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  1. #1
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    Hobart C64A Dishwasher refilling

    I have a Hobart C64A dishwasher that is opening the fill valve solenoid during the wash cycle dropping the finial rinse temp to about 150. This happens between 3 and 5 cycles and last a minute or more.

    Curtains are correct long short long long short short long - that is two long between wash tank and rinse.

    Upper float is sometimes in the down or closed position when this happens - at least when we look. Sometimes when we look it is up.

    Replaced lower float and switch same problem

    With switch disconnected and an ohm meter on the lower float has it closed with a nearly overflowing tan. One time even a after the unit was turned off and someone was removing the strainers to see what the float's position. When he laid down the basket the switch opened.

    I have a toggle switch in place of the float switch so after filling they can turn it off and there is no problem with finial rinse temp or fill valve (so the problem is the float switch?)

    Any ideas?

    Should there be a cover over floats to prevent turbulence?

    Am I losing just enough water that the upper float closes and the lower float due to turbulence closes normally as designed?

    Am i missing something?

  2. #2
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    The lower float has nothing to do with control of water level. It merely satisfies when there's enough water in the tank to safely energize the tank heat (steam, gas or electric).

    The upper float's responsibility is to add water. Water level will drop when the wash pumps come on and they fill the wash arm pipes, wash arms and the wash chamber with the heavy spray volume that contacts the dirty wares. That's quite a bit of water, so the fill float will make and bring in more water. Conversely, when the pumps stop and everything settles, the tanks are then overfilled. Since the tanks are then overfilled, the transfer pipe will allow all tank levels to equalize and the excess will drain off into the standpipe that's usually located in the prewash section.

    I'm not THE expert on the true purpose of the rinse tank. There are MANY machines that don't have one. Yet, it's there. Wash requires >150°. FINAL RINSE requires >180°. Basic sanitation standards require JUST those two things. So the rinse tank is supplemental in my eyes, being set to 160° (I think), and (to me) serves as just a second good washing.

    The final rinse comes from a separate source - a booster heater, so its temperature shouldn't ever be influenced by the tank temperatures in the machine.

    With all that said, you verified the curtains are good. The float switches seem to be working. DEFINITELY get that toggle switch out of there. If that was just for testing purposes, then NEVER-MIND.

    A few other things you should look for though are o-rings, o-rings (yes...twice) and wash arm plugs.

    There's o-rings where the wash arms attach to their supply pipes. Replace them. Otherwise, wash water blasts from those connections and blasts water out uncontrollably.

    There's rubber cap plugs on the wash arms that are often easily overlooked. Make sure they're there.

    There's o-rings on each tank's drain plug. Replace them. They deteriorate and expand in as little as six months and will allow a good amount of water to seep out to the drain, thereby causing the tank levels to quickly drop and therefore requiring constant topping off by the fil circuit.
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  3. #3
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    There are a total of 4 floats switches on this machine - 2 two wire and 2 four wire, 3 are located in the wash tank and 1 4 wire in the rinse. The 4 wire ones are water level and temp for the steam heat.

    The other 2 are simple 2 wire switches operated by magnetic float. The circuit looks like it is latching. With lower float closed and upper float closed through time delay 5 secs to coil on relay 1 closing NO contacts rerouting circuit from lower float to NO contacts on relay, and another NO contacts closes energizing Fill Solenoid. When upper float opens it breaks the power to the relay coil opening both NO contacts.

    So what I am seeing is with the tank full the lower float is closing, it only does this with the magnet present, switch alone is fine. After a few cycles the upper float closes during the cycle causing the fill SV to be energized and when the finial rinse is energized there is not enough water pressure or temp for a sanitizing rinse.

    This machine is about 8 years old and I have worked on the finial rinse before rack switch, solenoid and booster problems. So I have watched the rinse temp and pressure and never had this occur. It is something new.

    Fill and rinse plumbing done according to Hobart install manual.

    I don't think there is a water leveling connection between tanks but there is a feed to the wash tank catching water from the finial rinse.

    Going back today to run pump with doors open - fun - to see what is happening and yes I will be losing water

  4. #4
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    why is the lower float closing

    What I do not understand is why is the lower float closing while submerged under 8 - 10 inches of water?

