Fullsack wrote:Sorry, Nicholas. It is confusing because I'm a little confused. The pipe from the pump goes to the bottom of the HX tube, via the 3-way and the flow meter and the OPV comes from the bottom of the HX tube. If I am getting a pump pressure reading from the portafilter pressure test gauge then where do I take the OPV pressure reading?

It's OK. This is actually slightly complicated to think about at some level. In short, there's no easy way to SEPARATELY tell what your OPV and your pump are set at with just one pressure gauge at the grouphead. The trick is that the pressure your reading is gonna be ROUGHLY the minimum setting of the two. So, if one is set at 9 bars and the other at 11 bars, you will read 9 bars with your PF pressure gauge.

You need to set them one at a time, and you need to set the OPV first (since it has to be highest in the end). To do this, you need to set the pump bypass to deliver very high pressure. With the machine on and all hooked up and the lid off, and your portafilter pressure gauge installed, initiate the brew switch and tighten the pump bypass valve until you see about 12 bars *or* the pressure stops going up. If the pressure stops going up, you should see that there's water dripping out the OPV into the drainbox, and you need to tighten the OPV and the pump bypass until you see 11 bars at the PF pressure gauge. If you were able to get to 12 bars with the pump bypass, that means the OPV is set too high and you need to loosen it (again with the brew switch on and the pump going) till it's down to about 11. Keep in mind here that if your PF pressure gauge is a blind portafilter (i.e. you have static flow), you need to make sure that you test it at least twice by ending the 'shot' and starting over. There's a check valve in the line and if you get some thermal expansion in the HX it can make things read artificially high.

After you set the OPV, loosen the bypass screw on the pump and pull more simulated backflushes till you get to about 9 bars max. At this point you should be set. Remember again if you see it jump to 9 bars fast and then start to creep up, that's just thermal expansion and not the pump being set too high.

Does that make sense? That's how I'd do it. I bet there are other clever ways to do so as well, though.

I actually didn't know that, so thanks for sharing.