These rules for hot water boilers shall apply to all hot water heating and hot
water supply boilers to be designed for pressures not exceeding 160 psi and
temperatures not exceeding 250 degrees Fahrenheit.
(2) For conditions exceeding those specified
above, the rules for power boilers shall apply.
Except as provided in R 408.4253(4), the
following classifications are considered not to be within the jurisdiction of
this part of these rules: hot water supply boilers which are directly fired
with oil, gas, or electricity when none of the following limitations is
(a) A heat input of 200,000 Btu per
(b) A water temperature of
200 degrees Fahrenheit.
nominal water-containing capacity of 120 gallons.
All hot water supply boilers, including
those exempted in R 408.4253(3) shall be equipped with safety devices of proper
type and size as specified in
and be of code construction.
(5) For conditions exceeding those specified
in subrule (1), cast-iron construction is not permitted.