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Thread: Giotto Premium repair advise - lack of pump pressure at end of cycle

  1. #1
    msp
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    Giotto Premium repair advise - lack of pump pressure at end of cycle

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I have a Giotto, serviced last year here in Brisbane for about $1K - that included a new series 2 control board, descale, pump, gaskets etc.

    The machine has recently started to fail in delivering pressure during an extraction. The vibrating pump starts with the usual noise, starts to deliver, then the pump goes almost silent and the is very little flow. When I clean the machine with a blind basket, the same thing happens - it starts pumping up to a point then goes almost silent with minimal build of pressure.

    This machine has already cost me way more than $1/cup in capital and repair costs and I'm afraid to approach the local repairer again.
    Can anyone suggest what the cause may be. It seems that something is restricting flow when pressure is a little bit high.

  2. #2
    Site Sponsor coffee_machinist's Avatar
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    That noise from a vibe pump would indicate that the pressure buildup is high enough to completely stall it.

    Do you still get a burst of water from the group exhaust when you stop the pump during backflushing/extraction?

    If the pump is delivering a normal flow rate in terms of just pouring water from the group (say 200ml in 30 seconds or so) and there is pressure exhausted from the group, it will likely be a stuck OPV and you may need to back off the grind to get a good flow rate.

  3. #3
    msp
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    Thanks for your suggestions

    It does sound like the pump is stalling when pressure builds up.

    The flow rate with no load is about 250ml over 30 seconds. If I backflush, just a very small amount of water is discharged from the group - not anywhere near what it used to be like. Can you tell me what the OPV is? Is it possible that the pump itself is unable to deliver pressure?


    Quote Originally Posted by rick_bond View Post
    That noise from a vibe pump would indicate that the pressure buildup is high enough to completely stall it.

    Do you still get a burst of water from the group exhaust when you stop the pump during backflushing/extraction?

    If the pump is delivering a normal flow rate in terms of just pouring water from the group (say 200ml in 30 seconds or so) and there is pressure exhausted from the group, it will likely be a stuck OPV and you may need to back off the grind to get a good flow rate.

  4. #4
    Site Sponsor coffee_machinist's Avatar
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    Hmm ok, so flow rate is good. That does then seem like the pump is suspect, but it's very unusual for vibe pumps to fail and normally the culprit is something else in the HX circuit.

    The OPV (overpressure valve) is designed to open and direct flow back into the tank when pressure in the heat exchanger builds up to a set point, usually between 10 and 12 bar. In some cases if the OPV is seized closed, vibe pumps will build up to their max pressure (16 bar) against a blind filter and stall, making the noise you describe.

  5. #5
    msp
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    Thanks again for helping

    I've pulled the mushroom out and it is heavily scaled. I'm now in the process of descaling. I expect this will not solve the problem but who knows. When I pull a shot, or back flush, the pump does not completely stall - there is still a trickly of flow, but virtually no creme. My next thought is to disassemble the vibe pump and see if its parts are ok but I still think something is restricting the flow under pressure. If that could be the OPV, could you tell me where to locate it.

    I have some basic schematics but can't see that component.

    I'd love to just give to a service specialist but in Brisbane the will charge about $1k again.

    If I get things working again, I want to get the water right to minimise this problem. I have tried to use RO water but the sensor cuts out because there is low conduction with no minerals. Our tap water is obviously the cause of scale and probably other issues. There must be some solution to this issue because be have plenty of good coffee shops. What is a home user to do?


    Quote Originally Posted by rick_bond View Post
    Hmm ok, so flow rate is good. That does then seem like the pump is suspect, but it's very unusual for vibe pumps to fail and normally the culprit is something else in the HX circuit.

    The OPV (overpressure valve) is designed to open and direct flow back into the tank when pressure in the heat exchanger builds up to a set point, usually between 10 and 12 bar. In some cases if the OPV is seized closed, vibe pumps will build up to their max pressure (16 bar) against a blind filter and stall, making the noise you describe.

  6. #6
    Senior Member Yelta's Avatar
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    Quote Originally Posted by msp View Post
    I've pulled the mushroom out and it is heavily scaled. I'm now in the process of descaling. I expect this will not solve the problem but who knows. When I pull a shot, or back flush, the pump does not completely stall - there is still a trickly of flow, but virtually no creme. My next thought is to disassemble the vibe pump and see if its parts are ok but I still think something is restricting the flow under pressure. If that could be the OPV, could you tell me where to locate it.

    I have some basic schematics but can't see that component.

    I'd love to just give to a service specialist but in Brisbane the will charge about $1k again.

