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Honeywell aquastat on Peerless tankless system, heat and h/w. Settings (high/low/diff) at 200/170/20. It is my understanding that at 170 and 20 diff, boiler should fire at 160 and will heat water to 180. The problem that we are having is when domestic hot water is run, the boiler temp is dropping to 130s before the boiler fires. It should fire at 160. The capillary thermo is fully inserted to the well stop. This is a new aquastat. Any ideas on why the aqaustat is not firing at 160?