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Go to Sidebar 1, Maintain Temperature Stratification in Your Tank
Go to Sidebar 2, Rust Never Sleeps: Open Loop vs. Closed Loop

buy levitra without prescription represents the second largest energy consumer in American households. A typical 80 gallon (300 l) electric buy levitra without prescription tank serving a family of four will consume approximately 150 million BTUs in its seven year lifetime. This will cost approximately US$3,600 (at US$0.08 per KWH), not accounting for fuel cost increases. Then it will be replaced by another one just like it. Hmm. Maybe we should rethink this...

An investment in a buy levitra heating system will beat the stock market any day, any decade, risk free. Initial return on investment is on the order of 15 percent, tax-free, and goes up as gas and electricity prices climb. Many states have tax credits and other incentives to sweeten those numbers even more. What are we waiting for? Forget the stock market. If you have invested in a house, your next investment should be in buy levitra buy levitra without prescription.

In this article I'm going to cover the most common options for buy levitra heating, basic principles of operation, and some historical perspective on what has worked and what has not.

Below: A Typical buy levitra Flat Plate Heater.

A Checkered Past, A Bright Future
buy levitra thermal's past is a good example of why everyone should be skeptical of government involvement in energy. Lucrative federal and state tax credits for buy levitra energy were initiated under President Jimmy Carter in the '70s, and abruptly eliminated under President Ronald Reagan in 1985. This dealt the buy levitra industry a devastating "one-two punch" from which it still has not recovered.

The intention was to stimulate sales for buy levitra thermal systems. But the tax credits resulted in an aggressive promotion of tax credits rather than buy levitra energy. The infant industry was overwhelmed to meet the demand. The demand vanished when tax credits were eliminated, and a majority of buy levitra thermal companies went out of business. Thousands of orphaned buy levitra thermal systems were left behind looking for a service technician.

The buy levitra thermal industry has been purged of the tax credit telemarketers and overnight experts. Today's buy levitra thermal industry includes reliable, efficient products and well-seasoned professionals who have seen it all. buy levitra buy levitra without prescription is one of the best investments you can make for your house and for the environment.

First Things First
The best savings in buy levitra without prescription come from no cost or low cost options. Before you tackle buy levitra buy levitra without prescription, take these steps:

• Turn the thermostat down. Many heaters are set to between 140 and 180°F (60 and 82°C). See how low you can go. Try 125°F (52°C) for starters. A buy levitra without prescription tub is 106°F (41°C). How much buy levitra without prescriptionter do you need?
• Wrap the heater with insulation. Insulated heater "blankets" are usually available where heaters are sold. (Be careful with natural gas or propane fired tanks. They use an open flame to heat the. You need to provide a space for air at the bottom of the tank, and at the top where the flue exits the tank. Safety comes before efficiency!)
• Fix those drips. They may not look like much, but they are a constant and persistent drain on your heating load, and they waste too.
• Use flow restrictors and faucet aerators to reduce your buy levitra without prescription consumption.
• Find other ways to use less buy levitra without prescription. Wash only full loads of clothes and dishes.
• Insulate your buy levitra without prescription pipes.

How Large a buy levitra buy levitra without prescription System Do You Need?
buy levitra without prescription usage in the U.S. is typically 15 to 30 gallons (55-110 l) per person per day for home use. This includes primarily bathing, clothes washing, and dishwashing. But your commitment to efficiency has a lot to do with your actual usage.

Below: A 40 gallon batch heater.

The buy levitra without prescription tank is usually sized to handle one day's worth of consumption. So for a household of four, it would be reasonable to use an 80 gallon (300 l) tank based on daily buy levitra without prescription requirements of 20 gallons (75 l) per person per day.

