# 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 Heating, Low Pressure, and Hot Water Supply Boilers - Existing Installations

### § 33.1-14-09-01. American Society of Mechanical Engineers Code boilers.

The maximum allowable working pressure of a boiler built in accordance with the American Society
of Mechanical Engineers Code may not exceed the pressure indicated by the manufacturer's
identification stamped or cast upon the boiler or upon a plate secured to it.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-05
Law Implemented: NDCC 23.1-16-05
### § 33.1-14-09-02. Nonstandard riveted boilers.

The maximum allowable working pressure on the shell of a noncode riveted heating boiler must be
determined in accordance with section 33.1-14-05-01 except that the maximum allowable working
pressure of a steam heating boiler may not exceed fifteen pounds [103 kilopascals] and a hot water
boiler may not exceed thirty pounds [206.85 kilopascals] at a temperature not exceeding two hundred
fifty degrees Fahrenheit [120 degrees Celsius].
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-05
Law Implemented: NDCC 23.1-16-05
### § 33.1-14-09-03. Nonstandard welded boilers.

The maximum allowable working pressure of a noncode steel or wrought iron heating boiler of
welding construction may not exceed fifteen pounds [103 kilopascals]. For other than steam service,
the maximum allowable working pressure must be calculated in accordance with section IV of the
American Society of Mechanical Engineers Code.

History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-05
Law Implemented: NDCC 23.1-16-05
### § 33.1-14-09-04. Nonstandard cast iron boilers.

1. The maximum allowable working pressure of a noncode boiler composed principally of cast
iron may not exceed fifteen pounds [103 kilopascals] for steam service or thirty pounds
[206.85 kilopascals] for hot water service.
2. The maximum allowable working pressure of a nonstandard boiler having cast iron shell or
heads and steel or wrought iron tubes may not exceed fifteen pounds [103 kilopascals] for
steam service or thirty pounds [206.85 kilopascals] for water service.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-05
Law Implemented: NDCC 23.1-16-05
### § 33.1-14-09-05. Fired radiators.

A radiator in which steam pressure is generated at a pressure of fifteen pounds [103 kilopascals] or
less is considered a low-pressure boiler.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-05
Law Implemented: NDCC 23.1-16-05
### § 33.1-14-09-06. General.

If in the judgment of the inspector, a boiler is unsafe for operation at the pressure previously
approved, the pressure must be reduced, proper repair made, or the boiler retired from service.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-05
Law Implemented: NDCC 23.1-16-05
### § 33.1-14-09-07. Pressure-relieving devices.

1. Safety valve requirements for steam boilers are:
a. Each steam boiler must have one or more American Society of Mechanical Engineers
approved safety valves of the spring-pop type adjusted and sealed to discharge at a
pressure not to exceed fifteen pounds per square inch [103 kilopascals]. Seals must be
attached in a manner to prevent the valve from being taken apart without breaking the
seal. The safety valves must be arranged so that they cannot be reset to relieve at a
higher pressure than the maximum allowable working pressure of the boiler. For
iron-and-steel-bodied valves exceeding two inch [50.8 millimeter] pipe size, the drain
hole or holes must be tapped not less than three-eighths inch [9.53 millimeter] pipe size.
b. Each safety valve three-quarter inch [10.05 millimeters] diameter or over, used on a
steam boiler, must have a substantial device that will positively lift the disk from its seat at
least one-sixteenth inch [1.59 millimeters] when there is no pressure in the boiler. The
seats and disks must be of suitable material to resist corrosion.
c. A safety valve for a steam boiler may not be smaller than three-quarter inch
[19.05 millimeters] unless the boiler and radiating surfaces consist of a self-contained
unit. A safety valve may not be larger than four and one-half inches [114.3 millimeters].

