Ask the Architect

Tankless water heaters

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Q. My house had a fire, and everything is being replaced. While doing all this, we were told that the boiler, which partially blocks our basement stairs, could be replaced with a much smaller one, hung on the wall. This would give us more room to get down the stairs and even fit a new washer and dryer, so I’m wondering: Are these new types of boilers safe, how do they work, and is there any kind of special fuel, like nuclear or something, that needs a special permit? We’ve never heard of them before, and wonder how long they’ve been around. What can you tell us?

A. You might say that installing these higher-efficiency, wall-hung units is a tankless job, but somebody had to be the first. A man named Edwin Ruud, a mechanical engineer, developed the first tankless water heating unit in 1889, after emigrating from Norway and settling in beautiful Pittsburgh. The first units were actually gas-fueled, although later, more popular models were electric. Today you can get either.
Your question about fuel type must be due to how small the tankless units are compared with large boilers in the average home, assuming that they might be nuclear-powered, but rest assured, no radioactive fuel is required. If you did have a nuclear-fired boiler, I imagine the permitting process would only take about 16 years, including protesters on your front lawn and an evacuation plan in place. Tankless boilers are space-saving, replacing the big round hot-water tank and the separate boiler unit, which take up as much as 3 feet by 7 feet of floor space.
Tankless units are attached to a wall — usually an outside wall, where possible, so that the exhaust from the unit can be blown straight outside through the wall, avoiding the need for a chimney and utilizing what is referred to as a direct-vent metal duct. There is some danger if the wall vent is placed where it can be touched, since it gets very hot and must be at least 5 feet from other construction and 3 feet from windows. There also should be no windows, doors, decks or other construction within 15 feet above the vent, for safety reasons.

The reason these units are so efficient is that the moment you turn on a hot-water faucet, the flow triggers the boiler to turn on a flame just below a small caldron and coil, instantly heating water that flows immediately to the sink, shower or room heater. The big hot-water tank heaters have a thermostat and are usually set to 120 to 140 degrees. They will fire anytime they drop below that level and heat up many gallons of water. They do this all day long, regardless of whether you’re home or not. That’s why instant-on, on-demand tankless units save water, fuel and money. They only heat when you need hot water. Stay warm this winter!

© 2017 Monte Leeper. Readers are encouraged to send questions to yourhousedr@aol.com, with “Herald question” in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper, architect.