RayPac P-1571 Pool Heater sensor location

JUGHNE

Pool heater installed 2002, I was called for no fire because of water flow switch failure. The return pump ran constantly because relay probably stuck. No water in pool yet. Jumper flow switch & pilot will light.

The question is the location of the pool temp sensor, it is in the inlet of boiler 3" cu pipe. Book seems to indicate it should be on the main system loop (6"piping). You can see the 180 setting for it on the bottom t-stat, obviously it will never open. The center t-stat is set at 130, probe is in the discharge of header. The hi limit (manual reset) probe is also in the discharge header, and has never opened (according to pool personal) at it's 200 setting.

The pool temp sensor seemed to be located where it is because that is the length of the cap tube that is stretched to it's limit. It seems obvious to relocate it to the main loop return 6" piping.

This has been typically run at 10 TD. 85 in and 95 out. Book calls for 105 min inlet........so after perhaps 14 years of this setting what is the chances of liming of the copper tubes?? The refractory looks good.....the SS burner bottoms look very clean. No scorching of cabinet.

Thanks to any pool pros.