traderfjp wrote:So I guess what your saying is that I shoud have a 2nd circulator between the tempering tanka nd the boiler. I have an extra circulator anyway so that is not a problem. Are you saying to install check valves for each circulator? Also, I'm planning on using keeping my boiler running but to set the high/low about 120/140. My plan is that the boiler would only kick on if the stove wasn't lit or if there tempering tank can't provide enough reserve hot water to the boiler.
I'm not saying you need the second pump, I'm saying the way you show the plumbing on your drawing it more than likely needs one. Are you going to depend on thermosiphon to move the water to the boiler?
One pump will insure the water goes through the stove coil, tank and boiler if it goes in the tank from the stove and then exits to the boiler. By having four connections from the two other devices means you will have two loops, not one. Reducing the tank connections to two means the waterflow will be the same in all three units with one pump as it is three units in one loop. With four connections, there is no way of knowing what the boiler will get out of this.