High temp bypass

[speedbump]

I have a wood stove in my basement with stainless coils in it that circulate in parallel with my oil fired boiler, the water also goes through a 40 gallon storage tank to act as a buffer. my problem is sometimes the water temp gets upwards of 220 what I wanna do is put a hydronic modine heater in my garage and I have a spare zone on my boiler what kind of device would open the zone when water temp reaches lets say 200 degress and will close zone back at 180 would an reverse aquastat work I basically want to divert excess heat to the garage and I know a fan heater will disperse heat quickly