I have a Maxim pellet boiler connected to a forced-air furnace and a sidearm and no storage (I figure I don't need it for a pellet boiler). The boiler is easily able to keep up with the load presented by the water to air hx and the sidearm - I have it set to 180f, and the lowest I've seen it go is about 165f coming off a long idle (fire almost out). Once it clicks to the highest burn mode, it is able to gain temperature even under full load. My question is this: Using my infrared thermometer on the pex (not the best method ... but it's what I have), I believe that my return water temperature may be a bit below the 140f that I've read is a 'safe' temp. Do I need to be concerned, even though the temperature readout on the boiler shows that water temp in the boiler is never actually dipping that low? Will the low temperature water returning to the boiler cause problems before it has a chance to mix with the hot water in the boiler's tank? I could put a bigger circ pump in, but I've got a taco 007-f5 pushing water through about ~100ft equivalent length of 1" pex (not including the hx, for which I have not calculated the equivalent length), and from the information in Taco's sizing guide, I believe that I should be OK.