The pressure and/or suction may be operated directly by the system control. In
other cases, the opening and closing may be triggered by an electrical signal from
the control. This is usually low voltage: 12 or 24 volts. Check both the tubing and
any wiring when troubleshooting pool heating systems control valves.
4.3.9 Heat Exchangers, A reduction in heat exchanger performance may be
caused by scale from hard water, glycol sludge or reduced flow due to an airbound
loop, improperly positioned valve or defective pump. Any of these will cause an
overall rise in collector loop temperatures.
Leaks may be caused by improper installation techniques or materials, physical
stresses, corrosive fluid or incompatible seals materials.
Another common cause of leaks is freezing. If the solar fluid is circulating below
32F, it can easily freeze the water in the heat exchanger. This circulation may be
from reverse thermosiphoning or a defective control or sensor running the system at
If city water pressure is entering the solar loop in closed loop or draindown systems,
the loop pressure may be much higher or lower than normal.
4.3.10 Insulation, Inadequate, damaged or missing piping insulation will
reduce system performance considerably. However, before deciding pipe insulation
is the problem, make sure:
flow rates are proper and balanced
collectors are clean and unshaded
controls and sensors are operating properly
tank and heat exchanger piping is correct
valves are properly positioned
Tanks losing heat overnight may have inadequate insulation, but also check for:
o reverse thermosiphoning
o "invisible loads" (such as a dripping hot water faucet)
o inaccurate or poorly placed tank thermometer
o defective control or sensor running the system at night
Wet insulation offers very little resistance to heat flow, but may appear intact. If a
leak occurs in a system, check all the pipe insulation to be sure it is dry.
4.3 TROUBLESHOOTING OPERATIONS