    If I get things working again, I want to get the water right to minimise this problem. I have tried to use RO water but the sensor cuts out because there is low conduction with no minerals. Our tap water is obviously the cause of scale and probably other issues. There must be some solution to this issue because be have plenty of good coffee shops. What is a home user to do?
    Evening MSP, what are you using to descale with and how are you going about it? I find living in SA (highly mineralised water) that I need to descale approx every three months.

  7. #7
    Site Sponsor coffee_machinist's Avatar
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    hmm ok.The OPV *should* only release pressure above 10 bar. If for some reason it has failed and is releasing pressure below 9 bar, that could explain it as water will follow the path of least resistance.

    If water flows OK through the group with no pressure but as soon as you apply pressure into a restriction (coffee or blind filter) it slows or stops, it can only be not building up in the first place (pump failure) or going somewhere it shouldn't (OPV releasing before 9 bar, or some other internal leak). One question, is your steam pressure OK? By that I mean is it wetter than normal, and is the autofill working normally (ie. take a glass full of water out via the wand, a few seconds later the pump kicks in for 10 seconds or so then cuts out)?

    The OPV is listed in Giotto diagrams as expansion valve, it sits under the tank and is a brass cylinder connected to a T-piece at the front, and a white rubber elbow/silicone to the water reservoir at the back. Checking it's operation will involve pulling the top cover and side panels off, which is not something I suggest you do unless you're confident.

    The pump itself is a sealed unit, and if it's faulty will need to be replaced. There are good service agents in Brisbane, Barazi Bezzera in coopers plains may be worth contacting. If it is a straight forward pump replacement, I would estimate between $200-250 is what it should cost in parts and labour.

    Filtration for scale reduction is a complex issue and best left to the filtration pros to answer further - I'd be contacting Bombora Supplies and see what they recommend.

  8. #8
    msp
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    Hi Yelta

    I have only done one descale (unfortunately) and an no expert at all. My machine may require a strip-down with the amount of build-up which will be a job for a professional. I descaled following instructions at home-barista dot com. Search for simplified-hx-descale [this forum won't let me post the link directly]

    I just used a solution of "CleanMachine" descaler.



    Quote Originally Posted by Yelta View Post
    Evening MSP, what are you using to descale with and how are you going about it? I find living in SA (highly mineralised water) that I need to descale approx every three months.

  9. #9
    msp
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    Thanks again. The steam is fine and the auto re-fill works fine too. The boiler pressure reads a bit high though at 1.5 bar but thats probably not related.

    Quote Originally Posted by rick_bond View Post
    One question, is your steam pressure OK? By that I mean is it wetter than normal, and is the autofill working normally (ie. take a glass full of water out via the wand, a few seconds later the pump kicks in for 10 seconds or so then cuts out)?"

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    Unhappy

    Hi All,

    I have a Brasilia Club that has lost pressure when trying to pull a shot. The pump will operate when refilling the tank and when opening steam wand and letting cold water out (both by manual push of button).

    The pump starts noisy then drops to a hum. Even when no group head in it is just a dribble flowing out. Any thoughts on what I should do?

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    Hi Guys,

    Sorry to resurect an old thread, but i think i have the exact same problem as the OP, i have removed the "expansion" valve or OPV and i can't really tell if its faulty, it seems ok, and it wasn't stuck or anything, any tricks i can try to diagnose my problem?

    See attached Pic

    thanks in advance guys!

    warren
    Attached Images Attached Images

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    My machine has been doing this as well...

    To recap:
    1. When pulling espresso my pump starts normally, then goes silent/muffled.
    2. When using the blind filter, this happens as well.

    I have noticed that the pressure, when using the blind filter, shoots up to about 12psi.

    I've descaled it today, backflushed with descaler etc.... None of this has helped.

    Thoughts?
    Rob

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    I had what sounds like the same problem recently (different machine, but vibration pump) - started off at 12psi for a couple of seconds then dropped off to 8 or so and pump went quiet (still a hum but not as loud as usual). Took it to jetblack, they replaced the pump, all good now. They said vibration pumps typically need to be replaced every few years.

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    Looks to me that is the pump, if you are in Sydney we have 72 hours turn around at the moment

    Regards

    Renzo
    PS We open 7 days
    Last edited by Di_Bartoli; 19th February 2018 at 12:05 PM.

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    Quote Originally Posted by Di_Bartoli View Post
    Looks to me that is the pump, if you are in Sydney we have 72 hours turn around at the moment

    Regards

    Renzo
    PS We open 7 days
    Thanks Renzo,

    Confirmed my suspicions!

    I'm from Melbourne so it's a bit far for a Rocket service, but thanks for the info nonetheless.

    It can still pull coffee, but if i get close to choking the machine it stalls. I will just ease up on the grind for the next few days and get it to my local coffee machine guy.

    Thanks all,
    Rob



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