BoulderMike Posts: 137 Joined: 7 years ago
My LMLM has been showing an idle brew pressure of 15 to 16 for a while now. It drops to ~9.5 or 10 when I pull a shot. I know there is a nut behind the drip tray for adjustment. I can’t remember the process for adjusting the pressure up or down by turning that nut, and also am not certain that for this issue that is the correct fix, or whether it is a part inside the machine regulating brew pressure that needs to be replaced. Does anyone know the procedure for adjusting the nut behind the drip tray? And if so, which direction lowers the brew pressure? Thanks!
JRising Team HB Posts: 5414 Joined: 7 years ago
#2: Post by JRising » Yesterday, 10:03 am
9.5 Bar to 10 Bar is n…
BoulderMike Posts: 137 Joined: 7 years ago
My LMLM has been showing an idle brew pressure of 15 to 16 for a while now. It drops to ~9.5 or 10 when I pull a shot. I know there is a nut behind the drip tray for adjustment. I can’t remember the process for adjusting the pressure up or down by turning that nut, and also am not certain that for this issue that is the correct fix, or whether it is a part inside the machine regulating brew pressure that needs to be replaced. Does anyone know the procedure for adjusting the nut behind the drip tray? And if so, which direction lowers the brew pressure? Thanks!
JRising Team HB Posts: 5414 Joined: 7 years ago
#2: Post by JRising » Yesterday, 10:03 am
9.5 Bar to 10 Bar is not unreasonable. But if you want to lower it you would turn the "nut" (Bypass valve adjustment) countercloskwise (lefty-loosey).
BoulderMike (original poster) Posts: 137 Joined: 7 years ago
#3: Post by BoulderMike (original poster) » Yesterday, 10:08 am
Is it then normal for the idle pressure to be as high as mine is? If so, I should be good for now then. Maybe I might adjust it down to 9.
HB Admin Posts: 22597 Joined: 21 years ago
#4: Post by HB » Yesterday, 11:19 am
To clarify, there’s the brew pressure adjusted on the rotary pump itself. Then there’s the expansion valve; it allows a few drops to escape when water heats in a closed system to avoid over-pressurizing it. For a vibratory pump, the expansion value does double-duty, regulating the maximum brew pressure and expansion pressure. In your case, it only has to control expansion pressure and setting it to 12 bar is perfectly fine.
Dan Kehn
JRising Team HB Posts: 5414 Joined: 7 years ago
#5: Post by JRising » Yesterday, 12:20 pm
BoulderMike wrote:Is it then normal for the idle pressure to be as high as mine is? If so, I should be good for now then. Maybe I might adjust it down to 9.
It is higher than machines with their expansion valves set to 12 Bar, but it is not unreasonably high... Why, did it previously idle noticeably lower and it has suddenly started idling this high? If so, you could keep an eye on it or even clean the expansion valve, then if it keeps happening.
I’m not certain if the brew valve is reading before the brew circuit’s check valve, but if so, it’s possible the check valve now leaks internally so the brew-boiler pressure is visible now and wasn’t before... If this is so, you’ll want to clean and descale the check valve just to make sure that the brew boiler’s hot water isn’t getting far enough back to damage the pump and other things that aren’t supposed to get hot water.
BoulderMike (original poster) Posts: 137 Joined: 7 years ago
#6: Post by BoulderMike (original poster) » Yesterday, 1:32 pm
Thanks! I went ahead and schedules a service call with my local LM authorized service company. Seems like a good idea for peace of mind to have it looked at anyway.
joiglan Posts: 74 Joined: 6 years ago
#7: Post by joiglan » 11 minutes ago
When its idle, it’s not showing you brew pressure (as in pump) but the pressure in the boiler from heating pulses making expansion, the valve to the drip tray is what controls that set point and it should be set to 12 bar max. It will let a droplet of water out when the boiler pressure goes to exceed it.