The inlet opening must have an inside diameter equal to, or greater than, the seat
diameter.
d. The minimum relieving capacity of valve or valves is governed by the capacity marking
on the boiler.
e. The minimum valve capacity in pounds per hour is the greater of that determined by
dividing the maximum British thermal units output at the boiler nozzle obtained by the
firing of any fuel for which the unit is installed by one thousand, or is determined on the
basis of the pounds of steam generated per hour per square foot of boiler heating
surface. (One British thermal unit equals 1.055 x 10 to the third power joules.)
Boiler Heating Firetube Watertube
Surface Boilers Boilers
Hand-fired 5 6
Stoker-fired 7 8
Oil, gas, or pulverized fuel-fired 8 10
f. Safety valves must be installed with the valve spindle in the vertical position. Discharge
piping, to a safe location, may be required by the inspector.
2. When a boiler is fired only by a gas having a heat value not in excess of two hundred British
thermal units per cubic feet [745.58 x 10 to the fourth power joules per cubic meter], the
minimum safety valve or safety relief valve relieving capacity may be based on the values
given for hand-fired boilers above.
3. The safety valve or safety relief valve relieving capacity for electric boilers is three and
one-half pounds [3692.5 joules] per hour per kilowatt input.
a. The safety valve capacity for each steam boiler must be such that with the fuel-burning
equipment installed and operated at maximum capacity the pressure cannot rise more
than five pounds per square inch [34.47 kilopascals] above the maximum allowable
working pressure.
b. When operating conditions are changed, or additional boiler heating surface is installed,
the valve capacity must be increased, if necessary, to meet the new conditions, the
additional valves required, on account of changed conditions, may be installed on the
outlet piping provided there is no intervening valve.
4. Safety relief valve requirements for hot water boilers are:
a. Each hot water heating boiler must have at least one American society of mechanical
engineers approved pressure relief valve set to relieve at or below the maximum
allowable working pressure of the boiler. Each hot water supply boiler must have at least
one officially rated safety relief valve or at least one American society of mechanical
engineers approved pressure-temperature relief valve of the automatic-reseating type set
to relieve at or below the maximum allowable working pressure of the boiler. Pressure
relief valves officially rated as to capacity must have pop action when tested by steam.
When more than one safety relief valve is used on either hot water heating or hot water
supply boilers, the additional valve or valves must be officially rated and may be set
within a range not to exceed six pounds per square inch [41.47 kilopascals] above the

maximum allowable working pressure of the boiler up to and including sixty pounds per
square inch [413.69 kilopascals] and ten percent for those having a maximum allowable
working pressure exceeding sixty pounds per square inch [413.69 kilopascals]. Safety
relief valves must be spring loaded without disk guides on the pressure side of the valve.
Safety relief valves must be arranged so that they cannot be reset to relieve at a higher
pressure than the maximum permitted by this subdivision.
b. Each safety relief valve must have a substantial device that will positively lift the disk
from its seat at least one-sixteenth inch [1.59 millimeters] when there is no pressure on
the boiler.
c. Materials subject to deterioration or vulcanization when subject to saturated steam
temperature corresponding to capacity test pressure may not be used for any part.
d. A safety relief valve may not be smaller than three-quarter inch [19.05 millimeters] nor
larger than four and one-half inch [114.3 millimeter] standard pipe size, except that
boilers having a heat input not greater than fifteen thousand British thermal units per hour
[15.38 x 10 to the seventh power joules] may be equipped with a rated safety relief valve
of one-half inch [12.7 millimeter] standard pipe size. The inlet opening must have an
inside diameter approximately equal to, or greater than, the seat diameter. The minimum
opening through any part of the valve may not be less than one-quarter inch
[6.35 millimeters] diameter or its equivalent area.
e. The required steam-relieving capacity, in pounds per hour, of the pressure-relieving
device or devices on a boiler must be determined by dividing the maximum output in
British thermal units at the boiler nozzle obtained by the firing of any fuel for which the
unit is designed by one thousand or by multiplying the square feet of heating surface by
five. In every case, the requirements of subdivision g must be met. (One British thermal
unit equals 1.055 x 10 to the third power joules.)
f. When operating conditions are changed, or additional boiler heating surface is installed,
the valve capacity must be increased, if necessary, to meet the new conditions and be in
accordance with subdivision g. The additional valves required, on account of changed
conditions, may be installed on the outlet piping provided there is no intervening valve.
g. Safety relief valve capacity for each boiler must be such that with maximum heat input
the pressure cannot rise more than six pounds per square inch [41.37 kilopascals] above
the maximum allowable working pressure for pressures up to and including sixty pounds
per square inch [413.69 kilopascals] and ten percent for maximum allowable working
pressures over sixty pounds per square inch [413.69 kilopascals].
h. Safety relief valves must be installed with the spindle in the vertical position. Discharge
piping, to a safe location, must be installed.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-08. Steam pressure gauge.

1. Each steam boiler must have a steam gauge or a compound steam gauge connected to its
steam space or to its water column or to its steam connections. The gauge or connection must
contain a siphon or equivalent device that will develop and maintain a water seal that will
prevent steam from entering the gauge tube. The connection must be arranged so that the
gauge cannot be shut off from the boiler except by a cock placed in the pipe at the gauge and
provided with a tee or a lever handle arranged to be parallel to the millimeter] standard pipe

size, but where steel or wrought iron pipe or tubing is used, they must be not less than
one-half inch [12.7 millimeter] standard pipe size. The minimum size of a siphon, if used, must
be one-quarter inch [6.35 millimeters] inside diameter. Ferrous and nonferrous tubing having
inside diameters at least equal to that of standard pipe sizes listed above may be substituted
for pipe in which it is located when the cock is open. The connections to the boiler must be not
less than one-quarter inch [6.35 millimeter].
2. The scale on the dial of a steam boiler gauge must be graduated to not less than thirty pounds
per square inch [206.84 kilopascals] nor more than sixty pounds per square inch
[413.69 kilopascals]. The gauge must be provided with effective stops for the indicating pointer
at the zero point and at the maximum pressure point. The travel of the pointer from zero to
thirty pounds per square inch [206.84 kilopascals] pressure must be at least three inches
[76.2 millimeters]. On a compound gauge, effective stops must be set at the limits of the
gauge readings on both the pressure and vacuum sides of the gauge.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-09. Water gauge glasses.

