How can I adjust the brew pressure of a vibe pump espresso machine?

[yapit]

Hi everybody,

after suspecting it and wondering for a long time, I got a pressure gauge to test the brew pressure of my machine (Rancilio Epoca) and found out that it is indeed way too high at 12.5 bar. So the logical next step is to bring it down to between 8.2 - 9 bar....

That being said it seems easier than to do. After looking over the machine for many weeks, I still haven't got a clue what an OPV or some device to change the brew pressure should look like in general, or on the Epoca in particular. And besides the screw for adjusting the boiler temperature, I cannot make out any other obvious screw either.

Can anybody help me or provide a picture of the piece of evidence in question? Or would it help if post some pics from the inside, so someone could comment on that?

Thank you very much !!

[HB]

Sometimes knowing where is should be located is more important that knowing what it looks like. Assuming your machine has a vibration pump, Jim Schulman's Adjusting vibe pump pressure on HX machines explains the mechanics, including the diagram below:


(reproduced with permission)

Tracing backwards from the overflow into the tank, you should find the over-pressure valve. However, if your Epoca has a rotary pump, the OPV setting is only for safety reasons should the pressure rise too high. Rotary pumps have there own relief valve (shown in this exploded view) that serves a similar purpose as an OPV for vibration pumps.

[HB]

PS: Here's a really nice picture of the expansion valve / OPV for the Andreja Premium from http://www.chriscoffee.com/faq:


(image courtesy of Chris' Coffee Service)

I've not seen the inside of the Epoca, but I would expect to see one similar to this (also see the thread Valentina brew pressure adjustment for related discussion).

[yapit]

Thank you Dan for the pics and the diagram.

As to the pic, i cannot find such a device on my machine.

The diagram is pretty helpful though as I can locate the spot where the OPV should be. What i find there is a three way connection between the boiler, the pump, and the drip tray. What i cannot find is a nut that could be adjusted. All nuts are really big and solid, and none of them can be moved easily.

I put up some pics on coffeegeek, maybe you can comment on them (?).

Rancilio Epoca -- how to adjust the brew pressure?

[HB]

First of all, is this a rotary or vibration pump model? The pressure adjustment is different. I looked at the pictures on CG and saw no OPV. I suggest you take full-frame pictures from the two sides and one from the back. Following the plumbing to the OPV is alot easier than trying to spot it out of a bunch of close-ups.

PS: We discourage cross-posting between sites like CG, alt.coffee, TMC, etc. since there is an overlap in memberships. Please post to the site that seems best for your question or you frequent most often. If you don't get an answer elsewhere, it's no problem if you post "I asked about XXX (link) on YYY and got no answer. Can you help?"

[wookie]

The key thing is as Dan asks, does your Epoca have a rotary or vibe pump? The plumbed in version (rotary) has a OPV that looks like the picture below. The vibe OPV may or may not be the same.

n.b. this board won't upload an image directly. Check the Nuovaricambi.it site for an exploded Epoca parts diagram & a drawing of the OPV.

[yapit]

Thank you for your comments and suggestions and excuse when trespassing site policies -- maybe you might add the above p.s.-post to the FAQ file to make the point clearer.

Wookie, unfortunately you didn't leave the exact link. Following the link brings me to a page that doesn't seem to offer much. But i guess my machine has a vibration pump and not a rotary pump -- it is not the plumbed version but the tank version Epoca S1 /w tank. It is supposed to have independent heat exchangers though i am not sure what is meant by independent.

But here's a pic of the pump (sorry, i couldn't get a clear pic of the label on it -- it says: Ulka Italy, Model E Type EP5 120V 60Hz 1/1min. CI.A 41W)





Here are a few more pics. First the backside:



No idea, if my comments are helpful to the experts. On the right side you can the the Boiler Fill Solenoid (i guess), next to the left is the 3-way-connection i spoke of earlier, the third branch lies behind and leads to the drip tray. The brass loop right in front of the boiler connects to the pressure gauge in the front that measures the boiler pressure which will be adjusted by screw located in the black box.


