lowering fluid temperature from the wood boiler

LesliePercy

With a wood-fired boiler, the temperature of the water to the load will be high -- first, because it is necessary to prevent condensation in the boiler, so the temperature will be at least 140 degrees; and second, because it is not easy to control the burning so that the temperature may rise beyond this to near the boiling point. Thus the temperature of the outgoing water may be very much higher than the 120-130 degrees wanted for a low-temperature heating system. The method usually given to achieve this reduction is a mixing valve which combines the lower temperature water from the return to the overheated supply; however it does not seem to me that this would be enough. I suppose that one possibility is to install a large buffer tank before the mixing valve, but, unfortunately, we don't have room for such a tank. The problem may be particularly bad with plastic pipes. Any suggestions?

Ironman

Why do you think the mixing valve is not sufficient?

hot_rod

Is it a multi zoned system? Is the boiler sized to design load?

It is a challenge to control wood fired appliances to ever-changing heat loads. Most wood burners learn the value of a buffer tank early into their first year of burning

You want a return protection device, like a thermostatic mix valve, or pump/valve assembly. With a good protection you could crank down the boiler operating temperature.

A dump zone might be a good option also if you worry about more fire than load.

Solid_Fuel_Man

Mixing valves are used extensively for what you want to do. Not a unique situation, hot rod's suggestions are good.