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  • Correction to Oil Filtration Circuit Schematic

     fixbear updated 3 months, 3 weeks ago 4 Members · 9 Posts
  • ectofix

    January 1, 1970 at 12:00 am

    While working on an in-house project, I found an error in a small schematic that is illustrated in several fryer manuals.  The error is in how the schematic depicts operation of the filter pump control circuit in relation to the two solenoid valves in the filtration circuit.

    I’ve informed Frymaster of the error in the diagram and their response back is that their tech writing department has been contacted to request a change to it.

    The schematic is located in the H50 Series Gas Fryer S&P Manual (P/N 819-0001, Jun 2005) on page 1-27. The other that I I’ve found is in the Pro H50/55 Series Gas Fryer S&P Manual (P/N 819-6083, Jun 2009) on page 1-29. The diagram is also included in the several technical reference (factory training) books that I possess.  The electrical configuration of the circuit appears universal in all current-production Frymaster fryer models which have built-in filtration systems, but that little schematic isn’t in all manuals.  For instance, the RE Series E4 Electric Fryers S&P Manual (P/N 819-6150, Sep 2012) doesn’t provide the schematic, but the configuration of the circuit is the same in those fryers, with the only difference being that the primary voltage to the transformer is different..

    The error is seemingly minor, but it may lead to some confusion to newer techs when looking at the schematic. Here’s a brief overview of the filter pump circuit operation:

    Frymaster’s current-production oil return system design employs two normally-open solenoid valves to allow any oil trapped in the oil return manifold to drain back into the filter pan.  The solenoid valve coils are connected in parallel to the filter pump motor relay coil.  Any given cam-operated microswitch (whichever fryvat is being filtered) will supply 24 VAC to those component’s coils when turning the filter pump lever to the ON position.  As such –

    • When turning the filter pump lever ON, the pump motor relay and solenoids valves energize.  The solenoid valves then CLOSE while the filter pump motor is running, thereby directing oil through the oil return manifold to the opened oil return valve of the fryvat being filtered.
    • When the filter pump lever is turned OFF, the pump motor relay and the solenoid valves de-energize. The two solenoid valves OPEN.  One of the solenoid valve allows oil to drain back to the filter pan while the other solenoid valve serves as a vacuum-break to allow air to be drawn into the oil return manifold as the oil drains out.

    As seen in the picture below, the left-hand diagram show the solenoids connected to 24 VAC AT ALL TIMES, while the microswitches appear to supply power to JUST the pump motor relay. This diagram is essentially the same one you’ll find in the aforementioned manuals and is INCORRECT.

    The right-hand diagram is my “unofficial” correction to that schematic, which depicts the solenoid valve coils connected in parallel with the pump motor relay coil AFTER the microswitches.  As such, the solenoid valves receive power at the same time as the pump motor relay.

    This is how the units are actually wired.  I’ve traced a wiring diagram out just to be sure.  Additionally, I’ve observed a unit’s operation and that IS how they work.

    I’ve added a few other details of my own into the right-hand diagram for accuracy and clarity, such as actually depicting TWO solenoid valves, colorizing the source voltage and 24 volt circuits and how the relay is illustrated.

    The graphic shown below illustrates how the filtration system operates to control oil flow.

    • The solenoid valve to the left is the air-vent valve.

    In the illustration I’d chosen to use here, the solenoid valve connects to a T-fitting by way of a 2″ long nipple extending upward so the valve remains the highest point in the plumbing.  On some units, this valve may otherwise be connected directly to the top of the rear oil return manifold with that 2″ long nipple.

    The air-vent valve’s other port connects to one end of a Teflon tube that is routed to the front of the fryer for connection to the top of the drain manifold.  That Teflon tube is connected there for air because, if the valve so happens to become stuck open when the pump is running, the hot oil that is leaking by will be harmlessly diverted back into the the drain manifold.

    • The solenoid valve to the right is the drain-off valve.

    That valve connects between the oil return manifold and the filter pan.  When it’s de-energized, that valve allows residual oil to drain back to the pan once the filtration system pump has been turned off.

    Despite the flawed schematics within the service manuals, I hope I’ve provided some clarity in this system’s electrical operation and oil flow,  With that, you will find that maintaining the oil return system and inspecting its operation is simple.  Additionally, you may further understand the importance of certain components in the system to not only determine whether it’s operating properly, but functioning safely as well.

  • olivero

    December 7, 2019 at 3:00 pm

    Did you really post this in 1970?

    Tell me the truth.

  • ectofix

    December 7, 2019 at 7:28 pm

    LOL!  How’d you dig THAT up?

    No.  I was ten years old in 1970.

    I think I put that together around 2015.  A smidgen of a manual I put together for the guys at work that I decided to share on the old TechTown. 

    TechTown’s transition into this new platform did some weird stuff to old posts, including screwing up the dates of the original posts.

    • olivero

      December 8, 2019 at 10:14 am

      I was just looking through the archives for one of my own old posts and figured I would check for the oldest one, and this was one of them 😀

      I figurd you didn’t.

  • ectofix

    December 7, 2019 at 7:41 pm

    This new platform doesn’t allow me to put “things” together like the old platform did.  For instance, I can’t embed graphics or photos into my text like I formerly could.  Therefore, I can’t fully communicate FLUIDLY a composition of a post like I’d prefer to.

    I’ll just leave it at that.  Maybe the mayor will look into it. 

    Things at my CURRENT workplace, like forcing us to use the prolific and STUPID “Salesforce” APP has me aggravated enough as it is.

    Change is inevitable.  I’m getting older and favoring retirement, so books like “Who Moved My Cheese” just don’t mean anything to me anymore.

    • techtownmayor

      December 7, 2019 at 8:34 pm

      Definitely high on the to do list for early 2020. I am working on some major updates to the way media can be added to posts very soon. Thanks for the patience!

    • fixbear - ADK NY

      December 8, 2019 at 10:57 am

      Ectofix, does the machine attached schematic show the correct version?  I have found many over the years that the service manuals have been one way, but the attached one is different.

      • ectofix

        December 8, 2019 at 6:13 pm

        I don’t know.  I’ve never used Frymaster’s diagrams on their doors since they’re usually overly complicated (mostly are wiring diagrams) and typically covered with grease.


        The diagram I’d referenced is one in their service manual that’s set apart from the manual’s section referencing all their various wiring diagrams and schematics.  This schematic I’m referring to is more like a little illustration included within the manual’s text for troubleshooting JUST the filtration system.

        I’d communicated this error (as depicted in this old original post Olivero dug up) to Frymaster around 2015.  Whoever it was I talked to in tech support team AGREED that my diagram is correct and the ones in their manuals are wrong.

        Nonetheless, I happened to go look at their revised manuals JUST TODAY…and found their newest (update JUST LAST MONTH – Nov 2019)…is still showing the wrong info.

        Check  it on page 1-29 (34 in the PDF):

        Pro H50/55-Series Gas Fryers Service and Parts Manual

        For that matter, some of the rather significant part number changes that have occurred in the past several years (commonly replaced parts) aren’t even in there.  So…I don’t know what-the-heck they updated in this manual.  The ink is still wet, but it’s wrong on numerous accounts.

  • fixbear - ADK NY

    December 8, 2019 at 6:56 pm

    The old saying is;

    You can lead a horse to water, but you can’t make them drink.

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