axboe Senior Member Joined: 8 Jan 2013 Posts: 8 Location: Denmark Expertise: I live coffee
Posted Tue Jan 8, 2013, 5:27am Subject: Problem with continuous shots on Simonelli Musica
About three months ago, I decided it was time for my 6 year old Rancilio machine to be retired. So I bought a Simonelli Musica, and a new grinder as well. Honestly it took a bit longer to dial in a good setup than I had thought, but now I pull consistent good shots. So good in fact, that my wife stopped using sugar in her latte completely.
But I seem to have an issue with making repeated shots. Lets say the machine has been sitting idle for a few hours. The first shot pulled comes out nice and creamy, and extraction time (and volume) is as I expect. Taste great too. But if I do one more shot right after that, it's like it's running at a lower pressure. The pressure gauge reads the same, but for an identically stamped pod, extraction is much slower. If the machine is allowed to sit again for a while, then extraction speed goes back to what I expect.
Is this normal? Is there something wrong with the machine? Am I doing something wrong? I've tried tamping it a bit more lightly, but it doesn't seem to make a difference. It's as if it's just a lot weaker. I don't tamp super hard, btw. I grind the beans into the pod, flatten with my finger, than tamp lightly, then tap the sides a bit, and tamp it again a bit harder. But still within `~10 pounds of pressure or so.
I hope you guys have some clues for me, I'm getting a bit desperate here!
Markarian Senior Member Joined: 27 Jun 2012 Posts: 474 Location: Seattle Area Expertise: I love coffee
Espresso: Modded Nuova Simonelli Oscar Grinder: Vario-W, Mazzer Super Jolly Drip: Moka, Aeropress, Melitta 102 Roaster: Wear-Ever Popcorn Pumper
Posted Tue Jan 8, 2013, 12:08pm Subject: Re: Problem with continuous shots on Simonelli Musica
At least on my Oscar, controlling the brew temperature is often a crapshoot (gamble). For instance, I've been recently getting a lot of blond shots and I think I've been overflushing. I don't know how temperature control works on the Musica, but I think you still need to flush and water dance. I seem to recall the Musica is an Oscar with pretty lights, volumetric dosing, and a vacuum breaker. Crack the steam knob/lever just a bit to cause the boiler to kick in before your next shot and see if that improves things.
So here's a link to a (longish, 4 min) video I just made. Of course the problem doesn't REALLY manifest itself this morning, but you can still see the reduced power on the 2nd and 3rd shot. I rinse the pod in water in-between the shots, typically longer than I do in this video. Maybe that cooling down is enough to make it worse?
calblacksmith Moderator Joined: 25 Nov 2007 Posts: 5,684 Location: Riverside, Ca, U.S.A. Expertise: I live coffee
Espresso: ECM Veneziano A1 Grinder: Many different commercial Vac Pot: 40s era Silex Drip: Milita, Bunn&Curtis... Roaster: Cast iron pan, gas burner
Posted Wed Jan 9, 2013, 4:58am Subject: Re: Problem with continuous shots on Simonelli Musica
The pressure gauge you are watching is a temperature gauge not a pressure of the brew. Another thing you can do to help make your shots better is to stop tapping portafilter with your tamper all you are doing is risking cracking the puck and making channeling in your shot. I can see in last shot your temperature has dropped so perhaps there's something going on with your temperature system but there is no gauge that I saw that says anything to do with your brew pressure.
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
That's certainly doable, but I've had good luck with it so far, since otherwise I end up with a slight rising edge where the tamper doesn't touch the wall of the portafilter.
I can see in last shot your temperature has dropped so perhaps there's something going on with your temperature system but there is no gauge that I saw that says anything to do with your brew pressure.
Also, there are some other things here that threw the discussion a little off, namely you are using the wrong terms for what you are talking about. Some of this is the confusion that I tried to help with above with pressure but you also are talking about pods, pods are a pre ground dose of coffee, in paper wrapping. You place the entire pod, paper and all into a special porta filter basket that is designed for pods, no tamping, just load the PF and pull your shot.
Your machine is a Heat Exchanger based unit. The temp is adjusted and maintained by a device called a Pressure Stat. It measures the pressure inside the boiler and cycles the heater on and off to keep the same pressure in the boiler. With a closed boiler, the hotter it is the more pressure there will be in the boiler.
You say that after it has been on for a while, the shot is good but the next is not. In your video, you did not do a cooling flush which tells me that your boiler is too cool, regardless of what the gauge says. The water from the brew group when first activated when the machine has sat idle for a while, should be too hot, it should flash to steam until the over heated water in the brew system is purged, this is only 2 to 4 oz or so and is not a big deal. For an idea about how your system works, I am cut and pasting from another post I made which explains how it works.
There are several great articles about how HX machines work etc. I will try to just make it pretty simple here.
HX machines are the back bone of industry. They are dependable, work well and abundant.
They work by thermal mass, they have a lot of metal and large boilers. The Pstat (pressure stat) keeps the temp in the boiler to within 2 to 5 deg F, on the low side for a new machine and on the higher side for a well used machine due to mechanical wear but at any rate well within easy operating range.
