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  • About Descaling Rational Ovens

  • ectofix

    November 23, 2019 at 5:45 pm

     Rational has notoriously made their model numbers confusing. I don’t think they know that, though.  For instance

     They used the CombiMaster (CM) name for ovens made in the ‘80s-to early 90s (Classic-line ovens), then again for re-engineered ovens made in the late ‘90s to early 2000s (CPC-line ovens)…and THEN AGAIN for completely DIFFERENT ovens beginning in 2004 (SCC-Line ovens). They were ALL called CombiMaster ovens (with a CM in the model number), but were COMPLETELY different from one another. SO, a model number CM101 oven could be an archaic 1992 model of the Classic-Line (unlikely in the U.S.), a MUCH revised 2001 model CM101 with a totally different cabinet and components…or a 2010 CM101 that bears NO similarities (internally, externally or operationally) to the preceding TWO CombiMaster 101s. Thankfully (in 2011), they made their NEWEST model number more distinguishable by tacking a “P” on in there so they can be called the “CombiMaster Plus”.

     Have I confused you now?

    W-E-L-L, they ALSO made it confusing with the Self Cooking Center moniker (using “SCC” in the model number) as well:

    There were the ORIGINAL ones made 2004-2008, which just had a CleanJet feature using detergent and rinse tablets. Then there were updated ones made 2008-2011 (also with CleanJet, but adding the CareControl feature and its plumbing) which used the same detergent tablets, but eliminated the rinse tablets to, instead, employ a whole new system requiring Care tablets (a mild acid)…which get mixed with water in a special drawer and pumped into the steam generator.  They called this their CleanJet+Care system. In 2011, they completely re-engineered the oven internally, made it look different with a revised control panel, then tacked on the WE (white-efficiency) in the model number for those ovens. Those ovens also had the CleanJet+Care feature.  As if they couldn’t leave well enough alone, Rational shortly followed up by upgrading their software to make the 5S units (5 Senses).  THEN (wouldn’t you have guessed?) – they went back to just calling it a “Self Cooking Center” again after they added the triple-paned glass door and LED lights!

     For how Rational overly reuses their model numbers and oven names, it's no wonder that PartsTown's library of Rational ovens is often out in left field. (partstownmayor, you can PM me on that)


    ANYWAY – allow me to clarify a few things regarding the differing oven models with regards to descaling an oven. I’m talking ovens made from 2004 until NOW:

    CombiMaster and CombiMaster Plus ovens –


    Yes, in BOTH, they DO have an automatic descale program, from which you pump in descaler in when it tells you to. HOWEVER, since the two ovens are DRAMATICALLY different internally – without my looking too closely at comparing the manuals, I’ll say that you should probably consult the CORRECT manual – based upon whether it’s a CM or a CMP.

    Self Cooking Center ovens –

    The descaling program was only available on a limited basis.  So, when an SCC oven was manufactured means EVERYTHING here:

    Version E ovens (5th digit in their serial number) – made 2004-2008 – means that you have an automatic descale program immediately at your disposal. So, just like the CombiMaster (and Plus) ovens, you use a pump to put the descaler in when it tells you to. Version G ovens (5th digit in their serial number) – made 2008-2011 – were designed with the additional CareControl feature. As such, the CareControl tablets were intended to keep scale buildup at bey. In THOSE ovens, you only have the automatic descale program available when the oven senses that there’s significant scale built up.

    FWIW: I do NOT recommend using the program since there will likely be too much scale for even the strongest chemicals to address. It will need to be scraped out by a technician. Version “H”, then “I” ovens (5th digit in their serial number) – made 2011-present – were ovens which have absolutely NO AUTOMATIC descale program available.  If the CareControl feature hasn’t been used often enough, then a MANUAL descale will be necessary through the technician-level program.  It's NOT automatic, but a technician can individually operate components needed to drain the boiler and add the water…thus having full control over every step.

    What I'm getting at is that you MUST have the correct manual to maintain your oven properly.  Additionally, if you have an SCC made from 2008 to present – DO bear the expense of purchasing and using the Care tablets at LEAST once a week.  Those tablets will save you potentially high expenses down the road to avoid having a technician come to perform a manual descaling process.


    So now…here's me attempting to upload the CORRECT manuals.  PartsTOWN?  You might want to incorporate these into your library:     

  • ectofix

    November 23, 2019 at 5:54 pm

    Here are some videos to help with understanding some of what I was saying:

  • ectofix

    November 23, 2019 at 6:36 pm

    Original post changed by moderator, so…never mind.

  • fixbear

    November 23, 2019 at 7:16 pm

    Nicely done. 

