Temperature of sparge water

I know there is going to be some debate on this topic, but I'm very curious on the effects of temperture of sparge water on efficiency results. I understand the initial mash and going high with temperature generally makes a less attenuable beer and going lower makes a more attenuable beer, but what effect does the sparge water temp have on that. Oh, before we go any further I use a ghetto fly sparge technique. Generally I pour my sparge water through a strainer to difuse the water somewhat and not disturb the grain bed. I keep putting water in until I have enough to reach my boil volume.

I also have a piggy back question. Whats to keep someone from just dumping most of the sparge water in initially instead of trying to maintain a 1-2 inches of water ontop of the grain bed.

The more I brew the more this hobby consumes my life.

1st question - I don't worry much about the sparge temp. Usually try to be around 175F going in. I batch sparge. Which leads to your second question. That's batch sparging.

Doesn't batch sparging require stirring and then a rest. I was talking about dumping the water in the top while draining ala fly sparge. Basically I can put a lot more than 1 qt. of water per minute (My sparge draining rate) on top of the grain bed without disturbing it. So I can get much more than 1-2 inches of water in there without disturbing the grain bed. I'm wondering if adding that much water at once would be detrimental to the process.

I have batch sparged in the past and had decent success, so I may go back to that, but I'd like to give fly sparging a go.

I guess when I read "dumping most of the sparge water in initially" I thought batch sparge. That's exactly what I do so I don't have to stir the sparge as much.

My mash tun is a converted Sanke with a false bottom and a screw in Blichkman Thermometer. I use a old manifold for fly sparging and have been increasing my sparge water temp recently because my grain bed was at about 155 deg. I am now sparging with 190 deg. water and my grain bed temp is at 165 deg. It has improved efficency from mid 70's to low 80's.
Hope this helps

I've always heard that getting a too high sparge temp could increase the risk of pulling tannins.

In my experience when I was not being careful and allowing the water line above the grain bed to exceed 1-2 inches, some times 6-10 inches, I always ended up with a stuck mash. I am not a scientist but the heavier the water level can add more weight and make the mash denser and compact and push grain into manifold slots harder and halt the flow of sparge water. Which has led to a few bad brew days for me. When I keep the 1-2 inch line I have never had a stuck mash, and I don't ever use rice hulls either.