How can I handle excessive pressure in a water heat circuit?

Question

I am playing with radiant heating in my garage.  I want to put copper coil wrapped around the flue pipe, 5 feet out a SharkBite connector from copper to pex and the same for the cold water intake back to the coil on the stove.
Water expands when this gets hot, so I need a relief or discharge but can't find online what I should do for this.  Is there a like a pressure valve I could get at like home depot that discharges the hot water if there is too much pressure?
This is really just learning and playing around in an open garage.  I don't need to follow all the standards I just want to see how efficient it is...
any ideas would be appriciated.
thanks

Ecnerwal · Accepted Answer

You need an expansion tank on a closed-circuit hydronic loop. You'll also need air vents for removing the dissolved air when it comes out of solution as the water (or antifreeze) heats. These are commonly deployed on the bottom and top of an "air scoop" which is a standard hydronic heating component.
You ALSO need a pressure and temperature relief valve, but you don't want that venting on a regular basis - the expansion tank should deal with normal variation. The relief valve is for when things go wrong.

How can I handle excessive pressure in a water heat circuit?

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