Near the 6mm ALLEN bolt 'on the front of the group' the temperature will be about 20°F lower than the group idle temperature. You should see the temperature rise by a degree or two during a shot, then drop slowly back to the idle temp.

On a double shot, 30 sec = 60ml. With no pressure, 30 sec = 225ml ~4 shots.
Rough calcs show that Anita should be able to handle 60ml + 20ml clean flush every couple of minutes with ease, probably closer to every minute.

If the Hx on Anita is about 100 ml. then there is room in there for just about two shots if you don't have to flush at all on consecutive shots. If you want to pull several consecutive shots for guests and 1.5 minutes isn't enough time to recover then I ask if there is a way using the grouphead thermometer to determine when is a good time to pull the next shot without flushing?

Geoffrey -

It gets pretty complicated if you think about hx volume and shot volume in the same sentence because, while true that the hx volume is ~ 100 ml, there is also the tubing and small volume of water circulating in the grouphead.

Let me assume your Anita would follow the graph I posted earlier. That graph depicts a long flush of Anita which, by itself, reduces the grouphead temperature ~ 12 F. The remaining drop and inherent increase is all on the shoulders of the thermosyphon system. If you did absolutely nothing over the next 15-20 minutes, the system would restore itself to the point at which you started - 212 F. It would be very similar, if not identical, to the time required for this same temperature change during initial machine warmup.

Initiating your first shot at 197-198 F after the initial long flush (> 2 minutes) would give you a nice shot. Doing a short screen flush after the shot allows for the next shot about 2-1/2 minutes after you started the first shot. This 2nd shot would also be initiated at a grouphead temp of 197-198 F. Depending upon the number of guests I was preparing drinks for, I would opt for preparing the baskets ahead of time.

Have you tried simply letting the machine heat, then open the steam wand for 10 seconds? Does the boiler pressure go flat very fast? Being a used machine it could be heavy boiler scale (the mushroom indicates heat exchanger scale) or a sticky vacuum breaker so the machine builds false pressure.

Thanks Eric - that makes a lot of sense and fits my observations how my machine responds.

It does seem then that one could pull shots consecutively at a leisurely pace by carefully washing the screen and basket and monitoring the grouphead temperature initiating the shot at the same point each time. Now I just need enough friends to try the theory out

That's why Greg invented the ThermoFilter : Those with Few Friends

Alright, had a go at some measurements again last night. I had one thermocouple on the Allen bolt (Group Temp or GT), and another in the portafilter drain (Brew Temp or BT). Also watched the Boiler Pressure (BP) carefully during each pull. After sufficient warm up (cover off, single portafilter in place) the GT was cycling between 186-178F (seemed inline with Ian's statement that it would read ~20F lower than the actual group idle temp). Before starting I also opened up the steam wand to see if the pressure would drop. Got lots of steam, but no drop in pressure.

With 30 second pulls, and 1.5 minute recoveries, here is what I got:

Fist Pull GT = 182 - 172F, BT = 209 - 194F, BP = 1.225bar
Second Pull GT = 174 - 165F, BT = 200 - 181F, BP = 1.2bar
Third Pull GT = 163 - 162F, BT = 190 - 173F, BP = 1.2bar
Fourth Pull GT = 156 - 150F, BT = 176 - 166F, BP = 1.2bar
Fifth Pull GT = 151 - 153F, BT = 169 - 167F, BP = 1.2bar

Boiler pressure was very stable. After letting the GT get back up to ~180F I pulled into a blind basket (~20seconds). The GT didn't change. So gas in the Thermosyphon huh?

-Nate

Nate -

You are overtaxing the machine waaaay beyond its capabilities. A 30 second "pull" with essentially no restriction flows one heck of a lot more water through the hx than a normal shot.

1-1/2 minutes recovery is too little even if you were actually pulling a shot.

Still not clear how much water you are pulling in 30 seconds.
If you are not pulling through coffee, then you want to limit the water to 60ml.

E-61 HX should draw about a shots worth of water through an empty portafilter in 8 seconds or so. If it takes a lot less or a lot longer there is an issue.