Benefits of Installing a Noritz Combination Boiler, Part 2 (Demo)

Benefits of Installing a Noritz Combination Boiler, Part 2: Outdoor Temperature Reset

The new CB Combination boiler/tankless water heater (CB Combi) from Noritz has a number of installer and homeowner advantages — over not only traditional, stand-alone boilers and tank-type water heaters, but also other combination units on the market.

Previously in this series, we explained how the Combi’s unique flow control valve helps achieve desired water temperature for the user. In this post, we will discuss a Combi component that contributes to its energy-efficient operation and qualifies it for numerous rebates: the outdoor temperature reset control.

Noritz Combination Boiler Outdoor temperature

In any residential hydronic heating application, the heat load, or how much heat must be supplied to keep the home at the desired temperature, depends on the outdoor temperature. The larger the temperature difference between the outside and inside, the faster that heat will dissipate into the environment (depending on the home’s insulation).

“Oftentimes, when the outdoor temperature is really cold, the homeowner will know to raise the setpoint temperature inside,” says Randy Oshiro, Assistant Manager of Engineering at Noritz America. “However, when the outdoor temperature is really warm, homeowners often don’t know to lower the setpoint, which results in energy inefficiencies each time the boiler turns on and off.”

Short cycling occurs when a boiler fires on and off repeatedly, merely to raise the temperature of the water in its heating system, regardless of whether the home needs heat. This can happen when the boiler setpoint temperature is set unnecessarily high relative to the outdoor temperature. Since a boiler operates most inefficiently during its combustion and purging (turning off) stages, frequent cycles waste energy. To avoid this, the user needs either to remember to lower the indoor temperature manually; or to install an outdoor temperature reset.

Automatic Adjustment

An outdoor temperature reset control, such as the one that comes with the Noritz Combi, monitors the outdoor temperature and relays that information directly to the boiler, which adjusts the setpoint accordingly. So, if the outdoor temperature is warm, the hydronic system setpoint temperature will be reduced; if it’s cold, it will be raised.

This automatic adjustment keeps the boiler running for as long as possible, minimizing wasted energy during the start-up and shut-off phases and leading to energy savings.

The proper location of the sensor is critical. Place it on the northeast side of the home if possible, but certainly make sure it stays out of direct sunlight, which can mess with its temperature readings.

Several state energy rebates recognize the added energy efficiencies garnered by this technology and can be awarded to users who purchase units like the Combi, offsetting its initial cost. For example, Massachusetts offers a $1,600 rebate to homeowners who install an integrated condensing boiler and water heater.

Noritz’s outdoor temperature reset control is fairly unique in that it comes standard with each Combi unit. Many other manufacturers do not offer this, requiring the sensor to be purchased separately.

To learn more about the CB Combi, please visit