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Upgraditis: 2-group Grimac Commercial

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  • #31
    Re: Upgraditis: 2-group Grimac Commercial

    Im not sure Im understanding all this talk of back pressure from the HX. Unless the brew solenoid has broken nothing from the HX will flow back into the system.

    The brew solenoid is between the water supply/pump and the HX. The HX is open to the atmosphere via the grouphead and the 3-way pressure relief valve. As the water in the HX boils away it will simply vent out of one of these two openings, not back into the water pipe and into the pump.

    Such is the case on the Cimbalis anyways. Is there something different about this machines design that would allow this to happen?


    Java "Confuzzled" phile
    Toys! I must have new toys!!!

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    • #32
      Re: Upgraditis: 2-group Grimac Commercial


      There is no brew solenoid in most of the commercials Ive seen (Bezzera, Faema, La Pavoni and a few others). The water to the groups is controlled by opening the 3-way valve to allow water from the HX to flow to the group.

      The 3-way valve will usually withstand a back pressure of between 12 and 15 bar before opening, so can act as an expansion valve for the HX. This only occurs if there is a check valve in the system (or a brew solenoid in your case), otherwise the pressure will force water back through the system towards the pump.

      These check valves are very small and simple and are not easy to spot, but they usually have an arrow indicating the flow direction.

      Any flow of hot water back to the pump is best avoided as it usually causes the pump much consternation (as I have found out).

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      • #33
        Re: Upgraditis: 2-group Grimac Commercial

        All.

        The La Cimbali M20 I have also has NO brew solenoid - only the three way valve.

        Hence why the HX is pressurised (according to the diagram I have)

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        • #34
          Re: Upgraditis: 2-group Grimac Commercial

          Took your advice, JavaB and "recalibrated" the pump pressure side of the gauge by removing the pointer and resetting it at zero. Funny, I tried to do that last night but couldt budge it. Today it came out readily.

          Unfortunately, it now doesnt budge. May need more calibrating. More on the gauge further down.

          Im still familiarising myself with the myriad of plumbing. Ive worked where the two heat exchangers are. How they are fed, and how the boiler is fed. How the volumetric plumbing circuit works (cold water between pump and heat exchanger). Why am I surprised by that? Cos I always imagined it measuring what goes in the cup, not the amount of water that flowed to the exchanger to achieve that!

          I havent dismantled the groups, but each appears to have only a three-way valve. Perhaps I should investigate further.

          I cant find specs for the Grimac Eclisse, but for the TEN compact, which is similar, the specs are for 0 - 4 bar water intake, so using my 10-litre container should not be a problem.

          There also appears to be some sort of pre-infusion.

          When I press the dose button, I hear the 3-way valve kick in for a second, and then it clicks shut, pauses, then away it goes again. That would be handy.

          Had a devil of a time working out why no water was pumping today after I replaced the pressure gauge.

          Hours of checks -- it turned out to be that because Id removed the line to the pressure gauge, the pipe needed bleeding of air.

          Its handy to learn and know these things to avoid future trial and hour groping in the dark.

          --Robusto

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          • #35
            Re: Upgraditis: 2-group Grimac Commercial

            Im afraid my description may have caused some confusion with its poor wording. The brew solenoid I refer to is, on machies equipped with one, the 3-way valve/solenoid with the pressure relief valve also being incorporated into the 3-way.


            Java "Hopes he cleared it up" phile
            Toys! I must have new toys!!!

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            • #36
              Re: Upgraditis: 2-group Grimac Commercial

              That clears it up, Javaphile.

              More pix.

              The machine may be a pretty site, but the massive 20 ml  power lead (with provision for 3-phase), the water supply hose, and the drain hose, arent.  

              I hope my wife doesnt want access to the cupboard underneath.

              This pic shows the temporary installation, with water supply alongside.


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              • #37
                Re: Upgraditis: 2-group Grimac Commercial

                Robusto, pre-infusion sounds good, but youll need mains pressure to make it work well.

                I like the industrial look.

                Cheers,

                Mark.

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                • #38
                  Re: Upgraditis: 2-group Grimac Commercial

                  When you guys plumb in the machine to a mains, do you get a plumber in or just do it your self and dig a hole in your kitchen bench? haha and how would you know how much pressure is in the mains so you know if you need a restrictor?

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                  • #39
                    Re: Upgraditis: 2-group Grimac Commercial

                    A plumber? Whats that?

                    It doesnt take a tradesman with call out fees and hourly rate to use a hole saw on the bench top, and to use a spanner to install a T-junction where the cold water tap attaches to the wall.

                    Flexible hoses are soooo easy.

