Current through Register Vol. 49, No. 13, September 23, 2024
Subpart
1.
Construction.
A bored geothermal heat exchanger must be constructed
according to the construction standards in this part and the general
construction standards in parts 4725.2010 to 4725.3875.
A. Bored geothermal heat exchanger piping
must be high-density polyethylene or cross-linked polyethylene that meets the
following requirements:
(1) for high-density
polyethylene:
(a) the walls of the pipe must
be SDR 11 or thicker;
(b) pipe must
meet ASTM Standard D3035-15 or ASTM Standard F714-13;
(c) socket fusion and butt fusion connections
must be made in accordance with ASTM Standard F2620-19, and electrofusion
connections must be made in accordance with ASTM Standard F1055-16;
and
(d) socket fittings must be
manufactured in accordance with ASTM Standard D2683-14;
(2) for cross-linked polyethylene:
(a) pipe must be manufactured by the
high-pressure peroxide method and designated as PEXa;
(b) pipe must meet ASTM Standard
F876-20;
(c) all components of the
PEXa system must be from the same manufacturer;
(d) a fitting for a PEXa system must not be
buried in a pipe loop boring or between a pipe loop boring and the heat pump
unit, unless the fitting is located in a vault or other structure accessible
from the ground surface or floor of the building; and
(e) fittings must meet ASTM Standard
F1807-19b, ASTM Standard F1960-19a, or ASTM Standard F2080-16, and ASTM
Standard F877-20; and
(3) high-density polyethylene and
cross-linked polyethylene pipe must have a minimum pressure rating of 160 psi
at 73 degrees Fahrenheit.
B. The licensee must complete a successful
pressure test of the bored geothermal heat exchanger piping after the piping is
installed in the bore holes. Pipe must be pressure tested with potable water at
a pressure of 1.5 times the system operating pressure or 100 psi, whichever is
greater. The pressure must remain constant for 30 minutes without adding
additional water
C. The annular
space between the bored geothermal heat exchanger piping and a bore hole must
be filled with grout according to the procedures in part 4725.3050, subpart 2,
and according to the procedures in part 4725.3450 for a bored geothermal heat
exchanger boring from which groundwater flows above the established ground
surface. The annular space must be filled with:
(1) neat-cement grout or cement-sand grout in
bedrock;
(2) neat-cement grout or
cement-sand grout in a boring from which groundwater flows above the
established ground surface; or
(3)
neat-cement grout, cement-sand grout, bentonite grout, or thermally enhanced
bentonite grout in unconsolidated materials. Thermally enhanced bentonite grout
must consist of:
(a) a maximum of 17.5
gallons of water per 50 pounds of bentonite; and
(b) thermal enhancement material, including:
i. a maximum of 200 pounds of sand per 50
pounds of bentonite, with 80 percent or more of the sand smaller than 0.0117
inch (passing U.S. Sieve #50); and
ii. a maximum of 20 pounds of graphite that
meets the ANSI/NSF Standard 60-2016 requirements per 50 pounds of
bentonite.
D. Heat transfer fluids must be propylene
glycol or ethanol that meets the following requirements:
(1) propylene glycol must be food grade or
USP grade;
(2) a propylene glycol
with additives, including corrosion inhibitors and dyes, must be certified as
meeting the NSF Category Code HT1 for heat transfer fluids;
(3) ethanol products must be designed by the
manufacturer for use in bored geothermal heat exchanger systems. Ethanol
products must not be used unless approved in writing by the commissioner A
complete list of product ingredients and concentrations must be submitted for
review;
(4) ethanol may be used in
an ethanol-water solution of not more than 20 percent ethanol by volume.
Ethanol concentrates used to prepare heat transfer fuid must be diluted to not
more than 20 percent ethanol by volume before being brought into a building
where the heat transfer fluid is to be used;
(5) storing, handling, and using ethanol is
subject to the safety precautions and procedures specified by the ethanol
manufacturer, the applicable requirements of chapters 1305 and 7511, and NFPA
Standard 30: Flammable and Combustible Liquids Code, 2015 Edition; and
(6) no other fluids or additives
may be used except for potable water
E. A permanent sign must be attached to the
heat pump identifying the heat transfer fluid in the bored geothermal heat
exchanger and specifying that only heat transfer fluids approved in this part
may be used.
