Buffer Tank Bypass

van_2

The setup is a buffer tank on a condensing boiler. The boiler heats the buffer tank and all heat emitters (radiant floor and flat panel rads) pull their water from the buffer tank. The buffer tank prevents short cycling but when the return water from the emintters is cool and the boiler is firing, it would seem to make more sense to return the cooler water from the heat emitters to the boiler rather than having it pull the warmer water from the buffer tank. This would in theory promote more condensing in the boiler raising the efficiency. Has anyone done anything like this?

I was thinking of a three way valve that directs the return water either into the buffer tank or the boiler. A zone valve in the normal buffer tank return to the boiler would close when the three way was returning directly to the boiler. These valves would be controlled by sensors based on temp of return water and whether or not the boiler is firing.

Any ideas?

Uni R_2

Buffer Tank Return Bypass?

You are talking very marginal gains. Once you factor in any power consumption for the valve, the gains from a slightly lower return temp might be overshadowed.