How To – Solar Water Heating

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    Energy requirements for Hot water can account for 20% of an average homes fuel use but with Solar Hot Water Heating you can reduce or eliminate that cost from your budget. The average home even in northern areas can expect to reduce their heating costs by 50% or more with average paybacks within 15 years.

    The only downsides of Solar Water Heating is the initial expense. However there are a number of programs that will allow you to take deductions on your local, state and federal taxes. In addition if you time your install with a refinance or initial home purchase loan you can reduce your cost another 2 to 4 percent immediately, not to mention increased resale value.

    Although all homes can benefit from a Solar water heater in the summer months. Northern States will see less benefit during the fall, spring and winter months. For this reason if you are located in Minnesota or maybe even as low as Oklahoma during parts of the winter you will still need standard heating elements in your water heater when outside temperatures fall too low to be useful.

    To figure out the suns potential in your area you can use this website
    ! Select the following options for a fixed panel
    Data type = Average
    Instrument Orientation = Flat Plate Tilted South at Latitude

    Tracking Panels means the panel follows the suns path during the day. There are other options for degree offsets and horizontal or vertical positions if you want to mount the panel on the side of your home instead of the roof.


    So lets take a look at how a solar hot water system works.

    The basic parts include

    Hot water Storage Tank – Which is just a large hot water heater.
    Solar Collector Panel – Most people will purchase and not build their own.
    Circulating Pump – Pumps fluid to the Collector to gather heat.
    Thermostat Control – Tells the pump to turn off when outside temperatures fall.
    Fluid Lines – Used to carry liquid between the collector and the storage tank.

    As you can see from the parts list the system is fairly simple. The most complex part is the thermostat which can be a variety of different types to allow different programming for your location but for the most part it is really no different then a standard home heater thermostat.

    The Circulator Pump is the only real moving part. It will require replacement after a few years. Many are rated for high temperatures that exceed standard hot water needs meaning if you are use to a circulator pump being in your furnace you can expect a much longer life of maybe 10 years or more.

    The Solar Hot Water Collector should really be purchased and not built. The exact size of the collector will be based on meeting the daily needs of the number of people living in the home. For average homes you can expect to need about 60 square feet of area for four people.

    The Size of your storage tank is based on the number of people in ht house. Since the tank will need to store heat for evening hours they are larger then standard hot water heaters. You can expect to install a 80 or 100 gallon tank. The suggested storage is 1.5 gallons per square foot of collector but you may find that installing one tank and one water heater with elements can allow you to isolate the system during the winter.

    Fluid lines should be made of a material that can withstand both heat and cold. Although the fluid pumped through the system will drain out when the circulator pump is not running metallic lines are always best when plumbing outside a heated building. Soft Copper or Galvanized pipe should work well however some systems may be installed with a higher rated PEX or flexible tubing. This is fine if the product has a long life warranty and is easily accessible for repairs or replacement. Plastic tubing should not be exposed to the light as it will break down faster over time.

    Preparing for the Collector
    When you install the collector panels you may find that you need to beef up your roof to provide the extra support but for most homes this will not be necessary. You will not need to remove your shingles but you will need to take care when attaching the collector and use a sealant under any screws to reduce the chance of leaking.

    Sizing The Collector
    Once you have taken care of any support problems or have repaired or replaced old roofing materials as needed you will need to figure out the size of the collector that can serve your needs.

    Standard Single Collectors range in size from 10 to 40 square feet and a 20 square foot collector will produce about 16,000 btu per day.

    The minimum collector area for a standard home is 40 square feet or Two 4×5 collectors. This will provide enough for 2 to 3 adults. For every extra person you will need to add 10 square feet.  This is a rule of thumb and you should check with your manufacturer for exact specs.

    The location of the building will also have an effect. For people in the Northern Hemisphere you need an unobstructed Southern exposure but if the home is positioned a skew to the South then you may need to add additional collectors or tilt them by use of supports to get the best results.

    Installing the System
    If you are performing the work yourself you will need some extra help to move the storage tank and place the panel on the roof.

    The fluid lines can be installed the day before and should be run inside the home as much as possible. You don’t want to run lines up the side of your house because you will lose heat in cooler months even if they are insulated. Copper pipe should be used where you exit the roof and use a silicon sealer and roof flashing to reduce the possibility of leaks. A vent Pipe Flange should help in this area if you can find one small enough.

    Electrical will include a sensor and a shutoff switch when you need to turn the system off. Run a 15amp circuit to the area and make your connections in a switch box. Follow directions as provided by the manufacturer. If you have a hot water heater already installed you will probably just need to install a switch box and connect from there.

    Plumbing to the home’s Hot Water Lines. This process is just like any standard hot water heater. The fluid lines that feed up to the collector are a sealed system and do not mix with your homes water. All you need to do is relocate the cold water supply and hot water out feed to the storage tank. If you are keeping your water heater for use in the winter you can install a T adapter to cut off the feeds to the storage tank in the winter.

    Positioning the Collector Panels on the Roof
    Although a professional installer may wrestle these things up a ladder It is really worth it to pay $150 for 4 hours of rental on a boom truck with an operator. A boom truck is a smaller version of a crane and will be able to lift the panels to the roof in a few minutes. This will make the job much safer and reduce the risk of breaking the panels. Once in location with fluid lines attached you will need to make sure that the system will drain back when turned off. This will insure that the lines in the panel don’t burst during winter freezes. Your system should have a reserve tank next to the circulator pump with a level gauge that you can check to make sure all fluid returns.

    Once you have installed your system you should check all the connections for leaks for the first few days and then weekly or so for the next few months. Always make a good inspection of the panels after a storm and during the winter when snow will accumulate. The heat transfer fluid will need to be replaced on a schedule which will come with your system. You can expect it to last a few years.

    Solar Hot Water Heating is very simple and will last 20 to 40 years.


    Other Info

    Here is a video explaining a real world install in the state of Maine. You will see that even in colder months in northern states you can still capture heat from the sun and reduce your fuel use by 35%. In summer months the hot water heating needs should be served almost completely by the solar water heater except when there are long periods of rain or cloud cover. As in our HowTo they have done the work themselves reducing their costs and applied tax incentives that will lower their first year expenses. If you include the cost in a home loan or refinance you can see additional savings. Also with higher heating costs this home if sold will bring a higher asking price and will attract buyers that don’t want high heating bills.



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