North Dakota Administrative Code › Title 33.1 - Department of Environmental Quality › Article 33.1-14 - NORTH DAKOTA BOILER RULES › Chapter 33.1-14-09 - HEATING, LOW PRESSURE, AND HOT WATER SUPPLY BOILERS -EXISTING INSTALLATIONS › Section 33.1-14-09-15 - Provisions for thermal expansion in hot water systems

Current through Supplement No. 393, July, 2024
1. All hot water heating systems
				incorporating hot water tanks or fluid relief columns must be so installed as
				to prevent freezing under normal operating conditions.
2. Systems with open expansion tank. If the
				system is equipped with an open expansion tank, an indoor overflow from the
				upper portion of the expansion tank must be provided in addition to an open
				vent, the indoor overflow to be carried within the building to a suitable
				plumbing fixture or to the basement.
3. Closed-type systems. If the system is of
				the closed type, an airtight tank or other suitable air cushion must be
				installed that will be consistent with the volume and capacity of the system,
				and must be suitably designed for a hydrostatic test pressure of two and
				one-half times the allowable working pressure of the system. Expansion tanks
				for systems designed to operate above thirty pounds per square inch [206.85
				kilopascals] must be constructed in accordance with the American Society of
				Mechanical Engineers Code, section VIII, division 1. Except for prepressurized
				tanks, provisions must be made for draining the tank without emptying the
				system. Provisions must also be made for changing of all tanks without emptying
				the system.
4. Expansion tank
				capacities for gravity hot water systems. Based on two-pipe system with average
				operating water temperature one hundred seventy degrees Fahrenheit [76.7
				degrees Celsius], using cast iron column radiation with heat emission rate one
				hundred fifty British thermal units per hour per square foot [158.25 x 10 to
				the 3rd power joules per .0929 square meter] equivalent direct radiation.
Square Feet of Installed Equivalent Direct
								Radiation
Tank Capacity, Gallons
Up to 350
18
Up to 450
21
Up to 650
24
Up to 900
30
Up to 1,100
35
Up to 1,400
40
Up to 1,600
2-30
Up to 1,800
2-30
Up to 2,000
2-35
Up to 2,400
2-40
5.
				Expansion tank capacities for forced hot water systems. Based on average
				operating water temperature one hundred ninety-five degrees Fahrenheit [90
				degrees Celsius], a fill pressure twelve pounds per square inch gauge [82.74
				kilopascals] and a maximum operating pressure thirty pounds per square inch
				gauge [206.84 kilopascals].
System Volume, Gallons
Nonpressurized Tank Capacity Gallons
Prepressurized Tank Capacity Gallons
100
15
9
200
30
17
300
45
25
400
60
33
500
75
42
1,000
150
83
2,000
300
165
Note: System volume includes volume of water in boiler,
				  radiation, and piping, not including the expansion tank.
6. Expansion tanks for hot water supply
				systems must be constructed in accordance with the American Society of
				Mechanical Engineers Code, section VIII, division 1 if over five gallons in
				size of water and air.
General Authority:
NDCC 23.1-16
Law Implemented:
NDCC
					 23.1-16