GUIDE SPECIFICATION SECTION232117 - 1
Revised 16 February 2016Geothermal Hydronic Piping
SECTION 232117 – GEOTHERMAL HYDRONIC PIPING
PART 1 - GENERAL
RELATED DOCUMENTS
Drawings and general provisions of Contract, including General and Supplementary Conditions and Division 1 Specification Sections, apply to this Section.
SUBMITTALS
General: Submittals shall demonstrate compliance with technical requirements by reference to each subsection of this specification. Where a submitted item does not comply fully with each and every requirement of the Specifications, the submittal shall clearly indicate such deviations. Identification requirements for non-complying features of items are very specific. See Section 230210 for exact requirements.
Manufacturer's Data: Submit manufacturer's technical product data, including rated capacities, installation instructions, shipped and installed weights, certification of UL compliance, and furnished specialties and accessories for the tank.
QUALITY ASSURANCE
Comply with the applicable requirements and recommendations of Chapter 34, 2011 ASHRAE Handbook - HVAC Applications.
Comply with the applicable requirements of the International Ground Source Heat Pump Association (IGSHPA).
PART 2 - PRODUCTS
PIPE AND FITTINGS
Underground piping for geothermal hydronic systems shall be high density polyethylene (HDPE) meeting the requirements for geothermal (ground source heat pump) applications, as follows:
Material: All pipe and heat fused materials shall be SDR 9 or SDR 11, as required to meet system pressures (200 psig and 160 psig, respectively), manufactured from high density, extra-high molecular weight polyethylene resin. The material shall have a 1600 psi hydrostatic design basis at 73.4 degrees F per ASTM D-2837. The material shall have a cell classification of PE 345464C or greater as specified in ASTM D-3350 and shall exhibit zero failures when tested for 192 hours or more in accordance with ASTM D-1693, Condition C.
Pipe: Extruded pipe shall conform to the specifications and requirements of ASTM D-3035. Pipe used for vertical bore applications shall include fused, single piece injection molded U-bend fittings complying with ASTM D-2239.
Fittings: Molded fittings shall be manufactured to the specifications and requirements of ASTM D-2683 for socket fittings, ASTM D-3261 for butt fittings. All fittings shall be rated for pressure service equal to or greater than pipe.
//INCLUDE FOLLOWING SUBSECTION ONLY IF VERTICAL BOREHOLES ARE USED WITH THE SYSTEM.//
BOREHOLE BACKFILL
Backfill materials shall be a minimum 20% high sodium solids bentonite grout meeting the following requirements:
Thermal conductivity shall be 1.20 Btu/hr-ft-F or greater.
The maximum allowable permeability value of the set grout should be 1 X 10-7 centimeters per second, as determined in accordance with ASTM D5084-03, Standard Test Methods for Measurement of Hydraulic Conductivity of Saturated Porous Materials Using a Flexible Wall Permeameter. Permeability shall be verified by an independent testing laboratory and a copy of that report shall be submitted to the A-E.
Grout shall have a minimum mixture of 63.5% solids. A high-grade silica compound shall provide thermal enhancement and shall constitute a minimum of 50% by weight of the aqueous slurry.
Where geologic conditions, determined by test drilling, indicate that bentonite grout is not acceptable, a cementitious grout may be used upon approval by the A-E. Cementitious grout shall be a mixture of the following components, or other Portland cement-based admixtures designed for geothermal applications and approved by the A-E, as follows:
Six and two-tenths gallons (6.2 gal.) of potable water with chloride content less than 25 ppm, sulfate less than 25 ppm, and hardness less than 100 ppm.
Two hundred pounds (200 lbs) of silica sand with not less than 80% of the sand having a diameter of less than 0.0117 in. and passing through a U.S. Sieve No. 50.
One pound (1 lb) of 200-mess sodium montmorillonite bentonite.
Ninety-four pounds (94 lbs) of Type I Portland cement conforming to ASTM C-150, Standard Specification for Portland Cement.
Type F water reducing admixture or plasticizer conforming to ASTM C-494, Standard Specification for Chemical Admixtures of Concrete. Maximum allowable amount of admixture shall be determined in accordance with NSF/ANSI 60, Drinking Water Treatment Chemicals - Health Effects.
Grouting in bedrock lost circulation zones may be done with a mixture of cementitious grout and clean peastone gravel or a layered placement of cementitious grout and short intervals of bentonite chips or clean peastone gravel.
Surface seal material shall be 3000 psi concrete in accordance with Section 019913.
//INCLUDE FOLLOWING SUBSECTION ONLY IF ANTIFREEZE SOLUTION IS REQUIRED FOR BOREHOLE APPLICATIONS.//
ANTIFREEZE SOLUTION
Propylene Glycol: Minimum 99 percent propylene glycol with corrosion inhibitors and environmental stabilizer additives to be mixed with water to protect the piping circuit and connected equipment from physical damage from freezing or corrosion.
