[cknuth]

Sharing my experience and a question, relevant to this thread. I too have had good space and radiant heating running diesel or electric, but lukewarm DHW. Decided to pull the burner to get at the mixing valve. No problem with the burner. The valve was too tight initially to move by finger strength, but a little careful rocking with a pliers got it moving. I worked it both ways numerous times and was surprised to see that the eventual full range of motion was less than 360-degrees. The knob on the valve did not have any of the markings shown on photos I've seen; I set it to fully counterclockwise (hottest.) With everything reassembled, the boiler fired and heated up to 220F indicated (that's another story.) Temperature at the tap is now over 100F, a big improvement. Nonetheless, I would expect either 120F or 160F, depending on which cartridge is in the valve. So that's the lead-in to my questions: Should I still replace the valve guts? And should I use the lower (100-130) or higher (120-160) temp range?