The left side (left seen from the front):



That would be the 3-way-connection and the Boiler Fill Solenoid....


The right side:



This side is mostly electrics. The brass pipe in the background connects the adjusting box for the boiler pressure with the boiler.


The front side (for completeness):



The brass pipe on the right connects the 3-way-connection to the drip tray.


One more pic from above (front is left):



The screw located above and on the brewhead, which i mentioned before with a detail pic, can be seen on the left side between red electric cable and black insulated water tube. I have no idea what the function of this screw might be -- it looks almost like it might be possible to block the flow to the brew head or it might be related to the 3-way-solenoid valve under it.

The brass pipes in this picture are:
a.) in 12 o'clock direction: Boiler Fill Solenoid;
b.) 10 o'clock direction: hot water outlet;
c.) 2 o'clock direction: brew water, connects to the previous mentioned 3-way-connection;
d.) 3 o'clock direction: boiler pressure gauge;
e.) 4 o'clock direction: boiler pressure adjustment (black box);
f.) 7 o'clock direction: steam wand


Hmm.... did forget something? Hmm, yes, on the last pic there's a rather bright, big nut to see on the right side. This thing is directly on the boiler and looks like some safety valve but doesn't look like it could be twisted in either way. It also lacks the shape for attaching any tool.

Hm, thanks again and sorry to bother you.

[HB]

Thanks for the pictures, that helps a lot. The silicone tubing leading away from the vibration pump looks like an overflow. See the fixture encircled in red below:



I am hoping this is a shim-type adjustment expansion valve similar to the Giotto Premium's:



If so, the adjustment instructions I offered in Help Me Adjust Overpressure Valve on a Giotto Premium apply to your machine too, i.e., give the slotted shim a turn outward (CCW) to allow more water to escape (lower overall pressure) or inward (CW) to increase the spring tension and allow less water to escape (higher overall pressure). Keep in mind however that since you have a vibration pump, this will only affect the maximum pressure when pulling ristrettos. In other words, the actual brew pressure is the lesser of the puck's resistance, the pump's capacity at a given flow rate, and the expansion valve setting.

PS: No need to apologize and please don't hesitate to ask for help again. Cross-posting is one of those netiquette issues that isn't universally accepted; my reminder was primarily to avoid several people investing time answering the same question, that's all.

[erics]

Hi Yapit - Certainly everything Dan says is correct and the most important thing he is saying is

"Keep in mind however that since you have a vibration pump, this will only affect the maximum pressure when pulling ristrettos. In other words, the actual brew pressure is the lesser of the puck's resistance, the pump's capacity at a given flow rate, and the expansion valve setting."

Another poster on this site (and I wish I could give him due credit) also described the most correct method of measuring the OPV setting by bleeding off a chosen flowrate (his was 2 oz. in 25 seconds which I certainly agree with) by means of a needle valve tee'ed into the pressure gage line. I would also add that you need to seal the metal-to-metal contact surface between the basket and the portafilter (o-ring, rubber band, double layer of saran wrap, etc.).

The difference between zero flow at the portafilter and 2 oz per 25 seconds is 0.5 bar on my Silvia but yours may be different (nice machine you got there). With zero flow from the portafilter, you should also be able to measure the flow from the OPV back to the tank simply by putting the hose in a glass measuring cup (use a 2-cupper). Time an 8 ounce flow and do the math/conversion to cc/minute. The performance curve for the E5 pump you have is also somewhere on this site but for starters, you should be measuring about 110 cc/min in the OPV line if your 12.5 bar is correct. That 110 cc/min represents my interpretation of the E5 pump performance curve and as Ulka doesn't really give any explanation for their dashed lines, it becomes a little subjective.

Anyway, hope all is well in the cup and, if I were you, I would not make any rash adjustments.

