Operating instructions

4
IV. EARTH LOOP WATER
PIPING
Since water is the source of energy in the wintertime and
the energy sink in the summertime, good water supply is
possibly the most important requirement of a geothermal
heat pump system installation. There are two common
types of water supplies, closed loop systems and open
loop systems.
A. Closed Loop Applications
A closed loop system recirculates the same
water/antifreeze solution through a closed system of
underground high-density polyethylene pipe. As the
solution passes through the pipe, it collects heat (in the
heating mode) that is being transferred from the relatively
warm surrounding soil through the pipe and into the
relatively cold solution. The solution is circulated to the
heat pump, which pulls heat out of the solution, and then
back through the ground to extract more heat from the
earth.
The GeoSource 2000 is designed to operate on either
vertical or horizontal closed loop applications. Vertical
loops are typically installed with a well drilling rig up to
200 feet deep or more. Horizontal systems are typically
installed with excavating or trenching equipment
approximately six to eight feet deep, depending on
geographic location and length of pipe used. Earth loops
must be sized properly for each particular geographic
Figure 1 – Closed Loop Water Plumbing
area, soil type, and individual capacity requirements.
Contact your local installer or ECONAR’s Customer
Support for loop sizing requirements in your area.
Since normal wintertime operating entering water
temperatures (EWT) to the heat pump are from 25
o
F to
32
o
F, the solution in the earth loop must include
antifreeze. GTF and propylene glycol are common
antifreeze solutions. GTF is methanol-based antifreeze,
which should be mixed 50% with water to achieve freeze
protection of 10
o
F. Propylene glycol antifreeze solution
should be mixed 25% with water to obtain a 15
o
F freeze
protection. DO NOT mix more than 25% propylene
glycol with water in an attempt to achieve a lower than
15
o
F freeze protection, since more concentrated mixtures
of propylene glycol become too viscous at low
temperatures and cannot be pumped through the earth
loop. Insufficient amounts of antifreeze may result in a
freeze rupture of the unit, and can cause unit shutdown
problems during cold weather operation (when the heat
pump experiences the longest run time) due to loop
temperatures falling below the freeze protection of the
loop solution.
Flow rate requirements for closed loops are higher than
open loop systems because water temperatures supplied to
the heat pump are generally lower (see Table 3). Between
2.5 to 3.0 gallons per minute (GPM) per ton are required
for proper operation of the heat pump and the earth
coupled heat exchanger.