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Thread: HX Descale question

  1. #1
    gc
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    HX Descale question

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I have been following the instructions in the sticky at the beginning of this forum group (https://coffeesnobs.com.au/brewing-e...-properly.html). However, I 'think' that my old San Marino Compak has two heat exchanges - one for the brew and one for hot water? If that is the case, then water in the boiler is only used for steam and heating the HX's.

    So my question is: after filling the boiler with descaler as per the link above, how do I empty the boiler and flush it of descaler if the only exit is the steam wand?

    Hopefully, I'm completely wrong here and hot water comes directly from the boiler. Thanks for any assistance.

  2. #2
    Mal Dimal's Avatar
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    Is there not a bung under the boiler that can be removed for draining?

    Mal.

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    gc
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    Thanks for responding Mal. I don't think there is a bung (see attached image) and not being very experienced with such things I've been very reluctant to try to undo any of the fittings on the bottom as they are fairly welded on with age now. And don't have a "plan b". I think the boiler is brass, but not entirely certain. 2018-12-24 15.22.56~2.jpg

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    Mal Dimal's Avatar
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    Are you able to easily remove any of the top fittings, to give you access using a syphon to drain the boiler after flushing? Always more than one way to skin a cat, as they say...

    Mal.

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    gc
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    Good point! Ithink I could probably try the antivac valve. It was the most recently replaced item on a service some long time ago. Is it possible to tell from the drawing above whether the hot water is drawn directly from the boiler or goes through its own heat exchanger tube? What is ususal practise on HX machines? Is the San Marino Compac different?
    Last edited by gc; 24th December 2018 at 04:24 PM.

  6. #6
    Mal Dimal's Avatar
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    I don't "know" the machine 'gc', unfortunately and the drawing above doesn't really have enough info to determine what goes on inside the boiler. Was just offering generic advice since no one else had contributed. Maybe someone who has actually worked on one of these will spot the thread and pop in with some useful advice.

    All the best mate and Merry Christmas,
    Mal.
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  7. #7
    gc
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    I really appreciate your effort nevertheless. Many thanks and Merry Christmas
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    Senior Member topshot's Avatar
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    You could try opening both the steam and hot water valves, then blowing air (low pressure) into the steam wand.
    I use a Swiss ball hand pump.
    If your machine has one HX in the system, like 99.9% of HX machines do, water should come out of the hot water wand.
    Keep the air pressure up until the boiler is empty, then refill the boiler and flush again.
    Do this 6 or so times to flush the boiler using fresh water.
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  9. #9
    gc
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    A worthwhile experiement. I'll give it a try with a hand pump or if that doesn't work, my air compressor [gently]

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    Senior Member noidle22's Avatar
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    It has two heat exchangers, same boiler as a Wega Mini Nova and a few other machines.

    The only way to descale the steam boiler is to manually drain and fill.
    I have a spare Ulka pump and use it to drain and refill, works well. If you dont have one spare, you can just siphon it in and out with a length of thin tube or use some other liquid transfer pump.

    The anti vac or safety valve are easy locations for access.
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  11. #11
    gc
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    Quote Originally Posted by noidle22 View Post
    It has two heat exchangers, same boiler as a Wega Mini Nova and a few other machines.

    The only way to descale the steam boiler is to manually drain and fill.
    I have a spare Ulka pump and use it to drain and refill, works well. If you dont have one spare, you can just siphon it in and out with a length of thin tube or use some other liquid transfer pump.

    The anti vac or safety valve are easy locations for access.
    Ah! Thank you! I had the vaguest memory it was similar to a Wega but couldn't remember throughthe fog of age, any useful detail. So was hoping someone n CS would know for sure. Thank you for confirming this. Now I know what I must do to descale the boiler properly. Very grateful.

    One question though: How does it fill in the first place? Following the instructions referred to in my OP and disconnecting the water level probe to boiler while opening the steam valve certainly filled it to the top quickly. Does the same water just sit there as a heating tranfer medium to the exchanger tubes after that without ever being added to unless it is steamed off heating milk [if there is no other exit beside the steam wand]?

  12. #12
    Senior Member noidle22's Avatar
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    Quote Originally Posted by gc View Post
    Does the same water just sit there as a heating tranfer medium to the exchanger tubes after that without ever being added to unless it is steamed off heating milk [if there is no other exit beside the steam wand]?
    Yep, it's not a great design. Some machines may have a drain tap which would make flushing easier, my Mini Nova didn't, not sure about yours or others. The addition of a drain tap would be useful in this scenario, and for refreshing the boiler water during use.
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