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  • Dishwasher, 1 tank is low on temp, need some assistance

    Posted by guest on March 5, 2017 at 12:00 am

    Hello again guys

    I am fairly lost with my STPCW-30 Dishwasher from Stero.

    Been a headache for a while with all kinds of problems but I got one now that I can’t seem to solve.

    The machine has 5 tanks, 2 of them are scrapper (120-135*F), 1 is wash (150-165*F), 2 rinse tanks (165-190*F). Then it has a Final rinse which is the sanitizing spray at the end but is run off its own heater.

    We have an issue with our incoming water supply not being high enough so we can only maintain certain temperatures, on average this is how it looks, scrapper is 110-120*, wash is 140-150* and rinse tank 1 and 2 are 155-160* and normally a couple of degrees apart with the 2nd tank being slightly hotter.

    Problem is that now I am seeing the 2nd tank at about 140* when the 1st is at 150* which is very unusual, normally its a blown fuse or something easy to find but in this case I can’t find the problem.

    I have checked all the fuses, all legs of the heating circuit are pulling amps and the water does get to 160-180* when the machine is heating and they aren’t running it but the moment they start it the temp just starts dropping and stays at around 140*. Normally this is a blown fuse or a contactor leg is burnt up or something like this but it seems to be running just fine and the problem does not seem to be electric.

    I also confirmed the solenoid valve is not constantly calling for water, it has 2 float switches in every tank, 1 controls the low water cutoff for the heaters and the pump and the other controls the water level of the tank, I was thinking the float controlling water level might be malfunctioning and calling for water constantly but that’s not the case.

    So I looked into the machine and checked the manifold end caps and made sure they were all tight, even tried swapping some of them around but to no avail and the problem is still there.

    I confirmed the temp gauge is accurate with my Fluke meter.

    I emailed Stero to see what they say but I could use some help on trying to solve this as its driving me up the wall.

    Need you guys to help me out of this one

    olivero replied 6 years, 5 months ago 1 Member · 40 Replies
  • 40 Replies
  • ectofix

    Member
    March 5, 2017 at 8:48 pm

    Quite a monstrous flight machine there with all those tanks.  So…it’s all ELECTRIC heat then?  You mentioned current draw several times, so I assumed that.  OUR flight machines are all steam heated (heat exchangers).

     

    Typically, 140° incoming temp is what’s expected.  You said there’s a problem there?   That’s certainly a problem.  However, if the booster is capable of keeping final rinse temp above 180°, that may not be THE problem then.

     

    You so happened to mention wash and rinse tank temps.  What’s the final rinse temp?  As said before, it should be 180° or more.  If not, then there’s a major problem overall.

     

    Certain things I’d look for:

     

    Curtains.  Are they all there and in the right places.  Those and drain-off pans. All those manage water flow.  If they’re not in the right place or are missing, fix that first. Scale.  If the elements are scaled up, delime the machine.  Scale has an insulating factor that can reduce effectiveness of the heating elements by as much as 40%. O-rings.  If the drains use them, check to see if there’s loss of tank water past them when the machine is idle that may otherwise be going down the drain during operation. This shouldn’t be confused with normal drain-off which happens when the machine is initially shut off or the normal water cycle’s drain-off when the machine is running at full bore. Normal water cycle is run-off from the scrapper section (pre-wash) stand-pipe(s) when the machine is running with a constant load of dishes.  The scrapper section will be the only one having a stand pipe to do that.  During heavy operation, FINAL rinse water will cascade through and into the rinse tanks, then the wash tanks…and finally to the skimming action of the pre-wash standpipe.

     

    Off the top of my head, these are just a few things that I would check beyond what you already have.  Maybe I’ll think of others after I sleep on it.

     

    Good night and good luck.

  • olivero

    Member
    March 5, 2017 at 8:54 pm

    Hey Ectofix, meant to mention you as one of the saviours, don’t know how I missed you.

     

    The final rinse can stay above 180* its a very good booster they have.

