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Permalink Reply by Mike McGinness on August 17, 2011 at 6:22pm

GB5 has ONE pump regardless the number of groups. This means if you are pulling a shot and start another while first shot still pulling the pressure will ALWAYS initially drop when the additional shot is started then stabilize. Doesn't matter what your line pressure is, the pump is (or should) be calibrated to provide your desired shot pressure, set while actually pulling a shot for proper resistance. (versus with a blank) Now when you start a shot while another shot pulling it takes a moment for the new shot to saturate and then provide resistance, hence the initial drop in pressure. Absolutely no way around it with one pump, period.

 

You should never start a shot (or flush a group etc) while a shot pulling because of this. (have one 3 and two 4 groups LMs so very familiar with the phenom, but true for any multi-group machine with single pump, which is the vast majority) You can start two shots simultaneously, ie start them at the exact same time, to overcome the pressure drop issue pulling multiple simultaneous shots.

 

Or "upgrade" to a machine with a pump for each group.....

 

If you've had an espresso machine tech work on the "issue" and they didn't tell you the above, look for a different espresso machine tech that knows what they're doing, seriously.

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Permalink Reply by Daniel Isaiah Mckendrick on August 18, 2011 at 12:17am

Never purge, or pull shots while one of the groups is running. It's the same with many machines, including the synesso which is what i work on. If you are going to run three shots, it has to be at the same time. So do you experience this problem when you run all of the groups at the same time? or when you turn one on and then another?

 

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Permalink Reply by Brady on August 18, 2011 at 4:41am

+1 to everything Mike said.

 

Note that you to execute 2 shots simultaneously, it is better to park one on the counter and load them at the same time. This way, the first doesn't sit there cooking in the group while you prep the 2nd.

 

Oh, and you may or may not be able to get the full 9 bars of pressure when pulling 3 shots simultaneously, no matter what your start sequence is. If done as Mike suggests, 2 shouldn't be an issue.

Mike McGinness said:

GB5 has ONE pump regardless the number of groups. This means if you are pulling a shot and start another while first shot still pulling the pressure will ALWAYS initially drop when the additional shot is started then stabilize. Doesn't matter what your line pressure is, the pump is (or should) be calibrated to provide your desired shot pressure, set while actually pulling a shot for proper resistance. (versus with a blank) Now when you start a shot while another shot pulling it takes a moment for the new shot to saturate and then provide resistance, hence the initial drop in pressure. Absolutely no way around it with one pump, period.

 

You should never start a shot (or flush a group etc) while a shot pulling because of this. (have one 3 and two 4 groups LMs so very familiar with the phenom, but true for any multi-group machine with single pump, which is the vast majority) You can start two shots simultaneously, ie start them at the exact same time, to overcome the pressure drop issue pulling multiple simultaneous shots.

 

Or "upgrade" to a machine with a pump for each group.....

 

If you've had an espresso machine tech work on the "issue" and they didn't tell you the above, look for a different espresso machine tech that knows what they're doing, seriously.

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Permalink Reply by Patrick Burns on August 18, 2011 at 6:50am

thanks for the two shot simultaneous tip. did that this morning and they pulled perfectly. i haven't tried all three group heads at the same time but we will as we get busier.

 

appreciate the community and the great quality folks on here.

 

cheers

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Permalink Reply by Bryan Wray on August 18, 2011 at 7:06am

3 simultaneous shots on a Linea is no problem on the 3 group. (and trust me, I know that we set up our machines as Mike explained, as Mike set up our machines, lol)  Haven't tried it on the 4 to know, but my guess is just that the pressure would take longer to level out as there is more dead space to fill.

 

-bry

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Permalink Reply by Mathew on August 22, 2011 at 6:44am

Your Problem isn't water supply, the 1/3 hp motor should create plenty of water pressure and if your RO was running out of water it would be very clear by the sound of the pump getting louder as it runs dry. 

