Outdoor wood burners hot water?

I am wondering if their is a valve or something that I need to switch when using the wood burner to get the hot water from the unit. I heat otherwise with propane, we are not getting hot water like we should at all. 90 % of the time it is only for a few minutes. if someone knows if their is a valve i need to flip to switch it over between the wood vs propane please let me know and where it may be located. Thank you so much.