Section 408.4278. Relief valves.

(1) Each hot water heater boiler shall have at least 1 officially rated pressure relief valve set to relieve at or below the maximum allowable working pressure of the boiler.

(2)   Each hot water supply boiler shall have at least 1 officially rated safety relief valve or at least 1 officially rated pressure-temperature relief valve of the automatic- reseating type set to relieve at  or  below the maximum allowable working pressure of the boiler.

(3)   When more than 1 relief valve is used on either hot water heating or hot water supply  boilers,  the  additional   valve  or  valves   shall  be officially rated and may be set within a range not to exceed  6  psi   above the maximum allowable working pressure of the boiler up to and including 60 psi and 10% for those having a maximum allowable  working   pressure exceeding 60 psi.

(4)   Relief valves shall be spring loaded  without  disk  guides   on  the pressure side of the valve.

(5)   Relief valves shall be so arranged that they cannot be reset to relieve at a higher pressure than the maximum permitted by this rule.

History: 1979 AC.