Direct-fired heat sources within
a closed heating system shall have a low-water fuel cut-off
device, except as specified in Section 1214.3. Where a low-water
control is integral with the heat source as part of the
appliance's integrated control, and is listed for such use, a
separate low-water control shall not be required. An external
cut-off device shall be installed in accordance with the heat-source
manufacturer's installation instructions. No valve shall
be located between the external low-water fuel cut-off and
the heat-source unit. Where a pumped condensate return is
installed, a second low-water cut-off shall be provided.