Flashback

Mostly because of "Pumping Away", I pipe all my boilers basically that way. I just like the idea of being able to purge the entire system from one point, and to eliminate a lot of extra purge valves.
Rick

I believe that diagram was from the seminar that we first met Dan Holohan, I'm guessing it was around 1990? As a matter of fact we immediately started piping residential cast iron water boilers with this method following that seminar, thank you Dan!

The downside, is that we also learned that we could install a little less hwbb on new homes and conversion jobs (electric or hot air to hwbb) and simply raise the temperature of the boiler water to say 190 or 200 degrees. It worked well, but there were some downsides. Fast forward twenty five years, in our home for example, we replaced cast iron boiler with a more efficient condensing model. In order to take full advantage of the "condensing mode," we needed to increase the heat emitter output in some areas of the house to take advantage of the lower operating water temperatures.