(b) Closed loop or earth coil.

1. (1) Fluid is circulated in a continuous unbroken pipe beneath the surface of the earth or under ponds, swimming pools, lakes, or in a medium where the system can obtain a sufficient cooling or heat exchange.
2. (2) Normally no fluid is gained or lost.
3. (3) Depths of installation vary and are dependent upon the type and size of closed loop system, the land area available, soils/formation, climate, and seasonal variation in ground temperature, etc.

4. (4) There are three types of closed loop heat pump well systems:

   1. (A)

(i) Horizontal system.

1. (ii) A closed loop system where pipes are installed horizontally under the earth's surface or under ponds, swimming pools, lakes, etc.;

   1. (B)

      1. (i) Vertical system.
      2. (ii) A closed loop system where pipes are vertically installed beneath the surface of the earth; and

   2. (C)

      1. (i) Combination horizontal and vertical system.
      2. (ii) A system that has pipes installed beneath the earth's surface horizontally and vertically.

2. (5) Direct exchange (DX) wells.

   1. (A) A small diameter bore hole constructed for the purpose of sinking or sourcing thermal energy between the direct exchange loop and the earth.

   2. (B) Additional construction standards:

      1. (i) A DX well shall comply with 17 CAR §§ 11-502–11-503;
      2. (ii) The DX well does not have to be completely vertical;
      3. (iii)

(b) (b) A thermal fluid can be used to fill the DX well casing to within two feet (2’) of the top of the DX well casing.

1. (c) (c) A watertight sealing material will be used to seal the top of the DX well casing.

   1. (d) (d) The material can be:
2. (1) (1) Silicone;
3. (2) (2) Latex; or
4. (3) (3) Other material suitable for the seal.

(e) (e) The DX well casing shall comply with 17 CAR § 11-506(e);

1. (iv) DX well casing will be required if the pH of the material around the DX loop cannot be corrected to a pH of 8.5 or greater with the use of backfill or grout;

   1. (v)

(b)

1. (1) (b)(1) The DX loop is copper, which is more noble than steel.
2. (2) (2) Therefore, the steel acts as cathodic protection.

3. (3) (3) The joints will be threaded or welded;

   1. (vi)

(b) (b) The joint will be welded using Arkansas heating, ventilation, air conditioning, and refrigeration (HVACR) standards for joining refrigeration copper; and

1. (vii)

(b) (b) Any joint must comply with HVACR standards for joining refrigeration copper.

1. (c) (c) The copper tubing’s length and diameter must be sized for proper refrigerant flow.

   1. (c) Open loop or water source.
2. (1) Water is obtained from a source (water well, lake, river, etc.) and circulated, usually one (1) time, for the purpose cooling or heat exchange.
3. (2) Water quality, quantity and disposal are primary concerns with open loop systems.

4. (3) There are three (3) types/categories of open loop well systems:

   1. (A) General.

      1. (i) Open loop wells shall be constructed in the same manner and conform to rules for wells used for domestic purposes.
      2. (ii) This shall pertain to the supply well and return well;

   2. (B)

      1. (i) Single well open system.
      2. (ii) Water is obtained from a well, circulated, and returned to the same well;

   3. (C)

      1. (i) Dual well open system.
      2. (ii) Water is obtained from a supply well, circulated, and injected/dumped into a return well.
      3. (iii) These wells may be designed to switch roles and the return well becomes the supply well, the supply well the return well; and

   4. (D)

      1. (i) Single well/waste open system.
      2. (ii) Water is obtained from a well, circulated, and dumped/wasted into some other medium (land surface, lake, pond, ditch, sewer, etc.).
      3. (d) Vertical closed loop systems/wells.
5. (1) The contractor is responsible and shall ensure that water quantity and quality are not adversely affected.

6. (2) Grouting.

   1. (A) Closed loop wells constructed in consolidated formations shall be back filled with grout, prescribed in 17 CAR § 11-506, the entire length of the bore hole.
   2. (B) Wells constructed in unconsolidated formations may be backfilled with cuttings, sand, or native material, provided the material does not adversely affect the quality of the ground water.
   3. (C) The upper ten feet (10’) (minimum requirement) of wells constructed in unconsolidated formations shall be grouted (prescribed in 17 CAR § 11-506).
   4. (D) A well meeting requirements for a domestic water well is not required to be backfilled.

7. (3) Horizontal excavation.

   1. (A) The top of the bore hole may terminate at the bottom of the excavation for installation of horizontal pipes.
   2. (B) The horizontal excavation is not required to be backfilled with grout.
   3. (C) The grout shall be placed at least ten feet (10’) below the bottom of the excavation in unconsolidated formations.

(e) Approved fluids.

1. (1) The fluid or liquid used for circulation must be an approved fluid.
2. (2) Fluids that are highly combustible, corrosive, or toxic will not be used.
3. (3) A list of approved fluids will be maintained by the Arkansas Natural Resources Commission.
4. (4) Ethylene glycol is not an approved fluid.

5. (5) Approved fluids include, but are not limited to:

   1. (A) Water;
   2. (B) Salt water;
   3. (C) Calcium chloride; and
   4. (D) Food-quality propylene glycol.

(f) Joints and fittings.

1. (1) All joints and fittings installed and buried shall be heat, socket, or butt fused.

2. (2) Glue or clamps shall not be used below ground level unless the joint or connection:

   1. (A) Serves as a service outlet; and
   2. (B) Is not covered with earth.

(g) Circulating pipes.

1. (1) The circulating pipes shall be made of approved materials.
2. (2) Approved circulating pipe are approved gas rated materials such as polyethylene and polybutylene.
3. (3) Polyvinyl chloride (PVC) material is not acceptable for circulating pipes for closed loop systems below ground level.
4. (4) Polyethylene pipe meeting or exceeding PPI PE 3408, ASTM D 3350, cell classification 355434C, SDR-11 is approved.
5. (5) Polybutylene pipe meeting or exceeding ASTM D 3309, rated at one hundred sixty pounds per square inch (160 psi) at seventy-three degrees Fahrenheit (73°F) and also one hundred pounds per square inch (100 psi) at one hundred eighty degrees Fahrenheit (180°F), is approved.

(h) Pressure testing. Pipes:

1. (1) Shall be pressure tested at one hundred fifty percent (150%) of maximum working pressure for fifteen (15) minutes prior to installation; and
2. (2) Shall not leak.