Building Management

Don’t Sweat Temperature Taking

The classic movie comedy had it right: some like it hot. But, that’s some, not all. So, it’s important to get the temperature right. That means it has to be measured accurately for heating, ventilating, and air conditioning (HVAC) systems. The same attention to temperature is also important for water. Not only is that the key to comfort, it’s also critical to cutting energy consumption and achieving savings.

How much can be saved? The answer varies, depending upon the age and capabilities of the HVAC system, the state of the building, the local climate, and other factors. However, case studies have shown that it’s possible to achieve a 50% energy reduction through better building management. A lot of that comes from reduction in the energy consumption of HVAC systems. For instance, an eight hour thermostat setback of a few degrees in unoccupied areas of a building can cut energy consumption in those locations several percent.

So, an office with a sufficiently capable digital thermostat or building management system (BMS) can save 10% or more by adjusting temperature settings by 10o during those times, such as at night, when no one is present. Schools can do the same during winter or summer breaks. Similar savings are achievable in other settings.

Those significant savings are only possible, though, if the temperature is measured reliably and repeatedly. It’s information that necessary in order to cut energy consumption and realize savings.

As a result, you’re going to need a temperature sensor and probably many, with these sensors packaged in a thermostat or thermostats. Each thermostat will have to gauge conditions with the appropriate accuracy, linearity and speed over the required temperature range. It will also have to fit within a money and energy budget while satisfying other constraints.

For example, if you look at Schneider Electric’s tool for selecting HVAC temperature sensors, you’ll find hundreds listed. It’s a large array of products, each with different features, capabilities, form factors, and other characteristics. There are room, duct, immersion and strap-on temperature sensors.

But, inside those devices, they have something in common: the temperature is typically measured with a thermistor. Generally constructed out of a ceramic or polymer, a thermistor has a temperature dependent resistance. That resistance can change a lot due to even small temperature changes, which makes it possible for a thermistor-based device to achieve high precision over the temperature range a HVAC or BMS operates in.

Notice I said “possible”. Thermistors are not costly and so the technology is widely used in everything from toasters to hair dryers to modern digital thermostats. In the last category, circuitry ensures temperature measurement is linear and accurate. Those two attributes are important when trying to satisfy a picky building manager who’s squeezing out every last drop of cost cutting through energy savings. It’s vital that those energy savings not come by reducing the comfort of building occupants. Otherwise, people may be tempted to bypass the energy saving steps altogether.

So, the temperature sensing basics are important to energy savings, and so too is the rest of what’s inside the thermostat. That can be everything from sophisticated circuitry to built-in wireless transmitters. There can also be the ability to link up to other sensors or devices.

The key, as Goldilocks said when talking about hot and cold in a different context, is to get things just right. That all starts with measuring temperature.


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