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  1. #1
    I'm lookin at this meat case. Temp gage reads 20F. Meat man says he's not getting the longevity out of his red meat. I lean down and exhale and I can see my breath. (and by this time of the day ... that was NOT a pretty site).
    I check the rack pressure. I have Seven pounds on the suction header and Fifteen upstream of the EPR on that circuit.

    Hmmmm.....

    I checked the gang clock, four a day at 30 min each. I change that to 36min 3 times a day. 0600, 1400 & 2200 hrs.

    I go back down the ladder .....(that is getting real old, REAL FAST!!!)

    I pulled one of the pans and found a fan motor, running.

    I run by infrared along the honey comb and find the left half with 17F discharge air. The right side is 30F discharge air!
    hmmmmm.......

    What's on this circuit is sixteen feet of open case then an end cap of five or six feet of the same.

    Tyler cases. Single level, one shelf only.

    Since this sucker is 16ft long, there could be two coils under the hood or only one big one.

    But what doesnt make sense is the definitive temp dif I get RIGHT IN THE CENTER between the two halves.

    It was aproaching overtime and the customer wasnt gonna lose any meat over this. So I was advised to pull off and return in the AM. That's why I didnt pull the one side and inspect the whole thing.

    I am thinking I either got pluged honey comb or one of two coils under there Aint Doin it's job!

    What do you think?

    Me .... I dont even know what all is under there.



  2. #2
    Join Date
    Aug 2002
    Location
    Orange County CA
    Posts
    1,084
    I just re-read your post... I bet you have T-stat solinoid control. The stat is probably in the warm case and dragging the good(cold case down).

    The set up sounds like 2 8' cases. I bet you have a txv issue if all the fans are running.

    [Edited by NedFlanders on 05-06-2004 at 09:39 PM]

  3. #3
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,663
    No such thing as 16 ft case, look for the seam in the cases. You got one txv power head out i think.

  4. #4
    Hey thanks Ned.

    Once I've "been around the block" ... a time or two ... I will know better how to diag these little issues.


    But right now, I just look for the obvious and pray for wisdom.
    Oh, .... and when I get home, I come here and post.







  5. #5
    Join Date
    Aug 2002
    Location
    Orange County CA
    Posts
    1,084
    It takes time just like anything.Stick with it.

    Sometimes you just have to dig a little.

    I always pull the easiest section (the least product) and stick my head below to see what I can see. Usually the left side of the case in question(txv location).

    Sometimes you'll see obvious stuff,sometimes nothing.
    If the last guy had half a brain, he'd have marked the stats and solinoids on the "as built" prints hanging on the wall.Or he would have updated the Magic Marker Map on the motor room door.

    If it's a new account,you are an explorer hunting for elusive E.P.R. or liq. line sol.( how thrilling!!)

    I'd swear some guys don't mark stuff just so they are the only guys who know where the $hit is!!

    Probably a pissed off Hussmann guy (right Dave)

  6. #6
    Originally posted by Freezeking2000
    No such thing as 16 ft case, look for the seam in the cases. You got one txv power head out i think.
    Hey Freezeking, so your sayi there is no such thing as a sixteen foot case?

    Okay. So they all come in multiples of eight?

    Alright ... I can deal with that.

    I got one case that is not feed properly, or maybe iced up.
    I did notice one fan, visually, and it was working.

    I did the matches at the honeycomb. Got movement all along both cases.

    hmmmm.....

    I will pull that section in the morning. Thanks all.

  7. #7
    Join Date
    Feb 2003
    Posts
    1,166
    Most common case lengths are 8' and 12' with the odd 4' or 6' case. Usually there will be 2 fans for an 8', 3 for a 12' but not always. If you were checking the temp where these 2 8' cases join then you could just be looking at an area where the airflow does not pass thru the coil. Like it was said before you need to open up a section and take a look when checking out cases, could be fan plenum not in place properly, bad motor, wrong direction motor,plugged honeycomb,plugged air baffle above coil,package of bacon fallen down return air side, all kinds of influences inside the case or outside influences from store hvac system disrupting the airflow on case etc.,etc.
    Watts New, Ohm My, I been Electrically Commutated. Are U2.

