Anti-Legionalla Function of Chiltrix DHW Domestic Hot Water Tank Used w/ Air To Water Heat Pump

We Keep You Safe!

In addition to its high-efficiency heating and cooling capabilities, the CX34 can also make domestic hot water using an indirect tank. For safety, Chiltrix CX34 air to water heat pumps have a built-in automated anti-legionella function. Alternatively, there is a manual option. See the tank manual


Typical Chiltrix air to water heat pump used with domestic water heating design. Only major components are shown.

Legionella Danger Zone (and Safe Zone)

Above 70 °C (158 °F) – Legionella dies almost instantly

At 60 °C (140 °F) – 90% die in 2 minutes (Decimal reduction time (D) = 2 minutes)

At 50 °C (122 °F) – 90% die in 80–124 minutes, depending on strain (D = 80–124 minutes)

48 to 50 °C (118 to 122 °F) – can survive but do not multiply

32 to 42 °C (90 to 108 °F) – ideal growth range

Minimum requirements For Chiltrix automatic anti-legionella function:

* Follow the applicable sections of Chiltrix CX34 Manual and DHW Tank Manual.

* A 40a contactor as described in the CX34 manual must be installed on the power circuit to the thermostat.

* A commercial grade thermostat capable of a 170F set point must be installed along with the heating element.

* An anti-scald valve must be employed immediately after the tank hot water outlet, per local code, to prevent dangerously hot water from causing injury or death to a person. Water at 160F can be very dangerous.

* Expansion tank and/or pressure relief valve must be installed per local code.

* Use only a UL listed thermostat and element.

* All wiring must be performed per local code.

* Set the parameters in the Chiltrix controller up as desired and per instructions in the CX34 Manual, and enable.

Note - When using the anti-legionella function along with DHW domestic water heating backup heat (for times when the heat pump/coil cannot meet the load) the heating element is fully managed by the Chiltrix controller. The thermostat is generally not active and serves as an inline safety feature to prevent overheating of the tank in case of relay or sensor failure, etc. In this example Chiltrix controls all water heating functions.

Any questions? Please contact Chiltrix technical support. at 757-410-8640

What is Legionella?

Also known as Legionaires Disease, Legionella got its name from an outbreak of an unknown "mystery disease" that sickened 221 persons, killing 34 people. The outbreak occurred among people attending a convention of the American Legion in Philadelphia in July of 1976. In January 1977, the cause was identified as a previously unknown bacteria which was subsequently named Legionella.

Legionella bacterium are commonly found in low concentrations in groundwater, lakes, and streams, and can be found in municipal water supplies.
They reproduce to dangerous levels only after entering man-made equipment, such as water tanks, under certain conditions.
There is no vaccine.

Prevention of Legionella in Hot Water Tanks

Legionella growth can be prevented by providing temperature conditions that sterilize the bacterium.

Generally, water can be heated periodically to a higher temperature, and depending on the temperature achieved, hold it at that temperature for a certain period of time.

In the Chiltrix Anti-Legionella function, the tank is raised to a temperature of 160F and held for one hour, every seven days (default setting). The user can select various scheduling as desired.