Introduction
This section was developed to help share the reliability experiences of solar water heating professionals with other professionals and the public. This page was developed because repair and replacement cost information is so so central to the success of solar water heating, yet so difficult to obtain. This page is intended to grow as additional contributors come forward (if you have knowledge in this area, please Contact The Energy Guy. At this time, we have a highly informative look at solar repair frequency and cost from Steve Shewmake.

Contents

Part 1 - A Solar Repairmen's Notes on Reliability


Links

Part 1 - A Solar Repairmen's Notes on Reliability
By Steve Shewmake "The Solar Repairman." August 19, 1997

Forward
Pumps
Controls
Tanks
Collectors
A few last words

Foreword
The "Solar Repairman," began his solar career in 1977 by enrolling in the Solar Technician Program at San Jose City College in San Jose, California. From 1979 to 1985 he installed hundreds of systems, first in the San Francisco Bay area and then throughout the Sierra Nevada Foothills. After thirteen years of climbing on roofs and squeezing into tight mechanical room spaces, his doctor recommended a line of work a little less physically demanding.

Beginning in 1990, Steve became an author, writing a series of books on solar repair. He is currently working on a new book covering the repair of most common types of systems (under one cover). The following "Notes on Reliability" are a result of his review of "around a thousand" solar service receipts covering the five year period from 1985 to 1990. I'd like to personally thank Steve for his efforts in preparing this information as well as his willingness to share it with all of you!

- Ray Darby, "The Energy Guy"

PUMPS:
Pumps were the SDHW component most frequently replaced by this solar repairman (although freeze protection valves might be a close runner-up). The most commonly found pumps were Grundfos, Taco and Armstrong of the stainless steel or bronze type. The pumped system types were predominantly draindown, drainback or closed-loop (recirculation freeze protection systems were rarely found at this elevation).

Drainback systems experienced the most pump failures, generally due to insufficient reservoir fluid levels. These were also the most expensive to replace as the pumps were larger, due to head requirements, relative to the pumps found in other type systems.

Summary of findings:
Average age of the pumps replaced: eight years (range: 5 to 10)
The oldest pumps found were in closed loop systems that had never experienced system pressure loss and appeared to have little or no air in the system.

Most common causes of pump failure:
(1) plumbing leaks affecting pumpóelectrical
(2) air in the pump (cavitation) and
(3) overheating, often determined to be a product of poor system design, such as an undersized pump or improper collector (area) to storage (volume) ratio.

Average pump cost during this time period: about $140 (range: $80 to $200)
Average labor cost was about $50. In terms of service labor costs, pumps that are easily accessible are best.

Conclusions:
Proper system design and pump sizing are critical to pump life. Pumps should be in clean, dry, ventilated locations for the greatest chance of longevity. Other factors affecting pump life include water quality (minerals), pH (corrosion from acidity or buildup from alkalinity) and air in the pumping loop (inadequate air purging or air traps caused by improper plumbing).

CONTROLS:
Independent Energy and Heliotrope were the most commonly found controls. Although most control failures were a matter of replacement, it was often possible, with Heliotrope controls for example, to have the electronic circuit board repaired. A large part of the repairs involving controls had to do with sensor (thermistor) replacement and not the control itself. Actual control failures were rather uncommon.

Summary of findings:
Average replacement control cost: $80.
Average repaired control cost: $50.
Average control replacement service call: $120
Average rebuilt control install service call: $90
Average sensor replacement service call: $65
Average age of controls replaced: 7 years (range: 3 to 9)
Most common visible cause of sensor or control failure: moisture (in the case of thermistors), or improperly water proofed wiring connections. With controls, the problem was often linked to plumbing leakage.

While simple control or thermistor replacement was usually reasonable, replacement of controls with digital readouts, especially those controlling multi-loop systems (i.e. solar stove coil, solar spa) could run in the hundreds of dollars to replace. Labor would also double or triple.

Conclusions:
Protecting controls and thermistor wiring connections from the elements greatly increases their life expectancy. Electronic circuit boards and components can have an indeterminable lifetime regardless of their environment, but for best results they should be installed in clean, dry locations.

TANKS:
This section includes all types of tanks encountered, including four port water heaters, stainless drainback and passive thermosyphon tanks, and other types of storage tanks (i.e. glass lined steel, polypropylene). Also, tank replacements during this time period were uncommon so the random sampling is not as accurate as with pumps, for example.

Summary of findings:
Average age of water heater style storage tank replaced (usually 66, 82 or 120 gallon): 9 years

Average total cost of replacing an 82 gallon tank (the most common): $700

Some types of passive thermosyphon tanks developed leaks at stainless weld joints and were repaired at a total average cost of $260 (tank removed and Tig welded)

Average total cost to replace stainless type drainback tank: $650

Most common cause of premature glass lined steel tank failure (seven years or less): leaks in plumbing above the tank causing outside corrosion.

The only repairs involving polypropylene tanks (drainback) were minor repairs of the lid seals or internal heat exchanger. Not enough tank repairs were done to provide measurable data.

Conclusions:
The average life of a water heater style solar storage tank (Rheem, State, A.O. Smith, Bradford White) will probably be less than its conventional, non-solar counterpart due to temperature extremes beyond the manufacturers recommendations. If a SDHW system is properly sized to avoid excessive temperature extremes, the tank will have a better chance of longevity. The grade of stainless steel used and the quality of welding is critical to the life expectancy of stainless tanks.

COLLECTORS:
In terms of lifetime and replacement, this is the most difficult SDHW component to evaluate. Few solar technicians, if any, have observed solar panels long enough to see very many die of old age. The only ones I have replaced were damaged in some way by nature, highly acidic or alkaline fluid, or poor mounting. The system type would also have a great bearing on this. In a drainback or closed-loop system, for example, the pH and mineral content of the fluid could be controlled. In my opinion, a structurally well-built solar hot water collector with an all-copper absorber, extruded aluminum box and good low-iron glass cover, and mounted properly, should outlast most of us doing the evaluating (barring serious acts of God).

A few additional thoughts:
The other thing I did almost as frequently as replacing pumps and sensors was explain to solar system owners how their system worked and advise them on how to maintain things. This was probably as essential to system longevity as the other things mentioned.

And as an example of what's possible with proper care: my own SDHW system has an 82 gallon Solar Industries tank that's almost 18 years old!

Haven't yet found any - anyone know of a link? If so, please send me the URL.