Reply To: Descaling Rational SelfCooking Center Oven model SCCWE61E

[ectofix]

Well, if they clean it THAT often, then there shouldn’t be ANY scale buildup in the boiler.

You never said whether the oven is showing some indication of a need to descale.  Was there any such notification (such as CALC CHECK), or are you simply wanting to do it because it’s the right thing to do?
That oven has a water volume sensor which measures incoming water volume during each fill cycle of the boiler.  The water volume sensor is central to the calcium diagnostics system, or “CDS”. 
With that system, the results of its LAST fill cycle (measured in LITERS) can be viewed in technician-level programming.  Also in that mode, you can view the volume of what a pristinely clean boiler will take to fill (also in liters), and at what measurement the oven’s control will display CALC CHECK to indicate there’s heavy limescale buildup.
I can’t publish the password for entering into tech level of programming, but I found it publicly available on the internet anyway.  I think I can share that.  Page 53:
http://www.jeoushun.com/rational/8051113_SCC_Modul_en_V02.pdf

That’s an earlier manual, so if the oven’s software has been kept up-to-date, your oven’s display will different.  The password is the same, though.

<div>Anyway, you can use the aforementionednumbers in the CDS system to determine whether it needs to be descaled, or you can simply drain the boiler and do a visual inspection.  If you see any whitish flakes in the boiler, then it wouldn’t hurt to do a manual chemical descale. 
If there are ROCKS in there, then you’d want to employ a shop-vac, a hammer and a length of copper pipe as a make-shift chisel to break up the chunks through the SC pump’s port.  If it’s REALLY bad, you might have to remove the elements for greater access.  At any rate, if such physical extraction is necessary, after you’ve done so, follow up with a proper CHEMICAL descale.
SO…back to your original question.  How do you descale it? 
Well, the procedure is meant for factory-trained technician to do.  I can’t publish the manual that covers how to do that, but…guess WHAT!  It’s already been made public on the internet TOO!  I’ll share THAT with you.  Go to page 141:
Instruction for manual descaling
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Yes, that manual is for an earlier oven, but the steps are the same.

I caution you that the procedure requires knowledge of the components, how the oven’s overall system works…and a keen awareness of what’s going on every step of the way while you’re descaling it.
Again, if you don’t do it right and make a mistake somewhere, you’ll have a real mess of a very corrosive chemical on your hands.  It can hurt you…and it can ruin some components in the oven if it gets spilled into the component compartment.
FOUR key points to remember:

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The descaler should ONLY be put into the boiler through the steam port inside the oven’s cooking compartment by using a pump. If you spill any descaler…or if it comes bubbling out of the steam port from chemical reaction, thoroughly rinse out the cooking compartment with hand shower. Make ABSOLUTELY sure that the SC pump works BEFORE beginning, since that’s the primary means to remove the descaling solution. Once the descaling solution is out – flush, FLUSH and FLUSH – with clean water via function testing of the FILL valve.  OVERFILL the boiler until it’s running down into the floor drain…all three times.  Fill a forth time and run in steam mode for fifteen minutes.  Follow that by function-testing the fill valve again, letting the overflow run into the floor drain for awhile.  The idea here is to “temper” the water before function-testing the SC pump, thereby not making the pump work with boiling hot water – to avoid damaging it. Run the SC pump to drain the boiler one last time. Thoroughly rinse the cooking compartment one last time with the hand shower.

That’s it!  That’s how I do it.
Now you can let it fill on its own and let them use it.