Ken Fox wrote:Are you sure of this, Dan? I have never owned a vibe pump machine with autofill, but I think this would depend on where the OPV is located, assuming one has one and has adjusted the OPV in the machine. If the vibe pump would get up to 14 or 15bar in its unmodified state, and especially if the OPV is located distal to the input solenoid, I think it is very possible that the pressure at the puck would remain unchanged as the pump is capable of producing almost twice as much pressure at the group as one has the OPV set up to deliver. I think this all is going to depend on things such as how the plumbing is designed and configured in a given machine. Testing this would be very easy as all it would require is a PF Manometer; one could start a shot then immediately drain enough water out of the water wand to get the autofill to kick on, then look at how the PF manometer reading changes.

ken

Even if the shot pressure didn't dive if auto-fill kicked in during the pull the shot would be ruined anyway since shot temp would likely dive!

miKe mcKoffee wrote:Even if the shot pressure didn't dive if auto-fill kicked in during the pull the shot would be ruined anyway since shot temp would likely dive!

That would depend on when the autofill kicked in during the shot, the machine involved, and whether the shot being made was one in a series or if it was being made alone, with no shot immediately following. The autofill kicking in during the shot is more likely to effect the temperature of the NEXT shot than it is to effect the shot in question.

ken

Ken Fox wrote:That would depend on when the autofill kicked in during the shot, the machine involved, and whether the shot being made was one in a series or if it was being made alone, with no shot immediately following. The autofill kicking in during the shot is more likely to effect the temperature of the NEXT shot than it is to effect the shot in question.

ken

That would certainly be true with a mammoth boiler like on your Juniors! On the more average sized prosumer ~1.5 boilered HX machines if auto-fill kicked in at or near the start of a shot I'd suspect a goodly temp drop in the shot. Don't know but suspect. But now will have to play and find out, take the top off the Bric', and force a fill right after starting a Thermofilter shot and see what happens. (Since by design it's impossible for the Bric' to auto-fill during an actual shot on it's own. )

On my Isomac, if I am pulling a shot and the auto fill kicks in, the brew pressure drops like a rock, 9 bar to around 6 bar. The pump tone changes dramatically as well. I cannot comment on the temperature. When it happens, I just kill the extraction and sink shot it. Thankfully it only happens once every few hundred shots.

On my Faema, I removed the auto fill solenoid. I have a sight glass so I know where my water level is. I wired in a backlight on the sight glass so it is illuminated when powered on and put a 220v indicator light on the front panel and wired it to the solenoid relay on the level box. That way if the water does go below the probe, the relay will trip the light to remind the operator to hit the manual fill button.

on my giotto premium it drops as well. temp looks like it lowers, but this could just be because the pressure is so much less that the sputter stops.

HB wrote:The 14 or 15bar you refer to is a zero flow. The max pressure a vibe pump can produce drops off dramatically with an increase in flow rate... When the boiler refill solenoid opens, the water will flow into the boiler in a hurry as it's offering only ~1 bar of resistance, compared to the puck / OPV's ~9 bar.

Rather than speculating on this I think it would make more sense to test it, being as it is very amenable to testing and requires equipment that many have. I will attempt to test some of this on my plumbed in rotary machine, realizing that the results aren't necessarily applicable to a vibe machine with autofill.

There are two things to test: (1) effect of autofill on brew temp during the initial and maybe 1 or 2 subsequent shots made at reasonable shotmaking intervals for a particular machine, say one shot per 1.5 or 1 shot per 2 minutes; (2) effect of shot pressure measured by PF manometer before and during autofill engagement.

The equipment needed to accurately observe this would include a Scace Device (preferably) plus datalogger for #1, and a PF manometer for #2. I don't think that a front panel pressure gauge would necessarily be as accurate for this measurement but I could be wrong.

ken

Ken Fox wrote:Rather than speculating on this I think it would make more sense to test it, being as it is very amenable to testing and requires equipment that many have. I will attempt to test some of this on my plumbed in rotary machine, realizing that the results aren't necessarily applicable to a vibe machine with autofill.

There are two things to test: (1) effect of autofill on brew temp during the initial and maybe 1 or 2 subsequent shots made at reasonable shotmaking intervals for a particular machine, say one shot per 1.5 or 1 shot per 2 minuts; (2) effect of shot pressure measured by PF manometer before and during autofill engagement.

The equipment needed to accurately observe this would include a Scace Device (preferably) plus datalogger for #1, and a PF manometer for #2. I don't think that a front panel pressure gauge would necessarily be as accurate for this measurement but I could be wrong.

ken

why not the flow as i watch it come out of my grouphead? it slows down enough to be seen...

LeoZ wrote:why not the flow as i watch it come out of my grouphead? it slows down enough to be seen...

(1) Your machine may not be like all other machines

(2) The flow rate in a non pressurized situation (like watching water come off a grouphead without a loaded PF or a Scace or somesuch in place) might be different.

I don't claim to be any sort of expert in fluid dynamics, but given that there are many things that are difficult or impossible to test, why not test those things that are easy and straightforward to test? That would give real answers rather than guesses.

ken

This thread has gotten off topic into the issue of the effects of autofill on shot temperatures and pressures in HX Machines. I have started a new thread in this forum on this topic, in order to make this topic more searchable in the future should someone be interested in finding it.

ken