truemagellen wrote:Thank you Marshall. I will seek him out.

FWIW—Greg uses a TMFR pump in his profiling system, and I built something like his system minus the PID part (I may integrate that in the future, but it's quite expensive to add). Anyway, discussion of this method is here, and there are actually a lot of other cool pressure profiling ideas mentioned and discussed in that thread. I don't think it'll help you much with your FPR issue though.

I agree with Randy on the FPR, you need to make sure you get something rated for potable water and for the temperature you expect to use it at. I'd personally suggest putting any regulator upstream of the boiler, where the water is still cool. I don't see any big difference between the function of an FPR and, say, a needle valve or more traditional water pressure regulator if you want to pressure profile in this fashion. If you can get a choke that's controllable by a servo motor you could also rig up an electronic controller for such a configuration if you don't want to profile by hand. I suspect that this would be about as expensive as using a gear pump or TMFR pump as in the previous thread, though. Pressure regulators come in many shapes and sizes, and the most reliable ones, in my experience, are extremely expensive. I managed to get a really amazing Swagelok regulator for my TMFR set up about a month ago, the adjustment knob turns more like my stereo's volume knob than those stupid half-stuck screws on most regulators, even the nice Watts ones. Swageloks like this one will run you ~$300 unless you get lucky, though. You get what you pay for when it comes to this type of equipment, I suspect.

There's problems with cold side regulation on multi-groups. For multi group DB machines, pressure profiling has to be done on the heated water. For multi-group HX machines, you may be able to do it on the cold side, but you'd need to instrument each HX's inlet separately. Doing it at the group inlet seems more universla and elegant.

The device itself may not be adaptable to hot, potable water, but the principle looks like it could be the one used on the Slayer machines.

Do you think I could do cold side before the split since I only use one group at a time? I do have access to a fully brass FPR, but i'm not sure what the diagphram/gaskets are made of

It's not just about what it's made out of, it's also what (if anything) it's lubricated with, and, you're right, what the gaskets are made of. Not all brass is for potable water use, either. I seriously wouldn't recommend using something that's not rated for food use to pump water into your espresso that you drink. The risk is probably low, but it's not worth it: I strongly recommend you get a potable water pressure regulator if you want to pressure profile in this fashion.

And yes, doing one group at a time from the cold-water inlet will work fine. Just make sure the regulator is (a) rated for 150+ psi inlet (200+ is probably better) and (b) put it downstream of the machine's pump.