Monday, February 15, 2010
Tankless water heater nice for Earth and you
By Ann Robinson and Annie Schwemmer
Having hot water available at our fingertips has to be one of the great inventions of the past few centuries.
Credit goes to Edwin Ruud, a Norwegian mechanical engineer, as the inventor of the automatic storage water heater in 1889. Ruud later emigrated to Pittsburgh where he pioneered the early development of both residential and commercial water heaters.
The water heater in most of our homes has changed little from its first concept of a tank of water that is heated by electricity or some form of gas and sits waiting for someone to use it.
When the water in the tank begins to cool down, the unit is fired up to reheat the water to maintain it at the desired temperature. So, all day, when everyone might be at work and school, and all night when you are asleep, energy is being used to maintain the temperature of the water in your tank so it will be ready at a moment's notice.
This is obviously not the best scenario in terms of energy efficiency. Hence, the concept of the tankless water heater — a device that heats only the amount of water you need when you need it. Manufacturers tout these units as providing a 30 percent savings on energy used to heat water.
These units are about the size of a carry-on suitcase and are mounted on the wall. A water-flow sensor triggers the heating as soon as you turn on the faucet. A combustion fan forces air into the burner while an igniter sparks the electricity or gas into a flame.
The water supply line then passes through a copper heat exchanger that concentrates the heat around the pipes, quickly transferring the heat into the water. A bypass introduces cold water into the hot water if necessary to achieve the preset, desired temperature.
A printed circuit board is the brain of a tankless water heater. It monitors all these functions and fires the unit as needed. The supply flows to the tap at approximately 7.5 gallons per minute, varying slightly depending on the temperature of the incoming water.
The most effective placement of a tankless water heater is as near as possible to the fixtures that use the most water. However, the most cost-effective placement is to use the same location as the tank you are replacing. Tankless water heaters require a 3/4-inch diameter water supply line and a simple 120-volt electrical outlet.
Tankless water heaters must be ventilated just as your standard model. However, the vent pipe will need to be replaced with what is called a concentric pipe. With this type of setup, combustion air is drawn in through the outer ring of the pipe, while flue gases are expelled through the inner pipe.
The tankless unit itself costs around $1,000 and a "starter kit" for the concentric vent connection runs between $200 and $250. Other materials needed include some form of water connection piping (copper, CPVC or PEX), gas connections (black or galvanized metal piping or corrugated stainless steel tubing), and various valves and shut-offs.
In our opinion, it would require the equivalent of a master's degree in do-it-yourself skills to have the plumbing, electrical, and carpentry abilities required to handle this project on your own.
For the rest of us mortals, the quote from a local plumbing company was around $3,600 to buy the unit and have it professionally installed. Compared to the installed price of a standard water heater (from $700-$900 for a 30- or 50-gallon tank), you can see that there is some pay-back time until you break even and begin to reap the financial benefits of the more efficient unit.
As with many eco-friendly products, we need to factor in more than the initial cost into our decision-making process. Along with the pay-back time, consumers need to also consider the benefit to the eco-system and the wonderful convenience of continuous hot water they receive from Day 1.
If you want to do something nice for the Earth and for yourself, consider installing a tankless water heater in your home. As always, we welcome your home architect design questions at firstname.lastname@example.org.