After four brews on the new system I guess I can call it done. Well done would be harsh because are they ever really done. My thanks to all who helped, posted, and inspired. This forum is by far the number one source for brewing knowledge. Here's a description of my brewing process.
My typical brew day starts by flipping the water fill switch on the control panel. This opens solenoid valve sending water though the carbon filter and check valve filling the HLT from the bottom until the float valve at the top shuts it off automatically. The valves are then opened to fill the lines and prime the pump, and the strike water is pumped from the HLT to the Mash Tun. My custom built 5500 watt 240 volt immersion heater is put into the Mash Tun and the valves are opened so when the pump is turned on, the strike water will circulate bypassing the heat exchanger.
The two heating elements, controlled via separate process temp controllers, are set accordingly. The MLT controller is set for the strike temp somewhere around 161°F, while the HLT is set for my mash temp about 150°F. The strike water is recirculated to heat evenly and because the RDT (temp sensor) is in the plumbing on the discharge of the MLT.
The HLT has two RDT’s, one in the HLT itself (attached in the tee for the sight glass), the other in the plumbing on the discharge of the heat exchanger. During the pre heating process, the RDT in the HLT is used, later when I start to recirculate the wort; I switch to the RDT on the heat exchanger discharge. This way, my wort temp should never go over setpoint. There is also a stirrer in the HLT which keeps the temp homogonous and achieves better heat transfer through the heat exchanger.
When the temp setpoints are achieved, the pump is shut down, the immersion heater is turned off and transferred to the boil kettle, and the grain is added to the MLT. After a few minutes the pump is switched back on and the wort is recirculated through the heat exchanger. At this point the immersion heater is not being used but its process controller is reading the wort temp leaving the bottom of the MLT. The HLT process controller is reading the wort temp entering the MLT. When these two temps are the same I know the entire mash is at setpoint. After the conversion is complete the HLT controller is increased to 169°F for mash out. It takes about 20 minutes or so for the wort leaving the MLT to reach 169.
To sparge, the MLT valve is closed and the HLT valve is opened, and the valve draining the wort into the boil kettle is used to adjust the flow rate. The pump switch is set to “sparge” which pumps water from the HLT to the top of the MLT based on the position of a float switch on top of the grain bed.
After all the wort is collected, the immersion heater process controller is put in manual mode. I run it at 100% until a boil is achieved, then back it off to around 60% or so to maintain a nice rolling boil. While the wort is boiling, I set the HLT to 160°, empty the grain from the MLT, and recirculate a few gallons of powdered brewery wash. When the boil is complete, the immersion heater is removed and a sanitized immersion chiller put in its place.