W. Va. Code R. § 64-46-10 - Heat Pump Construction

10.1. Design Methods and Compliance.

10.1.a. The manufacturer's design procedure shall follow a recognized methodology as presented in the most recent editions of IGSHPA and ASHRAE.

10.1.b. The ground heat exchanger design shall be clearly documented in order to determine compliance with the heat pump manufacturer's or utility's specifications or both.

10.2. Location of Heat Pump Wells Criteria.

10.2.a. Heat pump closed-loop wells shall be located at least twenty-five (25) feet from sewage absorption systems and known sources of contamination.

10.2.b. A closed-loop shall be located twenty-five (25) feet from all water wells. An open-loop shall be one hundred (100) feet from all water wells.

10.3. Casing Material.

10.3.a. If permanent casing is needed in a heat pump well, it shall be new steel casing.

10.4. Heat Pump Loop Material.

10.4.a. All pipe and heat-fused materials shall be manufactured from a virgin polyethylene extrusion compound material in accordance with ASTM Standard D-2513, and located in accordance with subsections 4.1 and 4.2 of this rule. The pipe shall be manufactured to outside diameters and wall thickness as specified in ASTM Standard D-3035 or D-2447. Fittings shall be manufactured to diameters, wall thicknesses, and respective tolerances as specified in ASTM Standard D-2683 for socket fittings and ASTM Standard F-1055 for electrofusion fittings.

10.4.a.1. The material shall maintain a 1600 psi (110.316 bar) Hydrostatic Design Basis at 73.4^oF (23.5^oC) per ASTM Standard D-2837, and be listed in PPI TR4 as a PE3408 piping formulation. The material shall be a high density extrusion compound having a cell classification of PE345434, PE355434, or PE3455534 with a UV stabilizer of C, D, or E as specified in ASTM Standard D-3350 with the following exception: this material shall exhibit zero failures (F0) when tested for a minimum of 192 hours under ASTM Standard D-1693, condition C, as required in ASTM Standard D-3350.

10.4.a.2. Dimensions.

10.4.a.2.A. Pipe with a diameter of less than 11/4" (3.175cm) (nominal) shall be manufactured in accordance with ASTM D-3035 with a minimum (based on pressure rating) dimension ratio of 11.

10.4.a.2.B. Pipe manufactured with a diameter from 11/4"(3.175cm) (nominal) up to three (3) inches in diameter, shall be manufactured in accordance with ASTM D-3035 with a minimum (based on pressure rating) dimension ratio of 11.

10.4.a.2.C. Pipe 3" (7.62cm) (nominal) and larger shall be manufactured in accordance with ASTM D-3035, (with a minimum [based on pressure rating] dimension ratio of 17) or D-2447 (Schedule 40). Table 64-46 C of this rule indicates the Water Pressure Ratings at 73.4^oF (23.5^oC) for DR-PR PE 3408 Plastic Pipe.

10.4.a.3. Markings, defined by the appropriate ASTM pipe standard shall be permanently marked on the length of the pipe as required information.

10.4.a.4. The manufacturer shall supply a notarized document confirming compliance with these standards, called a Certification of Materials.

10.4.b. All pipe joints and fittings installed and buried shall be socket or butt thermally fused according to the pipe manufacturer's specifications. Glued or clamped joints shall not be used below ground. Joints shall not leak after assembly. Pressure testing of the closed-loop heat pump system network shall be conducted prior to putting the system into operation.

10.4.b.1. Acceptable methods for joining buried pipe systems are:

10.4.b.1.A. a heat fusion process;

10.4.b.1.B. stab-type fittings, quality controlled to provide a leak-free union between pipe ends that are stronger than the pipe itself or;

10.4.b.1.C. polyethylene pipe heat fused by butt, socket, sidewall, or electrofusion in accordance with the pipe manufacturer's procedures. The individual performing fusion shall possess a fusion technician certification from IGSHPA or the pipe manufacturer. The instructor shall be IGSHPA approved to conduct pipe fusion classes.