 

For a true pressure reading I would try to get a reading at the group head, the line pressure can be a little miss-leading sometimes.  There are modified portafilters you can get that have built-in pressure guages.  you may find that you have 9 bars at the group heads and only 8 in the line. 

That being said how old is your GB5? While I love La Marzocco they do have a few issues but many improvements have been made in recent years. With the dual boiler and saturated group heads it is easy for little leaks to show up internally that you would never know were there except by the performance of the machine.  I would start with inspecting the machine for any external leaks making sure the groups are properly bled of air (an air pocket in the boiler can rob you of pressure, from there I would inspect the expansion valve in the drain cup, then the brew valves to make sure they are sealing up.  If your machine is older there is the possibility of the banjo tube in the group head leaking. 

 

However before you do any repairs yourself I would strongly consider a trained technician, La Marzoccos are some of the more complicated machines out there and if you don't have the right seals taking the wrong thing apart may mean you are S.O.L. until you can get some more seals, such as the group head cap.

 

Hope that helps, It's kinda hard to guess with such limited info, but I can assure you the issue is not with your RO. although if you are in doubt bypass the RO and see if that makes a difference, a few shots on city water won't hurt your machine.

 

 

 

 

 

 

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Permalink Reply by olivier dutil on August 22, 2011 at 9:28am

Well i own and work on a GB5 for over a years with only one pump and pull shot and purge and pull a shot and purge and all that in the same time and never ever add a pressur problem so every that say that is normal well mayby for other machine but not for the gbe

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Permalink Reply by Mike McGinness on August 22, 2011 at 9:40am

No offense, but maybe you pay as much attention to the shot pressure gauge as spelling...

olivier dutil said:

Well i own and work on a GB5 for over a years with only one pump and pull shot and purge and pull a shot and purge and all that in the same time and never ever add a pressur problem so every that say that is normal well mayby for other machine but not for the gbe

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Permalink Reply by Patrick Burns on August 22, 2011 at 10:14am

Thanks for the all of the thoughts. I have started pulling simultaneous shots and thats been a great suggestion.

 

I am noticing a slight leak under the machine behind the drain pan. I thought that it was a loose connection from the drain pan but it's not. It's somewhere in the machine around the far left group head. I've looked for a diagram of the underneath view of the machine but I haven't come across one.

 

As for the age of the machine. I bought the GB5 off of a great guy who had a shop in Salt Lake City for a little while. He only had one year on the machine. Before that the machine was a regional competition machine for the USBC.

 

 

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Permalink Reply by olivier dutil on August 22, 2011 at 11:16am

Well no offense Mike but i am sure if you ware trying to comunicate on a french forum you would make as much or more mistake than i do. and for the pressure think well juste look at it and every time a  start a should it drop to 8.25 bar than in less then 1 sec it go back to 9 bar.
Mike McGinness said:

No offense, but maybe you pay as much attention to the shot pressure gauge as spelling...

olivier dutil said:

Well i own and work on a GB5 for over a years with only one pump and pull shot and purge and pull a shot and purge and all that in the same time and never ever add a pressur problem so every that say that is normal well mayby for other machine but not for the gbe

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Permalink Reply by Mike McGinness on August 22, 2011 at 11:47am

And the whole point of the OPs post was that while a shot pulling if starting another shot the pressure initally drops, which it does. Which means the first shot will have a pressure drop mid shot when the 2nd shot started. Yes, on a GB5. Which doesn't mean it will be a terrible shot, it WILL mean it's a different shot than usually pulled.

olivier dutil said:

Well no offense Mike but i am sure if you ware trying to comunicate on a french forum you would make as much or more mistake than i do. and for the pressure think well juste look at it and every time a  start a should it drop to 8.25 bar than in less then 1 sec it go back to 9 bar.
Mike McGinness said:

No offense, but maybe you pay as much attention to the shot pressure gauge as spelling...

olivier dutil said:

Well i own and work on a GB5 for over a years with only one pump and pull shot and purge and pull a shot and purge and all that in the same time and never ever add a pressur problem so every that say that is normal well mayby for other machine but not for the gbe

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