So, once I get my grouphead thermometer is that an adequate way of measuring the boiler temp (i.e., indirectly) or do I need to do the operation you suggested with the multimeter?

The group head thermometer will only measure the brew water temperature, which is not really reflective of the boiler temperature. In an HX, boiler water is not used to make the coffee. The brew water path is from the reservoir, through a tube inside the boiler and out to the group. On the way through the tube, the superheated water heats the brewing water, but not up to the temperature of the boiler. BTW, the thermometer is an indispensable accessory for your Stella. I can think of only two things for you to do. The first is to measure the actual boiler temperature and the second is to replace the pressure gauge and hope that the new one is right (and the old one was out of spec). Getting the case off is easy on the Stella; so measuring the boiler temperature should not be an onerous process. I've never tried it, as I have a multimeter with a thermocouple, but maybe you could use a BBQ thermometer if you have one.

I got the grouphead thermometer yesterday. When I turn the machine on and let it warm up, the thermometer stays at around 105 C. After flushing for 20 seconds it goes down to around 100. I have to flush for longer to get in brewing range of 90-94. Is it running too hot? Is it easy to turn down? Thanks for any input. John

John, That's the nature of a dragon HX. Mine took a good 20-seconds to get to around 95C. Rule of thumb, the temperature of the brewing water will be about 3-degrees cooler than what the thermometer shows.

There are a couple of things you can do to tame a dragon. The first is to turn down the boiler temperature (in your case turn down the pressurestat). Of course, you give up some steaming ability. The other is to add a restrictor. If you do a search here on H-B, you'll find all sorts of threads discussing this.

Oversimplified explanation: The easiest way to experiment with an restrictor is to make your own. You can cut a little disk from brass shim stock and drill a tiny hole in it. Remove the top fitting from the e-61 (or on the boiler end), insert the disk and replace the fitting. The way this works is it changes the water path. If you look at your e61 plumbing, you'll see two pipes from the boiler to the e61, one high up, one lower down. That's the thermosiphon 'loop' that heats the group. It operates by having hot water come in at the top, it gets cooled by the big bell on the e61, so it returns to the boiler via the lower pipe. An e61 sitting idle will keep doing this forever, gradually getting hotter. The cooling flush purges the water from the HX loop with cooler water from the reservoir.

More oversimplified explanation: Now, back to the restrictor. When you pull a shot with your Stella, water is pulled via both tubes, some comes from the hot top part of the boiler and some from the (relatively) cooler lower part. Now, if we restrict the flow from the top tube, more (cooler) water will come via the bottom tube and the group will cool with a lesser flush. But, this is a bit of a balancing act. If the hole is too small, then the circulation in the thermosiphon will be impaired, or even stall. Also, it lengthens the time it takes for the e61 to recover for the next shot. The idea is to start small and ream out the hole a bit until you find what works on your machine. BTW, another way of doing this, found on some older high-end machines is to install a needle valve in the top thermosiphon tube. If you're good with plumbing, you could remove the stock tube, make one of these up and have a variable restrictor fairly easily, while still being able to go back to stock by putting the old tube back. I intended to do this with my Stella, but ended up going to a DB before I had the chance and motivation to get'er done. Oh, another thing about the restrictor is that it is sensitive to the boiler temperature, so if you change the pressurestat,you'll change the needed size of the hole in the restrictor.