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Thread: Rancilio S26 running off tank letting hot water back through inlet hose

  1. #1
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    Rancilio S26 running off tank letting hot water back through inlet hose

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi CSers

    I've upgraded from my Silvia with a used Rancilio S26 from another CS member and trying to set it up this weekend.

    I'm having a bit of trouble reliably drawing water into the the machine & wondering if anyone has suggestions on what's going on.

    At the moment, I've set up an external water tank to feed the S26. I don't want to drill through the counter top just yet to plumb into mains and have read that running from a tank is commonly done successfully. There's a pressure adjustment screw on the rotary pump to increase pressure accordingly if not running on mains pressure.

    The machine pulls water from the tank easily when first switch on, but once the machine gets hot it won't reliably pull fresh water and instead will sometimes let boiling water/steam comes back through the inlet hose (hose gets too hot to touch). I've elevated the tank temporary but without seeing an improvement. It doesn't seem to be running the pump backwards but hot water and bubbles of air are moving through the hose and giving gurgling sounds at the tank. You can hear it at the end of this short video: https://www.youtube.com/watch?v=tHCv4TACW3Q

    In this second video, you can see the machine pull water fine at the beginning, then stop and be unable to draw any more water (to refill the boiler): https://www.youtube.com/watch?v=SXuGBmLzKaM

    I'll try to rig up a temporary mains connection but knowing others have run from tanks makes me think the issue is elsewhere. Is the pump misbehaving, a valve not closing or something else?

  2. #2
    Senior Member sprezzatura's Avatar
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    Wow! Nice to see a video! Are you using distilled water? Is your water level probe clean? The pump on and off can indicate a faulty signal from the probe.

  3. #3
    Senior Member sprezzatura's Avatar
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    Also, you have an issue with your OPV or/check valve downstream from pump. I'll look at the schematics for the S26

  4. #4
    Senior Member sprezzatura's Avatar
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    Try to take an image of the interior for us - especially the pump and hydraulic routing to the OPV. Your level controller may be an issue - or the wiring to and from it. Check your wiring visually if you feel competent enough (machine off, desteamed and unplugged from owner point).

  5. #5
    Senior Member sprezzatura's Avatar
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    Rancilio S26 running off tank letting hot water back through inlet hose

    The check valve and OPV should look like this.
    Attached Images Attached Images
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  6. #6
    Senior Member sprezzatura's Avatar
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    R.33 through R.36 is definitely a culprit and so is R.81 through F.70 (check valve from pump).

  7. #7
    Senior Member sprezzatura's Avatar
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    If none of this works, take it to a technician. Better than getting super frustrated.

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    Thanks so much sprezzatura!

    I will take photos and report back. The machine is very easy to pull panels and get interior access to.

    I'm happy checking wiring and probing with a multimeter. But yes if I can't diagnose I'll take it to a coffee tech.

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    I'm using bog standard Sydney tap water, less than 10L has gone through the machine though.

    I will have to check the water level probe, after I look up the exploded diagram to find it
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  10. #10
    Senior Member sprezzatura's Avatar
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    It'll be on top of the boiler, dude. A female spade connector will plug into it and the wire will go to the black box that is the level controller.

  11. #11
    Senior Member sprezzatura's Avatar
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    Standard water won't cause conductivity issues with the controller/probe.

  12. #12
    Senior Member sprezzatura's Avatar
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    ... standard Sydney bog water

  13. #13
    Senior Member sprezzatura's Avatar
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    ImageUploadedByTapatalk1446281139.966325.jpg

    Level probe is in the middle white connection with white or grey wire.

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    Hello voicecoils,
    Interesting challenge you have there however,you say your getting a reverse flow into the water tank and making the hose too hot !!That is not possible if you have correctly installed your inline one way valve (non return valve).
    I have two commercial espresso machines set up presently,both with Non return valves between the water tank and the rotary pump,one a fancy brass one and the other a cheap $10 unit from bu___'s.
    Both work perfectly well,I also have two other commercial single group's as my work identically set up,also with non return valves (essential when using rotary pumps).
    In your videos I was unable to see any,do you have them fitted?
    cheers,
    Mick.
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    I haven't fitted an external nonreturn valve, I thought the machine would have something internal, but may well be mistaken! Thanks for raising that point.