Good Luck,

Eric S.

[HB]

Another poster on this site (and I wish I could give him due credit) also described the most correct method of measuring the OPV setting by bleeding off a chosen flowrate (his was 2 oz. in 25 seconds which I certainly agree with) by means of a needle valve tee'ed into the pressure gage line.

That would be Bob and his pressure portafilter built from ordinary hardware fittings:

It seems to me that if your going to measure brew pressure and make adjustments, then you need to know the exact pressure that you have while pulling a shot. Most portafilter gauges measure only the static pressure at the brew head when the by-pass valve has opened. That is not the pressure you are getting when you are brewing espresso. The attached photo is a simple mod I made to the gauge I bought from Chris Coffee. I can adjust the needle valve to allow precisly 2 oz of water to flow in 25 seconds while reading the pressure. On my machine, the resulting pressure is 8 bar, as seen in the inset.

Bob



here it is in use:

[yapit]

Thank you for all the help so far and excuse me for disappearing for a while, as i wasn't where the machine is. I kept thinking a lot about it however....

Dan, seemingly you have identified the right spot for the OPV. I got a mail from someone pointing me to this website that talks about a pressure mod for the silvia. http://mysite.wanadoo-members.co.uk/m4tt5mith/SilviaPressureMod.html. Apparently it doesn't seem to be as convenient as the Giotto by adjusting a screw but requires an additional copper gasket to be put into. That would probably mean that there is no fine adjustment possible if i understand that right. But i haven't gone further to take it apart yet. In fact, I have no idea where to get that copper gasket if it would be the way to do....

Instead i have been thinking about the post of erics and tried to time the flow from the OPV. Well.... I am still wondering if i understood that right so let me repeat it: does zero flow at the PF mean no flow from the PF as if you would put a backflush disc in or use a PF with a gauge that does not allow any flow? If yes, that is what i tried --- but i got the problem that i couldn't observe any flow at all from the OPV !!! In fact, i have never seen anything flowing from the tube connected to the OPV. The pressure gauge at the PF needs some time to get until up around 12.5 bar but then nothing happens and after some time if falls slightly. What do i do wrong here?

Of course, besides looking just at the numbers, the taste should rule. I never had the chance to have a good coffee before, that is a fresh roasted coffee. I had one now. A blend called Malabar Gold. While i can perceive the greatness of this blend that produces lots of crema, straight espresso gets rather sour in the cup. I have the idea that this might also be related to my pressure problem, especially as a friend praises this roast as his favorite -- but i just cannot produce a balanced shot from it.


I like to add a general question about rotary pump vs. vibration pump. The former are of course rather expensive. Are they also easier to adjust in terms of brew pressure? Would that be one more reason to get a machine with a rotary pump?

[HB]

does zero flow at the PF mean no flow from the PF as if you would put a backflush disc in or use a PF with a gauge that does not allow any flow? If yes, that is what i tried --- but i got the problem that i couldn't observe any flow at all from the OPV !!!

It could be set higher than the pump's maximum pressure. Or what we think is an OPV is actually a fixed-pressure safety release valve. I've seen those on rotary machines; they allow water to escape from the closed system during warm-up (and hence why OPVs are also called "expansion valves").

I have the idea that this might also be related to my pressure problem, especially as a friend praises this roast as his favorite -- but i just cannot produce a balanced shot from it.

Maybe you should try Malabar Gold prepared by your friend? In my opinion, it's one of those "love it or hate it" blends.

I like to add a general question about rotary pump vs. vibration pump. The former are of course rather expensive. Are they also easier to adjust in terms of brew pressure? Would that be one more reason to get a machine with a rotary pump?

Yes, rotaries are much easier to adjust, but that wouldn't justify their cost. Their undisputed advantage is their quietness. Some feel they produce a superior shot, but that's hotly debated. In your case I would recommend deciding if there is indeed a problem.

