PROJECT
41
vertical ‘borehole’ loops, which would be used as the
geothermal field for the plant.
SYSTEM DESCRIPTION
The system encompasses all of the lodge’s heating/
cooling requirements and can be split into two sections:
the central plant and the terminals.
Central plant
The heart of the plant is a heat pump-chiller, which
transfers energy between the geothermal field, hot-water
tanks, and cold-water tank. From these tanks, the
terminals throughout the lodge are fed with hot/cold
water as required to meet to the demand.
The heat pump then absorbs/rejects heat to and from
the geothermal field as required, or it will transfer energy
directly from the cold tank to the hot tank. The heat
pump has built-in circulation pumps to meet the required
duty of these primary loops.
Heat is also transferred from the hot water tank, via a
coil and circulation pump, to the domestic hot water as
a pre-heating device. This keeps the municipal water
separate to the treated, closed-circuit of the HVAC system.
Hot or cold water is delivered to various terminals
through a series of pumps. Large flows required by the
FCUs are delivered with Wilo Giga variable speed pumps,
and Lovato mixing group-sets supply the underfloor
system and deliver water that is neither too hot in winter,
nor too cold in summer. This control ensures a constant
temperature of water supplied to the floors according to
the design parameters.
The swimming pools are equipped with dedicated
circulation pumps that supply the hot water required
UFH pipe spaced at 200mm
in one of the villa bathrooms.
to be low maintenance. As such, it had to be designed to
run “in the bush”. This particular “bush” also came with
extremely high ambient temperatures.
The requirement was for:
• Heating load: 175kW
• Cooling load: 143kW.
The proposal was for a central plant that met all the
demands for heating and cooling throughout the lodge.
To eliminate the need for cooling towers or condensers
(which would be quite visible), the suggestion was made
to use ground as the energy source/dump.
The decision was then made to instead install a vertical
geothermal loop field comprising 30m × 100m deep
Continued on page 43 >>
www.plumbingafrica.co.za
July 2018 Volume 24 I Number 5