Sensors for contractors: CO2 and beyond

April 4, 2000
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Sensor technology has come a long way in the last few years. Today there is a sensor for virtually any type of substance you can imagine. Some sensors may be considered more reliable than others, but manufacturers continue to improve the technology.

Consider, for example, CO2 sensors. Five years ago, many contractors considered the technology to be flaky, complaining that it was necessary to recalibrate the devices far more often than the manufacturers promised.

The manufacturers got busy, and today, CO2 sensors can be found in many different applications, helping to provide better air quality.

Costs have also come down drastically in the last few years, allowing contractors to offer a wider array of sensors to just about any kind of customer.

Some contractors are already knee-deep in sensors, installing them regularly to help provide better comfort for their customers. Other contractors use portable sensor technology to diagnose problems in building spaces.

No matter how you use sensors, they can help your business.

Diving right in

Will Sipe, controls group manager, Engineering Excellence, Cincinnati, OH, is one contractor who enjoys everything about sensors. “I love new sensor technology. I enjoy being the first one to use something that just came out. A lot of people refer to it as the bleeding edge of technology, but I love it.”

Sipe uses a wide range of sensors in the mainly commercial-industrial projects in which he’s involved. Many of his customers have a building automation system (bas), so it only makes sense to have numerous sensors around the building.

Temperature, humidity, and CO2 sensors are just a few of the “regular” sensors he employs. He’s also used everything from static pressure to ice storage sensors. As long as the technology is proven, Sipe is willing to give it a try.

CO2 is one of those “newer” technologies with which Sipe has had great success. He admits that the first CO2 sensors on the market weren’t great, noting that while the manufacturer said they only needed to be calibrated once a year, he found they needed calibration every season.

“Today’s sensors can go two years without calibrating them, and of the ones I’ve checked, I haven’t had to calibrate one of the new ones yet.”

CO2 sensors are not always an easy sell, though — especially in retrofit situations involving older buildings. “In a building from the 1970s, we were closing down the dampers for the energy crunch,” recalls Sipe. “When you now use a CO2 sensor to bring the dampers back open, you’re actually going to cost the customer money, because he has to heat or cool that outside air. It’s going to be making the building healthier, but the actual cost is going to go up.”

Sipe adds that it’s just a matter of contractors educating themselves and their customers.

Unfamiliarity

Another reason why CO2 sensors may be a difficult sell is that some building inspectors aren’t terribly familiar with the technology yet and may hesitate to sign off on it.

Mark Sims, president, Suburban Air, Minneapolis, MN, has had that problem. He’s been trying to convince the city inspector to allow him to use a CO2 controller in a local church he’s working on.

“It’s a 5,000-sq-ft building, and the city wants me to move 20,000 cfm of air through that building to meet the ventilation requirements for a 2-hour-per-week peak occupancy. It’s supposed to be quiet during worship, but with the noise of the air moving around, it wouldn’t work. And I can’t physically get that much air in the building anyway. It’s ridiculous,” says Sims.

The local city inspector is interpreting the code strictly, which states that the building must have the capacity to provide 15 cfm per person. Sims feels that it’s possible to use CO2 demand-controlled ventilation in lieu of that.

He remains undeterred, though: “I’m going to keep promoting the use of sensor technology to provide solutions.”

Portability & Professionalism

Being primarily in residential and light commercial work, Sims has not yet had the opportunity to use a sensor — temperature, humidity, CO2 or otherwise — to actually control any equipment. However, he does make use of portable sensing equipment to detect problems in building spaces.

Just recently he used a portable sensing unit that detects levels of CO2, CO, humidity, and temperature, for a regular customer of his whose employees were complaining of nausea and headache.

“We plugged in the sensor and left it there for a week, monitored and datalogged, and concluded that the problem came from three diesel trucks that were started in their garage every morning.”

The solution that Sims is proposing involves putting in a vent exhaust fan and CO2 controller. “The controller would sense a sudden rise in CO2 in the garage area and turn on the exhaust fan before any carbon monoxide would be produced.” The customer hasn’t decided what to do yet.

Sims says the portable sensing units are great, because he can just leave them at a customer’s site to monitor conditions for a certain length of time. It obviously would not be feasible to have a technician move into a space for five to seven days to record every environmental condition, so the portable units are very handy.

In addition to helping him diagnose problems, Sims thinks that the sensor technology helps him look more professional. “It’s one thing to walk in with a piece of paper and a pencil and maybe a thermometer in your pocket, which is what our industry is good at doing.

“It’s better to walk into a house or a building with equipment that really helps us diagnose the problem and propose the appropriate solution. When you’re dealing with an invisible issue like indoor air quality, diagnostics is very critical for us.”

Sipe agrees that knowing how to use sensor technology, particularly CO2 sensors, can make contractors look more professional. “It’s a good competitive advantage, but even for someone who doesn’t have their feet wet, it’s still new enough that those interested in it can catch up.

“It’s going to take some investment on the part of the contractor to get that knowledge, and he’s got to spend some time educating his customers. But once you make that investment, you can expect to see some returns from it.”

Sidebar: Helpful humidity hints

Humidity is one of the major issues many building owners and occupants are concerned with these days. Will Sipe says that humidity sensors are mandatory, or else you’re not going to be successful in controlling the environment.

“If people are complaining about the paper sticking together at the copier, or they’re getting shocked from walking across the carpet, you need to know what the humidity is in that space.”

Several years ago, customers might have balked at purchasing humidity sensors because of the cost. Sipe notes that price isn’t an issue anymore. “Sensors are available at a very reasonable cost for what you get. And the reliability is terrific. I’ll put a sensor in, and if it works the first 24 hours, it should work forever.”

Sipe also stresses that it’s important not to over-specify a humidity sensor for a space. For example, when specifying the sensor and a 5% sensor is adequate, use that rather than a 2% sensor. And it’s also important to shop around, as humidity sensors are available for a wide range of prices.

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