avalys Senior Member Joined: 16 May 2014 Posts: 1 Location: Colorado Springs, CO Expertise: I like coffee
Posted Fri May 16, 2014, 8:03am Subject: Quick Mill Anita: HX Flush at High Altitude
I just got a Quick Mill Anita. This is my first heat exchanger machine. I live at 7,000 feet in Colorado Springs, CO, and I'm having a bit of trouble correcting the advice I'm reading online regarding the HX flush volume with the reduced boiling temperature of water at this altitude: about 199-200F.
This recommends flushing about 2 ounces of water past the point where "the hissing stops", which it says happens when the group temperature is roughly 206F. This is 6F below the boiling point of water at sea level. However, since the boiling point of water at my altitude is actually 200F, I would conclude that the "hissing will stop" on my machine at around 194F, so perhaps I do not want to flush any more water past that point at all. The espresso seems to come out okay doing that, but this is my first decent espresso machine (last was a single-boiler Lelit that had pretty poor temperature control) so I probably don't even know what a really good shot actually tastes like and I'm sure I could be doing something better. I am using the "flush and wait" scheme, and it usually takes me about 60 seconds to grind and tamp after the flush.
Can someone tell me if I'm on the right track? I know I should probably buy a group head thermometer, but if I'm going to have to spend an additional $110 on this I'd have to think about just going straight for a PID double boiler machine.
Posted Fri May 16, 2014, 11:06am Subject: Re: Quick Mill Anita: HX Flush at High Altitude
You pose some interesting questions that have me by nature doing some thinking. You should consider that the brew temp and the grouphead temp, while somewhat related, are two different things. The hissing should stop on your machine when the water coming out is just below boiling. How hot the GH is at that point will depend on the boiler temp as well as the type of machine. My machine is a "dragon" and requires a VERY long cooling flush to get the GH temp down. I found this out a couple months ago after installing a GH thermometer, which greatly improved my shots.
At my last job I worked with gages a bit and learned that under different barometric pressures they would read off unless they were vented. They would have a small lever or just a rubber cap to pop out and the needle would adjust to zero for that pressure. If your gage is vented, which I'm going to take a guess and say it is, then 1 bar on your machine will be a lot cooler than 1 bar on mine. As 1 bar on your machine would be less absolute pressure and thus a cooler temp. If this is the case then the group head would run cooler as well, and you're right then that it will be cooler when the hissing stops, as it wasn't as hot to start with.
I would be interested to hear if people at higher altitudes adjust their boiler gages higher to compensate, it would make sense to me to do so, unless the gages are sealed and actually reading a pressure in relation to sea level.
As for installing a group head thermometer- to me it gives you the best of both worlds- I can see for myself what the grouphead temp is, which will affect the brew temp a bit, and don't have to wait for the PID to adjust the boiler temp if I want to go a little hotter or cooler for a given shot.
Some will tell you that with a bit of practice you'll find your sweet spot and have no need for the thermometer. This may well be true. For me, figuring this out at home and not knowing the nature of my "dragon", the thermometer was a big help.
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