Section 1009 Hot Water Boiler Expansion Tank
An expansion tank shall be installed in every hot water system. For multiple boiler installations, not less than one expansion tank is required. Expansion tanks shall be of the closed or open type. Tanks shall be rated for the pressure of the hot water system.
Exception: Expansion tanks shall not be required in the collector loop of drain-back systems.
Closed-type expansion tanks shall be installed in accordance with the manufacturer's instructions. Expansion tanks for systems designed to have an operating pressure in excess of 30 psi (207 kPa) shall be constructed and certified in accordance with the ASME Boiler and Pressure Vessel Code. The size of the tank shall be based on the capacity of the hot-water-heating system. The minimum size of the tank shall be determined in accordance with the following equation where all necessary information is known:
(Equation 10-1)
For SI:
where:
Vt = Minimum volume of tanks (gallons) (L).
Vs = Volume of system, not including expansion tanks (gallons) (L).
T = Average operating temperature (°F) (°C).
Pa = Atmospheric pressure (psi) (kPa).
Pƒ = Fill pressure (psi) (kPa).
Po = Maximum operating pressure (psi) (kPa).
Where all necessary information is not known, the minimum size of the tank shall be determined from Table 1009.2.
CLOSED-TYPE EXPANSION TANK SIZING
| SYSTEM VOLUME IN GALLONS | TANK CAPACITIES IN GALLONS | |
| Pressurized Diaphragm Type | Nonpressurized Type | |
| 100 | 9 | 15 |
| 200 | 17 | 30 |
| 300 | 25 | 45 |
| 400 | 33 | 60 |
| 500 | 42 | 75 |
| 1,000 | 83 | 150 |
| 2,000 | 165 | 300 |
For SI: 1 gallon = 3.795 L.