brewbeemer,
I am not by design making this more complicated - I thought it would be easier. I guess I could heat the strike in my mlt and then use my hlt for the sparge water -- I have a three keggle system and was just trying to use one flame to heat etc. make sense or am I crazy?
Hell yeah your crazy, the world would be boring with everyone being normal.
No worries I now see the position your in and why you started this thread.
I would make sure the MLT was insulated the best you can not a 1/8" covering but a full scale assault against the MLT's heat loss top and bottom ends included. Like I replied before it would be a good idea to keep notes on the different air temps and the MLT before adding your 170 or 175*F HLT water then checking the temp in the MLT after 6-8 minutes. That should be long enough for the keg to warm up and water temp both stabilized.
A 50 degree brew day might reqiure 178*F to reach your strike temp vs 171*F on a 90 degree brew day. Just examples not proven correction numbers. This will be something you will have to do to make a correction chart for your system. I would guess 3 different temp days like 50, 70 and 90*F air temps would be close enough unless you want 5 different temp corrections on your chart. This for 50, 60, 70, 80, and 90*F air temp day.
If your brewing in a windy day that's another factor to add in.
If your brewing below this 50*F or above the 90*F then yes i'll call ya crazy. J/K. All the above are just examples not real or proven numbers. Remember a 10 gallon brew batch will hold the MLT temp better than a 5 gallon batch due to mass alone.
Time to do some testing and note taking. JMO's here.