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Domestic Hot Water Systems

The principles involved in heating household water with the sun are not complex or new. However, state-of-the-art solar-heating equipment must be designed, installed and used properly to effect dollar and energy savings for the consumer.

The chief component of any solar water heating system is the collector. Solar collectors absorb the radiant energy of the sun and change it into heat energy. The flat-plate collector is the predominant type used in solar domestic hot water (DHW) systems.

A typical flat-plate collector consists of a rectangular surface (absorber) with a series of fluid tubes running lengthwise along it. Liquid (in Florida, usually water) from the storage tank flows through the tubes. The absorber is usually composed of a good conductible material, such as copper or aluminum, and is coated black to absorb as much sunlight as possible. As the plate is heated, by exposure to sunlight, it transfers the heat to the liquid in the tubes.

A second type of collector is the Integral Collector Storage (ICS) unit. The outstanding feature of this collector is that collection and storage are in the same unit. ICS units are very similar to standard flat plate collectors, though they contain either very large storage tubes or small tanks.

The bottom and sides of the absorber are insulated to minimize heat loss. In addition, a translucent glass or plastic cover placed above it allows sunlight to strike the absorber while reducing the amount of heat that can escape.

In most systems, the collector is mounted on the roof of the dwelling, oriented to the south or within 45 degrees east or west of due south, and tilted between 20 and 40 degrees to horizontal. Systems may be ground-mounted with the same orientation and tilt as roof-mounted systems.

When collectors are mounted on sloping roofs, they should be mounted parallel to the roof because of structural and aesthetic considerations. If the natural roof slope does not correspond to the optimum collector tilt, the collector still should be mounted parallel to the roof. The collector area may be increased if necessary.

The storage tank is the second major component in the solar DHW system. A conventional electric tank modified for solar service may be used, although specially designed, sized and super-insulated solar tanks are available.

In a pumped system, cold water is drawn from the bottom of the tank, circulated through copper piping to the rooftop collector, heated in the collectors, then returned to the top of the storage tank. In a thermosiphon system, pumps and controls are not necessary. Here, the tank is elevated above the collector; as the water is heated, it rises naturally and is returned to the top of the tank.

Similarly, ICS systems also do not require pumps or controls. On household water draws, hot water from the collector flows to a standard hot water tank where it replaces the water drawn. This system serves primarily as a cost-effective preheater to the conventional water tank.

The storage tank should be large enough to provide one day's hot water demand--i.e., 20 gallons per day per adult and 15 gallons per day per child. Standard tank sizes available are 40, 52, 82, 100, and 120 gallons. When converting from electric water heating to solar, an additional tank may be added to provide the needed capacity, or the conventional tank may be replaced with a solar-designed tank. Solar tanks are constructed with more insulation and piping connections than conventional tanks.

Backup heating can assist during extended cloudy weather and periods of excessive hot-water consumption. In converted electric water heaters, this is accomplished by leaving the upper element connected (the lower element must be disconnected) and setting the thermostat at 120 degrees F. If your home is equipped with a dishwasher (without an automatic water heater feature), a setting of at least 130 degrees F is recommended. Tanks designed specially for solar are equipped with a single electric element in the upper portion of the tank. In both electric and solar tanks it is desirable to leave the electric current to the element turned off as much as possible to maximize the solar contribution. A special switch may be installed in a convenient place for this purpose.

As a rule of thumb for Florida, the storage tank size (in gallons) should be between 1.5 and 2.5 times the size of the collector area. For example, a family of four using an average of 80 gallons of hot water a day would need an 82-gallon tank with between 32 and 54 square feet of collector area. However, individual calculations specific to the area and collector model are preferable. Several sizing procedures are available to the consumer and the installer. Generally, a solar system will provide a range of 75 to 90 percent of a household's hot water needs, taking into consideration cloudy weather and periods of excessive hot-water consumption.

Systems that use pumps and controls to circulate the water usually have these two components mounted near or on the storage tank. The pump is a small circulating type made of bronze, brass or stainless steel. The controller--which regulates when and how long, and in some cases, how fast the pump operates--is usually a solid-state electronic device. It senses when the collector is able to heat the water in the tank and turns the pump on. When the water in the tank approaches the collector temperature (within 3 to 5 degrees F), the controller turns the pump off.

Other devices are available to control the flow of water between the tank and collector. Timers are used to operate the pump in some systems, but you must exercise vigilance during unfavorable weather. A snap-switch control also is available. This device activates the pump when the collector heats to a specified temperature. The hot water in the collector is then returned to the tank, and cooler water is fed to the device. Sunlight striking the PV panel is converted to electricity, which powers the pump.

