yeh not sure about the pump, but i think they all seem to be much the same externally.

I also have a 3 group La Cimbali M31 from the 80s and a 2 group La Cimbali volumetric from the early 90s. bought the 3 group at auction for $200 (on impulse after I had bought a Rancilio MD50 grinder) and the 2 group from ebay for $300. 3 group has been stripped to the frame for a rebuild 2 group is running but is pumping out milky water so will do a descale when i get the 3 group running. plan was to use 2 group as a bit of a test bench or part it, but now will probably aim to get them both working and get rid of the 3 group as it is probably a bit big for home use.

but point of my post is that the pump on the 2 group had seized so I swapped it with the 3 group one. one pump was procon the other was a no name brand. but both appeared to be pretty much identical externally. only really some fins on the external case and the attachment of front part of the pump that were different. the motors were different though so not sure if that results in different flow rates for the two pumps.

I've avoided ebay, but maybe I need to give it a look. Check out this exploded view on the ProCon site, if you haven't yet. http://www.proconpumps.com/PDFs/Exploded%20View.pdf The parts that are different for different flow rates, according to the procon tech, are the rotor, the liner, and the vanes. So there would be no sign on the outside, other than a model number stamped in, showing the flow rate. But the graph at the following website shows how much the horsepower differs.http://www.proconpumps.com/Series%202.htm But none of that explains what if any difference there may be in the characteristics of the output from pumps of different flow capability (for the same actual pressure and flow). I can imagine that sensitivity (of pressure) to input pressure, output demand, pressure smoothness, etc. might all be possible and also depend on many other things as well. It's hard to think it would matter a lot, or even a little, (to the coffee) for a one-group machine.

DickC wrote:I can imagine that sensitivity (of pressure) to input pressure, output demand, pressure smoothness, etc. might all be possible and also depend on many other things as well. It's hard to think it would matter a lot, or even a little, (to the coffee) for a one-group machine.

For pumps that have a standard relief/regulating valve, the output pressure varies with the inlet pressure to the pump. For all practical purposes, it is a proportional relationship (1:1).

For pumps that have a balanced relief/regulating valve (like yours), the output pressure is essentially constant with varying input pressure within a reasonable range of input pressures (this is my opinion, not necessarily fact). By reasonable range of input pressures, I mean anywhere from, say, 20 psig to 60 psig. I have certainly not seen any test results from pump mfgs to verify this but if they say it will perform in this manner - ya gotta put a little faith in that.

The business of actually delivering a minuscule portion of the pumps output to the grouphead while still maintaining smooth output pressure is another story. Using an old(?) controls systems term, I believe that is approaching the turndown ratio limits of the relief/regulating valve. I do know that there have been posts to the coffee forums wherein "larger" pumps have been applied to one-group machines and I assume it was successful as I hope you will be. Another quick source, right in your neck of the woods is Chris Coffee who sells a ton of Vetranos. It would be a good piece of info to know exactly what Procon or Fluid-o-Tech pump is installed in Vetrano.

Thanks Eric,
Do you know, can you describe, what the difference in mechanism is between "standard" and "balanced" relief/regulating valve? (Just curious.) For example, what exactly is balanced against what? I'm not sure which type of valve is shown in the ProCon exploded view, but there isn't a lot to it. If you know or can suggest where I can read up on these things that would be great.

On delivering smooth output pressure, has anyone experimented with some sort of expansion chamber after the pump output? Perhaps one of those anti-hammer things, or just a length of pipe with a cap sticking up?

In a balanced system, the pressure of the inlet water places additional pressure on the spring loaded piston on the inlet side of the pump. As the pressure increases or decreases it balances against the spring tension to keep the pressure constant. An unbalanced bypass places pressure against the pistons pressure on the seat of the bypass. Increases in pressure result in higher than desired pressures on the output side of the pump.

Because carbonation pumps are not pressure critical applications, balanced bypasses are seldom used.

DO NOT use the expansion valve to adjust pressure.

If you do not install a check valve, an expansion valve may not be necessary as excess pressure will bleed back through the line into the water system. It will never flow back into the system, simply use the 45 pounds of water pressure as a buffer. Check valves are required by code because cities do not understand how espresso machines work.

Pressure regulator not needed at 45 PSI.

Use a braided high pressure hose between the pump and the machine. The plastic can handle the pressure, but not always the heat from the expansion of the heat exchanger and the hose will pulse under pressure. These plastic hoses slice against anything sharp and will result in a disaster unless properly protected. If you want to run plastic, get Teflon line from someone like Pisco Products and find some kind of sleeve to put around it. It slices very easily.

Forget the solenoid, the autofill solenoid is fine and the group solenoid/lever takes care of the rest. A shut off via the water softener should be sufficient.

Don't over complicate things.

erics wrote:It would be a good piece of info to know exactly what Procon or Fluid-o-Tech pump is installed in Vetrano.

Well, it would appear to be the Fluid-o-Tech MA054, thanks to a recent picture posted by Jon (RegulatorJohnson), link.

RegulatorJohnson wrote:

The MA054 is a compact design pump, slightly smaller then the typical Procon pumps, but it is still a 50-60 gph pump (near brew pressures), and has a balanced bypass. Spec sheet here.

(Dick, my apologies to turning your thread into a repository of rotary pump models and specs.)

mteahan wrote:In a balanced system, the pressure of the inlet water places additional pressure on the spring loaded piston on the inlet side of the pump. As the pressure increases or decreases it balances against the spring tension to keep the pressure constant. An unbalanced bypass places pressure against the pistons pressure on the seat of the bypass. Increases in pressure result in higher than desired pressures on the output side of the pump.

Thanks Michael, If I understand, balanced means the line pressure appears on both sides of the relief valve and therefore cancels out. Hence it's just the spring tension that determines the output pressure. I don't see just how that happens; must be some clever little chamber in or around the valve piston. Not balanced valve (or "solid"?) means the inlet pressure only adds to the spring pressure, increasing the regulating pressure setting.... ? Well, maybe I just need to be satisfied to know that "balanced means output pressure is independent of input pressure."

mteahan wrote:DO NOT use the expansion valve to adjust pressure.

I guess you mean the "OPV" here?

mteahan wrote:If you want to run plastic, get Teflon line from someone like Pisco Products and find some kind of sleeve to put around it. It slices very easily.

The only Pisco I could find specialized in hydralic stuff and listed no Teflon tube. Link?

jesawdy wrote:(Dick, my apologies to turning your thread into a repository of rotary pump models and specs.)

Thanks Jeff, but not a problem (for me, anyway). I welcome all rotary info, etc. Be nice if someone collected it all in a FAQ. I might volunteer, once I have mine working, but hesitate due to obvious fuzzy spots in knowledge and understanding (see above).