I have had people ask me in the past if it is possible to relocate the temperature sensors by extending the line connecting the temperature sensor to the wiring harness. My response has always been no because of support issues. But after receiving another inquiry asking if it could be extended by 75 ft. I decided to give it a try.
I measured out 75 ft. of standard telephone wire and crimped an RJ11 connector onto each end. I plugged the one end into the wiring harness and used a female to female telephone line connector to plug in the temperature sensor. I am happy to report that I was successfully able to make the temperature sensors work out to 75ft. After responding to the customer who inquired and telling him of my success, he went out and bought a 100 ft. telephone cable and a female to female connector and has reported that the controller if functioning normally.
Please note that this is outside the scope of my support, but if you would like to eliminate heating up a large section of your return plumbing, this hack seems doable.