                    I would recommend isolating the machines intake via an inline tap or valve.

                    The pressure reducer could be but probably wont be a problem. Im sure there are ways to convert how long it takes to fill a 10 litre bucket
                    into pressure.

                    --Robusto

                    Comment


                    • #40
                      Re: Upgraditis: 2-group Grimac Commercial

                      Originally posted by robusto link=1173088713/30#38 date=1173256234

                      The pressure reducer could be but probably wont be a problem. Im sure there are ways to convert how long it takes to fill a 10 litre bucket
                      into pressure.

                      --Robusto
                      Nah....

                      If you get your brew gauge working.... connect your machine.... slowly crack open the tap and watch the gauge climb.... mine got to 5Bar.... so sweet - no pressure regulator required!

                      The plumbing in the machine can withstand 9 Bar... so no problem with a static measurement (just dont run the machine until you have checked the pressure is within the allowed range).

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                      • #41
                        Re: Upgraditis: 2-group Grimac Commercial

                        This raises an interesting question. Im reading on Alt.coffee that the pump pressure regulator has to be adjusted if there is no supplementary mains pressure -- i.e, supply is from a tank as I am using.

                        Is that so, JavaB?

                        Since my pressure gauge doesnt work, is there a way of calculating whether the brew pressure is 9 bar?
                        Some sort of water deficit measurement?

                        Im thinking something like the Ulka vibe pumps where if 250 mls bypasses the brew head and back into the tank that equates to 9 bars.

                        Also...cooling flushes. how do you tell when enough water has been drawn? And is it drawn with portafilter in place, or without?

                        --RObusto

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                        • #42
                          Re: Upgraditis: 2-group Grimac Commercial

                          robusto,

                          The delivered pressure will drop a little without mains supply - but not much - as the regulator is on the output side of the pump.

                          There is no easy way to measure the pressure as unlike the ulka where there are graphs for delivery volume Vs delivery pressure..... with a rotary pump once the regulated pressure is reached the output is shunted back to the input and the pump will maintain constant (well near constant) pressure from nil flow to about 2 liters per minute for my pump.....

                          The actual delivery volume varies from pump to pump but the pressure will remain the same until you exceed that delivery volume.

                          So you really need a gauge.

                          Re cooling flushes - Mine needs about 200 ml if rested for >5 minutes. Basically I flush until there is no more hissing steamy water coming out..... leave it for a minute (whilst dosing).... then give a quick flush of about 50 ml.... lock and extract.

                          The actual volume varies with the design of the group... but flushing until you have got rid of the steamy water is pretty universal.

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                          • #43
                            Re: Upgraditis: 2-group Grimac Commercial

                            Thanks JavaB. Hours go by before I make an espresso, so looks like Ill be going through much cooling water.

                            Ive done a quick calculation of power consumption, and on this pretty warm day, the pressurestat cycles every 2 minutes, heating for 15 seconds.

                            Were I to leave the machine around the clock, that equates to about 90 cents of electricity a day.

                            Havent noted how long it takes to reach operating pressure from cold, and whether it is best to leave it off, and power it up say, 3 times daily.

                            The element is 3300 watts.

                            -Robusto

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                            • #44
                              Re: Upgraditis: 2-group Grimac Commercial

                              Robusto,

                              Well my element is 4000W and it is on for about 10% of the time.

                              It takes about 20 minutes to get a full head of steam from cold..... but about an hour for the temperatures to really stabilize.. (which is how long they turn them on before opening in a cafe).

                              So for the first 20 minutes its flat out heating - which equates to over 3 hours of 10% use - times 3 times a day = 9 hours plus the extra half an hour each time at 10%..... 10.5 hours all up.

                              Mine is on 24/7.... yeah it costs a bit more.... but I can walk up whenever I want and have a coffee.. (within about 1 minute from arriving on scene).... and my wife works shift..... and wants a coffee at weird hours.....

                              and its just so convenient that way!

                              EDIT: and I forgot... there is always hot water on tap... so the tea drinkers can have a cuppa when ever they want.... my son makes himself instant noodles etc.... it is even used to fill small saucepans.. all of which is a good idea- if you only use the boiler for steam- the only thing which leaves is pure water (the salts are left behind) .... by using the hot water tap you flush the boiler each time

                              Comment


                              • #45
                                Re: Upgraditis: 2-group Grimac Commercial

                                Yep, 10 per cent is what my calculation runs out to: 2.5 hours over a 24-hour period. The convenience factor is quite an important one.

                                I would imagine there would be less stresses on the machine is it keeps a constant temperature and pressure, rather than go from stone cold to hot and back again.

                                --Robusto

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