Quantity: Sufficient solution for initial system startup and for preventive maintenance for one year from date of Substantial Completion.
Dilution Water: Potable water with chloride content less than 25 ppm, sulfate less than 25 ppm, and hardness less than 100 ppm.
PART 3 - EXECUTION
//SELECT ONE OF THE TWO FOLLOWING PARAGRAPHS BASED ON THE GEOTHERMAL SYSTEM CONFIGURATION.//
HORIZONTAL PIPING INSTALLATION
Excavation and trenching shall be in accordance with Section 109919
Separate trenches by 10 feetminimum, unless otherwise indicated. Minimum trench depth shall be 60".
Install piping in trenches according to ASTMD2774 or ASTMF645, in compliance with Section 019919, with at least 24" separation.
Clean pipe and fittings and make heat-fusion joints according to ASTMD2657. Minimize number of joints.
Purge, flush, and pressure test piping in accordance with Section 230555 before backfilling trenches.
Backfill to minimum 36" depth above pipe with slurry mixed from excavated rock-free soil mixed with sand, pea gravel, and/or fly ash. Backfill from slurry level to grade with excavated soil, compacting as specified in Section 230230.
VERTICAL PIPING INSTALLATION
//DELETE THE FOLLOWING SUBSECTION IF BOREHOLE DRILLING IS SPECIFIED FOR THE PROJECT.//
Borehole drilling shall comply with the following:
//THE FOLLOWING REQUIREMENTS ARE BASED ON THE LAWS OF NORTH CAROLINA. IF THE PROJECT IS LOCATED IN A DIFFERENT STATE, THIS PARAGRAPH MUST BE EDITED AS REQUIRED.//
Borehole drilling shall be performed only by a well contractor certified to Level A by the North Carolina Well Contractors Certification Commission in accordance with the North Carolina Administrative Code, Title 15A, Chapter 27.
Well contractor shall hold accreditation as a geothermal installer or VCL driller by the IGSHPA or an equivalent accreditation or certification from a nationally-recognized organization, as determined by the A-E.
Permits for boreholes, as required by the North Carolina State Department of Environment and Natural Resources, Division of Water Quality, shall be obtained by the well contractor, as applicable. Permits, inspections, etc. required by local governments shall be the responsibility of the well contractor.
Boreholes shall be constructed in accordance with the North Carolina Administrative Code, Title 15A, Subchapter 2C, Section 0200.
Install piping in boreholes according to ASTMD2774 or ASTMF645 within five (5) days of completion of the drilling.
Clean pipe and fittings and make heat-fusion joints according to ASTMD2657. Minimize number of joints.
Purge, flush, and pressure test piping in accordance with Section 230555 before backfilling boreholes
After installation of loop pipe in borehole, fill piping loop with water or antifreeze solution, and pump backfill into borehole, as follows:
Backfill slurry shall be placed via "tremie" method from the bottom of the poring to the surface in accordance with the IGSHPA standard Grouting for Vertical GHP Systems. Install the grout to ensure that no air voids form. Fill borehole with backfill to a point 24-36 inches below grade.
After the initial fill, each borehole shall be visually monitored every 30 minutes for a 2 hour period and grout slurry added as necessary to compensate for settlement.
After 2 hours, backfill remainder of borehole with surface seal material.
Extend piping and connect to piping systems at outside face of building wall in locations and pipe sizes indicated on the Drawings.
Wall sleeves and seals for building wall penetrations shall comply with Section 230517.
//INCLUDE FOLLOWING SUBSECTION ONLY IF ANTIFREEZE SOLUTION IS REQUIRED FOR BOREHOLE APPLICATIONS.//
ANTIFREEZE SOLUTION FILL
Fill system with required quantity of food grade propylene glycol and potable water to provide minus 10 degFfreezing temperature.
Test the dilute solution to verify concentration of propylene glycol and submit report to A-E for review.
CONNECTIONS
Pipe and fitting joints shall be electrofusion and mechanical type made in accordance with the fitting manufacturer’s instructions.
FIELD QUALITY CONTROL
Piping Tests: Fill piping with potable water 24 hours before testing and apply test pressure to stabilize it.
Hydrostatic Tests: Test in accordance with Section 230555,allowing for static pressure of borehole depth, as follows:
Increase pressure in 50-psig increments and inspect each joint between increments. Hold at each test pressure for 30 minutes. Slowly increase to next test pressure increment and hold for 30 minutes. After testing at maximum test pressure, not to exceed the pressure rating of the pipe and fittings, reduce pressure to 30 psig. Hold for 90 minutes, and measure pressure at 30-minute intervals. Repair leaks and retest until no leaks exist.
Prepare reports of testing activity and submit to A-E for review..
OWNER INSTRUCTION AND TRAINING
Provide Owner instruction and training in accordance with Section 230240.