Steeping Volume

I brewed up an amber yesterday using 1.8 lbs of grains. I tried out my new larger BIAB bag, and steeped it in 3.8 gals of water. I still came out with a higher than estimated OG as I typically do.

Is there any real problem with steeping with large volumes of water? I did so as I didn't want to need to wait an additional 30 mins or so for the room temp water addition to reach boiling.

I don't think water volume is the reason.
Maybe you had higher boil off this time.

Well,you still had to wait for the large volume of water to come to a boil. so it doesn't matter when steeping if you steep in 2 gallons of water & sparge with 1 gallon or just dunk the bag a few times after steeping in a kettle full.
I prefer to steep in smaller quantities of water,then sparge like when I'm mashing. My efficiency,thus OG's are higher as well.

When I BIAB, I typically come out with higher efficiency, too. I just have to adjust brewing software so I can better estimate what I will end up with. If I leave it set to 75%, my numbers end up being off when I'm done.

Now that I have a 5G paint strainer bag for biab,I can stir the mash for higher efficiency. Stirring def helps loads in regard to eficiency. Mine are now going to or higher than 75% or so according to BS2. I'm still learning adjustments though...

"Well, you still had to wait for the large volume of water to come to a boil."

My top up boil water would be from the sink (filtered) unless I were heating up water in the ~1.3 gal pot I have been steeping in. So the temp would be ~80-100*, which would add a good bit of time to get to boiling. That's why I figured it was better to just steep in the full amount so I was starting at 160* instead of at 125* or so.

So there's no real difference in efficiency if steeping in 4 gals instead of 2? I certainly liked not having to dunk the grains for 30 mins!

How does additional water effect a BIAB? Say 2-3 qts/lb of grains?

A thin mash isn't as efficient,& the PH can go up,causing astringency. Use no more than 1-1.5 quarts of water per pound of grain. Since steeping is really just soaking the already converted sugars out of the grains,water volume isn't as critical as in mashing where enzymes convert starches to simple sugars that the yeast can metabolize.