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Water, Scaling and Descaling with HX machines?

Postby Teme on Sat Nov 12, 2005 7:22 pm

I'll try and keep this post short and start by stating my assumption that because HX machines are generally more difficult to descale than single boiler machines (see How do I descale my espresso machine? for details), many HX machine owners use water that is softer than is ideal for the taste of coffee. I think Jim Schulman's Insanely Long Water FAQ is mandatory reading (although I'm not quite sure I have still managed to absorb all of the information :D) and a comprehensive account of one of the key ingredients of espresso.

My questions (specifically applicable to those who do not plumb in their machines) relate to this:

- how often do you descale you HX machine?
- do you do it relatively frequently (meaning annually or twice a year) to avoid massive build-ups of scale?
- do you do it less frequently, i.e. only when the machine starts "acting up" and end up with a heavy and expensive descaling / overhaul at some stage
- do you filter your water or just use what comes form the tap (in either case, have you measured the water hardness?)?

or

- do you use very low mineral content bottled water and therefore compromise on the taste of the coffee?

I'd be interested in hearing thoughts on this. My current approach is to use bottled water with low mineral content and refresh the water in the boiler on a weekly basis to minimise its mineral content and hence the buildup of scale - I am not entirely comfortable with this compromise. While I do not foresee any need for descaling in the near future I guess it is inevitable at some stage. I have not managed to find a detailed how-to for this yet and there may be HX machine owners that are getting closer to the day this will come up...

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Postby another_jim on Sat Nov 12, 2005 11:38 pm

Whatever you do, don't wait until it acts up; at that point the flush type descale I describe won't work -- the machine will need to be disassembled and acid washed part by part.

I descale my machine about 4 times a year, more frequently than necessary, since it's relatively simple on the Tea (small boiler = less flushing to get the lemon out); and because I'm not nearly anal enough to regularly recharge my softener and flush the boiler.

If you are good on scheduling, the ideal is to use water at around 5 grains, run distilled into the boiler every week to keep it clear, and descale just the HX circuit quarterly. That part of the machine descales just like a single boiler, since the HX has a relatively small volume and is entirely filled with water. The boiler, being partially filled, will form scale at the rim, and on the autofill rod because it has a current. So the descale has to be done by force overfilling the boiler, which is the main pita.

I personally find ion softened water OK for most blends, which have low acidity; but it does show limits more sharply for SOs and blends with lots of high grown washed coffees, where the extra softness distorts the acid flavors and affects the already diminished crema formation.

I need to redo the FAQ since, thanks to the consumer friendly chinese manufacturing, the technology prices have gotten much more favorable. One can get small RO units now around $150 to $200 which can be attached to faucets to produce a few gallons in an hour, or plumbed in beneath a sink to fill a jerry can. TDS meters are down to $15, and can be used to roughly calculate hardness for tap water (but not ion softened water), and monitor RO performance. This means people could use them for pourovers by simply adding some tap water to the RO to get the right TDS (around 75 to 125 depending) and they can use the pure RO to flush out their boilers. This would make for a simpler and cheaper regimen than schlepping bottled water, and a potentially tastier one than using ion softeners.
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Postby Teme on Sun Nov 13, 2005 3:25 pm

Thank you for your enlightening reponse Jim.

My intention is not to wait until my machine starts acting up but to understand what steps I need to take and how frequently I should take them. Since this is a topic that has not in my opinion been discussed exhaustively on the various forums I am also still curious as to how many HX machine owners routinely do descale their machines - be it the heat-exchanger only or also the boiler. I would wager that a vast majority has not done either.

I also understand that some vendor and/or manufacturers actually advise owners against descaling routines. I have also heard stories that machines have been operating faultlessly but problems have occurred after descaling - perhaps this has been a sign of having waited too long before performing the descaling and substantial scale buildup has already occurred (and in connection to the descaling some of the dislodged scale particles end up in places where they start causing problems).

My Andreja is now 7 months old and personally I have not yet performed any sort of descaling. I have (perhaps falsely) relied on the low mineral count of the water and frequent refreshing of the boiler water. However, unless it is likely to cause harm to the machine, it looks like I may want to descale both the HX and the boiler. I will be out traveling for a bit over a week, but I would do it thereafter. Would someone be able to give me a step by step guide on how to do this or walk me through the process? In Jim's FAQ there is a pretty detailed description but I don't feel comfortable going ahead with that alone...

The prices for RO units and TDS meters you quoted do not seem frightening but managing water does start to sound relatively complex. Regardless, this is something I may look into.

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Postby another_jim on Mon Nov 14, 2005 1:58 am

Chris Nachtrieb has communicated that my descaling instructions on the FAQ are woefully incomplete. Judging by all the emails I get, I think he's right.

The key is the autofill sensor on the boiler:
-- when descaling the HX, you absolutely do not want the boiler refill to run
-- when descaling the boiler, you want the refill to run beyond the autofill setting and to flood the boiler to near the top (I actually like to be able to run the descaling solution out of my steam wand although this is not strictly necessary (both Jack Denver and I have found it reduces problems on the pressure stat diaphragm and the valves if one descales them occasionally).

I'm going to post instructions here and people can copy, report and use them as they please. It'll also give me a crib sheet when I do the FAQ rewrite.