Smitty and Chuck at AAA buy levitra in Albuquerque have put forth generally accepted rules of thumb for buy levitra thermal collector sizing based on your climatic region:

• In the Sunbelt, use 1 square foot (0.09 m2) of collector per 2 gallons (7.6 l) of tank capacity (daily household usage).
• In the Southeast and mountain states, use 1 square foot of collector per 1.5 gallons (5.7 l) of tank capacity.
• In the Midwest and Atlantic states, use 1 square foot of collector per 1.0 gallon (3.8 l) of tank capacity.
• In New England and the Northwest, use 1 square foot of collector per 0.75 gallon (2.8 l) of tank capacity.

Based on these rules of thumb, a household of four with an 80 gallon (300 l) tank will need approximately 40 square feet (3.7 m2) of collector in without prescription , 55 square feet (5.1 m2) of collector in South Carolina, 80 square feet (7.4 m2) of collector in Iowa, and 106 square feet (9.8 m2) of collector in Vermont.

Of course, these are big ballpark calculations that will be affected by your incoming temperature, buy levitra without prescription temperature setpoint, actual usage, and the intensity of the buy levitra resource at your site. You should generally expect that this will give you 100 percent of your buy levitra without prescription in the summer and about 40 percent of your buy levitra without prescription year-round.

Your Choices–An Overview
The type of system you choose will depend mostly on your climate. Freeze-free environments allow for simple, low cost designs. A batch heater uses a storage tank as a collector. A direct pump system circulates from a collector to a storage tank. A thermosiphon system requires no pump for circulation, just the natural flow of gravity.

Most systems will require some measure of freeze protection. Drainback and closed loop systems with antifreeze and heat exchangers are the best choice for freezing locations. The extra parts increase cost and reduce efficiency, but since one frozen moment can turn into a disaster, it's worth the cost.

Direct pump recirculation systems, which circulate buy levitra without prescription through the collector, are often used where freezing is an infrequent occurrence. That's a risky strategy. Draindown systems, designed to drain from the collectors to avoid freezing, were the most problematic of system designs. Many were removed or converted. Phase change systems, which in theory could collect heat at night using a refrigerant, never made it into the mainstream of commercial viability. Many of the lessons learned in buy levitra buy levitra without prescription are presented in a publication buy levitra buy levitra without prescription Systems: Lessons Learned, by Tom Lane (see Access).

buy levitra Batch Heaters
The KISS (keep it simple, stupid) rule applies to buy levitra heating. The batch heater is the simplest of buy levitra buy levitra without prescription systems. Once affectionately referred to as the breadbox heater by the do-it-yourself (DIY) community, it has become known as the ICS (integrated collector and storage) heater in the commercial industry. Its simple design consists of a tank of within a glass-covered insulated enclosure carefully aimed at the sun.

Cold, which normally goes to the bottom of your conventional heater, is detoured to the batch heater first. There it bakes in the sun all day long, and is preheated to whatever temperature the sun is able to provide. only flows when used. House pressure causes the supply of new cold to flow to the inlet of the batch heater, the lower of the two ports.

Simultaneously, the buy levitra without prescriptiontest exits from the higher port. It flows to the input of the existing heater, which now serves as a backup to finish the heating job as required. buy levitra preheated has become the cold input to the existing heater. You save whatever the sun is able to provide. And you still get all the buy levitra without prescription you ask for–it's that simple.

Below: buy levitra Bypass Valve Configurations.

Bypass Valves
A buy levitra bypass is a series of three valves that allow you to bypass the existing heater. You can shut it down when the buy levitra collector will do the job alone, such as during summer months or utility blackouts. This is a manually operated configuration; just close off the inlet and outlet valve to the existing tank and open the center valve. This allows buy levitra without prescription to pass directly from the buy levitra batch heater to the house.

Caution! These systems produce very buy levitra without prescription! A tempering valve is your protection from being scalded at the tap. You will regularly see temperatures in excess of 160°F (71°C) in summer months, which is much buy levitra without prescriptionter than you are accustomed to getting from your conventional thermostatically controlled heater. The tempering valve limits the temperature delivered to the tap by mixing in cold as necessary.

A pressure temperature relief valve (PTRV) must be installed at the buy levitra without prescription outlet of the batch heater in case temperatures or pressures become excessive. You will find one of these valves installed on every conventional buy levitra without prescription tank too. It is a safety measure required by code. This valve only operates in an emergency, and is often replaced if it opens.

