I too have heard that the HEX out is a more reliable indicator of the mash temp, although I personally have no evidence to support it.
I don't see the need for two PID's or temperature probes. Can someone please enlighten me? This is the way I see it...
For strike water:
connect water out to pump, pump out to HEX in, HEX out to water in. Input SP, prime pump, turn on pump, turn on element. This will give you the "Real" temp of the strike water, and the PID will control it's temp until it reaches SP. Then transfer desired volume, turn off element, turn off pump, mash in.
For mash temp:
Change SP, put MT out to pump in, pump out to HEX in, HEX out to MT return. Turn on pump, turn on element.
This allows you to use the same location and one PID to control both strike and mash temp. For mash out/sparge, you can just change SP, stop when it reaches it, and reconfigure to the "Strike" set up (this will also clean the coil now that hot water is rinsing it). Now SP can be changed to sparge temp, and repeat.
For the boil, couldn't you just use an element hooked up to a switch and pot? reduce pots resistance until boil is reached then reduce.
Am I missing something? Or will this produce less than favourable results?
Thanks, and sorry for the thread jack... this 2 PID just seems unecessarily complicated