post it due to 0 posts. Looks standard to me.


    Steps taken:
    1. My tech opened the king valves, first. Then he pressure tested all 4 zones with dry nitrogen, leaving the N2 in all zones while proceeding next step.
    2. Next, he began the usual process of commissioning one zone at a time: vent the N2 in the zone, evac, then release the pre-charge into the zone by opening the low side valve for that zone, finally open the high side valve.
    3. On the third zone, he opened the correct low side valve, which flooded the zone with refrigerant, but then he opened the wrong high side valve - it was the 4th zone's high side valve, and zone 4 was still pressurized with N2.


    He was smart enough not to just keep going, so now we're trying to decide how to proceed.

    Tech at our vendor seems to think there's a possibility the N2 could have bypassed around the EXV, even if it was closed, to contaminate the whole charge (i.e. through a check valve etc, since the system also operates as a heat pump), but after reviewing the schematic the EXV is directly in series with the high side valve, so it would fully control flow at that point. My argument is that if the EXV is even slightly open, we would see refrigerant pressure at zone 4's service port. I'm thinking if we vent the nitrogen from zone 4 and see 0 psig with the high side valve open, it means the EXV is fully closed and no damage was done - we can just evac zone 4 with high side valve open, and proceed.

    Obviously if there is refrigerant/pressure present in zone 4 when/after venting the N2, he contaminated the whole thing and it must be recharged. But if this is completely unnecessary we obviously want to avoid wasting time and materials.

    So I guess my main question is: am I on track with this line of reasoning, or missing something obvious?

    What would you do in this situation?

    Your advice much appreciated, thanks!

  2. #2
    Join Date
    Aug 2002
    Location
    Southold, NY
    Posts
    15,509
    Post Likes
    Recover the entire charge............

    Bleed the N2 off the top of the recovery cylinder

    or

    Just recharge with virgin refrigerant!

  3. Likes JeffWil liked this post
  4. #3
    Join Date
    Aug 2018
    Posts
    3
    Post Likes
    Thread Starter
    Quote Originally Posted by pecmsg View Post
    Recover the entire charge............

    Bleed the N2 off the top of the recovery cylinder

    or

    Just recharge with virgin refrigerant!
    Thanks for your reply.

    Yes I realize we can do a full recover/evac/recharge but I'm just trying to avoid wasting time/materials if no problem actually exists.

  5. #4
    Join Date
    Mar 2018
    Location
    Kansas Flatlands
    Posts
    121
    Post Likes
    Do the whole thing,sounds like you know what you're doin. If wasting time is your concern, get to work and quit reading this thread.

  6. Likes josegarcia, BALloyd, J2018 liked this post
  7. #5
    Join Date
    Aug 2018
    Posts
    3
    Post Likes
    Thread Starter
    Quote Originally Posted by theoldscroll View Post
    Do the whole thing,sounds like you know what you're doin. If wasting time is your concern, get to work and quit reading this thread.
    Ha ha, good one. Trust me we have plenty to do other places. This customer is not in a rush, so I was just hoping some of you long-time experts had seen something like this and might comment on whether I was on the right track with my reasoning. There's only so much labor available so we got to use it wisely.

    Thanks again for your reply.

  8. #6
    Join Date
    Jul 2009
    Location
    South Carolina
    Posts
    5,218
    Post Likes
    I'm not familiar with your system but why take any chances when you are doing a new install. It's easier to rectify any known mistakes before starting up the system than afterwards. I would bite the bullet, recover everything,vacuum & fill with all virgin refrigerant. If you're worried about spending the extra time just think of the possible time you might spend in the future to get it right if something happens as a result of nitrogen being in the system.
    Gary
    -----------
    http://www.oceanhvac.com
    The best things in life are free but not everyone is willing to pay the price.

  9. Likes JeffWil liked this post
  10. #7
    Join Date
    Jun 2018
    Posts
    9
    Post Likes
    So the client is in no rush. But your concerned about your labor hours. I hope you have a lot of warranty hours, cause you'll be burning though them. Don't cut the corners, it's gonna hurt. Spike Lee said "do the right thing". Listen to what is being said here, dump the charge, and learn how the system operates, and how to install it properly. Hint all EXV, come in the open position until powe

  11. Likes JeffWil liked this post
  12. #8
    Join Date
    Jul 2018
    Location
    Ohio
    Posts
    262
    Post Likes
    Open when not powered.
    If you know there is a possibility that it bled, your wasting hours by not recovering and evacuating and recharging with new.
    Wouldn't hesitate.
    If you don't have the time to do it right the first time, you'll spend more time doing it the second.

    Sent from my XT1710-02 using Tapatalk

  13. #9
    Join Date
    Feb 2010
    Location
    Lake Havasu AZ.
    Posts
    38
    Post Likes
    I would have leak test everything isolated from the condenser, then no chance of releasing the charge into the wrong line set.....they would of all been leak tested and under vacuum but the time I touched the king valves....and honestly if I messed up and mixed nitrogen and the r410 I would of ate the cost of the virgin 410 and you would of never known....

  14. Likes firecontrol liked this post

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

Related Forums

Plumbing Talks | Contractor MagazineThe place where Electrical professionals meet.