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Thread: Giotto Pressure cycle for steam

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    Giotto Pressure cycle for steam

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi all,

    As ACT temperatures have dropped latey, the Minister for Finance has been requesting hot chocolates to ward off the chills, with a shot of Baileys too! I digress...

    Anywho, I have noticed that while texturing milk, with the pressure guage at 1.2 bar, the guage will drop to lower than 0.7 bar before the pump kicks in, about 40 seconds. Im trying to texture a 2/3 filled 600ml jug and about the same time the temperature gets to 60 degrees, there is a hint of a screech beginning and the swirl slows down. I get the impression its about to run out of oomph.

    Without a jug, from 1.2 bar, tap open full, 40 seconds to drop to 0.7 bar, a pump cycle, mabye 3 seconds worth, impressive twin streams of dry steam clearly visible. Another 40 seconds, about 0.4 bar, another quick pump cycle, steam is no longer visible, wouldnt move coffee grinds off a tea spoon.

    My question for experienced Giotto owners is, does yours behave the same, machine that is? ;) What is the "normal" pressure drop before the pump kicks in? Is there a minimum? Im not really concerned about the pressure guage, its only an indication. My concern is that the Silvia can beat the pants off it. :o

    Boris

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    Senior Member Dennis's Avatar
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    Re: Giotto Pressure cycle for steam

    Quote Originally Posted by Boris link=1175907475/0#0 date=1175907475
    Without a jug, from 1.2 bar, tap open full, 40 seconds to drop to 0.7 bar, a pump cycle, mabye 3 seconds worth, impressive twin streams of dry steam clearly visible. Another 40 seconds, about 0.4 bar, another quick pump cycle, steam is no longer visible, wouldnt move coffee grinds off a tea spoon.
    Thats an interesting observation Boris that prompted me to check mine...
    No jug starting from 1.1bar, tap fully open drops to .9 immediately, then at 60 sec a 2-3 sec pump cycle and still heaps of steam until we get to about 90 sec, then like yours drops down progressively and quickly to .4bar and stays there

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    Re: Giotto Pressure cycle for steam

    The pump cant be looking at pressure for when to run , this would lead to the possability of no water but full pressure, not good on any pressurised steam system, BANG.

    The pump has to be level controlled, anything else would be dangerous.

    The pump is putting relatively cool water into the boiler, so cooling the remaining water, reducing steam production by the amount of heat required to raise the "new" water to the boiling point for the pressure.
    As the element is putting a finite amount of heat energy into the system, this produces a finite amount of steam, this amount of energy is set by the amount of "stored" energy in the system and the ability of the power source to supply energy to the element without overload, 240 volt/10 amp, 110 volt/ 15 amp.
    This is expressed as the wattage of the element, 2400 watts from 240 volts at 10 amps, but only 1650 watts from 110 volts at 15 amps
    This is why the euopean machines dont work well in the US, not enough energy comeing in. :-[

    Any addition of cool water reduces the steam produced by the amount of sensible heat energy required to raise this water to boiling, reducing the heat energy availble to be consumed as latent heat to fuel the phase change of water to steam, this equates to reduced steam production.
    The only work around that I can think of is to only allow the pump to top up the steam boiler when it is at full pressure, so there is no influx of cool water when steam is required, and so no reduction of the amount of steam being produced.

    This could be potentually dangerous, like in the situation of the steam wand being left open, lowering the pressure and so not allowing the pump to top up but at the same time using boiler water.
    This would lead to the water level dropping enough to allow the element to be exposed allowing it to over heat. :o
    The system as it stands will run the pump, topping up the boiler, until the water runs out, then the low water cut out will shut the system down, much safer.

    A larger wattage element would require a 15 amp power point, so while we are better off than the yanks, it is fixed when it comes to energy out of the system.

    You only get out what has been put in. :(

    I just had a thought, is your Giotto an old one?
    If it is then it has a smaller boiler, and so less stored energy in the form of heat in the water, the new Giotto premium has now got a larger boiler, and so can produce more steam from the "Stored" energy in the increased volume of water in the boiler.

    Sounds like a good excuse to upgrade to me ::)

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    Re: Giotto Pressure cycle for steam

    Just to compare I tried similar onmy Expobar.

    No jug starting from 1.2bar, tap fully open drops to .9 immediately, then at 25 sec a 1 sec pump cycle and still heaps of steam but pressure dropping to .8, at 50 seconds a 1/2 second pump.
    Stopped at 60 sec, pressure about .7

    - 1.8L boiler
    - 1300W heating element

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    Senior Member Dennis's Avatar
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    Re: Giotto Pressure cycle for steam

    Hi Andy G - some interesting comments. Bottom line is I have never run out of steam, so no problemo, and I do have a giotto premium which is only a couple of months old.

