Drilling for ground-source heat pump (GSHP) installation is different from traditional drilling activities as the depths that need to be accessed are much shallower. Traditional drilling – to lay gas, oil or water pipelines for example – can require boreholes of up to 12 km long. The drilling depths required to lay ground and water heat exchanger (GHX) loops (described on page 99) for a GSHP average 150 m for vertical loops, and just 1.5 m for horizontal loops.

Horizontal directional drilling (HDD) and low range vertical drilling is used to create these shallow boreholes. Both Tracto-Technik (TT) and Vermeer have designed drills that expand upon basic HDD and vertical drilling technology for use specifically in the drilling of boreholes within which to lay GHX loops.

The nature of the drilling site also sets traditional and GSHP drilling apart. GSHPs are often installed at residential properties, and installations are frequently retrofit projects. As such, drilling has to be conducted within small spaces and the equipment needs to be highly sensitive to the surrounding landscape. As to be expected, these considerations were dominant in the respective design processes for TT and Vermeer as they developed their GSHP drilling machines.

For TT, this process has givenrise to the Geodrill 4R, and for Vermeer, the D20x22FX Series II.

Article continues below…

The Geodrill 4R by Tracto-Technik Asia Pacific

The Geodrill 4R is a drill rig that deploys geothermal radial drilling technology (GRD), combining features of both HDD and low-range vertical drilling.

GRD uses a method where one central drill chamber is used to create a main vertical borehole and attached drill bits shoot out horizontally from the chamber in multiple directions and angles of inclination, much like the roots of a tree, explains a TT spokesperson.

The Geodrill 4R can achieve inclinations such that boreholes can be created under existing buildings, thus making retrofitting projects less of a challenge, and, because the central drill chamber is the only part of the drill that pierces the surface of the earth, the surrounding top soil remains intact.

The D20x22FX SeriesII by Vermeer

The D20x22FX Series II is a flex-angle drill, so called because the drill shaft can be rotated. The D20x22FX Series II drill shaft can rotate at any specified angle ranging from 18 to 90 degrees once inside the ground.

Like the Geodrill 4R, the D20x22FX Series II combines HDD and vertical drilling features. The drill is capable of completing vertical and steep-angle boreholes, and is also a fully functioning HDD drill.

The drill has been designed to be compact, and at 165.1 cm in width, the D20x22FX Series II is able to be manoeuvred in confined spaces. It is also equipped with rubber tracks which help to evenly disperse weight for minimal ground surface disturbance.