Fuel Safety Bulletin 2002-02a
The use of hot water heaters, in lieu of boilers, for space heating purposes, is not recommended. The final decision to accept a hot water heater for service in a radiant floor heating system is left with the design professional responsible for the radiant floor heating project.
Dual purpose water heaters certified and marked "Suitable for Water(Potable) and Space Heating" may be used for:
- combination potable water and space heating applications
- potable hot water applications
- space heating applications
The certification and installation of these units requires that:
- All piping and components, including the space heating components, connected to the water heater shall be suitable for use with potable water;
- Toxic chemicals, such as those used for boiler treatment, shall not be introduced into the potable water used for space heating;
- A water heater which will be used to supply potable water shall not be connected to any heating system or component(s) previously used with a non-potable water heating appliance; and
- When the system requires water for space heating at temperatures higher than required for other uses, a means such as a mixing valve shall be installed to temper the water in order to reduce scald hazard potential.
No modifications can be made to the temperature and pressure relief valve(s), gas controls or other operating components of the certified heater.