Manual 2100-537
I
Page 30 of 54
FIGURE 12
CLEANING WATER COIL
MIS-2836
PUMP
HOSE BIB (A)
HOSE BIB (B)
4. Scale Formation. Of all the water problems, the
formation of scale by ground water is by far the most
common. Usually this scale is due to the formation of
calcium carbonate but magnesium carbonate or calcium
sulfate may also be present. Carbon dioxide gas (CO
2
),
the carbonate of calcium and magnesium carbonate,
is very soluble in water. It will remain dissolved in
the water until some outside factor upsets the balance.
This outside inuence may be a large change in water
temperature or pressure. When this happens, enough
carbon dioxide gas combines with dissolved calcium or
magnesium in the water and falls out of solution until a
new balance is reached. The change in temperature that
this heat pump produces is usually not high enough to
cause the dissolved gas to fall out of solution. Likewise,
if pressure drops are kept to a reasonable level, no
precipitation of carbon dioxide should occur.
REMEDIES OF WATER PROBLEMS
Water Treatment. Water treatment can usually be
economically justied for water loop systems. However,
because of the large amounts of water involved with a
ground water system, water treatment is generally too
expensive.
Acid Cleaning the Water Coil or Heat Pump Recovery
Unit. If scaling of the coil is strongly suspected, the coil
can be cleaned up with a solution of Phosphoric Acid (food
grade acid). Follow the manufacturer’s directions for
mixing, use, etc. Refer to the “Cleaning Water Coil”, Figure
12. The acid solution can be introduced into the heat pump
coil through the hose bib A. Be sure the isolation valves are
closed to prevent contamination of the rest of the system by
the coil. The acid should be pumped from a bucket into the
hose bib and returned to the bucket through the other hose
bib B. Follow the manufacturer’s directions for the product
used as to how long the solution is to be circulated, but it is
usually circulated for a period of several hours.
LAKE AND POND INSTALLATIONS
Lakes and ponds can provide a low cost source of water
for heating and cooling with a ground water heat pump.
Direct usage of the water without some ltration is not
recommended as algae and turbid water can foul the water to
refrigerant heat exchanger. Instead, there have been very
good results using a dry well dug next to the water line
or edge. Normal procedure in installing a dry well is to
backhoe a 15 to 20 foot hole adjacent to the body of water
(set backhoe as close to the water’s edge as possible). Once
excavated, a perforated plastic casing should be installed
with gravel backll placed around the casing. The gravel
bed should provide adequate ltration of the water to allow
good performance of the ground water heat pump.
The following is a list of recommendations to follow when
installing this type of system:
A. A lake or pond should be at least 1 acre (40,000 square
feet) in surface area for each 50,000 BTUs of ground
water heat pump capacity or have 2 times the cubic feet
size of the dwelling that you are trying to heat (includes
basement if heated).
B. The average water depth should be at least 4 feet and
there should be an area where the water depth is at least
12 to 15 feet deep.
