3phase commercial dishwasher

Discussion in 'Electrical Forum discussion & Blog' started by mike1527, Feb 6, 2012.

  1. mike1527

    mike1527 New Member

    Messages:
    2
    Location:
    central wisconsin
    I wonder if anyone can help? I have a pretty good understanding of AC and DC electricity. My wife has a part time bakery business in our home. We have recently acquired a 3ph commercial dishwasher really cheap. I have looked into purchasing a phase converter to run the machine which has a motor load(3hp) and a resistive load (heating elements(3)12kw). One of the converter suppliers recommended a 25hp phase converter for $2800 to run the machine. Can't afford it. Question....Could I run the heating eelements on a seperate 220v/single phase supply line and run the pump and controls on a smaller 5hp phase converter? Thanks in advance for your help...mmd
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,009
    Location:
    New England
    Modifying an appliance usually voids the UL rating, and may affect your insurance. While not sure, I think this would apply to what you're considering.

    Without knowing the voltages and loads involved, it's hard to say what might work, assuming it's legal to do it.
  3. mike1527

    mike1527 New Member

    Messages:
    2
    Location:
    central wisconsin
    The 3 hp Baldor motor on the machine is wired for low voltage 3ph (220v) I'm not sure how to calculate the load for the 3 heating elements but in the control box they are wired through a 45amp three phase breaker. I know my idea is a stretch but the machine is a large pot and pan washer and it's exactly what we need. thanks for the help...mmd
  4. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    Look at the heating elements. I bet there aren’t but two conductors to each one of them.
    If so then they could be connected to a single phase circuit.

    The problem will be is your service big enough for this additional load. Probably not and you will run into a lot of problems. To run this dishwasher for just the heating elements will require at least a 150 amp circuit.
  5. ActionDave

    ActionDave Electrician

    Messages:
    346
    Location:
    Colorado
    Check the rating on those heating elements one more time. Three elements @12kw each or three elements @12kw total?

    How are you going to supply the elements separate from the motor? There is only one place to hook up power on this thing, right?

    There is a inverse relationship between the cheapness of many items and the cost required to make it work.
  6. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    One thing to keep in mind is that this converter will require a 125 amp circuit to supply it and again the service calculation has to be considered to keep from overloading the service.

    The circuit that supplies this converter will be a continuous draw while the dishwasher is being used and will drive the utility bill through the roof.

    The bottom line is the amount of energy being used is the same no matter the voltage or number of phases.
  7. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    I doubt very much if you have 3x12kw elements. Your aluminum pots would melt. This is not a kiln.

    A 3 phase 3 hp motor can survive with a capacitor type phase converter, especially since your starting torque may be assumed to be low. They are relatively cheap.

    Yes, the elements very likely have 2 wires only, perhaps some sequencers and other controls. But you better be very bright to figure where and how to put the 240v onto those elements, and the result will certainly be reduced draw and longer drying time. Since the main point of commercial machines is to sterilize the pans, you may not be meeting health code.

    If thats not the point, forget the dryers and buy a 15$ fan and blow dry the interior. If you are getting that serious, you might inquire about installing a 3 phase service, and reap the incredible benefits therof.

    You must have a tag that says FLA or full load amps - share that.
  8. jwelectric

    jwelectric Electrical Contractor/Instructor

    Messages:
    2,534
    Location:
    North Carolina
    You are right all but one thing you forgot. It also has thermostats so it would limit the amount of heat.

    The number and size of the elements will depend on how fast the recovery time of the washing cycle is. I have installed booster heaters for commercial dishwashers that had a 200 amp three phase 208 volt circuit ran to them. They would have five 12KW heating elements in the one heater. Recovery time three minutes for the water to regain to 180 degrees that required for sterilization.
  9. Smooky

    Smooky Member

    Messages:
    622
    Location:
    NC
    I recommend forgetting about the dish machine and getting a large two compartment sink or a three compartment sink with drain boards. The basins need to be large enough to wash your biggest pots bowls etc. Get a commercial faucet such as T&S Brass faucet with a pre-rinse sprayer. You may also need a larger hot water heater............The elements in the high temperature dish washers are designed to heat the surface of heavy plates up to 160 degrees to kill any bacteria that may still be on them after washing. Also the plates come out very hot and this aids in the drying process. This would be important if a restaurant does not have room or time to air dry the dishes. High temp dish machines are expensive to operate and expensive to maintain. You would better off to get a low temp dish machine if you are determined to get a dish machine or convert the one you have to low temp. Also many bakery pans are not required to be washed after each use if they are subjected to high heat during the cooking process.
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,636
    Location:
    Cave Creek, Arizona
    3 phase heating elements are usually, but not always, set up in sets of three and are wired to balance the load on each phase. If you wire them for single phase you may have to run a separate suppply to each one. There are also two element three phase units but these have a much larger load on the "center" tap than on the two outside ones. These can also be wired single phase but it takes two circuits and the second one is a single pole breaker that has to carry twice the power of the double pole one.
  11. ballvalve

    ballvalve General Engineering Contractor

    Messages:
    3,261
    Location:
    northfork, california
    Sell it again and buy a steam pressure washer, blast the pots potside.

    pots and pans really do not require sterilization, its more about glassware and silverware.

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