If you haven't read How I Stopped Worrying and Learned to Love HXs by our very own HB, now would be a good time.

The FAQ has a whole list of Heat Exchanger Operation threads.

If you never steam, turn down the pStat. If you steam a little, you can turn down the pStat a bit to reduce the flushing. If you steam a lot, then leave it alone.

On my PID Vibiemme HX, the PID runs the boiler @ 228°F [ ~0.5bar ] for flushless walkup shots. When steam is required, the pStat controls the boiler at ~1.5bar. ( I had to put a brick on the machine to keep it on the counter. ) It's the best of both worlds.

nixter wrote:I don't understand why a "consumer" machine would ship with defaults so out of whack.

"So people can buy stale, pre-ground coffee, overload the basket and still make espresso milk drinks to impress their friends. If you know what you're doing, you'll know how to set it up properly." Response of a manufacturer when posed a similar question

Well after re-reading HB's HX threads I feel a lot more informed. I'm thinking now that my reading of 19-21psi or 1.31-1.44 bar from my steam wand with my 0-150psi gauge might not be far off considering that my shots are more often then not bitter and the Oscar has locomotive-like steam. I think I'll try some various flushing times and see that goes. After that I may adjust down the pstat to kill two birds with one stone, reducing my brew temp as well as insane steam.

Thanks for all the help guys.

nik

Update! I feel like a supreme dumbass

After reading all the HX flushing info I just did some testing. I attached my gauge to my steam wand and opened it up fully. It may not be totally accurate but it lets me see where I'm at in the heating cycle. Until now I've been pulling shots when the heating element light turns off which of course is the exact WRONG thing to do with a heat exchanger, depending on a machine's settings of course. Anyhow, with gauge attached and steam valve open, I prepared my PF with very fresh beans and flushed until the gauge needle went down and began to hold steady. I immediately locked in the PF and brewed a 26 second, 1.5 once shot of the best stuff yet to come out of this contraption. It was the first shot no less! I can't believe I was brewing too hot all this time. No wonder my results have been so hit and miss. I did find that with the pstat's current setting that the low, brew end of the cycle is a very small window so I think I may adjust things so that the proper temp is at the top of the heating cycle instead of the bottom. That way I can brew when the light goes out, removing some guess work. I'll have to see how that affects my steam though.

Thanks so much for all the help guys, I was beginning to get a little frustrated with the process but now I realize what I've been doing wrong.

nik

nixter wrote:Update! I feel like a supreme dumbass

It's a prerequisite.

I wouldn't worry about when to pull the shot. The inlet to the group will vary less than 1°F over the pStat cycle and the outlet even less. The mass of the group will flatten any variation even further.

Remember, it's HX water, not boiler water that goes into the shot. Once you've flushed the HX, it takes a relatively long time for the heat transfer from the boiler to reheat the HX.

nixter wrote:Until now I've been pulling shots when the heating element light turns off which of course is the exact WRONG thing to do with a heat exchanger, depending on a machine's settings of course. Anyhow, with gauge attached and steam valve open, I prepared my PF with very fresh beans and flushed until the gauge needle went down and began to hold steady.

Huh? I pay virtually no attention to the boiler cycle on an HX machine. Instead, I adjust the brew temperature via the HX flush. This is distinctly different from "traditional" temperature surfing you might do on a single boiler Gaggia or Silvia.

I'd suggest rereading the HX Love article again... and again...

i read it and I understand the flush. What I was talking about was brewing at a particular point based on flush and gauge reading. I was just being overly specific. I wouldn't have to be so anal about the timing except your damn yogurt cup trick lengthens my whole grind and tamp routine! hehe.

n

Many pull the shot at the top of the pStat cycle, just after the heater clicks off, the raison d'etre being the heater won't come on again until after the shot is pulled. When the heater kicks on, the pump may slow slightly and the brew pressure drop by a fraction of a bar.

FWIW, I installed a relay to cut out the heater during the brew cycle because the PID pulses the heater. Later, I installed a switch so I could leave the heater on during the cycle because disabling the heater slows recovery. If it makes any difference in the cup, it's very slight.

AFA the yoghurt cup, it should speed things up. Dose, shake, tamp, pull.
Under 10 seconds for a single, 15 for a double with MaxH. Add ~5 / ~10 seconds for the MC4.

Slow < Finer <> Coarser > Fast
Sour < Cooler <> Hotter > Bitter

As Chris Tacy said the other day, "If it seems like 'it can't be that easy'... it probably is."

I have a grinta doserless grinder so it's grind on demand. I spend at least 10-15 seconds just grinding the proper amount into the PF.

n