Title: +175=737.001_IK001_Brukermanual for Refra varmepumpe.Produktinformasjon.pdf
Borehole Thermal Resistance Many factors affect the thermal resistance of the ground loop. These include the pipe properties, flow rate, backfill and grout properties, soil properties and fluid properties.Backfill and Grouts The backfill also plays a major part in performance. Air gaps or separation should be avoided as air is a natural insulator. Grouting is the most common material for backfill. It can seal the borehole off from surface water penetration. Standard grout actually has a poor conductivity, so the bore hole diameter should be minimized (Approximately 120 mm diameter) to limit the grout’s affect. There may be local code requirements to grout the entire borehole, or the borehole may penetrate multiple aquifers that need to remain isolated.