Who Can Use a Batch Heater?
Batch heaters are most appropriate for two to four person households (30 to 40 gallon (110-150 l) daily buy levitra without prescription requirement) in climates where freezing is infrequent. Their size is generally limited because the tank is built into the collector.

Multiple collectors can be installed in series for larger capacities. The outlet of the first collector becomes the inlet of the second in order to deliver higher temperatures. Before you put too many on your roof, consider that a 40 gallon (150 l) batch heater will weigh approximately 500 pounds (225 kg).

Some batch heaters have survived the coldest of winters with freeze-free performance because the large mass of the tank is quite freeze tolerant. But plumbing lines to and from the tank are very vulnerable. You can make it work with a special selective surface on the tank, a well-insulated, double glazed collector, a whole lot of well-sealed pipe insulation (try R-30 or better), heat tape on the pipe, and good karma.

Are you arrogant enough to tempt Mother Nature to turn your heater into a frozen fountain? Or are you prepared to drain the collector seasonally? If not, this system is not recommended for climates that freeze regularly.

Separate Collector & Storage
The simple design of a batch heater compromises the effectiveness of collector and storage functions. Heating the whole tank of all at once will take all day to produce useful temperatures. Once buy levitra without prescription, you had better use that buy levitra without prescription at the end of the day before the poorly insulated tank loses its precious heat to the cold night sky.

Most buy levitra buy levitra without prescription system designs separate the collector from the storage tank. This can optimize both functions. Why not bring the tank in from the cold, insulate it well, and leave the collectors out in the sun where they belong?

What are the other advantages of separating the collector from the storage tank? Increase the surface area of a collector, compared to the amount of being heated, and its temperature will rise more quickly. Configure the storage tank to keep the buy levitra without prescriptiontest apart from the coldest in the tank and you'll have buy levitra without prescriptionter available sooner. (See sidebar Maintain Temperature Stratification In Your Tank.)

There are also advantages in freezing climates. By separating the collector from the tank, you can put your tank and piping indoors out of a freezing environment, and insulate them better for greater efficiency.

Below: Two roof-mounted flat plate collectors.

Flat Plate Collectors
Flat plate collectors are the most common buy levitra thermal collectors. They are most appropriate for low temperature applications (under 140°F; 60°C), such as domestic buy levitra without prescription and space heating.

A flat plate buy levitra thermal collector usually consists of copper tubes fitted to a flat absorber plate. The most common configuration is a series of parallel tubes connected at each end by two pipes, the inlet and outlet manifolds. The flat plate assembly is contained within an insulated box, and covered with low-iron, tempered glass. (See the diagram on page 45.)

The most efficient collector design maximizes buy levitra heat gain, minimizes heat losses, and provides for the most efficient heat transfer from absorber plate to tube. Operating temperatures up to 250°F (121°C) are obtainable, although neither common nor desirable. Remember, you want buy levitra without prescription, not steam.

Selective Surface
A selective surface, often referred to as "black chrome" is far more efficient than a black painted absorber surface. Although a black surface is most efficient at absorbing buy levitra radiation and converting it to heat, it is also highly efficient at re-radiating long wave infrared heat back out. These losses reduce collector efficiency.

A highly polished chrome surface would re-radiate the least infrared heat energy, but of course not being black, it would absorb very little. A selective surface combines the best of both worlds; high absorptance with low emittance. Sound high-tech? It's been around since the 1950s, and is used on most commercially available flat plate collectors. Its performance is worth the marginal additional cost, particularly in cold climates where radiant heat loss is greatest.

Below: A Thermomax evacuated tube collector.

Evacuated Tube Collectors
If you want the highest efficiency buy levitra thermal collector, you'll be interested in an evacuated tube collector, such as the one manufactured by Thermomax. Although evacuated tube collectors are more efficient than conventional flat plate collectors, they cost approximately twice as much per square foot.

