erics wrote:That noise would drive me nuts. Adjusting the expansion valve changes the portion of the pump flow going into the system (obviously) and hence the change in noise. What is the noise level when pulling a shot or filling the steam boiler? What is the complete nameplate data on the pump; what is its pedigree?

I realize the motor is resiliently mounted at both bearings with a sorta rubber "surround" but the clamping arrrangement for same looks a little strange - just going by memory. Likewise on the clamp arrangement holding the pump to the motor - perhaps a little less so.

The inlet for the pump should not be such an abrupt 90 ell but rather a smooth radius bend even though the flow is relatively low as compared to the pump's capacity. Likewise the discharge hose should have a support of sorts to avoid being self supporting. The motor/pump assembly itself should also be resiliently mounted to a solid structure.

Its a Procon - Series 2 Pump, with clamp on mount. The faceplate just says "Procon Pump MFD by Standex at Mountmellick". The clamp has a rubber surround inside of the clamp itself, I'm guessing for both sound and vibration. The pump came with the inlet and outlet set up as seen in the video, though that does not mean the original owner had it correct either... The outlet hose is coiled around the water jug next to it, wraps around it once, and then goes up to the machine, so it is "supported" a little. I'm in the process of building cabinets for this stand that I just finished, once they get completed the motor will be mounted and not just "sitting on the floor"

erics wrote:I realize the motor is resiliently mounted at both bearings with a sorta rubber "surround" but the clamping arrrangement for same looks a little strange - just going by memory. Likewise on the clamp arrangement holding the pump to the motor - perhaps a little less so.

Looks very similar to the clamping arrangement on the motor my Speedster uses. What's odd about it?

Justin,
You are on the right track. PID does have something to do with this. The expansion and contraction of the water happens with temperature change. Larger temperature changes cause more expansion. With the PID your temperature remains pretty constant (unless you run a bunch of water through it). So at operating temperature you may not see the pressure gauge move after you stop brewing. During a cold start is when you see the most expansion. Since the pressure was going down to 3 bar it really indicates a leak of some type. If your pump is set to 9 bar and you turn and off a brew switch (to get system pressure to 9 bar) and then the pressure drops, it is because of a leak somewhere. Could be the expansion valve set too low. The expansion valve on the La Marzocco machines is only for safety and can be set anywhere below 12 bar (recommended maximum from LM). The squealing sound that you hear people talking about is when the expansion valve is set too close to the pump pressure. When the pump gets to full pressure it forces a small amount of water through the expansion valve causing a squealing noise. If it is difficult to adjust, take it apart and clean it. It is in the same area as the brew exhaust so it gets pretty dirty. It is the easiest to set when the machine is heating from cold because this is the time when the greatest expansion occurs.

BillC

Billc wrote:Since the pressure was going down to 3 bar it really indicates a leak of some type. If your pump is set to 9 bar and you turn and off a brew switch (to get system pressure to 9 bar) and then the pressure drops, it is because of a leak somewhere. Could be the expansion valve set too low. The expansion valve on the La Marzocco machines is only for safety and can be set anywhere below 12 bar (recommended maximum from LM).
BillC

Bill,

I used a the way Eric mentioned earlier in the thread to set the expansion valve, it is now set in the range of ~11bar or so, when I pull a shot, the pressure does not drop to ~3bar, instantly, but after a long idle when I return to the machine it's typically sitting around 3bar. I watched the gauge this morning and it hovered around 6bar after about 20 minutes of being idle.

I'm going to set the expansion valve higher and see if that does anything.

Also, the high pitch that I have been referring to is actually my pump, I posted a video of it, and now I need to figure out why it's doing that and what I can do to fix it, hoping I don't need to replace the pump.

Justin,
Still messing with that thing?
I would be looking at the one-way valve. Brew boiler should never go below your 9bar setting except when the machine has completely cooled down. This would happen when you pull a shot and then immediately turn off the machine. This is the reverse of the pressure build due to heating.
This very subject came up yesterday at breakfast. LaMarzocco taps the tank rather than the pump lines for the gauge so you never see the supply line pressure. Most machines show city water pressure with the pump off and operating pressure with the pump running. This was in reference to water spikes opening the steam boiler solenoid.
jpboyt

Pat,

I was actually thinking the same thing. On the outlet side of the pump there is 1 - one way valve, connected directly to the pump, which leads to the "y" which then feeds the Brew boiler and the Solenoid valve for the Steam tank. The line leading from the Y to the brew boiler has a 2nd one way valve if I remember correctly. I guess I'll have to check both of them, but I would assume the one directly before the brew boiler would have better chance of being the culprit.

I appreciate your advice as always.

-Justin