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Thread: Some BZ40 Questions

  1. #1
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    Some BZ40 Questions

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I picked up a BZ40 in a recent throw out. I thought it would make a fun christmas project.

    From the research I've been doing, it looks like it is the old style BZ40.

    I have a couple questions about the machine:
    1. There is too much water coming out the steam wand. Any pointers to fix this?
    2. Where can I get portafilters?


    It was missing a few things; a hot water knob, a drip tray, and a portafilter.

    I stripped it down to pieces and descaled the copper, cleaned up the metal, and got the pumping mechanism working again.

    The hardest part was replacing a compression nut on the drain hose that I cracked when trying to disassemble.

    Its all back together and making (slightly metallic flavoured) coffee.

    The main problem I'm having now is there is too much water coming out the steam wand.

    I suspect the boiler is overfilling, but the level probes look to be intact. I also can't push them any further into the machine.

    Any pointers would be appreciated.

    Thanks

  2. #2
    Mal Dimal's Avatar
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    What is the water source for the BZ-40 busker?

    Mal.

  3. #3
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    I've got it plumbed in, connected to the tap through a water filter.

    The pressure gauge is reading around 5 bar.

  4. #4
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    Just to add some more information pertaining to the wet steam:



    • When I froth up some milk, I'm adding around 30 to 50% weight in water (eg, 100 g of cold milk becomes 150 g of steamed milk), after purging the steam wand. Looking around it seems this should be closer to 10%.
    • Purging the steam wand can result in a few seconds of dry steam, before water starts splattering out. It is then pretty constant.
    • I've checked both level probes. They look pretty scale free, but I cleaned just in case.
    • I've pushed the probes down so the bottom of the spade connector is touching the top of sheath - i.e they can't go down any further.
    • I measured the length of the level probe, and it is 72 mm (including the spade connector). This seems to be the same as in the parts manual.
    • The top of the spade connector to the nut is 20 mm. The length of the connector is 9 mm.
    • I've cleaned all the ground contacts around the machine.
    • The resistance between the boiler and the probes range from approximately 13 to 17 kOhm.
    • I've confirmed that the probes are correctly wired (the longer probe to level min pin, and the other to level pin).
    • I confirmed that the pump is valve is closing when the water level reaches the probe (I forced a refill of the boiler. Then pulled the probe up slightly (~1 or 2 mm), and I no longer measure resistance between boiler and probe).
    • The pressurestat is turning the elements off at 1.5 bar. So unless the gauge is incorrect and the pressurestat has been calibrated to the gauge, I think this is fine.
    • Just to be pedantic, the coffee machine is on a level bench, and the machine is also level.



    I'm not sure what else I can check. I'm tempted to cut a couple of millimetres off the sheath so the probe can go down a bit. But it doesn't feel like it's the right solution.

  5. #5
    Mal Dimal's Avatar
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    Are you able to measure the water hardness (TH) of the water being supplied to the Boiler?
    If, for some reason, the water is just too soft then it may be that the sensitivity of the water level controller is just not able to detect the water level correctly.
    Try adding a pinch of salt to the water in the boiler, and see if that improves things...

    Mal.

  6. #6
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    Thanks for the suggestion Mal,

    However, I measured resistance on the probe just after an auto-fill. I then pulled them probe out ever so slightly, and measured infinite resistance.

    So I think that the auto-fill system is working as intended.

    Using a wooden stick as a dip stick - it does appear that there is at least some headroom in the boiler.
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  7. #7
    Mal Dimal's Avatar
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    Rightio...

    Without the machine in front of me, not sure where to head next.
    I know this probably sounds ridiculous, but someone wouldn't have reversed the Hot Water dispensing wand with the Steam wand would they?

    Grasping at straws now...

    Mal.

  8. #8
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    Thanks Mal,

    Its a confusing one, made harder by the fact that I don't know the history of the machine!

    I bet in the end its going to be something simple that I have overlooked.
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  9. #9
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    Ahh a follow up:

    I was trying some other experiments: e.g. refill the boiler. Ground the level probe. Emptying out some water. But was still getting water out of the sprout.

    Just for interest's sake I tried my 2-hole La Scala Butterfly tip instead of the original 4-hole tip that was on wand.... and dry steam!!

    Just for reference I've attached a picture of the old 4-hole tip that was on the machine.

    I'm still not really satisfied with my thirst for understanding what the issue was.... I struggle to believe that people using this machine originally would have put up with so much water coming out the wand (or maybe they were running a cafe and liked how much it stretched the milk!!).