    The line is definitely getting hot from boiler water. It stays perfectly cool up until the point where the pump starts making funny struggling noises then the hose heats rapidly with spitting gurgling steam sounds.

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    A few quick photos. Thanks for the replies so far guys. I have a lot more to consider now.

    uploadfromtaptalk1446297240684.jpg
    uploadfromtaptalk1446297277652.jpg
    Last edited by voicecoils; 1st November 2015 at 04:17 PM.

  17. #17
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    $10 from bunnings, in their plumbing section, inline so easy to fit, yes you do need one, everything will be OK then, please keep me posted.
    Cheers,
    Mick.
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  18. #18
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    Quote Originally Posted by sprezzatura View Post
    ImageUploadedByTapatalk1446281139.966325.jpg

    Level probe is in the middle white connection with white or grey wire.
    Bottom left of the photo is a 2 way solaniod and valve , the hot water should not be returning back from the heat exchanger past that , you do not want that hot water getting to the pump and it sounds to e that Is whats happening.
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  19. #19
    Senior Member sprezzatura's Avatar
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    Another possibility is that your bypass in the vane pump is stuck. Machines that sit for awhile can have the little o ring in the bypass 'stick' so that most of the water bypasses and never reaches full pressure. Field techs like myself will unscrew the bypass and pull the assembly out, use a tiny amount of food grade silicone on the o ring and reassemble. Cycling the set screw several turns in (counting) and then back out may free the bypass as well. We use a portafilter with a gauge to confirm pressure (6 - 9.5 bar depending on several top secret roaster factors).

  20. #20
    Senior Member sprezzatura's Avatar
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    Cleancup has a good point too. Your boiler fill solenoid may be fouled. Ensure there's a healthy 'click' (coil energised and mag field pulling nucleus plug up) and water flowing into boiler.

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    uploadfromtaptalk1446354241653.jpg

    Picked up a non return valve today which also has an isolating switch which is handy if disconnecting the tank.

    So far I've had the machine on for an hour running water through the group, hot water tap and steam wand without any issues at all. I'll provide and update if this changes.

    The fact that hot water was coming back through before is still a bit concerning and worth more investigation but I'm happy to have gotten to this point so I can actually try the machine out!

    Really impressed at the knowledge and helpfulness of you guys!
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  22. #22
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    Hi Voicecoils, where abouts did you purchase the non return valve? I've been chasing one like that, that will connect to the bottom of a container. Cheers

  23. #23
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    Quote Originally Posted by kyeba View Post
    Hi Voicecoils, where abouts did you purchase the non return valve? I've been chasing one like that, that will connect to the bottom of a container. Cheers
    Nefa 15mm DR Brass Female Non Return Isolation Valve | Bunnings Warehouse

    For my water container I also needed a 20mm to 15mm male-to-male reducer plus some plumbers tape!
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  24. #24
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    Awesome, thanks mate

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    voicecoils,
    Great to know you have sorted the pump problem,hopefully your rotary pump is running nicely now and will continue to do so for your ongoing coffee enjoyment!
    Still may be worth while following the mentioned suggestions of confirming the clearing/operation of your pump too.
    Cheers,
    Mick.
    Screen shot 2015-11-02 at 10.41.37 AM.png
    Last edited by mulquemi; 2nd November 2015 at 09:42 AM.
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  26. #26
    Senior Member sprezzatura's Avatar
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    Nice easy fix! Cheers!

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    Thanks again guys.

    My next 2 tasks are to calibrate pump pressure once the Pullman portafilter gauge arrives and to service my grinder.

    After that I'll work through the checklist for the S26 that everyone's given me so far:

    * clean water level probe
    * check function of OPV valve
    * check function of check valve downstream of pump
    * check level controller & wiring
    * check that hot water is not returning back from heat exchanger past 2 way solanoid & valve
    * check bypass in vane pump (calibrate pump pressure with gauge portafilter)
    * check that boiler fill solenoid makes healthy click and works properly
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  28. #28
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    Pullman gauge arrived so now I have my next challenge: group head pressure is at 3.7 bar!

    The adjuster screw on the procon makes no difference whether full in or wound full out.

    I checked the gauge on my Silvia and it is still solid 9 bar where I set it at months ago.

    Luckily I have a spare procon I can pull parts from or swap in. Fun for this weekend!

