Thermal Diverter Valve?

[kgallego]

Hello folks. I'm trying find a solution to the problem I have drawn below. I have a simple DIY radiant heating system in a barn that is plumbed into both an electric hot water heater and a wood stove boiler. The wood stove boiler only runs part of the time and the water temperature goes up to 175°F. When the wood stove is not running, the hot water heater keeps the water at about 100°. Currently it is plumbed straight through the hot water heater. The issue that I'm having is that when the wood stove boiler heats the water up past 140°, a safety internal switch shuts down the hot water heater and it does not come back on when the water cools back down. It then has to be manually reset. I would like to put a bypass in so that when the temperature of the water goes above approximately 130°, the water is diverted and does not go through the hot water heater. Additionally, whatever valve I need to do this has to have very little head pressure loss through it, as the system is just about at it's limits for the pump capacity. I would appreciate any direction on what kind of valve I need to achieve this. Note: the system is all 3/4" copper.

Thanks to anyone and everyone!

 

[Twowaxhack]

When you fire the wood stove up you couldn’t just manually turn a couple ball valves off to direct your flow ?

 

[kgallego]

When you fire the wood stove up you couldn’t just manually turn a couple ball valves off to direct your flow ?

No, it needs to be automated for a couple reasons.

 

[Twowaxhack]

Use heating zone valves to direct your flow. Wire a transformer and thermostat to control it.

You’ll need a thermal expansion tank for the water heater and make sure you have temp and pressure relief valves are in working order

But I dont do heat Maybe someone who does hydronic heat systems will give solid advice.

 

[kgallego]

Use heating zone valves to direct your flow. Wire a transformer and thermostat to control it.

You’ll need a thermal expansion tank for the water heater and make sure you have temp and pressure relief valves are in working order

But I dont do heat ✌ Maybe someone who does hydronic heat systems will give solid advice.

Thank you! That's kind of what I was thinking as well but I've never done anything like that before. Do you happen to have any links to an example valve, transformer, and thermostat that I would need?

There's a thermal expansion tank, radiators, pressure relief valve, and heat exchanger in the system that I didn't draw in for simplicity purposes. Thanks again for your help!