The autofill is a "normally closed" switch. This means when the sensor is grounded, normally by making contact with the water in the boiler, and does pass current, it does NOT refill. If it is not grounded, it DOES refill.
-- To prevent it from overfilling, one can remove the wire from the top of the wire and ground it on the boiler case (or use an insulated wire with alligator clips on the ends to ground it). Do this when descaling the HX circuit
-- To force it to fill, once can simply pull the wire off, and let it hang in the air. Do this when overfilling the boiler. Use the machine's on/off for control. When overfilling the boiler, make sure the machine has reached operating temperature on the regular boiler level, since over filling it when the vacuum breaker is open will be very messy!
-- If you plan to descale regularly, attach a 3 position "descaling switch" to the autofill circuit. Cut the wire running from from the brain box to the autofill wand. Attach the wire from the logic box to the middle terminal. Attach the wire to the autofill wand to one of the outer terminals. Attach a wire to ground (there's ground terminals on all machines, or stick it on the piping, if you don't trust your house wiring) to the other outer switch terminal. When you switch this to ground, the autofill never works, when you switch it to the wand, it works normally, in the middle position it just keeps filling. This switch can (and should) be left inside the machine, since one doesn't want to operate it inadvertently. Any small Radio Shack low voltage switch (1 amp is plenty) will work, just make sure it's designed to operate up to 250F.
-- If you don't understand or don't want to understand these instructions, my advice is to learn how the machine works before doing this, or not to attempt descaling, and use softened water instead.

The descaling solution of choice is 1.5 to 2 table spoons of citric acid powder per liter/quart of water. It is at proper concentration if you see a light blue/green tinge in the flushed water when descaling. The reason this is the choice is that some citric acid will remain in the boiler when you descale that, unless you can drain it from the very bottom. Citric acid is odorless and, in low concentrations, tasteless, so it ill not mess up your steaming to have a little left. The alternatives are not as good: Vinegar smells, and industrial solutions (as well as CLR) are based on hydrochloric acid and are not food safe -- they would require a lot of extra rinsing flushes to remove.


Descale the HX like you descale a home machine:
-- ground the autofill wand (see above)
-- fill the tank with the descale solution.
-- flush the group with four ounces worth, wait 10 minutes, and repeat.
-- repeat this 4 to 6 times.
-- refill the tank with water
-- restore the autofill
-- flush the group till the taste is gone (start with 1 quart before tasting). If anyone has one with a big honking HX like the Cimbali's, please jump in with revised quantities.

Descaling the boiler is more of a pita:

-- The machine should be at operating temperature.
-- turn the machine off, and run as much water out of the hot water tap as you can. Tilting the machine towards the side the pipe attached to the boiler helps.
-- Fill your tank with descaling solution.
-- Turn the machine on, and let the autofill fill the boiler to the normal level with descaling solution.
-- Wait for the machine to reach operating temperature.
-- Disconnect the autofill (see above) and let the boiler overfill. Open the steam valve slightly as this is happening. When the solution starts squirting out of the steam arm (into the bowl placed there), the fill is done. Turn the machine off, and restore the autofill to its normal postion.
-- Let the machine descale hot for several hours. If doing the HX, you can do that while this is happening.
-- To rinse the boiler afterwards, repeat this entire process, including the overfilling and running water through the steam arm once.
-- Repeat the emptying of the boiler through the water tap, and ordinary refill (no extra water) until the drained water is tasteless (for me this happens on the second round -- your results may be different).

I hope this is complete enough to answer all questions.
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Postby Teme on Mon Nov 14, 2005 4:55 pm

Thank you again Jim for taking the time to write such a detailed response. Upon my return home (and as soon as I have the time), I will go ahead with the descaling...

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Postby cannonfodder on Mon Nov 14, 2005 11:44 pm

I am in the same boat as Teme, I have had my Isomac for about 8 months and I think it is time to descale. I use filtered water so excessively hard water is not an issue but I want to do it before it becomes an issue.

Excuse me for being a little naive, but could you point out the fill switch? I am acquainted with most of my machines workings but not the fill sensor that I need to override. I believe it is the green wire attached to the sensor on the top of the boiler (brass fitting) but want to make sure before I create a ground fault and melt everything.

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Postby another_jim on Tue Nov 15, 2005 10:16 am

Right the first time! It's the rod, top/middle of the boiler, next to the vacuum breaker drain, with the green wire attached. Cut the green wire, and attach the switch there. For the Tea, you drain the boiler by tilting it towards the steam arm side, i.e. left, (odd, but that's where the water pipe attaches -- you can remove an extra 1/2 cup of water that way and cut the flushing after the descale by a round).
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Postby cannonfodder on Tue Nov 15, 2005 8:44 pm

Here are two photos that show the line a little clearer and another with most of the boiler works labeled.

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Postby another_jim on Tue Nov 15, 2005 10:49 pm

cannonfodder wrote:Here are two photos that show the line a little clearer and another with most of the boiler works labeled.


They've rearranged the top of the boiler since my model to make room for the pstat facing upwards instead of sideways. You have the wand labelled correctly. However, the vacuum breaker is the valve inside the basket, the safety valve is the one on the same tap as the pressurestat. You've labelled them the other way on the picture. BTW, Dan disagrees and thinks you have them right.
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Postby cannonfodder on Wed Nov 16, 2005 11:11 am

Interesting. I assumed the one on the pstat T was the vacuum breaker because when the machine heats, I get a bit of gurgling around the pin in the cap. Once hot it stops (like a breaker).

I would have thought the valve in the black container would have been the emergency pressure release valve. If you overheat the boiler and that opens, you would blow superheated water everywhere. I assumed that they would enclose that to prevent the water/steam release from blowing all over your machine. Electric circuits and water don't get along very well. That silicone tube runs to the drip tray.

With the pstat in its current location, you can get to the adjustment screw with the top on. You have to use a long thin Phillips head (longer than a jeweler's screwdriver) and take the cup warmer cover off. You can not see the screw in the photo; it is in the center top hidden behind the water tap pipe and leads.

I have made a few enhancements, that is the stock photo, here is the current.

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