  29. #29
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    A bit of success, but not quite there. I pulled apart the pressure adjustment mechanism on the procon in the S26. It actually was in great condition and far less crusty than my spare pump's parts.

    I stretched the spring out a bit and reassembled. This time, adjusting the grub screw with the 19mm hex nut loosened I was able to raise the pressure close to 6 bar. Then I added a few spacers to put more force on the spring situated between the grub screw and spring. This got pressure up to 6 bar as pictured. Sadly I could get no higher. I'm not sure if more spacers will have much affect in raising the pressure if the bypass is fully closed off than that would be the max pressure the pump is capable of without mains pressure I would assume.

    Also I noticed while working on the pump that hot water is still flowing back to it. I can't tell exactly what situation it happens in but the pump body became hot to the touch until I drew water from the hot water tap to force fresh cool water through the pump and cool it down. The anti return valve between the tank and pump is clearly working to keep hot water flowing back to the tank which *is* good to see.

    Perhaps the old pump has been damaged by the heat of the hot water.

    Attachment 10871
    uploadfromtaptalk1446880398815.jpg
    Last edited by voicecoils; 7th November 2015 at 06:09 PM.

  30. #30
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    voicecoils,
    Good to know you have the machine operating,despite your lower then expected delivery pressure....how does it go actually operating,good/great coffee?
    I really believe the proofs in the delivered shot,fussing about whether its exactly 9 bar is neither here or there.
    I try setting my machines close as possible and the resulting performance is never disappointing.
    How did you go regarding following the list you set yourself?
    I'd reckon your machine is pretty sorted by this stage.
    Life's great with a operational coffee machine (or two).
    Cheers,
    mick.

  31. #31
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    Of my checklist, I still need to read up on a number of these things to learn what they are, how they work, where they are in the S26. Iím learning as I go.

    Ok, 'how's the coffee' is an excellent question but I've got the flu at the moment which is quite limiting my sense of smell and taste. I had a double espresso at Sensory Lab this morning and could barely relate to anything in their tasting notes. Anyways...

    It seemed a good time to pull back to back shots with S26 vs Silvia and compare. Each had:
    * 18g of 13 day old Mecca espresso blend beans (past prime but on hand...)
    IMG_20151107_225542-2.jpg
    * same grind, tamp, basket & portafilter
    * 26 sec extraction from hitting brew button.

    Result:

    S26 (6 bar @ grouphead)
    * 9 sec dwell time
    * 29.4g output
    Video: https://www.youtube.com/watch?v=SANYShkphJ0

    Silvia (9-9.5 bar @ grouphead)
    * 5 sec dwell time
    * 32.5g output
    Video: https://www.youtube.com/watch?v=Tq8YDOqM77Y

    Considering the pressure and dwell time differences, I was surprised to see the shots come out at similar weights.

    Limited taste impressions:
    IMG_20151107_224930-2.jpg
    Silvia - right - good syrupy mouthfeel, balanced start but finished with a less than ideal burnt orange peel aftertaste.
    S26 - left- thinner mouthfeel, bitter start with sour mouth puckering finish.

    Not smitten with either but it's a start.

  32. #32
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    voice coils,
    Looking at both videos you made,seems you have two winners there,taste is difficult to judge from my end and as far as you are concerned it's up to your experimentation with flavours/blends.
    Both brews looks splendid, can't fault either,S26 hasitated initially but recovered and poured beautifully.
    Once your check list is completed,by all means have another look at the pressure produced by the procon,don't sell your soul on it though!
    Enjoy your lovely rebuilt espresso machine and rest easy knowing you have" achieved mightly"
    Thank you for the entertainment!
    cheers,
    Mick.

  33. #33
    Mal Dimal's Avatar
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    G'day v-c...

    Just looking at the beans you are using, I imagine that they will produce quite a bright result in the cup independent of the brew method/machine used. Given the S-26 is running under pressure, you would expect the result in the cup to be quite a bit less than optimal. You might notice a bit of an improvement if you tightened the shots up a bit, never hurts to experiment...

    Mal.

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    Thanks Mal. When you say tighten the shot... Updose/grind finer? Sorry I'm a still a noob!