The controller also may be designed to provide freeze protection by turning the pump on to run warmed water through the collector when its temperature falls near freezing. This type of freeze protection results in a loss of hot water and will not work in the case of power failure, which often accompanies freezing conditions. Other methods of freeze protection include manual and automatic draining of the collector, a freeze prevention valve, or they use a close-looped rather than an open-looped system. A freeze prevention valve is installed near the collector. Whenever temperatures approach freezing, the valve opens to let warm water flow through the collector, thereby preventing water freezing in the collector pipes. Freeze protection is an essential feature to any solar system, even in the usually warm Florida climate.

In an indirect system, an antifreeze solution circulated through the collector, and a heat exchanger transfers the heat from the antifreeze solution to the tank water. The heat exchanger prevents the antifreeze solution from coming into contact with the potable water. In this manner, there is never any water in the collector--only antifreeze solution. This system is common in climates where freezing weather occurs frequently.

Drainback systems also are frequently used in areas susceptible to freezes. In these systems, water in the collector and exposed piping drains into an insulated reservoir tank each time the pump shuts off. During freeze conditions, there is no water in the collector or collector piping.

Comparison Shopping

Purchase of a solar energy system is a major consumer decision. Comparison shopping is essential and will pay off in the long run. There are many solar equipment manufacturers and distributors in Florida; consequently, your selection of systems and installers may be larger than you thought.

Prior to contacting a solar equipment supplier or installer you should be familiar with the various types of solar equipment described in this booklet. If you'd like additional information on solar equipment you can contact the Florida Solar Energy Industries Association at 1-800-426-5899 or the FSEC Public Information Office.

You do not need to be a technical expert to purchase solar equipment. It is more important for you to deal with a reputable company in your area that has the appropriate license(s). Most areas require a permit from the building department to install a solar system.

In addition to solar contractors, plumbers, mechanical contractors, some HVAC contractors and others may be licensed to install solar equipment in your area. If you have any questions about permitting or licensingin your area, contact your local building department.

It is recommended that you also contact the local consumer protection office and the Better Business Bureau to check on the contractor that you plan to do business with.

To select contractors in your area you can consult the Yellow Pages or you can call the Solar Hotline at 1-800-59-SOLAR for a list of licensed contractors in your area who have successfully completed the installation and service training workshop offered by FlaSEIA.

In addition to price considerations you should ask to see the FSEC collector and systems certifications for the solar equipment that you are considering. Florida law requires that all solar systems be approved by FSEC. This requires testing and certification of the collector and submittal of system diagrams, homeowner manuals, and a list of system components to be approved. For a list of approved systems contact the FSEC Public Information Office.

Thermal Performance Ratings: Current collector ratings for pool and DHW applications are published by the FSEC Public Information Office on a quarterly basis. While a collector is rated at three different operating temperatures, the list provides the rating appropriate for the particular application. Therefore, the pool collector list provides low temperature ratings and the DHW collector list provides intermediate temperature ratings.

The rating is presented in two forms: total output, or Btu/day; and output per square foot, or Btu/square foot x day. To approximately compare the thermal efficiency among various collectors, use the Btu/square foot x day figure. The higher this number is, the better the thermal design of the collector, which means it will require fewer square feet of collector area to heat the water.

To determine the amount of energy delivered per dollar of investment, use the Btu/day figure. Divide this figure by the total cost of the installed system. Multiply the result by the number of collector panels or piping modules used. This comparison can be made you receive several estimates from different vendors.

FSEC Certification Label: Collector manufacturers and their licensees are required to affix a label to each collector indicating FSEC certification. This label presents much of the same data as the summary information sheet. The consumer can verify that the collector installed is the same as the one sold by comparing the label and summary information sheet data. The building inspector also can use the label to verify that the collector has been certified and is the model specified on the permit application supporting documents.

Summary Information Sheet: Each FSEC-certified collector is issued a Summary Information Sheet which contains detailed data on the collector such as model number, construction materials, size, test results and rating. The rating is presented in both Btu/day and kilojoules (kj) per day. The kilojoules figure can be used to measure electricity savings. Divide the kj/day figure by 3,600 to find the daily energy savings in kilowatt hours (kWh). That figure can then be multiplied by the current price of electricity (cents/kWh) to find the approximate daily money savings. The Summary Information Sheet may be available from the vendor or from the FSEC Testing Office.

FSEC Approved Solar Energy System Sheet: All solar energy systems sold or manufactured in Florida must be approved by FSEC. Each system is issued an approval sheet indicating the various components that make-up the complete system. A schematic of the system as installed also is provided. This sheet again may be used as verification by the consumer and the building inspector that the equipment installed matches specifications, and, in fact, has been approved as required by law. The system Approval Sheet may be available from the vendor or the FSEC Testing Office.

