Boiler Control

Kressler

Have a W-M Gold CGa6 boiler with two heating zone circulating pumps (on the supply side to each zone) controlled by room tstats.  I'd like to add a bypass to prevent condensation because the boiler return water doesn't always heat up to 130 degrees before the tstats turn off the circulators and, in turn, the boiler.  CGa manual has a sketch and instructions on how install the bypass.  Simple enough but I'd also like to add an outdoor reset controller.  W-M manual warns not to apply their sketch if using an outdoor reset controller and to contact the local W-M rep for suggested piping and control methods.  Unfortunately, local W-M rep wasn't any help.  Any recommended piping and control schemes on how to utilize outdoor reset while at the same time preventing boiler condensation?

SWEI

A motorized mixing valve

can do both.   http://www.taco-hvac.com/track_file.html?file_to_download_id=17513 shows several piping variations.  Heat-Timer, Tekmar, and others offer solutions as well.



When you implement ODR control, it's best to set your thermostats a couple of degrees above the desired room temperature and leave them there as high limit controls.  Adjust the ODR parameters until you get a stable room temp.  Be patient -- it can take some time to perfect.