    Maybe the 2-holes is delivering less steam and therefore hiding the fact that the boiler is overfilling and I'm not really fixing anything just hiding the problem!

    I was planning on upgrading the wand to the Rancillio one in the new year, once the coffee parts shops reopen. So hopefully this will be a satisfactory fix.

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  10. #10
    Mal Dimal's Avatar
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    The mystery deepens...
    Glad it seems to be working Ok for you now though.

    Mal.

  11. #11
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    Maybe I spoke too soon.

    It seems better - I'm getting between 20 and 30 % water weight in my milk.

    Hopefully this will keep me satisfied until part stores open up next week.

  12. #12
    Senior Member robusto's Avatar
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    Ha ha, I did that once Mal. I didn't want to reach across the machine to steam. Crossing over the wands was very simple. But the result an abject failure.
    Water our of the steam wand, and steam out of the water one.
    Back they went.
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  13. #13
    Mal Dimal's Avatar
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    I can imagine...

    Mal.

  14. #14
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    Hopefully final update:

    Since I've ruled out the water level, the next obvious thing is too little pressure build up in the boiler.

    The guage on machine was reading 1.5 so I assumed it was alright. But looking closer at the gauge when its turned off - its not returning to 0, it got down to 0.2 bar!!!!

    I nervously adjusted the pressure stat, half a turn at a time. until the steam was dry. I brought it up to 1.6 / 1.7 bar on the gauge.

    This will have to do until I replace the gauge.

    I feel alright knowing there are two safety measures built in: the pressure relief valve and the inline temperature fuse..
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  15. #15
    Senior Member robusto's Avatar
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    It is mysterious. But I'm inclined to think it's overfilling.

    Or as Mal suggests, the wand/tap have been reversed.

    Incidently, I weighed the amount of steam after steaming 340 grams of milk on my Grimac. It was 28 grams, so 8% by weight is being added.

    The 2 probes setup I'm not familiar with. If one is a minimum level and the other a maximum, wouldn't the maximum also be the minimum? Maybe it's a failsafe?

    Is the probe the right one for this machine If it can't be pushed any deeper and the water level is still too high?

    Try removing it (with machine cold and switched off), and put it on the outside of the boiler with the top of the probe at it's usual height. How far down is it going? About halfway down the boiler?

  16. #16
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    Thanks for the measurement robusto! From what I've been reading that seems to be on the good end of whats expected. 12% looks like the higher end. I'm going not going to give up until I have 10%!

    I've got the parts book for the machine, available here: https://www.1st-line.com/wp-content/...DEPM-Parts.pdf

    I've measured the probes, and they the same length as in the parts manual (~70 and 80 mm).

    The hot water and steam wands are in the same position as in the manual - so that's good! And, the hot water wand does just produce hot water...

    From my understanding, the pump turns on (and fills the boiler) when the level drops below the longer probe. It turns off when it reaches the shorter probe. Therefore the level stays in the 10 mm range.

    My reasoning for thinking that the water level is correct is:

    * The probes match specifications.
    * I've run the fill cycle until the pump turns off. I then measured the resistance on the shorter probe - it was measuring some resistance. I pulled the probe up slightly (around 1 mm) and it no longer measured resistance.
    * I also used a wooden dowel and stuffed it down the steam hole to determine the level and it line up approximately where the end of the probe was (which was slightly higher than half way, but there was head room).
    * Just for fun I stuck an endoscope down the hole - it didn't tell me much really. Just confirmed the boiler was full.

    However, the difference between wet and dry steam is pretty small - so I'm not discounting bias in my measurements (and hope that they are right). It could still be overfilling!

    I don't trust the pressure gauge as it's not zero'ing out when the machine is cold. I suspect the pressostat would have been calibrated against the gauge, and therefore a bit low.

    I tried to get an adapted to attach an external gauge to the steam wand... but my 1/8" BSP adapted don't thread on! - plumbing fixtures are so frustrating....

    I've been enjoying the coffees out the machine so far - the milk has been slightly disappointing. But I think I can live with it until I can get a replacement gauge.

    Once I have the pressostat properly calibrated, and if the steam is still not correct, I'll relook at the water level.

  17. #17
    Mal Dimal's Avatar
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    Quote Originally Posted by robusto View Post
    If one is a minimum level and the other a maximum, wouldn't the maximum also be the minimum? Maybe it's a failsafe?
    Yep, the long one is usually a Boiler Safety Probe.
    When water is no longer detected, power to the element(s) is removed...

    Mal.
    robusto likes this.



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