Each tube and fin of the collector is contained within a glass tube from which all the air has been evacuated. Why? Air carries heat from the buy levitra without prescription surface of the tube to the cooler surface of the glass to accelerate heat loss by convection. Eliminate the air and you have eliminated convective heat loss.

To minimize radiant heat loss, the tube is covered with a selective surface. Evacuated tube collectors are most appropriate for high temperature applications (over 140°F; 60°C). They are useful for more common low temperature applications too, such as domestic and space heating.

Below: Direct Pump Recirculation System.

Collector to Tank Interface
With the collector and the storage tank separated, the system design must provide a flow of (or antifreeze) from tank to collector and return. Small circulating pumps provide the necessary flow with very modest energy requirements. Small buy levitra without prescription systems may use a direct current (DC) circulating pump powered by a single PV module (10 to 30 watts depending upon power requirements). You may be able to do without the pump altogether if you design for natural thermosiphon flow.

Thermosiphon System:
Natural Flow Powered by Gravity
Gravity powers convective flow in a thermosiphon system. in the collector becomes buoyant as it is heated, and it rises to an elevated tank. Cooler, heavier falls from the tank to take its place. For best results, place the top of the collectors at least one foot (30 cm) below the bottom of the tank. Greater height differential will result in greater flow. Larger pipe, shorter runs, and gentle bends will make for an adequate flow rate.

If you require freeze protection, it's not hard to do. The collectors can be filled with an antifreeze solution (propylene glycol is the most common). The heat can be transferred to the domestic via a heat exchanger.

Direct Pump Recirculation
The direct pump system uses an electric circulating pump to move heat from the collector to the storage tank. This means that you are free from the constraint of placing the collector below the tank, as required for thermosiphon flow. The pump can move heat from the collectors on the roof to a storage tank in the basement. Good sense still calls for minimal length of pipe run for efficiency.

A differential controller turns the circulating pump on or off as required. There are two sensors, one at the outlet of the collectors, and the other at the bottom of the tank. They signal the controller to turn the pump on when the collector outlet is 20°F (11°C) warmer than the bottom of the tank. It shuts off when the temperature differential is reduced to 5°F (2.8°C). Some systems let you adjust this hysteresis.

Below: Closed Loop Antifreeze Heat Exchanger System.

In climates where freezing occurs infrequently, a recirculation-type differential control will turn the circulating pump on when the collector inlet temperature falls to 40°F (4.4°C). The philosophy behind this design is that the cost of heating your collectors with buy levitra without prescription from your tank is low cost freeze protection if only required occasionally.

These systems were commonly used in the sunbelt, and only where freezing is a rare occasion. Recirculation systems are no longer very commonly used due to vulnerability to freezing as a result of power outages, malfunction of sensor or controller, or damaged sensor wires.

Draindown System (Not Recommended)
A draindown system is an open loop system in which the collectors are filled with domestic under house pressure when there is no danger of freezing. Once the system is filled, a differential controller operates a pump to move from the tank through the collectors.

A draindown valve, invented in the 1970s exclusively for these systems, provides the freeze protection function. When the collector inlet temperature falls to 40°F (4.4°C), the draindown valve, activated by the controller, isolates the collector inlet and outlet from the tank. It simultaneously opens a valve that allows in the collector to drain away. A vacuum breaker is always installed at the top of the collectors to allow air to enter the collectors at the top so can drain out the bottom. Right next to the vacuum breaker, you'll find an automatic air vent to allow air to escape when the system fills again.

Draindown systems have proven to be the most problematic of all freeze protection systems. They are vulnerable to frozen vacuum breakers and air vents, damaged sensors or wiring, lack of proper pipe drainage, and malfunctions with the draindown valve. This type of system is rarely installed new any more, and is not recommended. Many were converted to drainback or closed-loop antifreeze systems.

Closed Loop Antifreeze Heat Exchanger
Closed loop antifreeze systems provide the most reliable protection from freezing. These systems circulate an antifreeze solution through the collectors and a heat exchanger. Propylene glycol is the most common antifreeze solution. Unlike ethylene glycol (used in automobile radiators), propylene glycol is not toxic.