     

    Curtains are all in place, I will check the drains tonight but as it was sitting there heating, there was no heavy stream of water going down the drain so I doubt that’s it but I will check regardless.

     

    I doubt Scaling is the problem as its only in 1 of the tanks and not all 3. That’s what’s tripping me up, its only 1 and its not related to that 1 tanks heating circuit so its gotta be something else.

     

    I will rebuild the solenoid valve for that tank tonight and see if it makes a difference, my water meter for the machine busted about the same time this problem occured so I don’t know if I am using more water than before -.-

     

    Who knows, maybe a piece of it is stuck in the solenoid valve

     

    Its either that or the float maintaining the fill level but I would see that on the solenoids reaction time and frequency its staying on….. Driving me nuts.

     

    I probably won’t sleep on it until I get it fixed  

     

    Good night though.

  • techjoeb

    Member
    March 6, 2017 at 7:52 am

    Man you have the best problems. That incoming water temp is a beast! Please let us know because I’m so curious I could explode. Take pictures if you can! 

     

    -Joe 

  • olivero

    Member
    March 6, 2017 at 8:30 am

    I wish I didn’t have all these problems……….. I feel like I am aging years by the weeks

     

    As an update, I checked the drain last night, its not leaking, I checked the solenoid valve feeding that tank  also not damaged, scarred or obstructed, it was actually really clean.

     

    Also verified the float controlling the water level was working and responding to being moved, confirmed it by checking for continuity in the float switch as someone moved the float up and down at different speeds, didn’t fail once……………..

     

    I could also see the heating elements work when I looked in the tank, they had bubbles on them which means they are heating, I could see it on every one of them, so I am pretty sure its not electrical, but its something else. 

     

    I just don’t know what.

  • fixbear

    Member
    March 6, 2017 at 8:52 am

    Look at the machine overall and ask yourself how it heats the tanks.  Each individual or a system heater.  How is it controlled?   Is each heater drawing the proper amperage?  Are the air dampers set correctly?    

  • olivero

    Member
    March 6, 2017 at 8:57 am

    I have been taking care of this unit for 4 years now, it is operating the same fashion it always has, heaters are all drawing normal amperage, all the fuses are ohming out at 0.01-0.03 ohms. 

     

    Confirmed CFM exhaust is the same as it used to be, it is.

     

    I understand how the unit heats, and its doing that, problem is its somehow loosing the heat faster than the other tanks. It will heat up and gets to temp, it just looses it too fast.

  • fixbear

    Member
    March 6, 2017 at 9:08 am

    If all that is good, then you have a constant loss of water from the low temp tank.  Either it is carrying over to another tank or going down the drain. 

     

    What type of heat system does it have?

  • olivero

    Member
    March 6, 2017 at 9:14 am

    Its electric heaters, 5 KW heaters in each tank, scrapper is not heater, wash, rinse I and rinse II are all heated with the same elements, contactors, fuses, etc. 

     

    I checked the drain, I am not loosing water due to a drain leak, I am not leaking water into the tank through the solenoid either.

     

    Rinse I and Rinse II share their water, there is a pipe connecting the 2 tanks together so if one is going low, the other will help replenish it. But its only rinse II that has this problem, rinse I is fine.

  • fixbear

    Member
    March 6, 2017 at 9:28 am

    Immersion heaters?  Correct?   Not loosing water,  Then you do not have heat in that tank.  Temp control,  contractor or Heater element for the low tank.  If you have two adjacent tanks with a common connection one heater can bring both to temperature due to convection flow.  But once there is a load the unheated tank will drop back.  . 

  • olivero

    Member
    March 6, 2017 at 9:41 am

    Yes, Immersion heaters.

     

    I have heat in the tank, I have visually and temperature wise confirmed that the heaters are operating in both tanks, I can see the heat waves above the heating elements as they heat the water, I can measure the load on the legs of each tank and they are around the same amps. I have confirmed the T-stat’s are working, the tank is set for a max of 200* and will go to 200* and shut off, once the machine starts and tank temp drops, it kicks back on.

     

    I am 100% sure both tanks are heating on their own.

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