Announcement

Collapse
No announcement yet.

EM6910 - deep clean?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Originally posted by RichardP View Post
    There is conflicting info. In my opinion, NEVER try to descale the steam side by running the machine normally.

    The reason for the conflicting information is that Sunbeam simply says don't do it, but doesn't say why. That has lead to different people coming up with their own theories, but still having the desire to do the descale, which is not unreasonable, because the descale is actually required. It just should not be done by having the coffee machine running. Instead, use one other other methods that people talk about. Which one you use would depend on your own preferences and tecnical ability.

    First off, the reason you shouldn't: to understand that, take a step back and think about the reason you need to descale. When you have a water heater, the minerals in the water solidify around the hottest parts of the heater. This means we need to descale both sides. My guess is that the steam side needs to be descaled less often, since less water goes through it.

    So if we need to descale both sides, why is Sunbeam saying not to descale the steam side? To understand that, step back and think about the descaling process. The idea is to have water sitting in the heater system, warm but not hot, so that the descaling chemical (whatever it is) has time to react with the accumulated limescale. The warmth helps speed up the reaction. This works on the coffee side of the machine, but does not work on the steam side because in the steam thermoblock there is no water - the temperature is above boiling point to produce steam, so you cannot have water sitting inside the steam thermoblock while the machine is on. What's worse is that if you boil vinegar or any of the other descaling liquids, you produce solids which will end up becoming a problem in themselves.
    Another problem that happens if you try, is that there's a chance you will kill your steam pump in the process. Not a high chance, but it's not insignificant either. The steam pump in the EM6910 is of a type called a "metered pump". That brr-brr sound it produces is an oscillating rod inside. It moves back and forth, and in one direction it draws water in from the tank. In the other direction, it seals off the inlet and pushes the water out to the thermoblock. Inside it are parts that slide against each other. When the thermoblock produces steam, the pressure inside it increases, and the steam is happy to move in either direction. With plain water, that direction will always be towards the steam wand, because the steam pump's design allows flow only in one direction, so it's effectively blocking off one side of the thermoblock. Boil a vinegar solution, however, and you are producing solids that for short periods will block off the one side or the other before the pressure blows it out again. If you get a situation where the wand side of the thermoblock is blocked off, the steam will run backwards towards the steam pump. It won't get through the pump, in probably won't get close to the pump because there's a coiled piece of pipe in between them, but it may get close enough, for long enough, to heat up the water inside the pump, or in may cause the pump to overheat internally because the pressure makes it work harder. Either way - since the pump is not designed to handle higher temperatures - the rubber rings and seals in the metering mechanism will distort and start to bind against each other. When that happens, you still hear the pump working, but no water gets pumped through.
    Turn down the steam thermoblock temperature all the way and turn up the steam pump rate all the way. This will mean there's more water in the system when descaling as less will be converted to steam. It's effective in my experience.

    I've tried descaling steam thermoblocks warm, cold and hot and pumping solution through, letting it sit, cycling it frequently, cycling it less frequently, none of the methods have ever been as effective as turning the thermoblock temp down and the pump rate up and running the machine normally, letting it pump solution through for 30 second increments then allowing it to rest for 5 minutes or so with the machine off. Repeating this as many times as required until the solution coming out of the system returns to a normal colour.

    Regarding your claim of potential steam pump damage, the steam pump has a relief valve fitted at it's outlet to resolve this exact type of problem. When the steam knob is shut completely, the excess steam pressure in the system vents out of the relief valve to the tray. If often makes a strange squeaking sound.
    None of this steam gets to the internal parts of the steam pump. It does affect the rubber o-ring at the tip of the pump fitting though, over time it goes hard and leaks and is a primary cause of steam pump failures.

    Perhaps you were referring to the Ulka pumps used in the EM6900, they experienced failures due to not having a relief valve fitted. The workaround was to file a slot on the steam tap pin which allowed the excess steam to vent through the steam tip. Not a great fix but it was effective and really the only option they had other than a system redesign (enter the 6910).

    Comment


    • #17
      An old thread, but a good thread.

      Comment

      Working...
      X