  • techtownmayor

    November 23, 2019 at 9:33 pm

    Some great information here – I'll make sure to pass it on to the author of the article. 

    Thank you for taking the time to write this up!

  • rationaltechnician

    December 9, 2019 at 4:45 pm

    Awesome summary ectofix.  You brought up some points and I would love to contribute.

    I wanted to mention the Care tabs 56.00.562 is a good idea to use them daily (as the display requests) in what I call the “complete” cleanings (light, save, medium and strong).

    Reason is these double as your rinse tabs.  It is critical to the inside of the cabinet that chemical is rinsed out and dried so the stainless steel can perform it's “healing” (chromium regeneration to keep it simple).

    To add, no detergent shall ever be heated up in a stainless cabinet (or any metal) to avoid chemical burns (which sometimes looks like rusting or corrosion).  Many customers do not understand this and jump right to questioning the product quality.

    So what are the “incomplete” cleanings?  These are your rinse, rinse without tabs and interim cleanings.  These cleanings are convenience cleanings a customer can use during the day to get them through but shall never replace one of the complete cleanings performed daily (if they truly love and cherish their Rational).

    Why clean everyday even if all I do is steam and the unit looks clean?  Chlorides in the water and salts from the foods are corrosive to stainless steel.  A low cost “Save” clean will make sure these are cleaned away daily and cabinet dried so the stainless steel can do its thing overnight.  Door open after cleaning, if possible, really helps but not critical.

    Number of Care tabs requested on display units effective index H (Approx. Oct. 2011) and its relation to measured scale volume in the steam generator.

    When the unit measures more than 4% scale of steam generator volume, it requests more than 1 pack Care tabs, cleaning takes longer.

    Less than 4% scale measured, it requests only 1 pack of care tabs, care tabs do not remain in steam generator, care phase is skipped and cleaning takes less time with less use of water.  Care tabs are only used for the rinsing of the cooking cabinet.

    If the unit measures 20% or more scale by volume, when unit switched on, customer is prompted with “Calchek urgent descale – call for service”.  The descale program will now be visible to the technician.  Calchek message is displayed to the customer for 2 minutes and then goes away.  This allows customer to continue cooking – until help arrives 🙂 .

    Technician hint:  Ever notice steam generator volume isn't matching even with a clean steam generator and after resetting volume of steam generator?  This is because it is displaying the average of the last 10 fills.  To reset, use reset volume of steam generator 3x in a row.  Should match again assuming Y1 Fill, CDS, SC pump and venting valve steam generator are all operating correctly.

    Hope this helps somebody, happy fixings.

    • ectofix

      December 11, 2019 at 7:41 pm

      I'm always open for your input since I haven't been to their training seminars.

      Of our twenty-six Rationals (we're like a MUSEUM of them),  we have THREE “H” units and eleven “E” & “G” units.

      So, you're saying that the descaling program is available on the “H” units?

      NONE of my manuals reveal that.  The operator OR training manuals.

      So, I REALLY need to attend their training classes…

      • rationaltechnician

        December 11, 2019 at 7:56 pm

        For a tech who has never attended a Rational training, you have really grasped a lot.  More than many trained techs.

        From my memory, since CareControl once an index G, H or I unit detects more than 20% of steam generator volume as scale (difference of last fill to size of steam generator), the display locks out customer for 2 minutes with a Calchek message.

        After the 2 minutes lapse and the unit goes back to the standard screen, you can select the oven symbol, wrench and screw driver and then a descale button should be available.   If not, try opening door.

        If it is still not there, it may be in the technician level after entering a password.  I will check this again next time I come across a unit requesting descale.

        That being said, because of CareControl, these units should never ask to be descaled because daily use of Care tabs would prevent the formation of scale from reaching that point.

        This of course depends on customer cleaning behaviour and if Care tabs are actually used.

        I’ll follow-up on this thread once I can confirm a few details. 

      • rationaltechnician

        December 11, 2019 at 8:06 pm

        BTW, congrats on all those Rational units.  It appears the Chefs are sold on the value of these units and how it reduced the labour and improved food quality.  Very soon, every kitchen in the Americas will have a Rational or another combo oven as a standard piece of cooking equipment much like in many European countries.

        Us as technicians would rather be working on them when compared to fryers.

        There are rumours they will also introduce the VarioCooking Centre (VCC) soon as well.  There will be a new learning curve for us but a few common components with the SCC units.

  • techtownmayor

    December 11, 2019 at 12:42 am

    Phenomenal instructions, thank you for sharing! Bonus points heading your way ?

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