1. Each steam boiler must have one or more water gauge glasses attached to the water column
or boiler by means of valved fittings not less than one-half inch [12.70 millimeter] pipe size,
with the lower fitting provided with a drain valve of the straight type with opening not less than
one-quarter inch [6.35 millimeters] diameter to facilitate cleaning. Gauge glass replacement
must be possible under pressure. Water glass fittings may be attached directly to a boiler.
2. The lowest visible part of the water gauge glass must be at least one inch [25.4 millimeters]
above the lowest permissible water level recommended by the boiler manufacturer. With the
boiler operating at this lowest permissible water level, there must be no danger of overheating
any part of the boiler. Transparent material other than glass may be used for the water gauge
provided that the material will remain transparent and has proved suitable for the pressure,
temperature, and corrosive conditions expected in service.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-10. Stop valves and check valves.

1. If a steam boiler may be closed off from the heating system by closing a steam stop valve,
there must be a check valve in the condensate return line between the boiler and the system.
2. If any part of a steam heating system may be closed off from the remainder of the system by
closing a steam stop valve, there must be a check valve in the condensate return pipe from
that part of the system.
3. If more than one boiler is connected to a system, they must each be equipped with main stops
on the discharge and return side, in such a manner not affecting operation of any other boiler.
4. When single boilers are located above the system and can be drained without draining the
system, stop valves are optional.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07

### § 33.1-14-09-11. Feedwater connections.

1. Feedwater connections must be independent of any water gauge connections and be made to
the condensate return pipe or reservoir of the condensate return tank.
2. Alternatively, makeup water or water treatment may be introduced through an independent
connection. The water flow from the independent connection may not discharge directly
against parts of the boiler exposed to direct radiant heat from the fire. Makeup water or water
treatment may not be introduced through openings or connections provided for inspection or
cleaning, safety valve, safety relief valve, blowoff, water column, water gauge glass, pressure
gauge, or temperature gauge.
3. When there is more than one boiler connected to a system, each boiler must have an
independent feedwater line.
4. There must be a stop valve and a check valve in the feedwater line at the boiler. For hot water
heating boilers, the check valve must be a backflow preventer approved by the state plumbing
board.
5. Hot water heating boilers, not equipped with an approved low-water fuel cutoff, must be
equipped with an automatic feeding device or pressure-reducing valve method of feeding, in
addition to a manual bypass capable of feeding the boiler at a pressure of six percent above
safety relief valve setting.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-12. Pressure or altitude gauges.

1. Each hot water boiler must have a pressure or altitude gauge 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 gauge. The handle of the cock must be parallel
to the pipe in which it is located when the cock is open.
2. The scale on the dial of the pressure or altitude gauge must be graduated to not less than one
and one-half nor more than three and one-half times the pressure at which the safety relief
valve is set. The gauge must be provided with effective stops for the indicating pointer at the
zero point and at the maximum pressure point.
3. Piping or tubing for pressure or altitude gauge connections must be of nonferrous metal when
smaller than one inch [25.4 millimeter] pipe size.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-13. Thermometers.

Each hot water boiler must have a thermometer located and connected so that it is easily readable
when observing the water pressure or altitude. The thermometer must be located so that it will at all
times indicate the temperature in degrees Fahrenheit [Celsius] of the water in the boiler at or near the
outlet.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07

### § 33.1-14-09-14. Temperature control.

Each automatically fired hot water boiler must be protected from over temperature by two
temperature-operated controls.
1. Each individual automatically fired water boiler must have a safety limit control that will cut off
the fuel supply to prevent water temperature from exceeding the maximum allowable
temperature at the boiler outlet. The water temperature safety control must be constructed to
prevent a temperature setting above the maximum allowable temperature and be of the
manual reset type.
2. Each individual hot water boiler or each system of commonly connected boilers without
intervening valves must have a control that will cut off the fuel supply when the water
temperature reaches an operating limit, which must be less than the maximum allowable
temperature.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-14.1. Pressure control.

