What is a Water Heater?
First, before we say one more word. It is a water heater. Many will say “Hot water heater” and they would be WRONG. If it was a “hot water heater” the water would be supplied to the home or the unit already hot.
Like many other household conveniences, a good supply of hot water is only truly appreciated when it stops. And if it stops when you’re in the shower, this realization can arrive quite abruptly. Fortunately, it doesn’t happen that often.
The systems that provide hot water are generally reliable and operate for years. Most homes have a tank-type water heater. While others have a stand-alone instantaneous water heater. Either way, there is an appliance present which creates the hot water for a home or a fixture.
Not all water heaters are created equal. What is a tankless water heater? What are the differences between a tankless water heater and a conventional tanked water heater. This article will look at the differences.
Tank-Type Water Heaters
The standard water heater comes in two flavors: electric and fuel-fired. In the latter, the fuel most commonly used is gas, either natural or propane, but oil-fired heaters are popular in many areas. Fuel-fired units have a vent pipe at the top to carry away exhaust gases. Electric models, on the other hand, simply have a power cable that connects the heater to your electric service panel.
The job of the tank-type heater is not only to heat the water, but to store it until it’s ready to use. Therefore, in addition to the tank’s heating system, every tank is equipped with insulation to help keep the water warm between heating cycles.
On top of every tank you’ll find the water supply and delivery pipes. The supply pipe routes cold water to the bottom of the tank through the dip tube. The hot-water delivery pipe takes water from the top. For safety, all water heaters are equipped with a T&P valve (temperature-and-pressure relief valve). This valve opens if either the temperature or pressure of the water exceeds a safe limit. The valve is connected to a pipe that runs down the outside of the tank, ending about 6 in. from the floor. It’s a good idea to keep a bucket under the end of the pipe to catch water if the valve opens. The T&P valve should not be connected to a drain. If the valve did open, a sign that a problem exists, you might never know that it had opened.
Most tanks are made of steel, which is glass-lined on the inside to help prevent corrosion. In fact, corrosion is the primary reason that tanks fail. Once rust produces a hole, there are temporary fixes, but the tank should be replaced. All tanks also have an anode rod to control corrosion. The magnesium anode rod protects the tank by corroding in place of the steel. Because the rod is designed to corrode, it will eventually wear away. After this happens, corrosion of the steel accelerates. It’s a good idea to check the anode rod once a year, and replace it if necessary. At the bottom of every tank is a drain cock to empty the heater, and a valve on the supply pipe allows you to shut down the hot-water plumbing without affecting the cold-water supply to the house.
Because water heaters both heat and store water, the rate at which the water is heated and the capacity of the tank affect the supply of hot water at your fixtures.
The speed at which a unit heats water is called its recovery rate. This figure indicates the amount of water in gallons that can be heated to 100 degreesF in 1 hour. Once you draw water faster than it’s heated, the temperature drops.
However, because the tank stores hot water, its capacity also affects the ongoing availability at the tap. Choosing a water heater that has an appropriate capacity and recovery rate depends on how much water your home demands and how your unit heats the water. Typically, heaters with low recovery rates have a high tank capacity. Although it takes longer to heat the water, there’s more of it for intermittent use. Electric heaters fall into this category. On the other hand, a fuel-fired heater with a high recovery rate needn’t have a large tank, because it can heat the water faster. In general, electric models have the lowest recovery rate, and oil-fired units have the highest.
Tankless Water Heaters
Tankless water heaters, a.k.n as On-demand or Instantaneous water heaters, provide hot water only when it is needed. They do not have a reservoir holding heater water for or the storage of heater water waiting for use or distribution in a home.
HOW THEY WORK
Tankless water heaters heat water directly without the use of a storage tank. When a hot water tap is turned on, cold water travels through a pipe into the unit. Either a gas burner or an electric element heats the water. As a result, tankless water heaters deliver a constant supply of hot water. You don’t need to wait for a storage tank to fill up with enough hot water. However, a tankless water heater’s output limits the flow rate.
Typically, tankless water heaters provide hot water at a rate of 2–5 gallons per minute. Gas-fired tankless water heaters produce higher flow rates than electric ones. Sometimes, however, even the largest, gas-fired model cannot supply enough hot water for simultaneous, multiple uses in large households. For example, taking a shower and running the dishwasher at the same time can stretch a tankless water heater to its limit. To overcome this problem, you can install two or more tankless water heaters, connected in parallel for simultaneous demands of hot water. You can also install separate tankless water heaters for appliances — such as a clothes washer or dishwater — that use a lot of hot water in your home.
ADVANTAGES AND DISADVANTAGES
For homes that use 41 gallons or less of hot water daily, demand water heaters can be 24%–34% more energy efficient than conventional storage tank water heaters. They can be 8%–14% more energy efficient for homes that use a lot of hot water — around 86 gallons per day. You can achieve even greater energy savings of 27%–50% if you install a demand water heater at each hot water outlet. ENERGY STAR® estimates that a typical family can save $100 or more per year with an ENERGY STAR qualified tankless water heater.
The initial cost of a tankless water heater is greater than that of a conventional storage water heater, but tankless water heaters will typically last longer and have lower operating and energy costs, which could offset its higher purchase price. Most tankless water heaters have a life expectancy of more than 20 years. They also have easily replaceable parts that extend their life by many more years. In contrast, storage water heaters last 10–15 years.
Tankless water heaters can avoid the standby heat losses associated with storage water heaters. However, although gas-fired tankless water heaters tend to have higher flow rates than electric ones, they can waste energy if they have a constantly burning pilot light. This can sometimes offset the elimination of standby energy losses when compared to a storage water heater. In a gas-fired storage water heater, the pilot light heats the water in the tank so the energy isn’t wasted.