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

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yapit
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Postby yapit » Aug 04, 2005, 10:46 pm

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 !!

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HB
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Postby HB » Aug 04, 2005, 11:04 pm

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:

Image
(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.
Dan Kehn

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HB
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Postby HB » Aug 04, 2005, 11:10 pm

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

Image
(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).
Dan Kehn

yapit
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Postby yapit » Aug 05, 2005, 1:38 am

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?

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HB
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Postby HB » Aug 05, 2005, 10:10 am

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?"
Dan Kehn

wookie
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Postby wookie » Aug 06, 2005, 2:53 am

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
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Postby yapit » Aug 06, 2005, 8:32 am

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)

Image



Here are a few more pics. First the backside:

Image

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):

Image

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


The right side:

Image

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):

Image

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


One more pic from above (front is left):

Image

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.

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HB
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Postby HB » Aug 06, 2005, 8:58 am

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:

Image

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

Image

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. :-)
Dan Kehn

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erics
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Postby erics » Aug 10, 2005, 4:00 pm

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.

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HB
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Postby HB » Aug 10, 2005, 4:18 pm

erics wrote: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:
bobroseman wrote: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

Image

here it is in use:

Image
Dan Kehn

 
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