Tankless water heaters are popular for their compact size and low energy use, and propane fuel means they can be installed virtually anywhere. In regions that see snow and frigid temperatures, keep these eight tips in mind when specifying, installing, and maintaining tankless units.

1. Choose a size that’s cold-weather ready.

In a cold climate, the first consideration is to size tankless units properly, says Linda Cahill, vice president of Tankless Concepts, in Falls Church, Virginia, which sells and installs Rinnai and Navien products. “In winter, when the incoming water temperature is colder, the tankless unit can’t heat as much hot water,” she says. “We size units based on winter temperatures, making sure there will always be enough hot water for the house.” For example, in the Washington, D.C., area, a unit that can produce about 8.5 gallons per minute in summer might produce only 5.5 or 6 gallons per minute in winter.

2. Design for the coldest conditions.

Jason Fleming, senior marketing and customer care manager at Noritz, says it’s important that builders consider the “worst-case scenario” in terms of how low the ground water temperature can go and how much water a household uses, and to understand the delta T, or the difference between the set temperature of the unit and the ground water temperature. (For example, a 120-degree Fahrenheit setting and 60-degree Fahrenheit ground water temperature requires a 60-degree Fahrenheit rise, which is the delta T.) “The larger the gap, or higher the delta T, the lower the performance flow of the unit,” he says. “Our sizing charts show performance, or flow rate, at each delta T.”


Noritz’s propane and gas tankless water heaters are protected from freezing weather through an electric ceramic heater that surrounds the heat exchanger.


3. Indoors or outdoors?

Noritz’s tankless water heaters have freeze protection through an electric ceramic heater that surrounds the heat exchanger, but some are rated for lower temperatures than others, so installers need to check the unit specs to determine what works best in their climate. That said, while water heaters in southern California, where the company is based, are usually installed outside, they must go indoors in climates with sustained freezing temperatures.

4. Be sensible with venting.

Proper venting is critical, too: “Make sure the heaters are not vented into oncoming freezing winds, and that the vent run is long enough to keep the heater working properly,” Fleming says. “Six feet is the recommended minimum for cold areas.”

5. Offer snow advisories.

During a record-setting snowstorm in Washington, D.C., Tankless Concepts reminded its customers to clear the snow from around the vents. “The vent is supposed to be 12 inches above the ground when vented out a wall,” Cahill says. “Our recent snow was high enough, especially with drifting, to cover the vent pipes. Rinnai models take in air from the outer pipe, and if it is blocked by snow, the unit turns itself off. You need a couple feet of clearance around the vent for the unit to work properly; as soon as you clear it, you’re back in business.”

6. Remind recirculators.

As a precaution, Tankless Concepts tells its customers with units that have a recirculating loop (which shortens wait time for hot water) to turn off that function overnight in a storm. That’s because if the vent termination is snowed under, the unit will try to keep working until it turns itself off with an error code.

7. Consider the condensation.

Fleming offers another freeze-prevention measure: When installing a condensing unit, be sure to run the condensate drain in a conditioned space, he says. Otherwise, if the condensate drain freezes, an error code will stop the unit from creating hot water.

8. Have a backup power option.

The best policy is to be prepared. Many tankless water heaters require electricity to operate their freeze protection features and to power the ignition of the heater when demand is required. A propane standby generator or battery backup system ensures your customers will keep the hot water flowing even during a power outage.

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Cheryl Weber