10.4.b.1.D. Fusion transition fittings shall have threads used to adapt to copper, or fusion transition fittings shall have threads or barbs used to adapt to high strength hose. Barbed fittings shall not be permitted to be connected directly to polyethylene pipe, with the exception of stab-type fittings as described in subparagraph 10.4.b.1.B of this section. All mechanical connections shall be accessible.

10.5. Heat transfer liquids shall be IGSHPA approved fluids.

10.6. The diameter of a heat pump well shall be sufficient to allow placement of grout. The minimum diameter shall be four (4) inches.

10.7. Heat Pump Vertical Closed-Loop Wells.

10.7.a. Approved Grout Materials.

10.7.a.1. Approved sealing and filling materials shall include high solids bentonite grout-20-30% solids by weight, bentonite pellets or chips, or approved high efficiency, thermally enhanced grouts designed for heat transfer in geothermal applications. All shall meet manufacturer's specifications.

10.7.a.2. All materials placed in the borehole shall be uncontaminated. All sand and gravel placed in the borehole shall be silica based and inert, unless a material other than silica is used in an IGSHPA approved, commercially available product that meets all other requirements.

10.7.a.3. Drill cuttings shall not be placed in the borehole as fill material.

10.7.b. Grouting.

10.7.b.1. Grout the entire length of the borehole from bottom to top with bentonite or thermally enhanced grout specifically designed to facilitate heat transfer and provide low permeability.

10.7.b.2. Boreholes with temporary casing may be grouted during or before removal of casing depending on borehole stability.

10.7.b.3. Grouting shall be completed immediately after installing the geothermal loop when reasonable to do so.

10.7.b.4. Boreholes with permanent casing shall be grouted before the top of the casing is terminated below ground level.

10.7.b.5. Boreholes with no casing shall be looped and grouted immediately after drilling.

10.7.b.6. Boreholes drilled with a mud system in unconsolidated formations shall be looped and grouted immediately after drilling.

10.7.b.7. Slurry mixtures shall be installed by pumping through a tremie pipe using a positive placement technique.

10.7.b.8. When voids are encountered (i.e. mined coal seams or caves), the borehole shall be cased from below the void to the surface.

10.7.c. Flushing, Purging, Pressure, and Flow Testing.

10.7.c.1. Loops shall be pressure tested before installation.

10.7.c.2. Loops shall be pressure tested after installation and grouting.

10.7.c.3. All horizontal components of the ground heat exchanger shall be flushed, pressure tested, and flow tested prior to backfilling.

10.7.c.4. Heat exchangers shall be tested hydrostatically at 150% of the pipe design rating or 300% of the system operating pressure if this value is the smaller of the two.

10.7.c.5. No visible leaks shall occur within a thirty (30) minute period.

10.7.c.6. Soil thermal conductivity testing overseen by an IGSHPA certified designer or comparable certification, shall be required for all systems with 50 or more tons capacity. The thermal conductivity test shall be conducted for a minimum of 48 hours.

10.8. Heat Pump Open-Loop Requirements.

10.8.a. Open loop wells shall be constructed in the same manner and conform to the water well construction standards set forth in this rule. This applies to return wells, standing column wells and supply wells. DEP generally requires permits for injecting or returning water to the subsurface and for surface discharges. It is the homeowner's responsibility to obtain any required permits.

10.8.b. Pump tests shall be required for all open loop wells. The pump test shall demonstrate the well's ability to produce 150 percent of the anticipated demand by sustaining this level of volume for twenty-four (24) continuous hours of stabilized flow; recovering to pre-pump test levels within twelve hours.

10.9. Direct Exchange Wells.

10.9.a. Direct exchange wells shall be constructed in the same manner and conform to the construction standards set out in this rule.

10.9.b. The direct exchange loop shall be constructed of copper tubing or other material approved by the Commissioner. All joints in the direct exchange loop shall be soldered and not brazed. The solder used shall withstand stresses associated with the direct exchange process.

10.9.c. The thermal fluid or refrigerant used in the direct exchange well tubing shall be biodegradable and non-toxic.

10.9.d. All loops shall be at least ten (10) feet from underground utilities due to the potential for freezing as heat is removed from the ground for heating.

Notes

W. Va. Code R. § 64-46-10