Originally Posted by Monster Mash
Your second addition of water should be 170 degrees, that is your mashout.
If your sparge water is 170, your grain bed will never hit 170. I use water about 190F for batch sparging, which gets me close to a 170 grain bed. But for a true mashout, you need to hold the 170+ temp for at least 20 min. Most homebrewers don't do that, and for batch sparging a mashout it really unnecessary.