  8. #8
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,663
    I found that the TXVs are mostly located on the left side of each case section. If you had airflow and enough gas you probably have a clogged strainer on the txv inlet or a bad powerhead on the txv valve. I know you will figure it out. Do not hesitate for a customer to PULL the whole case so you can get a good look when there.

  9. #9
    R-12,

    As stated before the vast majority of supermarket cases are either 8 or 12 feet (except for door cases, which are 2,3,4, or 5 doors normally). These are then piped together to form line-ups of as much as 48-60 feet on one circuit.

    If one case in a line-up is acting up, then you probably have a bad fan or a TXV issue (could also be bad heater if electric defrost). If the entire circuit is giving trouble, and the whole thing isn't iced-up and/or the drain blocked, then the problem may be at the rack.

    Don't forget that some cases, like Hussmann Impact, have multiple evaporators in a single case. You'll also find some older multi-deck fresh meat and frozen food cases with multiple evaps. This can lead to really strange things like a case flooding and starving at the same time. That sort of problem will test your diagnostic skills.

    The biggest difference between supermarkets and the stuff you worked on before is this idea of multiple components (compressors or evaporators) in parallel. The basic laws of thermodynamics and physics still apply: heat flows from hot to cold, water flows downhill, pressure drop is a bad thing (except in TXVs and orifices), etc. Everything you know from before will still be useful, but sometimes you need to think in multiples.

    Good luck,

    emerson

  10. #10
    Join Date
    Jan 2004
    Location
    Earth
    Posts
    4,879
    Sometimes The pressure is telling you to react. Just step back and think about it. You'll see the answer, if you do that.

    To tell your case's apart, look at the joints on your trim. Not always apparent on the tag rails, look at the canope, and front trim panels. A twelve footer has three shelves, eight footer only to two.

    Emerson brought up a good point about glass doors not being the same. They are thirty inches per door. All these dimentions are without end caps you have to add them.
    A Diamond is just a piece of coal, that made good under pressure!

  11. #11
    Originally posted by Freezeking2000
    I found that the TXVs are mostly located on the left side of each case section. If you had airflow and enough gas you probably have a clogged strainer on the txv inlet or a bad powerhead on the txv valve. I know you will figure it out. Do not hesitate for a customer to PULL the whole case so you can get a good look when there.

    I attempted to pump down the circuit. Big joke for sure. Ball valve leaks like a stuck pig!

    I got the pressure reasonably low and pulled the screen. AFTER putting on safety glasses!
    Screen was clean as a whistle.
    I ran for a powerhead. Replaced it and was back online in short order!
    Oh what a feeling!!!

    Why dont these racks have Henry hand valves for shutting down circuits for isolation purposes? I never knew a Henry to fail me.


  12. #12
    Join Date
    Aug 2002
    Location
    Orange County CA
    Posts
    1,084
    Originally posted by R12rules
    Why dont these racks have Henry hand valves for shutting down circuits for isolation purposes? I never knew a Henry to fail me.

    [/B]
    more $ at install time...ain't it great?

  13. #13
    Originally posted by NedFlanders
    Originally posted by R12rules
    Why dont these racks have Henry hand valves for shutting down circuits for isolation purposes? I never knew a Henry to fail me.
    more $ at install time...ain't it great? [/B]
    Ya know .. I closed that ball valve and stodd there like fifteen minutes and my gages did nothing!!! I even felt downstream of the ball valve and no temp dif.

    So I finally started dumping refrigerant into the susction header. That got me down in short order.

    But hey ... what is that much tech time worth during installation? A 5/8 Henry valve CANNOT cost more than fifty bucks! And that market paid alot more than that for me fartin around with the valves upstairs!

    Plus, if I would have had to make a weld .... I would certainly have demanded lower than 10 PSIG on my lines!

    Hussman Engineering .... strikes again!



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