What to consider
Ensure the circuit between the water jacket and the storage cylinder is open vented for safety this means that either a low pressure open vented cylinder is required or that an isolated circuit separate from the water in the cylinder is open vented and heat is supplied to the water in the cylinder by a heat exchanger coil (this option allows the cylinder to be run at mains pressure).
Wetbacks represent an efficient auxiliary method to heat water but as a primary water heating source are inefficient.
Typically a wetback connection to an enclosed wood burner has an output around 10 per cent of the solid fuel burner output.
The burner and hot water cylinder need to be in close