FSEC Approved Solar Energy Systems List: This list provides a quick reference to approved systems for the consumer and building official. Systems are listed by company, model number and date of approval. The list is published on a quarterly basis.

Warranties And Insurance

As with any consumer product, the warranty for your solar energy system should be your assurance that the manufacturer and installer stand behind the system. The terms of the warranty indicate how strongly they will stand behind it. State and federal warranty laws have been designed to protect you.

Federal warranty law stipulates requirements where a written warranty is made available on a product. It defines a written warranty as an affirmation of fact or a written promise for a specified period of time. For example, if your sales contract contains a clause that guarantees installation and materials for a year, you have a written warranty. This triggers the requirements of the federal law. The law does not require that a written warranty be offered. If you receive nothing in writing, the product is covered by an implied warranty.

Written warranties are differentiated in the federal law as either full or limited, and the appropriate designation must appear on the warranty document. The full warranty provides for the following:

-A defective product will be fixed (or replaced) free, including removal and reinstallation if necessary.
-The product will be fixed within a reasonable time after you complain.
-You will not have to do anything unreasonable to get warranty service (such as shipping the collector back to the factory).
-The warranty is good for anyone who owns the product during the warranty period.
-If the product can't be fixed (or hasn't been after a reasonable effort to do so), you get your choice of a new product or a refund.

The limited warranty provides less protection than the full warranty. For example, a limited warranty may:

-Cover only parts, not labor.
-Allow only a pro-rata refund on credit.
-Require you to return a heavy product to the store for service.
-Cover only the first purchaser.
-Charge for handling.

The implied warranty is imposed by law automatically upon the sale of a consumer product. First, the product you buy must be fit for its ordinary purpose; for example, a solar water heater must heat your water. Second, if you buy a product relying on the seller's advice that it can be used for a special purpose, then this advice may create a warranty. However, all implied warranties may be avoided by the seller if he states that no warranty is given, or that you buy it "as is." This is unacceptable in a solar transaction.

Certain system defects or disrepair discovered during the warranty period may not always be covered by a warranty. For example, if a component fails because of faulty installation rather than a product defect, the manufacturer of the product may not be required to repair the component under the warranty. For this reason it is often critical to secure warranty coverage from the installer for the entire system, including design and miscellaneous parts. A desirable period for such warranty coverage is one year from the date of installation.

Another potential gap in warranty coverage falls in the area of freeze damage. Exposure to freezing temperatures can cause a solar collector to sustain serious damage in the absence of adequate freeze protection. Where freeze protection is provided, and fails, the consumer may be left with a damaged collector and no recourse under any product warranty. The typical collector warranty contains a disclaimer which effectively relieves the manufacturer of any obligation to repair or replace a freeze-damaged collector. The typical freeze protection device contains a disclaimer limiting coverage of "incidental damages." Failure of the device will obligate the manufacturer to repair or replace it, but will not require him or her to repair or replace the collector that froze as a result. Experience has shown that recourse to your homeowner's insurance is the most expeditious and least costly method to cover repair or damage caused by freezing conditions.

According to the U.S. Department of Housing and Urban Development (HUD), insurance companies have indicated they foresee no difficulty in providing coverage to homeowners with well-engineered and soundly constructed solar energy systems. The system may be underwritten in the standard homeowner's policy.

The Sales Contract

Prior to making a final purchase decision, you should obtain written estimates from various companies selected for comparison. Most companies will provide an estimate free of charge. The written contract proposal will make comparison shopping much easier. It should contain a description of the system and components, including make and model number (and size where appropriate). Total system cost including all materials and labor must be provided. It is advisable to include a clause deferring full payment until your system is installed and operational.

Other provisions that may be included in the contract are warranty coverages--especially any installation warranty--and details regarding responsibility for procurement of and payment for necessary building permits.

Once the proposal is accepted and signed by both parties, it becomes a binding contract. Some contracts may fall under provisions of Florida law which require a three day "cooling off period." A clause advising the consumer of his or her rights and responsibilities under this statute must be place conspicuously in the contract.

Economics And Financing

Electric-resistance water heating represents about 25 percent of the average electric bill in Florida. A solar water heater usually will provide about 75-90 percent of the household's hot water requirements on an annual basis. Therefore, a solar system owner can achieve an overall 20 percent annual energy saving.

