Wetback Info

 

Note: The following information is a guide ONLY.
Consult qualified personal and follow local regulations (E.G. AS/NZS 3500.4)

Ideal Wetback installation schematic

Pumped Wetback with a coil in the cylinder
As recommended by The Smart Hot Water Company. This configuration has the best features of a modern wood-burner wetback hot water heater;
  1. Cylinder location is flexible; other end of house, above or below wood-burner, it doesn't matter.
  2. Open vented wetback loop for safety (a requirement by some authorities)
  3. Heat exchanger coil to isolate medium or mains pressure water from very low pressure wetback loop water (typically 5 metres head). Showers can have good strong pressure
  4. Pump with sensors (working with a controller) for managed control of heat transfer; for protecting the cylinder from overheating, boiling and over pressure. It becomes a controlled heat source
  5. Avoids overpressure which will lead to water discharge from the ECV and overtemperature (or extended over pressure) will open the TPR valve and cause the entire cylinder of stored hot water to be dumped from time to time

Wetback Info

Pumped Wetback with no coil in the cylinder
With the advantages of a pump control but entire hot water pressure is low;
  1. Cylinder location is flexible; other end of house, above or below wood-burner, it doesn't matter.
  2. Open vented cylinder and wetback loop for safety (a requirement by some authorities)
  3. Pump with sensors (working with a controller) for managed control of heat transfer; for protecting the cylinder from overheating and boiling. It becomes a controlled heat source
  4. Cost effective
  5. Note: low hot water pressure

Wetback Info

Thermosiphon Wetback without a coil in the cylinder
There are strict regulations on this type of installation. Consult AS/NZS3500.4 or appropriate equivalent.
Building consent might be required
  1. Cylinder must be close to wetback
  2. This is an uncontrolled heatsource
  3. There must be a gradual rise in pipes from wetback to cylinder (see regulations)
  4. Minimal cost
  5. Functions without electricity or any moving parts
  6. Note: low hot water pressure

Safety and Critical issues
  • There must always be an unrestricted pipe directly venting the wetback plumbing to the atmosphere
  • Never place a valve or tap in the open vent pipe from the wetback coil
  • Plumbing to be undertaken by a qualified plumber
  • All appropriate regulations to be complied with and finished work officially 'signed off'

Other Issues
  • Wetback heat exchangers might need approval to be fitted to some wood-burners under certain conditions.
Click here to view the New Zealand authorised list of wood-burners with wetbacks
Note: If your computers security blocks this action then open a new tab and type;
https://www.mfe.govt.nz/air/home-heating-and-authorised-wood-burners/burners
Check the box marked YES under "Water Heater"

 
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