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  1. #1
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,415

    I need some Kraus chiller help please...

    MN KPC 212-L-U/S
    Product # 212.4001.03.427.0404

    Problem, circuit 1 is going off on low pressure safety, also the desuperheater freezes up while it's running. Past the main TXV it's just as warm as the liquid entering the TXV (but the 1st circuit will maintain water temp aside from going off on low pressure).

    We figured the TXV was bad so we ordered a new power assembly and also the guts to swap it out. Did that, changed the drier pulled a good vac and dumped the charge back in. Same thing happened.

    Noticing the desuperheater is freezing up we thought maybe the txv for that is stuck wide open and robbing too much liquid causing the main txv not to have anything to flash off. We swapped that out today to no avail, same thing continues to happen.

    I called tech support, we walked through the programming to ensure it was all set up like it should be (this was his last guess as to what's wrong, the tech support guy has been involved since the start). I did also check the hot gas valves were both backed out 3/4 of a turn (same as circuit to and what the factory recommends).

    Prior to this I was basically a parts changer following instructions from a coworker (who on a side note isn't normally stumped by much). After that all didn't work, and watching this system operate I noticed a few things.

    When circuit 2 is running, the 2 solenoids for the hot gas that feeds the desuperheater cycle quite often to keep the suction pressure around 2 bar, maybe creeps up to 2.5.

    Circuit 1 will run around 1.5-2 Bar while it's trying to get the water temp down (set temp is 9.5 deg C, I let it get up to around 12 to get a good load), but once the water temp gets in the mid 9's those solenoids quit cycling and slowly the suction pressure drops until it gets low enough to shut off on the LPS.

    I think there's multiple problems on this system, but I'm not real sure what.
    I know the TXV should be cold right after it (circuit 2 is), and if it's not all the liquid is flashing off deeper into the evap than it should, which is limiting it's ability to pick up heat from the water and causing the lower suction pressure.

    Also it almost seems like the temp sensor that controls when those valves kick on and off gets "lost". Like it's out of calibration or has the wrong settings... but it might be drifting due to the above problem too, I'm not real sure.

    So do any of you Kraus experts have any suggestions?
    "If you call that hard work, a koala’s life would look heroic."

  2. #2
    Join Date
    Sep 2002
    Posts
    13,548

    What is the verified subcooling immediately before each TXV?

    What is the verified subcooling immediately before each TXV?

    What is the SSH out of each heat exchanger?

    Too much subcooling - that is: liquid temp being too close to suction temperature - will trick a chiller.
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  3. #3
    Join Date
    Sep 2002
    Posts
    13,548

    What is the head pressure?

    What is the refrigerant?

    What is the discharge pressure?

    What is the liquid line pressure?

    What is the minimum required pressure differential across the TXV's? What does the TXV manufacturer want to see as a minimum?
    PHM
    --------
    The conventional view serves to protect us from the painful job of thinking.

  4. #4
    Join Date
    Dec 2003
    Posts
    2,432
    Quote Originally Posted by amickracing View Post
    MN KPC 212-L-U/S
    Product # 212.4001.03.427.0404

    Problem, circuit 1 is going off on low pressure safety, also the desuperheater freezes up while it's running. Past the main TXV it's just as warm as the liquid entering the TXV (but the 1st circuit will maintain water temp aside from going off on low pressure).

    I think there's multiple problems on this system, but I'm not real sure what.
    I know the TXV should be cold right after it (circuit 2 is), and if it's not all the liquid is flashing off deeper into the evap than it should, which is limiting it's ability to pick up heat from the water and causing the lower suction pressure.
    I dont think you have any liquid passing through the txv. If you did the line would have to be cold. The only thing that would keep the line from being cold, if you are passing liquid, would be a stopped up evaporator. It could be logged with oil, but Im still thinking you dont have any liquid. If there is a liq line sol valve are you sure it is opening?

