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  1. #1
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    May 2018
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    Lennox Zonemaster/M099

    Dad said I had to get a certain number of posts in before I could become a professional and move over to tech to tech, but what the heck, ill just bring it up here and pray for a reply. Got a Lennox zonemaster that has me scratching a hole in my head. Building engineer decided they could save money by changing zonemaster system from R22 to M099. Well now were in 105* days here in Texas and none of the AHU (8 heads) will get better than an 8 degree split across the coil. My thought is to revert back to R22 but was curious if anyone had experienced this much efficiency loss?

  2. #2
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    Southold, NY
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    http://hvac-talk.com/vbb/showthread....nical-Question!


    You've given us NOTHING, NADDA, ZERO information so how can we tell

  3. #3
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    Thread Starter
    Alright I get that. I had a super simple question as to if you’ve seen efficiency loss with M099. Nobody is still using zonemasters so I don’t really expect anyone to have experience in my exact situation.

    Not trying to come off as a prick just trying to feel out everyone.

    I can give you all my pressures and SH/SC and all of my numbers if you’re interested. My question was referring to M099 not necessarily my situation. Just giving some background so you knew where the question came from

  4. #4
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    Quote Originally Posted by Iamwildbill View Post
    Alright I get that. I had a super simple question as to if you’ve seen efficiency loss with M099. Nobody is still using zonemasters so I don’t really expect anyone to have experience in my exact situation.

    Not trying to come off as a prick just trying to feel out everyone.

    I can give you all my pressures and SH/SC and all of my numbers if you’re interested. My question was referring to M099 not necessarily my situation. Just giving some background so you knew where the question came from
    I know of no manufactures that have tested there equipment with alternatives.
    Most refrigerant manufactures claim a minimum capacity loss.
    Personally I never measured all the parameters to give an educated statement either way.

  5. #5
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    Jan 2004
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    Considering that MO99 is about a 10% capacity loss over R22 at rate conditions. I wouldn't expect it to do well at 105°F ambient conditions.

    But without knowing the readings, no way to know if that is the full problem or not.
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  6. #6
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    May 2018
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    Thread Starter
    I have been through every scenario in my head as to what could possibly cause this and I just don’t think a system like this is compatible for a drop in. I have been out a couple days looking over the system and it’s the only conclusion I could come up with. I have tried running a higher superheat (less refrig) and I have overcharged Lennox standards which is 15-20 SH. It didn’t seem to make a difference what I did the cooking wouldn’t improve. I am pulling all of the 99 out and putting 22 back in on Monday. If it alleviates the problem then I’ve learned something to share.

    Carrier 16 ton (semi hermetic) condenser
    Lennox zone master box
    (8) 2 ton AHU

    69/227
    Suc sat 46
    Suc line 61
    Liq sat 105
    Liq line 103
    Ambient 99

    Across 4 AHU the best split I got was 78/70

  7. #7
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    Did you try shutting down 2 of the air handlers and see if the temp delta improved. If its problem with the MO99, then it should be able to handle a reduced number of units. If reducing teh number of air handlers doesn't improve the delta. Then it may be another issue.
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  8. #8
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    Thread Starter
    I did try that. I was thinking it may have been short on refrigerant so before adjusting the charge I tried that. No change anywhere. Maybe I should have picked y’all a brains earlier on this issue for ideas!

  9. #9
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    Also, that condenser should have a higher SC.
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  10. #10
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    Ohio
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    I would expect to see higher head pressure on 105 degree day too. M099 is usually pretty close to 22 but a slightly higher head pressure.

  11. #11
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    Thread Starter
    Alright guys. One of my biggest problems with postings on here is never hearing what came of the situation. I believe there was a combination of issues with the unit. One, definitely undercharged. I was fooled because the day prior to making the M099 conclusion I had just added a 30lb jug, and my SH came so far down I figured my charge was OK. I definitely charged more than I pulled out, should have weighed it out to see the actual numbers. In good news, I charged the system back up with the R22 and it is back to happy. Cooling as it was designed. I am still real skeptical about the drop ins, but I don't feel like this test was conclusive.... frustrating. Thanks for all of yalls input

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