  5. #5
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    Ah! Sorry.

    I had my head wrapped around our units - which are mostly new construction. Our CLe-line conveyor machines, which replaced the C-line A models, use just two float switches per tank. A four wire on bottom and a two wire on top. Same for our FT900s.

    I only recently had to work on our one old FT900 and, indeed, it does have THREE float switches per tank. Two lower and one upper. AND...TODAY I stuck my head into our only remaining C-line A unit (because of your post) for curiosity's sake. It's a CRS-110A (a C-88A + a RS22 [22" recirculating scrapper]). Didn't get to dwell on it much since I was busy, but it also has three float switches in the wash tank, but also has three in the rinse tank.

    AND...like you indicate, the two bottom float oppose each other. Obviously the one that floats up to MAKE the Reed switch stem is for heat. The other lower one next to it floats up away from its stem. The latter certainly would appear to have something to do with water level management.

    Maybe somebody else will chime in. I won't see a schematic until Sunday. Never really studied up on the operation of those two lower float switches.
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  6. #6
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    ...even still, DO bear in mind other possible contributing factors. The plugs and o-rings I mentioned earlier should always be checked. Best practice is just to replace the o-rings regularly. Our new CLe units seem to go through those faster than the older C-line or C-line A units (HA! We Do still have several prehistoric C-line units!). The o-rings swell up and get bigger. The CLe's standpipes are plastic and therefore lightweight, so the if the o-ring isn't tight in its groove, a gap forms and an inordinate amount of water leaks by. This is most visible when the unit is static for a five minutes, the drain is still draining and tank level shows that.

    I don't know why Hobart put so much plastic into their plumbing in the new machines, but that's another recurring problem altogether. Wasn't a good decision on their part.

    You said it's STEAM heated?

    I go through allot of steam valve service kits and coils on our nine conveyor and flight machines- with around 30 psi steam pressure. Particularly the newer machines (with the LED control panels). There's two, distinct part numbers for the water and the steam rated coils on those Parker valves in there, but they look and fit identically and can be easily interchanged. Obviously you're better off with the ones that actually say STEAM on the little label on the coil. The one they list for WATER doesn't show that distinction on the label and are more general purpose. STEAM valves have a tough life.

    Anyway, you never mentioned any diagnosis for actual heating problems with the steam system, but I run across problems with those almost weekly. But since you're having temperature issues, be sure it's operating properly.

    I'll amplify on that some. Awhile back, our C-line A unit had rinse temperature issues. First couple of racks was at temp, but the booster wasn't keeping up. Temperature dropped and settled to around 170°. Booster tstat was calling for heat the whole time.
    I finally resorted to putting a pressure gauge at the inlet to the booster's steam line. Static pressure was fine, but the running pressure (booster calling for heat) was way low. To make a long story short (I spent a day and a half figuring this out), I took the steam lines apart (what a PITA) to find a big glob of black, crusty stuff trapped at one of the 90° elbows. All other pipes and fittings were clean as a gun barrel. Just THAT. I removed THAT...and my running pressure dramatically improved.

    Problem was solved. The familiar "gu-u-u-sh-sh-shing" sound of steam rushing through the pipes once again returned to the being comforting cyclic tempo as the tstat cycled - as if the steam system didn't even need to flex a muscle.
    Last edited by ECtofix; 01-21-2015 at 08:18 PM.
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  7. #7
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    Thanks for the info

    Went back today and did find an o-ring swollen on the upper wash spray and replace it and the others.

    For the most part the problem is gone except if they run a large flat item or trays fall out and direct the spray out of the wash tank area (outside or into rinse). When this happens the unit refills diverting water from the finial rinse.