    Found the cause of the hot water backflow today: the check valve at the tee between the pump and boiler fill solenoid had a mangled spring. I need to locate and replace the spring or whole unit.

    uploadfromtaptalk1446972690598.jpg
    uploadfromtaptalk1446972722413.jpg

    I also found one of the connections to the boiler heating element was poorly repaired/connected previously with low conductivity nuts and bolts causing high resistance and enough heat to totally melt a screw down terminal block. I redid this wiring and it now has good enough conductivity not to even get warm when the boiler heating indicator light is on.

    uploadfromtaptalk1446973152701.jpg

    Lastly I pulled apart the procon and could see signs of wear but no obvious damage. I'll try swapping in the spare procon after I get my check valve in the machine sorted.

  35. #35
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    Quote Originally Posted by voicecoils View Post
    Thanks Mal. When you say tighten the shot... Updose/grind finer?
    Just gradually set the grinder a little finer until the resulting pour starts off with a few glutinous drops that slowly develops into a continuous stream that is lovingly referred to as a mouse-tail. When it starts get a bit watery and paler (called blonding), stop the shot and sample the brew... Repeat until such time as you're happy with the results in the cup...

    Mal.
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  36. #36
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    Thanks Mal, I'll work on my mouse tails

    After some more cleaning, descaling and oring changing on the internal check valve returning from the boiler, I think I've got my hot water backflow problem fixed.

    That gave me the confidence to swap the procon out and I'm happy to report the new pump is hitting full pressure with ease :-)

    A little explanation and group head pressure demo here:

    https://youtu.be/d2NfPojL-5U
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  37. #37
    Mal Dimal's Avatar
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    Excellent stuff mate...

    Mal.

  38. #38
    Senior Member sprezzatura's Avatar
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    Have a look at your OPV - is it returning water (too much bypass?) or dumping it into the drain tray?

  39. #39
    Senior Member sprezzatura's Avatar
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    Your pump may be generating enough pressures but a bad OPV will bleed it off before it gets through your puck.

  40. #40
    Senior Member sprezzatura's Avatar
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    Oops! Just read that new pump solved issue: I'll just say I covet your Park tools

  41. #41
    Mal Dimal's Avatar
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    Quote Originally Posted by sprezzatura View Post
    Have a look at your OPV - is it returning water (too much bypass?) or dumping it into the drain tray?
    These don't use an OPV as such, rather, they have a bypass valve fitted to the pump itself which recirculates water from the high-pressure side back to the low-pressure side, once the preset pressure adjustment has been reached... Nothing gets vented back to the drain-tray, or at least, it shouldn't...

    Mal.

  42. #42
    Senior Member sprezzatura's Avatar
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    Ah, ok. My bad. Must be some sort of check valve or expansion valve system between the pump and boiler fill and h.e. system maybe then?

  43. #43
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    Quote Originally Posted by sprezzatura View Post
    Oops! Just read that new pump solved issue: I'll just say I covet your Park tools
    Yes, I'm really happy the new pump worked! I imagine the previous owner's connection to main pressure plus the old worn pump's 4-6bar combined to give ok or just slightly low pressure so it went unnoticed.

    I do have good bike tools from quite a few years working in bike shops, they're quite handy on the coffee machine

    This morning I pulled a great double ristretto shot and enjoyed it immensely as a piccolo. Hopefully many more good pours to come
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  44. #44
    Senior Member sprezzatura's Avatar
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    Cool! Nice machine. I like Rancilio machines - always have. The Park tools would be GREAT to get inside machines! I'm going to look for some spanners.

  45. #45
    Mal Dimal's Avatar
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    I reckon a good set of Flare Nut Spanners are worth their weight in gold when working on commercial/prosumer espresso machines. Wouldn't be without mine...

    FlareNutSpannerSet.JPG

    Mal.
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  46. #46
    Senior Member sprezzatura's Avatar
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    Yep, those are mighty pretty, Mal!

  47. #47
    Senior Member sprezzatura's Avatar
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    We should start a What I Have In The Jewel Box sub forum
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  48. #48
    Senior Member sprezzatura's Avatar
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  49. #49
    Senior Member sprezzatura's Avatar
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    ::squints:: note to self - set selector on AC to read amperes to element, not DC (I broke my reading glasses last night). Thought that reading looked wrong.
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  50. #50
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    Amazing the versatility of hall effect sensors.

    Current clamps are handy tools!



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