    TG - Im not sure if Expobar owners are allowed to post here ;D Jokes aside, why did you stop at 60sec? Your machine seems comparable at that point. Take her to the limit TG!

    I feel like Scotty from the starship enterprise ;D

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    Re: Giotto Pressure cycle for steam

    You answered the question Dennis.
    Seemed so close that I couldnt be bothered going any longer.


    P.S. My Expobar sits nicely in this category thank you very much. (Bloody ECM Snobs)


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    Senior Member Dennis's Avatar
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    Re: Giotto Pressure cycle for steam

    Quote Originally Posted by Thundergod link=1175907475/0#5 date=1175942602
    You answered the question Dennis.
    Seemed so close that I couldnt be bothered going any longer.

    P.S. My Expobar sits nicely in this category thank you very much. (Bloody ECM Snobs)
    Thank goodness my new glasses arrived this week - what a great idea for a t-shirt..."Im an ECM Snob"

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    Re: Giotto Pressure cycle for steam

    Bling on its own does not a great coffee make...... Lets leave the machine snobbery for another forum shall we,

    Mal.

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    Re: Giotto Pressure cycle for steam

    Well so far the concensus is that my Giotto (yes its a new type) is performing the same as others. :-?

    Id be interested to hear from anyone with a Expobar Minore II. Ill assume that as they have a seperate boiler, there is no preformance loss. ;)

    Any chance we can have a comment from the guru of ECM? Id love to see the design intent / quoted capability. Ill be in Italy later in the year, might swing by if were close enough. ;D

    Boris

    P.S. Thundergod, I would like to order a XL T shirt please!! "Im an ECM Snob" Love it. ;D

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    Re: Giotto Pressure cycle for steam

    Quote Originally Posted by Boris link=1175907475/0#8 date=1175988697
    Well so far the concensus is that my Giotto (yes its a new type) is performing the same as others. *:-?

    Id be interested to hear from anyone with a Expobar Minore II. Ill assume that as they have a seperate boiler, there is no preformance loss. ;)

    Any chance we can have a comment from the guru of ECM? Id love to see the design intent / quoted capability. Ill be in Italy later in the year, might swing by if were close enough. ;D

    Boris

    P.S. Thundergod, I would like to order a XL T shirt please!! "Im an ECM Snob" Love it. ;D
    Seems to me, that each machine is capable of turning out two milky drinks and doing that pretty consistently. The bottom line is not really how much steam, more can it keep up with you- i.e recovery time. Try making 10 and see what happens...Ultimately, steam comes out of a 1.8L boiler which contains a HX- in both machines. Performance would be similar when the pressurestat is set identically- BUT I suspect the Giotto would have a slight edge as it has a larger element (1300W) than the Minore which has 2 x 1200W. Neither is a commercial machine and neither can be expected to keep up with one....

    2mcm

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    Re: Giotto Pressure cycle for steam

    Im pretty sure recovery time is more than adequate.
    It would just be a matter of how you made the drinks.
    Shot, steam, shot steam or whatever.

    I havent tried it but with two PFs with double baskets I reckon I could make four coffees in a minute and texture enough milk in a large jug for those and by the time Id cleaned, refilled and tamped the PFs it would be ready for another go.

    As it is though the machine more than adequately keeps up with me.

    The only thing Ive noticed recently that would slow it down is drawing 400 mls from the tap for two mugs of tea.
    In which case they would be done last if required.

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    Re: Giotto Pressure cycle for steam

    Yep,

    Prosumer machines dont have the boiler volume or heater power to steam forever....

    There is a HUGE thermal capacity difference between a 17 L boiler of water at 125C and a couple of litres at the same temp..... Add enough water to replace that given off as steam.... and the temp of the 17L barely drops..... but for the 2 L you have just added a significant percentage of cold water- which reduces the temperature very significantly.....

    Then you have a 4Kw heater restoring the temp (the couple of degrees needed) in the commercial compared to 1.3Kw to make a much larger increase in temperature with the prosumer.....

    A prosumer, (as Thundergod said above) is really designed for shot / steam...... allow recovery whilst grinding then shot / steam again...... and that will work really well....

    If you want to texture half the milk in the dairy in one sitting - then you need a full commercial (and allocate the space and be prepared to pay the power bill to use it)

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    Re: Giotto Pressure cycle for steam

    Had people over tonight and made 8 milk coffees, a hot chocolate and two teas.