Remember that for a true double, all this OPV stuff is irrelevant because the flow rate of the pump is such that the pressure is 9 bar at that volume. Only for ristrettos will you see any difference. Or to put it another way, if you pull true doubles, the OPV isn't supposed to open. For that matter, some very good machines (e.g., the Salvatore) don't have an OPV at all because they assume any serious barista would only pull doubles.

[erics]

Thank you for all the help so far and excuse me for disappearing for a while, as i wasn't where the machine is. I kept thinking a lot about it however....

Dan, seemingly you have identified the right spot for the OPV. I got a mail from someone pointing me to this website that talks about a pressure mod for the silvia. http://mysite.wanadoo-members.co.uk/m4tt5mith/SilviaPressureMod.html. Apparently it doesn't seem to be as convenient as the Giotto by adjusting a screw but requires an additional copper gasket to be put into. That would probably mean that there is no fine adjustment possible if i understand that right. But i haven't gone further to take it apart yet. In fact, I have no idea where to get that copper gasket if it would be the way to do....

Instead i have been thinking about the post of erics and tried to time the flow from the OPV. Well.... I am still wondering if i understood that right so let me repeat it: does zero flow at the PF mean no flow from the PF as if you would put a backflush disc in or use a PF with a gauge that does not allow any flow? If yes, that is what i tried --- but i got the problem that i couldn't observe any flow at all from the OPV !!! In fact, i have never seen anything flowing from the tube connected to the OPV. The pressure gauge at the PF needs some time to get until up around 12.5 bar but then nothing happens and after some time if falls slightly. What do i do wrong here?

Of course, besides looking just at the numbers, the taste should rule.

I never had the chance to have a good coffee before, that is a fresh roasted coffee. I had one now. A blend called Malabar Gold. While i can perceive the greatness of this blend that produces lots of crema, straight espresso gets rather sour in the cup. I have the idea that this might also be related to my pressure problem, especially as a friend praises this roast as his favorite -- but i just cannot produce a balanced shot from it.


I like to add a general question about rotary pump vs. vibration pump. The former are of course rather expensive. Are they also easier to adjust in terms of brew pressure? Would that be one more reason to get a machine with a rotary pump?

That's good that you haven't taken it apart because, in fact, you may not need to. The copper gasket for your particular machine should be available from a variety of espresso machine dealers and you could always start with whomever you originally bought the machine from. Should you eventually take your OPV apart, it would be nice to have a spare gasket on hand. While copper gaskets can be reused, it is good practice to replace.

I BELIEVE your OPV is adjustable as per Dan's previous instructions but the only way to know for sure would be to disassemble it. But I wouldn't disassemble it before I knew what the true brew pressure is and had a spare gasket on hand.

If you try to measure brew pressure simply with a gage attached to the PF and normal basket in place, you should get some leakage between the basket and the PF body. The amount of this leakage will depend upon the "seal" between these two parts. In this case, your flow is the leakage plus whatever is flowing in the OPV line.

Under normal espresso brewing conditions, you don't need a "perfect" seal between these two parts because there is essentially zero pressure on the joint - the espresso is flowing from the PF spout(s).

When you use a blind basket, you are NOT subjecting the seal I speak of to any pressure but are depending on the seal between the rolled ridge at the top of the basket and the grouphead gasket to prevent any leakage. When the blind basket is in place and pump running, you should have no leakage at the grouphead, but you SHOULD have flow in the OPV line back to the tank. That flow SHOULD be ABOUT 110 cc/min at 12.5 Bar pressure. If such is NOT the case, then something else is amiss and we will need to "talk" further.

When you use any basket other than a blind basket, attach the pressure gage, and run the pump, you should get some leakage between the basket and PF body. Depending upon a couple of factors, this leakage may very well be close to "normal" espresso flow rates - you can choose your own numbers here but 2.0 oz in 25 seconds is certainly not unreasonable. If this is the case with YOUR machine, then your true brew pressure is 12.5 Bar as you measured.

