37train5k wrote:OK, interesting. Thanks for the reply. Can someone check my logic here, then? Doesn't the valve determining reservoir or plumbed only determine where the pump's suction comes from?

I turned my valve to "main water" and tried it and the temp still rose and water still came out. if my machine is built the same way yours is, then am I safe to assume the preinfusion water always comes from the preheater and the lack of cool water coming from a main source is the culprit in the rising temperature since it is not cooling the preheated water?

If I go mid position while plumbed in (regulator set to about 2 bar) more water comes out (compared to when plumbed source shut off) and the PID display stays put. My guess is that when there is no active source to the pump, steam boiler water/steam is getting to the brew boiler temp sensor through expansion, which explains the drop in pressure seen on the steam boiler gauge.

BTW, I've experimented with the mid position for additional puck wetting, but have settled with going full on and only using the built in pre-infusion function of the E61. Maybe that's why I never noticed this phenomenon.

Jeepin' Geo wrote:BTW, I've experimented with the mid position for additional puck wetting, but have settled with going full on and only using the built in pre-infusion function of the E61. Maybe that's why I never noticed this phenomenon.

Yes that's exactly how it's designed to work. I looked at the Video again and with the sound turned on, then I realised what he is doing.

The middle position of the E61 is not designed for preinfusion, if it does this it's purely an accident and ideally the brew switch should be wound out a little. If the machine is not plumbed, the dribbles out VERY slowly. The pressure within the HX system forces it out and no cool water enters the HX, this means a very small amount of 125C water enters the brew boiler near the thermal sensor.

The design of the device in HX preheat system to prevent overheating absolutely cannot function correctly in this situation, in fact no preheat system could. When plumbed into the mains you are getting 2 bar pressure and an equal volume of cold water entering the HX. This allows the system I designed to function perfectly. In fact again a normal small preheat HX still wouldn't function normally, but the Duetto one just about will under passive mains pressure if it's high enough.

You really should use the machine as Jeepin Geo does, that is how it's designed to be used and how it gives the best results. It's one of the reasons I added the the Preheat HX off function to the Vesuvius design (even with the steam boiler running). This is because that steam boiler can run at 130C and if set to a 2 bar preinfusions the flow rate on a LONG (up to 99s max) preinfusion is quite low...and there could be brew boiler overheating.

Panic over, your machine is working normally...the operator is not.