The HX (Heat eXchange) system works by keeping the boiler at steam temp of about 235 to 240F or even higher depending on how you want your machine to work. The temp is indicated in Bar thus you have a gauge that reads from about .8 bar to about 2.5 bar or so, with an operating range from 1.1 bar to about 1.4 bar. This is nothing more than just a thermometer with a scale that reads in bar, you can look up the temps if you like they are widely available online.
The temp of the boiler stays constant by the use of a Pstat. This device is sensitive to pressure (bar is a measure of pressure) and the Pstat keeps the boiler at the set temp within it's range of operation accuracy or the 2 to 5 deg f. (if set for 240 f this would give you a range of say 237.5 to 242.5 or Plus or minus 2.5 deg f for a pstat that swings 5 deg.
When someone uses a PID on a HX machine, it replaces the Pstat which is operating well within need accuracy so a PID really does not add anything to the system but if you like digital readout of numbers, it does not hurt either but it does NOTHING to improve the machine.
The HX system, think of it as simply a tube that passes through the boiler but does NOT connect to the water in the boiler. As water passes through the HX tube, it is heated by the water in the boiler. The tube is designed to a size and distance so that in constant operation, say pulling a shot every minute or minute and a half, the water will be heated to the proper brew temp of 195 to 205. If you continue to work at the same speed, the water temp will be the same shot to shot and all is well with the world.
The problem comes when you stop pulling shots. Now the water in the HX system is sitting inside the boiler longer than it was intended to and it becomes the same temp as the water in the boiler. This is not a big deal as you simply FLUSH this over heated water out of the system and return the system to normal brew temp. If you do not flush a lot of water, you can make the shot temp rise a little or if you pull a couple shots quicker than the system is designed for, you can get a cooler shot, but unless you are all thumbs, you will be in the proper brew zone of 195 to 205 and this is the way a HX machine will allow you to make one shot warmer or a little cooler, depending on what you want for the shot. If you work at the machines design rate, the temp will be the same within a deg or so time after time.
Now, adding to the way the system works, you will have a lot (LOT) of metal in the brew group, in the case of the E61, this is 8 pounds of brass that is also being temp regulated through a balance of exposure to air and active heating of water from the boiler flowing through water passages in the brew group. This is eight POUNDS of mass that is at temp. Your shot of water is (for a double shot) two OUNCES of weight or mass, the affect of the heat stored in the group head acts on the temp of the water that is flowing through it, either warming or cooling the water passing through it, depending on if the water is hotter or colder than the brew group temp.
You can see that there are a lot of design factors taken into account in a HX machine to regulate the temp of your brew water. Yes, you can affect the temp of the water you brew with but it will not be wild swings of temp, just a little warmer or cooler depending on your actions. As long as you flush long enough for the water to stop flashing to steam (an easy thing to tell when you listen to the flow of the water and watch the flow of the water) you will be darn close to brew temp. If you flush just a couple of oz past this point, you will be in the zone, if you flush a little more, you will be on the cool side, a little less and you are on the warm side. It really is as simple as that. No drastic failure of the brew either way, just the ability, through your actions, to alter the temp of the shot a little warmer or cooler.
DB machines also have a great deal of thermal mass in the brew system. The do not have a single boiler (hence the name Double boiler) They use a PID to (the new ones anyway) maintain the temp of the brew water to a set temp. This water then flows through the group head where it's temp has an affect on the brew water. In MOST instances, the brew group will be COLDER than it should be due to sitting, exposed to the air, bleeding heat to the air. The first shot through the group will then WARM the brew group to it's operating temp but the result is that the first shot or so of water through the system will be too cool to properly brew your espresso, thus you need to flush the system to WARM the brew group so the machine pulls shots at the desired temp. Either way, you are flushing the system.
There are double boiler machines with actively heated and thermostat regulated temp (brew group) but they are not part of this discussion nor are they in the price range of what we are discussing. So for this discussion, they are a moot point.
One is not "better" than the other, it really comes down to how your brain works, what floats your boat and how you like to work. While it is true, you can just change the temp of a shot on a PID controlled DB (or sbdu for that matter) machine with a touch of a button as some are fond of saying, you need to wait for the whole machine to change it's operating temp and normalize at the NEW operating temp. This can take about 15 minutes or so. Not a big deal but not as rapid as watching the number change on the digital readout either.
I hope this helps to clear things up a bit.
In real life, my name is Wayne P.
Feed the newbs, starve the trolls and above all enjoy what you drink!
Coffeenoobie Senior Member Joined: 11 Dec 2011 Posts: 2,320 Location: PNW Expertise: I like coffee
Espresso: N S Oscar Grinder: Vario W
Posted Wed Jan 9, 2013, 10:50am Subject: Re: Problem with continuous shots on Simonelli Musica
I also notice a lot of movement in your streams, I believe you are getting heavy channeling. The first pull the right side sputters a lot. That is probably cutting down on your taste and crema. I am used to a lot of crema using a bottomless portafilter so your shots look very thin to me but that might be my fresh beans as well.
I also wondered how the first shot was good on an HX the others not. That also makes me question your temps and is part of what I wanted to see. Your 2nd shot crema looks very gold in the video, that also points to under extraction.
I believe you might have a 2 fold problem. Temp and channeling. You are drying the portafilter between pulls right?
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