[Diarypoint = Reporter Choi Seung-jin] When stepping out for work or school pickup, it's better to lower the thermostat or use the boiler's away/timer function according to how long you'll be gone and how well-insulated your home is, rather than switching the unit off entirely. If the indoor space and pipes cool down too much after the boiler is turned off, it takes much longer to warm up again once you're home, and during a cold snap the risk of frozen pipes also increases.
For outings of two to three hours, lower the heat but keep it running
If you're only stepping out for two to three hours rather than leaving in the morning and returning in the evening, it's better to lower the indoor temperature setting than to turn the boiler off completely. The Korea Energy Agency recommends keeping winter indoor temperatures between 18–20°C, and advises closing doors to unused rooms while adjusting the distributor and the room shutoff valves together for the best energy savings.
Homes with good insulation, such as well-sealed apartments with little draft, can use the away mode. However, away mode doesn't work the same way across all boiler models. Some units maintain a minimum temperature and activate freeze-prevention functions, while others barely heat the space at all and only keep hot water running—so it's important to check your controller's manual first.
For absences of a day or longer, don't shut off the power or valves
Before a long winter trip or extended time away from home, unplugging the boiler or shutting the gas valve and distributor valve can disable the freeze-prevention function. Manufacturers advise that during extreme cold, the power should stay connected and the room valves and gas intermediate valve should remain open. If the boiler room is exposed to outdoor air or pipes run outside the house, wrapping the pipes with insulation is also recommended.
If your water meter and boiler pipes are prone to freezing, it's safer to keep the indoor temperature lowered rather than relying on away mode. If you won't be using the boiler for an extended period, don't drain the pipes on your own—contact the manufacturer's customer service or building management for guidance suited to your plumbing layout.
For timer mode, check the cycle interval and run time
Timer mode runs the boiler at set intervals. Some Kyungdong Navien controllers allow users to set intervals of 1 to 12 hours and run times of 10 to 50 minutes, but the available range and operation differ by model. If you assume timer mode keeps the room at a constant temperature, the actual comfort level and gas usage may turn out quite different.
Timer mode works well in homes with little draft and a consistent return time. In poorly insulated detached houses, lower-floor units, or during forecasted cold spells, setting too long an interval can let the interior and pipes cool down excessively. Even when scheduling the heat to kick in right before you get home, factor in the time it actually takes for heating to start and for the floor to warm up.
To cut heating costs, the basics matter more than simply switching modes: keep the indoor temperature in the 18–20°C range, seal drafty window gaps with weatherstripping and curtains, and close doors to unused rooms. If you notice unusual noise, overheating, pipe leaks, or a carbon monoxide alarm going off, stop using the boiler immediately and have it inspected. If heating fails or you suspect frozen pipes, don't try to thaw them yourself—have the manufacturer or a professional technician check the system.