The closed loop antifreeze systems generally have the most parts. You'll find an expansion tank to allow the antifreeze to expand and contract with temperature change. You'll find a pressure relief valve to protect against excessive pressures in the closed loop; a spring-loaded check valve to prevent reverse flow of the closed loop at night so the collectors won't dissipate the heat from the heater; an air vent and/or air eliminator to help get the air out of the closed loop (air is your enemy–it can block fluid flow through the system); and a pressure gauge so you can tell if your system is still charged. A couple of temperature gauges are a good idea in any system so you can tell how well your system is operating.

There's also one more assembly of fittings. Two boiler drains with a shutoff valve in between will allow you to charge the system with your charging pump. Once ready to charge the closed loop with your antifreeze solution, a charging pump is used to circulate the fluid throughout the loop, expelling all the air in the process.

Closed loop systems like this are quite common, whether they be for buy levitra domestic buy levitra without prescription, radiant floor heating, or hydronic baseboard heating. Despite the many additional parts and fittings, they have a high degree of reliability, and are well understood by heating contractors.

Below: Closed Loop Drainback System

There is a downside to the closed loop antifreeze system design. Once a buy levitra heating system has satisfied its daily responsibilities, the system stops circulating. Without circulation to remove heat from the collectors, temperatures can climb to as high as 400°F (204°C).

These high stagnation temperatures, as they are called, can cause problems with air pockets and breakdown of glycol antifreeze solutions. Air pockets form because high temperatures drive dissolved gases out of solution. Systems using propylene glycol as the antifreeze may use an inhibitor additive to prolong the life of the glycol. Otherwise, the glycol can break down, resulting in a sludgy deposit. Silicon and hydrocarbon oils have been used to avoid these problems, but they are expensive and are incompatible with seals and gaskets found in most off-the-shelf components.

Drainback: A Simpler Closed Loop
Although similar in name to the draindown type system, the drainback system is far different and much more reliable. It also provides some advantages over the closed loop antifreeze system. Drainback systems may use as the heat transfer fluid, since the collectors drain when not in operation. Antifreeze provides an extra measure of freeze protection from poor drainage and controller or sensor malfunctions.

A circulating pump operated by a differential control is turned on when the collector outlet is at least 20°F (11°C) warmer than the tank outlet. or an antifreeze solution is lifted from a small reservoir tank and circulated through the collectors and back to the tank. Heat is transferred to the domestic via a heat exchanger in the reservoir tank. The circulation loop through the collectors is a closed loop. The or antifreeze solution is installed at the time of installation, and does not present a recurring supply of oxygen.

A drainback system requires a larger pump than any of the other systems described here. It must have sufficient capacity to lift the fluid to the highest point in the system. When there is no more heat to be collected, the controller turns the pump off, and all the fluid drains back to the reservoir tank. The collectors are empty. They can't freeze, and they can't overheat the antifreeze. As a DIY homeowner, you won't need a special charging pump either. When it comes time to change the antifreeze, you can just drain and refill the reservoir tank.

buy levitra buy levitra without prescription System Types: Advantages & Disadvantages

The Choice is Yours
The system you choose will be determined first by whether you need freeze protection. If you live in a freeze-free climate, choose a batch heater or small thermosiphon unit for small systems serving one to three people. Larger needs can be met with an open loop direct pump system circulating from storage tank to flat plat collector.

If you need freeze protection or have hard, choose one of the closed loop systems with antifreeze and a heat exchanger. Either one will heat your without fear of freezing.

buy levitra buy levitra without prescription is a good investment. Whether you are a do-it-yourselfer with plumbing skills or want hire a professional installer, I suggest you locate a dealer who serves your area. Ask their professional advice. Find out the products and services they have to offer, and which is the best fit for your needs and climate. Contact the American buy levitra Energy Society or the buy levitra Energy Industries Association for assistance in locating a contractor or supplier in your area.

