schiarelli Senior Member Joined: 8 Oct 2013 Posts: 28 Location: New York, NY Expertise: I love coffee
Posted Fri Oct 11, 2013, 11:14am Subject: Re: Can I have your opinion on this sale?
Ok guys, just to clarify, I went home last night and removed my shower head to clean everything up. The gasket is there. I played around with different grinder settings and tamping pressures and finally was able to pull successful shots. But I am running at 12 psi, I think I need to adjust the OPV.
Posted Fri Oct 11, 2013, 1:29pm Subject: Re: Can I have your opinion on this sale?
The OPV is easy to reach with the top cover off. 10mm wrench. Try adjusting to 10-10.5 with a blind basket. .... but you may find the valve body will leak as the seal backs out of the body. I (and many others) had to cut the spring to get it in the good range. I have read of others compressing the spring and someone bored the spring seat deeper (not the valve seat!) .....hope you are handy with such tasks.
Posted Fri Oct 11, 2013, 1:52pm Subject: Re: Can I have your opinion on this sale?
You can adjust down until you reach the point it starts to drip, then tighten until it just stops (this leak is on the low pressure side of the valve, not the brew pressure side) This should at least get below 11 bar. It's been so long since I did this (within the first week of getting the machine) I don't recall specifics...
Very little shortening of the spring is required; Set the OPV to your brew pressure. Now measure how far you need to tighten the OPV to stop the dripping. ....now get out your caliper and measure. Also, be sure you do the calibration with the boiler hot as the OPV is on the hot side (...yes, I know )
A quick search of 'Isomac Venus' here and on HB will turn up some pictures and details.
PLEASE unplug the machine anytime you are wrenching under the hood. this is so important for safety!
Posted Fri Oct 11, 2013, 2:28pm Subject: Re: Can I have your opinion on this sale?
Sorry there are so many machines that brew pressure is set too high. Year after year they continue to roll off the assembly line.
The Over Pressure Valve is really required only as a safety devise to release boiler expansion pressure should it climb to dangerous explosive levels. ( Many machines the OPV never opens during normal brewing.) In this case brew pressure is determined only by the 'pressure/volume' curve of the pump; ristretto will be higher pressure, lungo will be lower.
Somewhere along the way, many years ago, coffeegeeks figured out you can also use the OPV to regulate proper brew pressure.
You can just leave it alone and try to brew at 12 bar.... I think that is a waste of time, taste and coffee myself. (edit; actually, if your meter is at 12, brew pressure is closer to 11-11.5 bar; still too high.)
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