Temp Control Problems

Yesterday I brewed a British Dark Mild. I normally just fly sparge with 170* water, but my temp always drops to the low 140's as I sparge. So I tried a mash out with near boiling water. I was able to bring the temp up to about 165 then I fly sparged with 170* water thinking it would stay more or less close to 170. But again the temp slowly dropped to around 145* as I slowly fly sparged.

1. What are the affects of this?

2 How can I keep the temp from dropping so much?

With fly sparging this can be a problem.

#1. It is best to engineer a way to keep a lid on the mash while fly sparging.
#2. A mashout is great, if you get the bed up to 165F or so, then sparge with 170F water, it will go a long way to keep the temp in th 160s
#3. Use water that is about 175-180F... by the time it gets to your fly sparge equipment and to the grain bed, it will be much cooler than that.

By keeping a lid on my MLT during the fly sparge, mashing out to 166F and using 173F water to sparge with, I keep my grain bed about 165F duirng the 40 minute process.

Cold sparges can reduce eff. but this has been debated, it shouldnt reduce it by much at all.

In a practical sense, for our scale, I don't think it actually matters. But you will get a few more points in efficiency at higher temps though.

+1 to what the pol posted. If your loosing temperature you need to engineer ways to insulate your MLT and sparge water.
I really don't have everthing dialed in so well that I can see an impact on my efficiency, but I have seen more gummy mashes and slower draining. My short term answer is to batch sparge and have the water very hot and add cooler water if ever needed to keep the grain bed below my target of 167F, which has been maybe twice.