Each automatically fired steam boiler must be protected from over pressure by two
pressure-operated controls.
1. Each automatically fired steam boiler must have a safety limit control that will cut off the fuel
supply to prevent steam pressure from exceeding the fifteen pounds per square inch
[103 kilopascals] maximum allowable working pressure of the boiler. Each control must be
constructed to prevent a pressure setting above fifteen pounds per square inch
[103 kilopascals] and be of the manual reset type.
2. Each individual steam boiler or each system of commonly connected steam boilers must have
a control that will cut off the fuel supply when the pressure reaches an operating limit, which
must be less than the maximum allowable pressure.
3. Shutoff valves of any type may not be placed in the steam pressure connection between the
boiler and the controls described in subsections 1 and 2. These controls must be protected
with a siphon or equivalent means of maintaining a water seal that will prevent steam from
entering the control.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-15. Provisions for thermal expansion in hot water systems.

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].
Nonpressurized Tank Prepressurized Tank
System Volume, Gallons Capacity Gallons 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.

History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-16. Return pump.

Each condensate return pump where practicable must be provided with an automatic water level
control set to maintain the water level within the limits of two gauge cocks.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-17. Repairs and renewals of fittings and appliances.

Whenever repairs are made to fittings or appliances or it becomes necessary to replace them, all
work must comply with all requirements for new installations.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-18. Low-water fuel cutoff.

1. Each automatically fired hot water heating boiler must have an automatic low-water fuel cutoff
that has been designed for hot water service and which can be tested without draining the
system or the boiler. It must be so located as to automatically cut off the fuel supply prior to
the surface of the water falling below the lowest safe water level as established by the boiler
manufacturer.
2. A coil-type or watertube boiler requiring forced circulation to prevent overheating of the coils or
tubes must have a flow-sensing device installed in the boiler or piping in lieu of the required
low-water fuel cutoff that will cut off the fuel supply when the circulation flow is interrupted.
Functioning of the low-water fuel cutoff due to a low-water condition must cause safety
shutdown and lockout. Where a reset device is separate from the low-water fuel cutoff, a
means must be provided to indicate actuation of the low-water fuel cutoff. The manual reset
may be the instantaneous type or may include a time delay of not more than three minutes
after the fuel has been cut off.
3. Low-water fuel cutoff requirements for steam boilers are addressed by section 33.1-14-03-07.
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-19. Modular hot water heating boilers.

1. Individual modules must be limited to a maximum input of four hundred thousand British
thermal units [4.22 x 10 to the eighth power joules] per hour (gas), three gallons [11.36 liters]
per hour (oil), or one hundred fifteen kilowatt-hours (electricity).
2. Each module of a modular hot water heating boiler must be equipped with the following:
a. Pressure/altitude gauge (see section 33.1-14-09-12).
b. Thermometer (see section 33.1-14-09-13).
c. Operating temperature control (see subsection 2 of section 33.1-14-09-14).

d. Safety relief valve (see section 33.1-14-09-07).
e. Drain valve (see section 33.1-14-09-20).
3. The assembled modular hot water heating boiler must be equipped with the following:
a. High-limit temperature control (see subsection 1 of section 33.1-14-09-14).
b. Low-water fuel cutoff (see section 33.1-14-09-18).
c. Makeup feedwater connection (see section 33.1-14-09-11).
d. Expansion tank provisions (see section 33.1-14-09-15).
e. Stop valves (see section 33.1-14-09-10).
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-20. Bottom blowoff and drain valves.

1. Each steam boiler having a capacity over twenty-five gallons [94.6 liters] must have a bottom
blowoff connection fitted with a valve or cock connected to the lowest water space practicable
with a minimum size as shown below:
Minimum Required Safety Valve Capacity in Steam Boiler Blowoff Piping Valve Size,
Pounds of Steam/Hour Inches (Min.)
Up to 500 3/4
501 to 1,250 1
1,251 to 2,500 1 1/4
2,501 to 6,000 1 1/2
6,001 and larger 2
2. Each hot water boiler and each steam boiler having a capacity not exceeding twenty-five
gallons [94.6 liters] must have a drain valve connected to the lowest water space practicable.
The minimum size of this drain valve is three-quarter inch [1.9 centimeters].
History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
### § 33.1-14-09-21. Emergency shutoff switches.

1. A manually operated emergency shutoff switch or circuit breaker must be located just outside
the boiler room door and marked for easy identification. Consideration should be given to the
type and location of the switch to safeguard against tampering. If the boiler room door is on
the building exterior, the switch must be located just inside the door. If there is more than one
door to the boiler room, there must be a switch located at each door.
2. The emergency switch or circuit breaker must disconnect all power to the burner controls.
3. This requirement is limited to single and modular boilers exceeding four hundred thousand
British thermal units per hour input installed after January 1, 2006.

History: Effective July 1, 2020.
General Authority: NDCC 23.1-16-07
Law Implemented: NDCC 23.1-16-07
