OPV pressure setting

Post by **ebprod** » Thu Jul 05, 2007 2:24 pm

We just got our VII. The brew pressure seems to be set kind of low- when pouring a shot it never goes above 8 bar, even on very long shots. Is this normal, or should we try to adjust it? How hard is it to adjust the OPV?

Thanks.

-Joe

Post by **Niko** » Thu Jul 05, 2007 2:56 pm

Hey Joe,
8 Bars is a little on the low side, you should try setting it at 9 for better results.
What is your incoming water pressure at? This also affects the brew pressure, I know that Chris' Coffee adjusts all the machines at 9 bars before they ship. If your pressure is a little on the low side, try adjusting the pump pressure to 9 bars.

Post by **ebprod** » Thu Jul 05, 2007 4:47 pm

How do I measure my water pressure? I see that Chris Coffee sells a pressure regulator- how do I know if I need one?

Is the over pressure regulated at the pump? Is this adjustment done differently than my Relax because the VII has a rotary pump?

It looks like there are two different adjustments to make- are they both necessary? Or is only one of them actually adjusting the OP.

-Joe

Post by **Niko** » Thu Jul 05, 2007 5:47 pm

Look at your manometer, when it's idle the left gauge should read about 1.7 bar (roughly).
The correct way to read incoming pressure would be the regulator with gauge attached.

I wouldn't worry too much about your incoming water pressure, it sounds like it's a little lower than the average. A little adjustment to your pumps pressure should remedy this.
Here's a pic Chas posted in the S1 section of photos, he marked the brew adjustment screw with the letter "F".

I never had the need to adjust this on either of my units but I think you'll need to have a blind basket in your PF to check pressure (or the rubber disc might help), hopefully some of the guys who have done this will chime in.
I know Chas played with the brew pressure on his ol' S1, so he might have some good advice.

chas · Post by **chas** » Thu Jul 05, 2007 8:43 pm

http://www.rimpo.org/s1v2/images/S1%20V ... Manual.pdf

Check page 16. This actually shows the procedure for the S1. For the V2 rather than using a PF pressure gauge, use the built-in group pressure gauge and a blind filter basket

Post by **ebprod** » Thu Jul 05, 2007 8:56 pm

My incoming pressure on the manometer is at about 3 bar. I think I will get a pressure regulator just to be safe. But how does that affect my low brew pressures?

-Joe

Niko wrote:Look at your manometer, when it's idle the left gauge should read about 1.7 bar (roughly).
The correct way to read incoming pressure would be the regulator with gauge attached.

Post by **ebprod** » Thu Jul 05, 2007 9:55 pm

I adjusted the brew pressure to just under 9 bar. It was ALOT easier to do on the VII than it was on my old Isomac Relax.

Thanks for all the help.

-Joe

chas · Post by **chas** » Thu Jul 05, 2007 10:11 pm

3 bar is about 45psi. The rotary pump adds to the line pressure. If you add a pressure regulator and drop the line pressure to 30psi, your group pressure will be back down to 8 bar and you'l need to adjust it up again.

Post by **ebprod** » Thu Jul 05, 2007 10:36 pm

Does the pressure regulator keep the line pressure at a constant, or does it only prevent it from going over a set amount? So if my water pressure dropped, for example, because someone was in the shower, this would keep the pressure up?

-Joe

chas wrote:3 bar is about 45psi. The rotary pump adds to the line pressure. If you add a pressure regulator and drop the line pressure to 30psi, your group pressure will be back down to 8 bar and you'l need to adjust it up again.

Post by **Niko** » Thu Jul 05, 2007 11:21 pm

The regulator will really help, it keeps it at a constant pressure so you don't have to keep adjusting the pump pressure.
Although I've seen my incoming water pressure move slightly up or down even with a regulator installed, it stays within specs enough to keep a good 9 bars every time.

MDL · Post by **MDL** » Fri Jul 06, 2007 11:10 am

I think that adding a pressure regulator and guage like the one that Chris sells iis both cheap insurance and a valuable addition to improve function.

Remember that the regulator is simply a spring against which the water pushes. If your incoming pressure varies substantially you will see changes in the output pressure from the regulator; it is not an active regulator that is able to maintain the set output pressure.

Depending on how much your line water pressure varies you may have to play with the regulator to get it set at the appropriate middle ground; my pressure is very unstable and it took me some fiddling to get it right. However, now that it is dialed in around the middle of the range for my input water pressure it is great.

