Personally, I heat my sparge water to 170*F, has always worked for me. Also, I use just under .5 gallon of water per 1lb of grain. So, if I'm using 10lbs of grains, I'll sparge with 5 gallons of 170* water.
I also batch sparge.
Drain as much as you can from your mash goop after vorlaufing. Once you run dry, close the valve on your mash tun, add your 170* water & stir vigorously. Wait about 10 minutes, drain all THAT water out (or whatever preboil volume you're looking for)
Again, personally, for my 5 gallon batches, I try to start with 7 gallons pre boil, cause I routinely boil off almost 2 gallons over 1 hour.
Good Luck!!