Borrowed from another thread - Seems to make sense to me why CB and many others are doing this now to avoid early failures within the fireboxes.
If you run your stove at 150-160 and you pull off 20-30 degrees at times, your return water comes back to cold and it really impacts the life of the boiler, because, moisture from burning wood will gather on steel cooler than 140. If u have a spot on your stove where the return water is cooling the steel down to below 140, moisture will develop there, and run down into the ashes
Its not recommended for anyone to run less than 175
It's scientific fact that moisture will gather on steel that's cooler than 136 degrees, some links from the candaian govt I beleive about to never slow your boiler to see temps that low..
So if you have return water coming back at 110-120 or whatever where that water encounters the firebox it makes a cool spot where moisture can gather and thus corrosion can occur over the long haul.
Central and Empyre aren't making folks install boiler protection because they want to, it's because it's very important, they don't want to have to add cost to there products but by doing so, there protecting the boiler from future claims and replacments.