Hi Asher,
My brewery is fairly new and i have built mine so that I can recirculate wort from the mash tun through a coil in the hlt and back.
Now there is a few problems that I have noticed.
First up I haven't tried any stepped mashes yet so I cant help with that one, however, if I mash for 90 mins and want to increase the temp for mash out I find that when I start recirculating the wort through the hlt it seems to take a long time to go from say 66 deg to 74 deg and I have to have the temp of the HLT at 78 deg to achieve this.
I also found that I got a stuck sparge on one brew and I put this down to over recirculation.
Now, I have got 5 metres of 3/8" id copper pipe to form my herms coil and just maybe this is not long enough.
I could of course, increase the temp of my hlt but then it is too hot for sparging.
I am now forming the opinion that it is quicker to mash out by infusion rather than increasing the temp by the herms.
I have also found that with my system I tend to drop somewhere between 5 and 10 points by batch sparging, so what i am noting is that for time and efficiencies sake I am better off to mash for 90 mins then add infusion water to raise temp for mash out, then use the pump to recirculate the wort till clear, begin the run off and fly sparge the rest until i have the quantity required.
Although my tower is high, it means that i have taken full advantage of gravity for sparging and run off so that I only need the pump to recirculate the wort and to pump from the kettle to the CFWC and into the fermenter.
If I were to build another one I would consider running the wort from the mash tun through another small tank or vessel that could be heated by gas flame or by an electric element as I have seen the yanks do, and this way you could raise your mash temps a lot quicker without getting too hot in your HLT. I wold also include another pick up pipe in the mash tun so that you are not compacting the grain bed while you are recirculating.
I hope I haven't rambled on and I hope I have covered som of the info you were after.
Cheers