The cost of a solar system varies greatly, depending upon the materials of the various components and services offered by the seller. Current average price for an installed, active system ranges between $2,000 and $3,500. Specially designed low-cost systems also are now available which provide about 40-50 percent of the household's hot water requirements for an installed cost of less than $1,000. Compared with the cost of a conventional (electric or gas) water heater, a solar system has a higher initial cost. However, to make an accurate economic comparison, the cost of operating a conventional heater and renewable energy financial incentives also must be considered.

Consider the following example: If the average installed system cost is $2,500 and the electric utility offers a $400 rebate, the net system cost is $2,100.

A family of four consumes, on the average, a total of 3600 kilowatt hours per year to heat water electrically. A solar water heater can save 75 to 90 percent of this electric consumption or approximately 3200 kilowatt hours per year. At an average of 9 cents per kilowatt hour, this is an annual savings of $288. Additional benefits to consider are that the savings are in after tax dollars; you're using an environmentally clean source of power to heat water; and you've made a real property investment in your home which will appreciate over time.

A "simple payback" analysis [$2,100 net investment) /$288 (annual savings)] shows a payback of 7.29 years of 13.7% tax free return on your investment. Considering that the average system last over 20 years, the savings over the remaining life of the system (12.71 years) are additional tax free dollars in your pocket.

Once the feasibility of a solar system and its cost/benefit aspects have been investigated, you may need to consider financing. Financing is available through commercial banks, savings and loan associations, credit unions and some system dealers.

It is important that you take the following three steps to ensure the fairest financing terms your credit merits:

1. Make sure the interest rate quoted to you conforms with federal truth-in-lending statutes, which require the lender to disclose to the borrower the annual percentage rate charged in the loan. This percentage includes the interest rate, discount points and other charges collected by the lender.
2. If the rate does not equal or better the equivalent FHA maximum rate, find out why.
3. Negotiate the best possible rate and check other lending institutions for a better deal in terms of interest rate, down payment and length of loan.

-A satisfactory credit record.
-The cash needed at the closing of the mortgage.
-Enough steady income to make the monthly mortgage payments without difficulty.

The Veterans Administration strongly supports energy conservation and will guarantee loans to purchase, construct, refinance, repair or improve homes with solar energy systems. Eligible veterans can obtain loans for the full value of a solar system.

Operating And Maintenance

It is essential that you understand the operation and maintenance requirements of your system. This will prevent minor problems from becoming major ones or avoid common system malfunctions altogether. The best route to this understanding is through careful review of the operating and maintenance instructions manual provided by the seller.

While each system is different--and consequently operating and maintenance instructions differ--there are certain basics that should be included in every manual. FSEC has made inclusion of these basics mandatory under the solar standards program. Under law, a manual including the following information must be provided with every solar water and pool heating system:

1. Seller's name, address and system model number;
2. Explanation to the buyer of the requirements for installation, operation and maintenance;
3. Procedures for start-up, shut-down, collector draining and any special emergency procedures and safety precautions;
4. Description of major components;
5. System diagram;
6. Parts list and the name and address of a company offering service on the system.

As with any major appliance, even the finest system may malfunction from time to time. You may be able to solve simple problems yourself with relative ease, using the troubleshooting checklist developed by FSEC in diagnosing system malfunctions. However, be sure you are familiar with recommended procedures before attempting a repair. Note also that unauthorized repairs may void the warranties on the system or components. When in doubt, contact the responsible firm listed on the warranty, which may be the installer, distributor or manufacturer. If the system or the faulty component is no longer under warranty, ask the installer about proper procedures to remedy the problem. If for some reason the installer cannot be contacted, try the manufacturer.

Consumer Complaints

Local agencies, such as a consumer protection office or a Better Business Bureau, may be able to investigate complaints and problems that have not been resolved by other methods.

The division of Consumer Services in Tallahassee maintains a toll-free number (1-800-342-2176) as well as several district offices to assist in complaint resolution. The Attorney General's Office and local state attorney offices receive and investigate complaints regarding unfair or deceptive business practices.

The Department of Professional Regulation maintains a toll-free number for consumer complaints (1-800-342-7940) and another to report unlicensed activity or verify a contractor's license (1-800-851-1204). That office has jurisdiction over licensed contractors and may intervene where a violation of the state's construction contracting laws may exist. If your contractor is not licensed, you also may check with the enforcement arm of your building department or the state attorney's office. Installation of a solar system by an unlicensed contractor (unless it is the homeowner) is a violation of state and local law.

The Department of Banking and Finance also may have jurisdiction over your problem if the system was financed. This may be especially important if the company which sold or manufactured your system is no longer in business. The financing entity may be liable for repairs to you system in certain case. For more information, contact the Department of Banking and Finance (904/487-2583).