F. Water make-up lines
to the bored geothermal heat exchanger must be protected with backfow
prevention according to UPC sections 602.0 to 603.5.23.4 as incorporated by
part 4714.0050.
G. The isolation
distance between a water-supply well and a bored geothermal heat exchanger
constructed according to this part must be no less than the distances specified
in part 4725.4450, subpart 1, items F and H.
Subp. 3.
Marking locations.
The locations of all buried bored geothermal heat exchanger
piping from the point where the pipe loop exits the bore hole to the point
where the pipe is exposed above the ground surface or floor of a building must
be marked by:
A. tracer
wire;
B. underground marking tape
detectable from the ground surface; or
C. a ferromagnetic metal marker, detectable
from the ground surface, located above the point where the pipe loop exits the
bore hole.
Subp. 4.
Separation under buildings.
A bored geothermal heat exchanger boring installed using
directional drilling technology that extends under a building or within three
feet horizontally of the farthest exterior projection of the building must be
located at least ten feet below the lowest part of the building, including the
foundation and footings. Supply-return piping that is plumbed through the
building wall or floor is exempt from this requirement.
Subp. 5.
Isolation distances from
certain contaminant sources.
The point where the drill bit penetrates the ground surface
for a geothermal heat exchanger boring must be located at least ten feet
horizontally from a contaminant source that has contaminants directly entering
the soil, including:
A. the absorption
area of a soil dispersal system;
B.
animal feedlot, confining area, or feeding or watering area;
C. cesspool;
D. landspreading area for sewage, septage, or
sludge;
E. manure basin, lagoon, or
storage area;
F. rapid infiltration
basin;
G. seepage pit, leaching
pit, or dry well; or
H. wastewater
spray irrigation area.
Subp.
6.
Bored geothermal heat exchanger borings onto the property
of another.
Bored geothermal heat exchanger piping must not be installed
on or under property other than the property identified in the approved permit
without the affected property owner's written consent or other legal
authority.
Subp. 7.
Accessibility.
The ends of each pipe loop must be accessible within a
building or buried no deeper than ten feet below the ground surface. The buried
ends of a pipe loop must not be built over or otherwise made
inaccessible.
Subp. 8.
Pipe loop not connected to a geothermal heat exchanger system.
A pipe loop that is not connected to a geothermal heat
exchanger system, such as a loop installed for thermal conductivity testing,
must be protected by:
A. extending the
ends of the pipe loop to at least one foot above the ground surface;
B. encasing the ends of the pipe loop in an
ASTM Schedule 40 steel or plastic outer protective pipe that is at least four
inches in diameter and extends at least one foot above and two feet below the
ground surface; and
C. covering the
outer protective pipe with an overlapping cap or cover
Subp. 9.
Sealing of bored geothermal
heat exchangers.
When sealing all or part of a bored geothermal heat
exchanger:
A. all heat transfer fluid
must be removed from the bored geothermal heat exchanger piping that is to be
sealed;
B. the heat transfer fluid
must be contained and recycled or disposed according to applicable federal,
state, and local requirements;
C.
the ends of each pipe loop must be accessed and grouted by pumping grout
through a tremie pipe inserted to within ten feet of the bottom of the loop, or
by pumping grout into one end of the loop until grout flowing from the other
end of the loop meets the minimum specifications and densities in part
4725.0100, subpart 21d, 22b, or 30n;
D. the portion of the piping in
unconsolidated geologic materials must be filled with bentonite grout,
neat-cement grout, or cement-sand grout; and
E. the portion of the piping in bedrock must
be filled with cement-sand grout or neat-cement grout.
Subp. 10.
Notice of loss or
leak.
The owner of a bored geothermal heat exchanger system
must:
A. notify the commissioner of
leakage from the system piping or loss of pressure in the system within 24
hours after the owner becomes aware of the loss or leak; and
B. notify the Minnesota duty officer of a
bored geothermal heat exchanger leak according to Minnesota Statutes, section
115.061.
Statutory Authority: MS s
103I.101;
103I.111;
103I.205;
103I.221;
103I.301;
103I.401;
103I.451;
103I.501;
103I.525;
103I.531;
103I.535;
103I.541;
103I.621;
144.05;
144.12;
144.383;
157.04; 157.08; 157.09; 157.13
