This is my ongoing basement project:
It is a 3o year old Utica boiler, 80k BTU output. We have been messing around with it over the years but the latest experiment was a Hydronic heat scavenging system.
It utilizes 1 zone circulator and 1 digital timing 24v relay per heating zone. We can set the digital timing relay to literally any amount of time using the 3 switches on the relay, the circulators will then run purging any USABLE heat left in the pipes into the living space.
We set each relay for between 10-20 minutes, these relays are wired to start timing down when the thermostat satisfies and the boiler shuts off.
We are getting at least 2 more degrees off free heat from this system...not to mention the fun we had playing around with the idea.
this is just one way to maximize your heating doller with an old system like this...also since we installed this sytem, my supply and return delta T's are nearly equalized, so now I can add more register to the additions of the house without addding a new boiler or increasing BTU output.
THere are a few quirks however: because I took out the zone valves, 1 circulator will induce flow in the other zone wich tends to over heat that part of the house... its a work in progress and fun to play around with!