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  • Hobart UW50/ aka dinosaur…Boosters not heating

    Posted by DanC on January 27, 2022 at 8:50 am

    Our 20+years old UW50 High Temp dishwasher is working fine except for the boosters not heating the rinse water up to temperature. We have the old construction model, i think. In the ‘Catalogue of Replacement parts’ it says (before S/N 851081922) The model with two stainless booster tanks each with a 7000w heater element.

    I tested the heating elements and they’re not getting power. In the booster control box the contactor is getting proper voltage but not pulling in, I tested the contactor with the unit de-energized and the contactor seems to be in fine condition.

    I believe that there are two circuit boards (one in booster control box and one in the other control box) with a red light labeled ‘heat’ that goes on when the boosters are being energized. Those lights are on yet the boosters still have no power. At one point the light went off when I was looking at it, I adjusted the plastic screw on the board used to set the temperature, the red light came back on and still no power to the boosters.

    Anything else I can check? High Limit Protector?

    fixbear replied 3 months, 3 weeks ago 3 Members · 5 Replies
  • 5 Replies
  • fixbear

    January 27, 2022 at 7:32 pm

    Does the contactor for the heat element have coil power?

  • fixbear

    January 27, 2022 at 7:44 pm

    Most dish machines of that age have a mechanical high limit on the booster as well as a thermostat system. The thermostat system can be either electronic with a thermistor for sensing or a remote thermostat with a bourdon tube in the booster. Look at your booster tanks for taps for control. Hobart also used a remote safety on some of there machines. Has a red button for reset.

  • DanC

    January 28, 2022 at 2:59 pm

    I only had a little time to check it out today, but there is no power going to the contactor coil.

    I must have the bourbon tube version you mentioned, like this:

    Is there a way to test this, maybe isolate it out?

    • ectofix

      January 29, 2022 at 2:05 am

      I must have the bourbon tube version you mentioned, like this:

      Is there a way to test this, maybe isolate it out?

      Just chiming in…

      I like bourbon like the next guy, but that's neither here nor there. However, that hi-limit is a bourDON tube…probably with a snapdisk.

      IT'S a SAFETY device.

      YES, you can test it with a VOM. It should read continuity using an ohmmeter when it's at room temp or at normal operating temps. I don't know the cutout temp, but its probably 212°F.

      However a better test is under the load it's designed to operate under (ALWAYS the best troubleshooting practice), then do a voltage drop test.

      ISOLATING it out? Only for a short term test by a tech. NEVER, EVER leave a circuit in that electrical configuration, though…for reasons I shouldn't need to explain…since you're a tech.

  • fixbear

    January 29, 2022 at 8:26 am

    In the booster control box, you have a temp controller/thermostat. Has it got power into it? I believe it also is electronic. (ie, you said circuit board) And there-fore will have a sensing thermistor. Ohm the thermistor.

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