    What I do not understand are:
    why refill with such a minimal water loss?
    why refill while continuing washing - not pausing so finial rinse is not compromised?
    (I do not see this break in conveyor in wiring diagram)
    why is the lower float closed during wash cycle, is the pump causing a suction/whirlpool?
    Is there supposed to be cover over the floats to prevent this? (don't see this in the parts list from Hobart)

    Attached is the control circuit for the fill valve. I do not have a full wiring diagram



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  8. #8
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    if I'm looking at the wiring diagram correctly it seems that both floats are normally closed contacts. It's a latching circuit so both floats have to open for the r1 coil to loose it's voltage and remove power to the fill valve.
    The problem could be with the lower float have a small pin hole in it. I've seen that before on dish tanks. When the pump motor kicks on the water level will drop a little closing the upper float. If the lower float has a small hole in it, water will fill it up and lower it also. This would cause the issues you're having.
    The only components that would cause your r1 relay to get coil voltage are the floats (and timer). I would start with the lower float,

  9. #9
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    Swiney

    I did replace the lower float and had the same problem

    The wiring diagram is how Hobart shows it - tank empty - my drawing is a bit off it should have shown the switch opening on water rise.

    timer has only 2 terminals as shown and simply delays for 5 secs

  10. #10
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    Does anyone have the service manual for this unit? I have the IOM

  11. #11
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    Swiney has a point there. I've seen that too. Been awhile though.

    You said you replaced a float and switch but, upon rereading what you said, appears you replaced the upper one only (correct me if I'm wrong).

    If that's the case, then YES, we know the upper float switch will close when tank water is demanded by the pump (wash cycle ON). However, the lower two-wire switch should hold off any refilling until it closes too. Apparently it's a lower level limit for the fill circuit. So if the upper switch makes (which is likely) and the lower one ALSO makes, then YES, the fill circuit is completed and (after 5 seconds) will energize the fill solenoid.

    So...if the lower two-wire switch's float is waterlogged (due to a pinhole), that would be your problem.

    Quote Originally Posted by richvacr View Post
    For the most part the problem is gone except if they run a large flat item or trays fall out and direct the spray out of the wash tank area (outside or into rinse). When this happens the unit refills diverting water from the finial rinse.

    What I do not understand are:

    1. why refill with such a minimal water loss?

    2. why refill while continuing washing - not pausing so finial rinse is not compromised?
    (I do not see this break in conveyor in wiring diagram)

    3. why is the lower float closed during wash cycle, is the pump causing a suction/whirlpool?
    Is there supposed to be cover over the floats to prevent this? (don't see this in the parts list from Hobart)
    For questions 1 and 3, we might have your answer now. Check that lower float. For that matter, just replace it. If it's discolored and not looking healthy, it may have water in it. No, there is no cover over the floats.

    For question 2, all I can say there is that I regularly witness our machines do a topping-off fill while in a wash cycle - with no interruption of the wash cycle functions. Again though, remember that most all of MY machines are newer don't have that lower two-wire switch. Just the four-wire for heat down there. Therefore my units lack the hold-off period that the lower switch provides. Apparently the Hobart engineers rethunk that particular float switch and decided it wasn't necessary in their new models.

    Today, being my day off, I had time to find this photo of the diagram from our CRS-110A that I'd lost track of in my computer. As you'd questioned it, I also wanted to see the electrical link between the fill and wash/conveyor circuits...and maybe learn how the machine keeps on churning wash water uninterrupted while doing a top-off fill.

    As with most diagrams involving circuits with control boards in them, it'd be impossible to depict every single detail and I guess Hobart didn't think we need to see that electrical link. We both have witnessed that though. When the machine does its initial fill, it WILL NOT let you start the wash pumps/conveyor until it's done filling.

    Yet again, I've learned that Hobart's diagrams just don't show everything. I looked and looked and...the diagram doesn't show it. If it did, then the numbers on the right would lead you to that line number on the left in their ladder-type schematic. They ARE tied together though.

    :
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  12. #12
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    Quote Originally Posted by richvacr View Post
    Does anyone have the service manual for this unit? I have the IOM
    While busy composing my above post, I didn't see your updates.

    I won't be back to work until Sunday. I'll look and see if we have one.
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  13. #13
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    I have looked at several wiring diagrams for the hobart rack machines and they all seem to have the same fill circuit. The timer is just a delay to prevent the solenoid from chattering. The wash and conveyor motors will run even if water is not in the tanks (On the diagrams I looked at). There is no way your fill valve will get voltage unless r1 closes. If your floats are new and wired up correct I guess it's possible that your r1 normally open contacts are stuck closed and it is just cycling off the top float.

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