BTW, I would disconnect and put a small piece of electrical tape on the heating element wires while doing all of this experimentation to simply avoid getting splashed with hot brew water.

You said "Of course, besides looking just at the numbers, the taste should rule."

Absolutely, positively, let there be no doubt that this is CORRECT.

That, by itself, should not be on a "list of reasons" to get a machine with a rotary pump. Espresso machines which have rotary pumps are high-end prosumer/commercial machines which are a cut above what you have and many cuts above what I have. But, as I said before, it appears you have quite a gem and I'm pretty happy with what's on my countertop although I do have this strange Brewtus itch that comes and goes.

Eric S.

[glenn.magill]

Hi,
First of all, I'm impressed with the amount of knowledge demonstrated on this site. You guys seem to be in the upper
echelons of the espresso machine tuning business.

Sadly i'm kind of at the other end of the scale . I've recently upgraded from my rancilio silvia to a rancilio Epoca.

The Epoca is a great machine, however I am a little disappointed in the amount of steam it can create and am wanting
to increase the steam output... can this be done without affecting the quality of shots I can create?

I've had a look over all the camera shots above of my machine, but wouldn't know which screw/valve to adjust to increase
the steam....

Can anyone point me in the right direction?

regards
Glenn

[HB]

I've not opened an Epoca myself, but the black plastic box in the upper left corner looks like a pressurestat to me. If so, there will be a wide-slotted screw underneath the cover that presses against a spring plate. It is marked with ± arrows. If it is a Sirai, the adjustment is fairly small, around 1-1/2 turns for a 0.1 bar increase. You will have to adjust the flush amount to compensate for the hotter boiler.

Another option instead of raising the boiler pressure is changing the steam tip. The specs say it has a 1600W heating element and a 3.9L boiler. That's should give you some serious steaming power anywhere at 0.9 bar or higher. Maybe it is the smaller water surface, but I've noticed vertical boiler machines will have more "oomph" at the same boiler pressure compared to the same sized horizontal boiler.

[glenn.magill]

Hi Dan,
you were 'right on the money' the black box is the pressure control. Have fitted a commercial steam tip and also turned up the pressure on that black box and it steams milk like a commercial machine.... I mean my cats run for cover when I turn on the steam wand!!! Can froth half a litre of milk at a time no problem and very fine froth too. The pressure does drop off consistently while steam wand is on full power, but it takes a couple of minutes to run out of oomph, and recovery time is very good... perhaps 1 min to return to normal.

Just wanted to say thanks very much for your advice!

[DaveC]

Another option instead of raising the boiler pressure is changing the steam tip. The specs say it has a 1600W heating element and a 3.9L boiler. That's should give you some serious steaming power anywhere at 0.9 bar or higher. Maybe it is the smaller water surface, but I've noticed vertical boiler machines will have more "oomph" at the same boiler pressure compared to the same sized horizontal boiler.

I found this on many of the machines I reviewed. My personal belief as to the reason for the increased steaming power size for size is: The vertical boilers of the machines are filled with a greater % of water than a Horizontal boiler machine. The larger mass of water acts as a bigger steam "battery" and can create more steam for longer.

I don't think this is due to any planning by the manufacturers to achieve this result, but an issue of practicality to ensure the element is fully covered.

P.S. This also accounts for some of the longer recovery times of the HX units in these type of machines (as they are often sized the same as for HX units in a horizontal boiler), because more of the HX is submerged. This because of the rule when adjusting the water level in a HX machines (Horizontal and to a much lesser extent Vertical) boiler:

Increase boiler water level = better steaming, longer HX recovery/cooler brew temps

Decrease boiler water level = weaker steaming, quicker HX recovery/Hotter brew temps

I have many times come across people who have lowered boiler water level in the mistaken belief they will get better steaming (rationale is a larger area of steam) and actually got the opposite effect.