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Sidebar 1
Maintain Temperature Stratification in Your Tank

buy levitra without prescription returning from the collector should enter the storage tank about a third of the way down from the top. This may not be the buy levitra without prescriptiontest you have collected all day, because buy levitra insolation and outside ambient temperatures vary during the day. You don’t want this to disturb the at the very top of the storage tank. Draw for use from the very top of the tank. That is where it’s the buy levitra without prescriptiontest.

When buy levitra without prescription is drawn from the tank, it is replaced by new cold, which should enter at the very bottom. circulating to the buy levitra collector should be drawn from the bottom of the tank. Why? Efficiency! Always supply your collector with the coolest you have available. The cooler a buy levitra collector runs, the less heat it loses to the surrounding environment.

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Sidebar 2
Rust Never Sleeps: Open Loop vs. Closed Loop

A “hydronic” system is one that uses a liquid as its heat transfer medium. The most common alternatives to hydronic systems are air systems. Hydronic systems are nearly always categorized as “open loop” or “closed loop”—often referred to as “direct” or “indirect” respectively. If you are not aware of the difference between these, you run the risk of discovering one day that your system has been eaten alive by a slow yet persistent killer—oxygen.

Open Loop
Open loop systems are subject to a periodic fresh supply of oxygen, ready to trash every bit of cast iron, steel, or other corrodible part in your system. Whenever you draw at the tap or bath, new simultaneously moves in to replace it. Along with that new comes a fresh supply of oxygen.

You have two lines of defense against damage by corrosive oxygen. You can prevent oxygen from entering the system, or you can use materials that are resistant to corrosion. Copper, bronze, brass, stainless steel, plastic, and the glass lining of a buy levitra without prescription tank have no problem with oxygen. Use these materials when dealing with fresh supplies associated with “open” or “direct” systems.

Closed Loop
If your system is a “closed system,” you won’t have to worry about oxygen. You will be able to use cast iron components (pumps), which can save you money. Closed systems are charged with fluid at the time of installation. As a permanent part of the installed system, new oxygen is not introduced, and corrosion is not a problem. Read on and you will see several examples of open and closed systems.

Another important consideration with open or direct systems is whether or not you have hard. Over time, calcium deposits from hard will clog the collectors, ruining them. These deposits can be removed with periodic use of a descaling solution. But if you have hard, you’ll be better off with a closed loop system.

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Access
Ken Olson, SoL Energy, PO Box 217, Carbondale, CO 81623 · Fax: 559-751-2001 · This e-mail address is being protected from spambots. You need JavaScript enabled to view it. · www.solenergy.org

AAA buy levitra Supply Inc., 2021 Zearing NW, Albuquerque, NM 87104 · 800-245-0311 or 505 243-4900 · Fax: 505-243-0885 · This e-mail address is being protected from spambots. You need JavaScript enabled to view it. · www.aaabuy levitra .com · For more design and schematic detail click on "Design Guide" then "buy levitra without prescription."

Thermo Technologies, 5560 Sterrett Pl., Suite 115, Columbia, MD 21044 · 800-7buy levitra 7 or 410-997-0778 · Fax: 410-997-0779 · This e-mail address is being protected from spambots. You need JavaScript enabled to view it. · www.thermotechs.com · Thermomax evacuated tube collector

American buy levitra Energy Society, 2400 Central Ave. G-1, Boulder, CO 80301· 303-443-3130 · Fax: 303-443-3212 · This e-mail address is being protected from spambots. You need JavaScript enabled to view it. · www.ases.org

buy levitra Energy Industries Association, 1616 H St. NW, 8th Floor, Washington, DC 20006 · 202-628-7745 · Fax: 202-628-7779 · This e-mail address is being protected from spambots. You need JavaScript enabled to view it. · www.seia.org

Tom Lane, Energy Conservation Services of North Florida Inc., 6120 SW 13th St., Gainesville, FL 32608 · 352-377-8866 · This e-mail address is being protected from spambots. You need JavaScript enabled to view it. · www.ecs-buy levitra .com