    I couldnt be bothered setting up my 2nd PF with another double basket to push (test) the machine so just split the shots for two coffees at once and steamed milk then did two more until I was done followed by the hot chocolate.
    Then poured the water for the teas and as expected the boiler refill dropped the pressure to billy-o.

    By then I was sweating but the machine didnt bat an eyelid.

    While everyone enjoyed their drinks I backflushed, refilled the reservoir and cleaned the bench - all done.

    As JavaB said, shot / steam works really well.
    It doesnt actually need grinding time to recover.
    Empty / clean PF + dose tamp time is more than enough if it hasnt already recovered by the time Ive poured the milk.
    Ive never actually noticed any need to recover whilst making multiple coffees.

  14. #14
    Senior Member Dennis's Avatar
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    Re: Giotto Pressure cycle for steam

    Quote Originally Posted by Thundergod link=1175907475/0#10 date=1176003781

    As it is though the machine more than adequately keeps up with me.
    In my case its more a matter of me keeping up with the machine than the other way round :D

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    Re: Giotto Pressure cycle for steam

    My machine had its first test yesterday - knocked out 10 milk coffees without any fuss at all. Like TG, it was me working up the sweat.

    Very happy with the end result.

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    Re: Giotto Pressure cycle for steam

    ecm website states not to froth milk under .5bar as milk can be sucked up into your boiler..

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    Re: Giotto Pressure cycle for steam

    Interesting statement.

    At .5 bar the steam is still coming out of the wand.
    Thats positive pressure, definitely not sucking.

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    Re: Giotto Pressure cycle for steam

    Yeah- You read some really interesting things in user manuals ;)

    Theyre being way overcautious IMHO....All Giotti ship with an anti-vac valve on the boiler. Unless this failed andthe boiler was allowed to cool with a wand immersed in milk or other fluids, I cant see how youd suck nasties into the boiler. At any rate, as TG correctly states, we all know that 0.5 bar is positive pressure ...

    2mcm

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    Re: Giotto Pressure cycle for steam

    Either they were being overly cautious or amusing themselves.

    I was reading a testing document, for the Y2K program, that ran to hundreds of pages, when about 2/3rds of the way through I ran across a line that said something like "if you have read this far you owe me a case of beer".

    Well, not only did I point out to the writer that it was very unprofessional and that he should immediately revise the document and resubmit it, but I pointed out that if we operated that way it would be he that owed me the beer.

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    Re: Giotto Pressure cycle for steam

    ahh that ecm website....no beer ;)

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    Re: Giotto Pressure cycle for steam

    Cant see why the pump would kick in at all.

    Steaming milk causes a pressure drop not a water level drop that would be so large as to result in the auto fill kicking in, except if the water level was already low......& you cant pick where that might be at any particular time.

    All you can say as far as "normality" is concerned, is that as soon as you crack the steam tap open hard the pressure drop in the boiler should result in the element switching on immediately. *Anything else happening around the same time is pure coincidence.

    If you instead fill your 600 ml jug to 1/2 instead of 2/3, the situation will change especially as you wont pull as much capacity out of the boiler at once. Somewhere between 1/3 and 1/2 a 600ml jug worth of milk is just the right volume for 2 standard size capps......it can be said that to ask a machine that size to froth any more in one lot, is to venture outside what might be called "reasonable" for such a machine and what it was designed to do by its ristretto drinking Italian designers. * The other side of the coin is because of their small size, they recover extremely quickly so there is no need to overdo the steaming.

    The other positive is if you steam less milk, you also get a better (more well textured) result.

    If worried about the pump kicking in while steaming, first pull hot water out of the tap to cause an auto fill to occur, wait for that to stop and then for the pressure to build back up and the elemt to cut out, then steam your milk. At that stage there will be far less likelyhood of the pump kicking in while your steaming.

    So I think the answer to the question is...its all a matter of management.

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    Re: Giotto Pressure cycle for steam

    Quote Originally Posted by Curmudgeon link=1175907475/15#20 date=1176292901
    Cant see why the pump would kick in at all.

    Steaming milk causes a pressure drop not a water level drop that would be so large as to result in the auto fill kicking in, except if the water level was already low......& you cant pick where that might be at any particular time.

    All you can say as far as "normality" is concerned, is that as soon as you crack the steam tap open hard the pressure drop in the boiler should result in the element switching on immediately. *Anything else happening around the same time is pure coincidence.

