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  1. #1
    Join Date
    Oct 2008
    Location
    In a kitchen with my head stuck in an oven
    Posts
    1,539
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    A RATIONAL oven REVALATION

    I take care of twenty-six of 'em. Seven are gas. Although I've had fewer problems than the norm here, I'm still not so fond of the gas ones. Here's an excerpt of an e-mails I'm sending to their service director here in the U.S.A. Just some FYI:


    "As you know, the SCC-202G oven has two AIR heat exchangers. Each heat exchanger has its own separate gas valve, air inlet shroud, gas/air mixture components (discs), burner blower and burner. Of those components, many of them are made of plastic.

    Here's the issue I've discovered:

    IF an AIR burner blower fails to receive power and doesn't run, the oven will still heat to some capacity by way of the OTHER heat exchanger. The oven will certainly go into a GAS RESET fault after some time, but all a user has to do is press GAS RESET. The oven will heat more and get hotter - up until GAS RESET shows again. I haven't studied on or kept track of when/if the unit will completely lock out due to this fault, but our users have figured that they can just keep resetting it...and it will cook. As such, they'll still cooking hundreds of meals that way. At some point, they eventually call it in for service. MEANWHILE, the damage is done.

    When I say DAMAGE, here's what I mean:

    • The oven's user manages to get the oven to sustain cook temperature of, say 375F, by doing constant gas resets. They'll do this for HOURS to get the product cooked. They will succeed in cooking their product by doing this.

    • All that time, the errant burner blower is NOT supplying its stream of airflow that's meant for burner operation.

    • That failed burner's heat exchanger assembly, being located inside the oven, gets HOT from that oven temperature of 375F.

    • Without the failed burner blower running, the dormant hot air within that inoperative heat exchanger conveys back to and through wherever there's an opening. Namely, the exhaust flue and the inoperative burner.

    • The dysfunctional burner blower's metal enclosure will ultimately get too hot to touch. The plastic blower wheel inside of it will MELT. Further back, the plastic gas/air mixture discs and plastic air inlet shroud will also melt.


    This has happened to our SCC-202G oven three times. Obviously this doesn't happen on table-top units since there's only one AIR heat exchanger, so there's no other source of hot AIR heat in those models.

    As it stands, I'm presently ordering the parts needed to repair our latest occurrence. However, in each case, I've attributed the problem to the blower motor's electrical connector (pictured below).



    This specific connector has given me problems on several of our table-top models as well. The wires in the connector get abraded due to vibrations from the motor and will slowly cut through the wire until there are no wire strands left. Yet, compression by the connector body will seemingly keep the wire up "in there" by virtue of the wire's insulation ONLY. I've found that a gentle tug on each of those wires during troubleshooting will release that final grip to reveal the connection was compromised before I ever even removed the side panel to do my troubleshooting.

    It's definitely a weak point in the design. I've managed to disassemble these plug several times to renew their connections, but it's CERTAINLY not an easy or readily evident solution.

    With my latest go-around with this, I'm ordering some spare burner blower cables (for this oven, TOP: PN 40.01.485; BOTTOM: PN 40.00.221). Our former off-line parts breakdown didn't include these part numbers, but I see that they're there now.

    Obviously this doesn't happen on table-top units since there's only one AIR heat exchanger. There IS no other source of hot air heat.

    I'm writing to inform you of this problem and to make some suggestions to resolve the issues. A revised and higher quality connector would be the ultimate solution. Otherwise, a Technical Information (TI) bulletin to address this should be in order. Perhaps informing technicians of this potential problem, how to disassemble the plug and renew the connections and maybe urge technicians to order & replace the burner blower wire harness along with the other parts necessary to fix an oven with this issue."


    "You never know what others don't know." -

    If I can't laugh at myself...then I'll laugh at YOU! -

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  3. #2
    Join Date
    Jun 2013
    Posts
    335
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    Very good, EC. I've always marvelled at that connector, looked like stone-age engineering on a space shuttle.

    I'm working on a '202 Eloma combi (Don't get me started). Almost identical blower assembly, but has a tradtional Molex style plug, if I remember correctly.

  4. #3
    Join Date
    Aug 2013
    Posts
    88
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    Never had to order one yet. Although we typically work in businesses that have planned replacement.

    Rational does take failures pretty seriously. This is what caused them to send out dielectric grease with pretty much every electrical component that requires it.

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