Be sure that you buy the pressure guage on the regulator so that you know what pressure you have at the output.

Post by **Niko** » Fri Jul 06, 2007 12:14 pm

MDL wrote: Be sure that you buy the pressure guage on the regulator so that you know what pressure you have at the output.

Good idea, Mark.
When I ordered my first machine, I made the mistake of not getting the gauge on the regulator. It's one of those things you don't think about until you realize it can be helpful.
Now about that other type of regulator (active), have you looked into it?

MDL · Post by **MDL** » Fri Jul 06, 2007 1:19 pm

Niko:
I don't know of any more sophisticated approach to pressure regulation. I am sure that there must be more sophisticated active regulators, but I have never seen them and I imagine that they would be very expensive.

For example, I have a regulator on the main water line coming into my home that is exactly the same type as the little one we bought from Chris (although much larger and brass instead of plastic). When I asked about other ways to go the plumber (and an engineer friend) had no suggestions.

If I find anything I'll certainly let folks know.

chas · Post by **chas** » Fri Jul 06, 2007 7:10 pm

If you ever get a chance, take yours apart. There isn't much too it and nothing that you can hurt by taking it apart and putting it back together. It's not much more than a small chamber with a spring loaded diaphragm. The adjustment screw adjusts how far up or down the diaphragm is in the chamber.

MDL · Post by **MDL** » Fri Jul 06, 2007 7:46 pm

The output pressure from the regulator is a function of the incoming pressure and the pressure exerted by the spring on the diaphragm. When you adjust the "pressure" you are adjusting the tension of the spring and therefore the pressure that you are setting relative to the incoming pressure. If the incoming pressure changes so will the output pressure. An active regulator would have to compensate for the incoming pressure and any changes of that pressure.

Nevertheless, Chas is correct, the device is tremendously simple.

Post by **ebprod** » Tue Jul 17, 2007 12:29 am

I got the pressure regular attached. My manometer now shows a steady 3 bar. Is that an OK setting, or should I try to adjust it a little lower?

-Joe

Niko wrote:Look at your manometer, when it's idle the left gauge should read about 1.7 bar (roughly).
The correct way to read incoming pressure would be the regulator with gauge attached

Post by **Niko** » Tue Jul 17, 2007 12:36 am

Joe,
Did you get the water pressure gauge also?
If so, try not to let it hover over the 30psi mark. 22-30 is a good range.

If you didn't get the gauge, you can try and adjust it but I think they might come pre-adjusted for about 30 psi (not sure, but 3 of my regulators showed pup that way).
Yours seems a little on the high end, keep an eye on it and how your machine reacts but you should be OK. Water pressure varies throughout the day anyway.

Post by **ebprod** » Tue Jul 17, 2007 12:54 am

I didn't get the pressure gauge (didn't know that I should). Chris's is cheap enough, but could I get one from the local Home Depot? I suppose I would have trouble finding one with the JG fittings.

-Joe

Niko wrote:Joe,
Did you get the water pressure gauge also?
If so, try not to let it hover over the 30psi mark. 22-30 is a good range.

Post by **Niko** » Tue Jul 17, 2007 1:00 am

The gauge just screws right on the regulator, Joe.
First you remove the cap that plugs the threads and then apply some Teflon (not too much) on the regulator threads and then screw it on.
You can probably find one at your local hardware store.

Post by **coffeeowl** » Mon Mar 17, 2008 2:12 pm

coffeeowl wrote: (...)anyway Niko's pressure report also keeps me thinking: on my machine I have straight 9bar on a free run; with coffee (16g for the beans I currently use) it hits 9 and then at the moment right after bidding, when the nectar starts hanging heavily and then makes a cone - it builds up to almost 10.

So I adjusted my brew pressure a hair down, now my machine fires blank shot just below 9bar and on bidding gets a bit above.
On backflush it used to build up to 10bar before flashing; now it reaches about 9.5bar.
Am I happier?

My usual ristretto seems to have a clearer bright notes (vs a bit distorted with the previous setting). Didn't drank too much yet for I'm short on coffee

have to wait till tomorrow to get it from the roasterie.
Only worry for now is if I would be able to alter the brew to get the same caramel notes as before with 1s grinding time less coffee in the basket? I loved that!

Post by **coffeeowl** » Fri Mar 21, 2008 3:24 pm

Can anyone explain how is that in a machine with no OPV, like for instance the Semiautomatica, the rpessure during brewing a single is much higher then the pressure during brewing a double? I don't get it. :?