    If you instead fill your 600 ml jug to 1/2 instead of 2/3, the situation will change especially as you wont pull as much capacity out of the boiler at once. Somewhere between 1/3 and 1/2 a 600ml jug worth of milk is just the right volume for 2 standard size capps......it can be said that to ask a machine that size to froth any more in one lot, is to venture outside what might be called "reasonable" for such a machine and what it was designed to do by its ristretto drinking Italian designers. * The other side of the coin is because of their small size, they recover extremely quickly so there is no need to overdo the steaming.

    The other positive is if you steam less milk, you also get a better (more well textured) result.

    If worried about the pump kicking in while steaming, first pull hot water out of the tap to cause an auto fill to occur, wait for that to stop and then for the pressure to build back up and the elemt to cut out, then steam your milk. At that stage there will be far less likelyhood of the pump kicking in while your steaming.

    So I think the answer to the question *is...its all a matter of management.
    It may if you are in the process of pulling a shot whilst texturing...which is why we buy HX and dual boiler machines ;)

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    Re: Giotto Pressure cycle for steam

    Not sure on that. If you pull a shot at the same time as pulling steam, you are still not lowering the boiler water level...simply lowering the boiler pressure much more quickly due to the heat exchange going to the brew water.

    Yes this will kill the boiler pressure much more quickly, but it wont necessarily result in an auto fill.

    I assumed the question concerned pulling steam while not running the group. Could be my mistake.

    Does any one really try and pull coffee and steam at the same time with these little babies????????? I know its a selling point but............


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    Re: Giotto Pressure cycle for steam

    I do with my Expobar.
    Arent they similar?
    Their steaming ability seems to be.

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    Re: Giotto Pressure cycle for steam

    Quote Originally Posted by Curmudgeon link=1175907475/15#22 date=1176295079
    Not sure on that. If you pull a shot at the same time as pulling steam, you are still not lowering the boiler water level...simply lowering the boiler pressure much more quickly due to the heat exchange going to the brew water.

    Yes this will kill the boiler pressure much more quickly, but it wont necessarily result in an auto fill.

    I assumed the question concerned pulling steam while not running the group. Could be my mistake.

    Does any one really try and pull coffee and steam at the same time with these little babies????????? I know its a selling point but............
    Yeppers- all the time.....Theyre designed to do it....

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    Re: Giotto Pressure cycle for steam

    To return to the "dont steam at under 0.5 bar boiler pressure" thread, On reflection I thing this is a worst case situation, and is realy driven by the temperature of the milk.

    Consider this, If you start texturing COLD milk with the boiler at less than 0.5 bar, then the cold milk will be condensing the steam very well. with a restriction (the valve) in the steam line, then it is very possable to pull the milk up the wand.

    The original Newcomen steam engine was realy a vacuum engine, and the vacuum was created by condensing the steam, see http://en.wikipedia.org/wiki/Steam_engine

    All it would take to pull milk back into the boiler from this is for the "auto fill" to start, dropping the boier pressure even further and so milk in the boiler.

    This would probably happen at a pressure a lot less than 0.5 bar, but ECM have applied a "Bugger factor", also known as a "factor of ignorance" to this, and decided that 0.5 bar is safe.

    On a tangent, the water level in the boiler acts in the reverse of the steam demand, that is, when steam is drawn off the boiler, the pressure drops, the water level in the boiler actually goes up, this is know as "Swell", and when the steam demand is reduced, the pressure increases and the level drops, this is known as "Shrink".
    What is driving this is the volume of water displaced by the steam forming around the element, at lower pressure the bubbles are bigger and so displace more water, raising the level.

    The boilers I am working on now produce 80 tonnes of steam an hour at 6 Mpa (900 psi), but only contain about 14 tonnes of water in the whole system, so boiler level control is both complex and essentual, and is probably the most complex system on the ship.
    Boilers look simple, until you start to to look closely at them, then they are very complex indeed.

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    Re: Giotto Pressure cycle for steam

    Another good reason to have a working anti vac valve in my opinion....

    2mcm

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    Re: Giotto Pressure cycle for steam

    someone asked about the steaming and minoreII.... well, this morning i thought i would test it a little with my minore I.... my understanding is that both the machines are pretty much the same in this area...

    well, it sits at about 1.1, and dropped to about 0.9 when i started steaming..
    after 40 secs or so, the boiler light came on, and the needle wavered a little, but was pretty much at 0.9... another 40 secs and i was getting a bit wet from the condensation so i stopped.... but the preassure didnt seem to move from 0.9.






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