  5. #5
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,415
    Sorry for the delay, worked 10 hours monday, drove across the state and slept 4 hours last night, then was in a boiler school most of today, drove back home... and here I am... about ready to nod off.

    This system has 134a freezone in it. I don''t know what the discharge pressure is, high side runs around 10 bar, varies some but not too terribly much.\

    I can't answer what the TXV has for pressure on both sides, and I have no clue what it wants, I don't have that info handy but I can likely get it from the numbers I wrote down.

    I didn't measure much for temps since it doesn't really run consistent enough for anything to stabilize. To check it you'd have to unhook the desuperheater, but doing that makes it run down to the LPS mighty quick.

    From the hand-o-meter, the line going into the txv is warm, seems a bit warmer than it should be, outdoor temp was mid 60's and it was probably in the 80's or 90's. The line after was not cooler at all, same temp (measured this on the previous visit). The superheat measured right before the compressor (which isn't really far from the evap) was running 15-18 the previous time. I measured the subcooling but don't remember what it was, it had to be in the normal range (10-15) or I'd think that would have set some sort of red flag in my head.

    The reason why I'm kind of believing the refer is flashing off deeper into the evap is because with that circuit running it will maintain temp. The temp swing is a bit more than circuit 2, but considering circuit one cycles off on LPS and isn't running right it's kind of understandable. But if it wasn't flashing any off and just blowing gas through there it should loose ground on the set temp or even heat the water up, which it doesn't do.

    Oil level is right around 1/3 in the sight glass, which is normal so I don't think the evap is logged with oil. I've also thrown a magnet on all 3 solenoids (LLSV and the 2 hot gas one's), you can feel and hear them click, and with the LLSV closed the unit pumps down.

    I don't think this is an overly complicated problem, but it's not too obvious either.
    "If you call that hard work, a koala’s life would look heroic."

  6. #6
    Join Date
    Jan 2007
    Location
    Charm City--the city that bleeds
    Posts
    2,790
    with both parts of the low side on circuit 1 being affected, could it be a water issue?
    But then no problems observed with circuit 2... hmmm


    And you say that it pulls down...
    Is it (microprocessor) going into a pumpdown somehow?

    You could pull the gas and weigh in new, rather than reuse old. Has anyone else possibly charged it. I've run into a lot of 22 Kraus chillers, and only a handful of 134s. Maybe they grabbed a jug...
    It's great to be alive and pumping oxygen!

  7. #7
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,415
    It doesn't really go into pump down, (goes off on LPS before it cycles off, and this thing never really is designed to shut off). When it did pump down was when I was running the solenoid by hand (magnet).

    This last time I was there I did replace the refer with 134a and weighed in the 24# charge, I was pretty sure it wasn't the problem, but was one more item I could check off the list if possibles.

    I'll admit I never thought, for what ever reason, that it could be a water problem or an evap problem. But... if it was a water problem (blocked flow or restricted, what ever the case may be) the refer leaving the txv on that circuit should be cold, not warm even still.

    I love a challenge... but I like challenges I can fix too
    "If you call that hard work, a koala’s life would look heroic."

  8. #8
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,415
    Any random guess's?
    "If you call that hard work, a koala’s life would look heroic."

  9. #9
    Join Date
    Aug 2006
    Location
    Ohio
    Posts
    2,089
    If you are having low pressure trips on any chiller you need to start with water flow. Insure you have what is required and then you can start digging into the refrigeration side.

    Check your pumps, filters/strainers, circuit setters, etc...

  10. #10
    Join Date
    May 2004
    Location
    Rapid City, SD
    Posts
    7,415
    So.. the saga continues...

    We pulled the TXV and found this...
    LMH-01.jpg
    I'm not real sure why there's a screen after the TXV, but not one before the TXV. It's a pretty heavy screen too with small holes, which looks like a pretty good restriction itself (even if it was clear).

