First let me assure everyone I am not getting rid of my Harman VF3000 coal boiler. I could not be more pleased with it as it takes me into it's 10th heating season. I hope to continue using it at least another 10+ years. However it's been pointed out to me that I am not going to live forever. I was naturally disappointed to hear that but have decided to move on and make the most of my remaining time.
My wife will not deal with the coal boiler when I'm gone so I want an alternative for her that will be easy to deal with. Currently I have a cast iron Weil-McClain oil fired boiler. It's 25 years old and undersized for my home. I bought it used from a bar owner who was going out of business about 20 years ago. When I bought it, it was adequate for my home but since then I have made 3 additions to my home and it's undersized now. I don't want to stick with oil for several reasons. An oil boiler requires cleaning and servicing annually. Oil is too subject to world energy demand. I can get rid of the tank from my basement.
I've already got a 1,000 gallon underground propane tank and black iron pipe roughed-in to my basement. I want to plan this so that I don't install it and then later say, "why didn't I do such and such." There is a wealth of knowledge on this forum and I want to take full advantage of it.
Here are some things that I know I want to incorporate into the system. Please add (or subtract) anything else you think would be an advantage.
The zone pumps would pump away off of the supply side of the boiler
All circulators will have shut offs on both sides of the flanges for easy replacement
Air purger with shut off on the air vent device for easy replacement
Diaphragm type expansion tank with shut off for easy replacement
Backflow preventer on supply from domestic water
Low water cut off
Thanks in advance for all of your input.