I like playing with boiler controls…
In my house I used a Tekmar 260 boiler controller to control three zones of heat and one indirect fired water heater all with individual circulators.
I have a 20 amp contactor that I use as a safety loop, a low water cut-off and Fireomatic thermal switch over the system hold the contactor closed.
A variable speed circulator on a bypass line keeps the return water at 135 minimum.
Edited to shrink image.
[This message has been edited by Roger (edited 12-04-2005).]