I have read with some interest some articles on brew temperature, in particular as relates to E61 group head. I have an ECM Giotto and recently installed a digital thermometer into the group head and have been trying to figure out how best to brew and steam.

My problem is that if I lower the pressure stat so I have a brew temperature of 200, I drop the pressure to the steam wand making milk steaming difficult. I have a three hole nozzle on the steam wand. Currently the brew temperature is 212 which provides adequate steam but creates a bitter espresso. As a milk drink though, the cappuccinos are good, I guess because the milk hides the flaws in the coffee.

Any thoughts? Or does one basically need a two boiler machine?

You should be using a cooling flush as a way to regulate the brew temperature, rather than the pstat.

Are you flushing before brewing?

Yes I am. Temperature of brew water starts off at around 212 and with flush drops to 210. How long a flush should it take to drop down to 200?

Long enough to bring it down to 200 °F...

IMO, use the flush to set the initial brew temperature and adjust the boiler temp to get the right amount of temp drop (perhaps 6F) throughout the remainder of the brew.

Use a low mass temperature sensor in with the coffee to accurately measure actual brew temperatures.

Your machine is a heat exchanger, and requires a cooling flush before pulling shots. A short flush is not enough, it can take many ounces to reach the proper temperature.

You need to review the HX love article, Managing the Brew Temperature of HX Espresso Machines.

Also, check out the instructions for Eric's thermometer to see how to use it effectively. Even if you have a different thermometer setup, the concepts should be the same.

http://users.rcn.com/erics/DigThermAdptr6.pdf