Troubleshooting Your Solar Water Heating System
Troubleshooting Your Solar Water Heating System

When hot water is used in a home, it is often difficult to know whether it was heated by the sun or by an auxiliary water heater.
Some solar water heating systems may have indicators which show when there is a problem, but many do not. This fact sheet is
designed to help the homeowner determine whether or not their solar water heating system is working properly and, if not, some
possible steps to remedy the problem. For those that are uncomfortable with small repairs, any reference to remedies requiring repair
work should be referred to a repair contractor. Lists of repair contractors are available from the North Carolina Solar Center.
The first step in determining if a solar water heating system is operating properly is to turn off the auxiliary water heater. This is
accomplished by turning off the circuit breaker to an electric unit or turning a gas unit to pilot or off. This test should not be attempted
in winter months since the availability of solar energy is less and may cause a shortage of hot water even when the system
is working properly. During periods of sunny weather and moderate hot water usage, most solar domestic water heating systems will
be sufficient to handle the water heating needs of a typical home. If the auxiliary unit has been off for more than a day and bright
sun is striking the collectors, the piping to and from the storage tank should be warm to the touch (or very hot--BE CAREFUL).
This means that the collectors are supplying heat. If no heat is felt or significant shortages in hot water are experienced, it is likely
there is a problem with the system.
The following is a listing of components contained in most solar systems which may be responsible for poor system performance:
Possible Cause
1. Partially shaded
2. Improper orientation
3. Improper tilt
4. Insufficient area
5. Improperly plumbed
6. Dirty glazing
1. Improper operation (cycling,
late turn-on)
2. Improper wiring or loose connections
3. Faulty sensor wiring
1. High heat losses
2. Nighttime thermosiphoning
3. Improperly plumbed
4. Isolation valves closed
5. Flow blockage
6. Low system pressure
1. No power
2. Faulty pump
3. Runs continuously
4. Improperly installed
1. Insufficient size
2. High storage losses
1. Reduce shading or move collectors.
2. Check direction; face south +/- 45 degrees.
3. Check tilt; set equal to latitude +/- 15 degrees.
4. Install more collectors.
5. Compare with system schematic.
6. Clean--only when cool.
1. Check sensor placement. Adjust for good contact with
piping. Insulate from surrounding air.
2. Compare with system schematic. Check for proper
connections. Tighten loose connections.
3. Check wiring for breaks, metal contact, water exposure
and/or corrosion. Seal all splices.
1. Check insulation for splits, deterioration, absence.
2. Check if collector pipes are warm at night. Check for
pump running at night. Contact installer.
3. Compare with system schematic. Check flow direction.
4. Open valves.
5. Flush system. Check effluent for dirt/scale.
6. Check pressure gauge. Refer to ownerÂ’s manual for
correct pressure.
1. Check breaker, pump cord, controller fuse--if any.
2. Listen for irregular noises in pump operation. Feel
pipes for temperature difference. Pipe returning from
collectors should be warmer than pipe going to
3. Check control system for breaks and shorts.
4. Compare with system schematic.
1. Tank should have roughly 1.5 gallons of storage per
square foot of solar collector area
2. Check insulation and location of tank.

For more specific symptoms and remedies, the following is a list which may help pinpoint specific problems:
Pump runs
No hot water in
Noisy system
Does not drain
Fluid leak
High electric use
1. Turn to normal "run" or "auto" mode.
2. Check wiring for continuity. Repair or replace.
1. Replace check valve.
1. Check wiring and connect properly.
1. Oil per manufacturerÂ’s recommendation.
2. Loosen vent screw, if any. Bleed air.
1. Purge system by running water up supply pip
and out drain on return line (isolation valves
2. Isolate piping from walls.
1. Disassemble and clean. Replace if necessary.
1. Check for vertical drop in all horizontal runs.
2. Check for high points in collector piping.
1. Isolate system, turn off collector and contact
1. Tighten adjustable connections.
1. Tighten nuts. Replace seal/packing if necessary.
2. Replace seat washers. Redress seat. Replace valve
if necessary.
1. Check wiring. Contact installer if necessary.
2. Check setting and adjust to desired temperature.
1. Check tank plumbing. Contact installer if
Check Valve
Vacuum breaker/
Air vent
Possible Cause
1. Controller in "on" position
2. Shorted or open sensor
1. Stuck open (nighttime
1. Sensor wires reversed
1. Bearings need lubrication
2. Air locked
1. Entrapped air (direct
systems only)
2. Pipe vibration
1. Dirty or stuck seat
1. Insufficient slope
2. Air pockets
1. Burst due to freezing or
excessive pressures
1. Thermal expansion
loosened connections
1. Valve gland nuts loose
2. Seats deteriorated
1. Lower element connected
2. Thermostat set too high
1. Collector return above
tank thermostat

North Carolina Solar Center ce
Box 7401, NCSU, Raleigh, NC 27695-7401
(919) 515-3480,
Toll free in NC: 1-800-33-NC SUN
Comments: 0