N.Y.C. Admin. Code § MC 1009: Section MC 1009: Hot Water Boiler Expansion Tank

1009.1 Where required.

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. Lockable shutoff valves shall be installed at connections to all expansion tanks. Valves shall remain locked in the open position.

1009.2 Closed-type expansion tanks.

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 (205.8 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:

V

t

=

(0.00041T - 0.0466)V

s

(Equation 10-1)

(P

a

/P

f

) - (P

a

/P

o

)

For SI:

V

t

=

(0.000738T - 0.03348)V

s

(P

a

/P

f

) - (P

a

/P

o

)

where:

V

t

=

Minimum volume of tanks (gallons) (L).

V

s

=

Volume of system, not including expansion tanks (gallons) (L).

T

=

Average operating temperature (°F) (°C).

P

a

=

Atmospheric pressure (psi) (kPa).

P

f

=

Fill pressure (psi) (kPa).

P

o

=

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.

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

1009.3 Open-type expansion tanks.

Open-type expansion tanks shall be located not less than 4 feet (1219.2 mm) above the highest heating element. The tank shall be adequately sized for the hot water system. An overflow with a minimum diameter of 1 inch (25.4 mm) shall be installed at the top of the tank. The overflow shall discharge to the drainage system in accordance with the New York City Plumbing Code.