875—94.5 (89) Hot water heating boilers installed before July 1, 1960. Hot water heating boilers installed before July 1, 1960, shall be constructed and installed in accordance with this rule.
	 94.5(1) Safety relief valves.
	  a.   	 Each hot water heating boiler shall have at least one safety relief valve bearing the National Board “HV” stamp of the automatic-resetting type set to relieve at or below the maximum allowable working pressure of the boiler. The safety relief valve shall have pop action when tested by steam. When more than one safety relief valve is used on a hot water heating boiler, the additional valve or valves must bear the National Board “HV” stamp and may be set within a range not to exceed 6 psig above the maximum allowable working pressure of the boiler up to and including 60 psig and 5 percent for those having a maximum allowable working pressure exceeding 60 psig. Safety relief valves shall be so arranged that they cannot be reset to relieve at a higher pressure.
	  b.   	 No safety relief valve shall be smaller than ¾-inch nor larger than 4½-inch standard pipe size, except those boilers having a heat input not greater than 15,000 Btu’s per hour may be equipped with a safety relief valve of ½-inch standard pipe size bearing the National Board “HV” stamp. The inlet opening shall have an inside diameter equal to or greater than the seat diameter. In no case shall the minimum opening through any part of the valve be less than ½-inch diameter.
	 94.5(2) Temperature and pressure gage.
	  a.   	 Each hot water boiler shall have a temperature and pressure gage properly calibrated to the altitude connected to it or to its flow connection in such a manner that it cannot be shut off from the boiler except by a cock with tee or lever handle placed on the pipe near the gage. The handle of the cock shall be parallel to the pipe in which it is located when the cock is open.
	  b.   	 The scale on the dial of the temperature and pressure gage shall be graduated approximately to not less than one and one-half nor more than three times the pressure at which the safety relief valve is set. The gage shall be provided with effective stops for the indicating pointer at the zero point and at the maximum pressure point.
	  c.   	 The temperature gage shall be so located and connected that it shall be easily readable. The thermometer shall be so located that it shall at all times indicate the temperature in degrees Fahrenheit of the water in the boiler at or near the outlet.
	  d.   	 Piping or tubing for temperature and pressure gage connections shall be of nonferrous metal when smaller than 1-inch pipe size.
	 94.5(3) Temperature control.
	  a.   	 In addition to the operating control used for normal boiler operation, each individual, automatically fired hot water boiler shall have a separate high-limit, temperature-actuated combustion control that will cut off the fuel supply to prevent the temperature of the water from rising over 250° F. Separate controls may have a common connection to the boiler.
	  b.   	 In a multiple boiler installation where the operating temperature actuated control may be installed in a header or other point common to all boilers and can be isolated from any or all of the boilers, there shall be at least one high-limit, temperature-actuated combustion control mounted on each boiler.
	 94.5(4) Low-water fuel cutoff.
	  a.   	 Each automatically fired hot water heating boiler installed after July 1, 1977, shall have an automatic low-water fuel cutoff which has been designed for hot water service, and it shall be so located as to automatically cut off the fuel supply when the surface of the water falls to the level established.
	  b.   	 As there is no normal waterline to be maintained in a hot water heating boiler, any location of the low-water fuel cutoff above the lowest safe permissible water level established by the boiler manufacturer is satisfactory.
	  c.   	 A coil-type boiler or a watertube boiler installed after July 1, 1977, and requiring forced circulation to prevent overheating of the coils or tubes shall have a flow-sensing device installed in the outlet piping in lieu of the low-water fuel cutoff to automatically cut off the fuel supply when the circulating flow is interrupted.
	 94.5(5) Stop valves.
	  a.   	 On single hot water heating boilers, stop valves shall be located at an accessible point in the supply and return pipe connections as near the boiler nozzle as is convenient and practicable to permit draining the boiler without emptying the system.
	  b.   	 Where two or more boilers are connected in a common system, a stop valve shall be used in each boiler’s supply and return pipe connection.
	 94.5(6) Provisions for thermal expansion in hot water heating system.
	  a.   	 All hot water heating systems incorporating hot water tanks or fluid relief columns shall be so installed as to prevent freezing under normal operating conditions.
	  b.   	 Systems with open expansion tanks require an indoor overflow from the upper portion of the expansion tank in addition to an open vent. The indoor overflow is to be carried within the building to a suitable plumbing fixture or to the basement.
	  c.   	 An expansion tank adequate for the volume and capacity of the system shall be installed. If the system is designed for a working pressure of 30 psi or less, the tank shall be suitably designed for a minimum hydrostatic test pressure of 75 psi. Expansion tanks for systems designed to operate above 30 psi shall be constructed in accordance with ASME Code, Section VIII, Division I, in effect when installed. Provisions shall be made for draining the tank without emptying the system, except for prepressurized tanks.
	  d.   	 The expansion tank capacities for gravity hot water heating systems shall be as follows:

Sq. Ft. of Installed Equivalent	Tank Capacity	
Direct Radiation	Gallons	
Up to 350	18	
Up to 450	21	
Up to 650	24	
Up to 900	30	
Up to 1100	35	
Up to 1400	40	
Up to 1600	2-30	
Up to 1800	2-30	
Up to 2000	2-35	
Up to 2400	2-40	
2400 and up	1 additional gallon per 33 square feet of
additional equivalent direction radiation	
	  e.   	 The expansion tank capacities for forced hot water heating systems shall be based on an average operating water temperature of 195°F, a fill pressure of 12 psig, and a maximum operating pressure of 30 psig as follows:

System Volume,	Tank Capacity,	
Gallons	Gallons	
100	15	
200	30	
300	45	
400	60	
500	75	
1,000	150	
2,000	300	
In calculating, include the volume of water in boiler, radiation and piping but not the expansion tank.