    We ordered up a new heat exchanger from Kraus.
    LMH-02.jpg
    There's a few obvious differences between the old one and the new one. Aside from the obvious difference of different M/N..

    and different size threads on the water side...
    LMH-03.jpg
    LMH-04.jpg

    oh and the different numbers
    LMH-06.jpg
    LMH-07.jpg

    I called the factory rep to get the right HX coming. We exchanged several phone calls and every time he said that's the direct replacement. I told him about the different numbers, and the different pipe size. He argued that it was the same thread size I was doing something wrong. Then he contacted the people in Germany, they basically told him "it's right, leave us alone" from what I gathered.

    Later he explained to me (like I was a 10 year old trying to do HVAC) that there are 3 pieces to the union and I have to remove the piece from the old HX and install it on the new one. Wow, I'll admit it, he's lucky he wasn't standing in the same room as me! No matter how many times I told him it was the wrong thread size he argued. Finally he told me to just "get a coupler or bushing and do what ever you have to do to make it work".

    A seemingly simple job, so I grabbed a 1.25 coupler, it made it around 1/4 turn before it was tight, obviously this wasn't pipe thread, which was evident by the straight threads. I called him back to find out what size threads these were, he had no answers but said he would check with the engineers 1st thing in the morning (it was late afternoon when I called him). The next day I called back to have him tell me "oh, they are probably metric, go try some metric pipe". Living in SD has some benefits... but finding metric pipe isn't one of them. He told me "oh we have access to that out here (where ever he's at). I asked if he could ship me some stuff... "oh, sorry we don't deal with pipe fittings". AHHHHH!

    I told him if he was sure this was the right one, and he wanted us to "make it work", I was going to silver braze some fittings in there and make them work, he tried one more time to explain to me that I was taking the union apart wrong before our conversation ended.

    Today we got up there, ripped the old one out, heck I even took apart the union they way he described, but try as I might I couldn't get the threads to start.
    LMH-05.jpg

    Onto the solution... "what would McGyver do?!"
    LMH-08.jpg

    All wrapped up in some insulation (and lots of duct tape)
    LMH-09.jpg

    All back together, this was taken while we were leak checking, thus no insulation.
    LMH-10.jpg

    Good news, it's up and running, nothing a day playin in the 30 deg weather and one of the 1st snow storms of the season.

    My huge grumble now *steps on soap box*
    1st off, with the parts we've ordered for this unit we've had the wrong stuff shipped 3-4 times, then getting this HX, being told it's right, we just don't know what we are doing, but receiving NO help from the factory guy, and finding out he has NO clue what he's doing and at best was just throwing out excuses trying to buy time or hope we quit calling. I did find out later, thanks to the help of a supply house guy and his magic book of phone numbers the threads are BSP threads... go figure!

    In short... I'm beyond displeased with Kraus tech support and parts dept (all handled by the same guy).

    P.S. If anyone from Kraus is reading this, feel free to contact me off site if there's any chance you can help remedy these kind of problems in the future!
    "If you call that hard work, a koala’s life would look heroic."

  11. #11
    Join Date
    Dec 2002
    Location
    SouthEast NC ICW & Piedmont Foothills
    Posts
    7,635
    the old threads looked ----------coarse

    the new ones looked ------------fine
    It`s better to be silent and thought the fool; than speak and remove all doubt.

  12. #12
    Join Date
    Jan 2004
    Location
    PA
    Posts
    68,773
    Moved to Chiller forum.

    Maybe you'll get some more help here.
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    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  13. #13
    Join Date
    Oct 2004
    Location
    Metro ATL
    Posts
    454
    Was there a screen in the new HX? I have had similar head aches with a Kraus machine. Great chiller, love the engineering but what a pain trying to get parts and tech help.

    I just spent an awesome week in your great state. 30 degrees and snow, sounds like I left just in time! It was wet already, you guys didn't need snow on top of it.

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