How to keep my tankless water heater safe in a cold room?

Question

I have a room in my apartment that can sometimes get around 40°F (4°C), and that's where my new tankless water heater is stored. Should I take any special precautions to keep my pipes from freezing or to avoid any other weird problems with my water heater? I live in the US Midwest in a second-floor apartment.

Other details from the comments:

• Model: Rheem RTEX-24
• The room is on an exterior wall, some of the plumbing goes through an exterior wall, and the water heater is about 3 feet from an exterior wall.

Answer 1

Since the water heater is not on an exterior wall, it is likely that the pipes you mention which do pass through the exterior wall would freeze before pipes inside the heater do. This would cause damage, of course, but might spare the heater.

Addressing the issue with pipes freezing, there's an interesting discussion over on HomeImprovement.SE: "What is the minimum temperature for house heating system to keep pipes from freezing?".

To monitor the pipes for freezing, there are a number of commercially available alarms -- some stand-alone, and some sold as part of alarm systems. There's also plans on Instructables to build one yourself with an Arduino.