Quarterly Maintenance News
Is it about to fall apart?
This time of year we always face the same battle of needing our heating system in the morning and our cooling system in the afternoon. Well if you are responsible for a system that has a capacity of 7.5 tons or more, you probably have an air-side economizer-and chances are if you don’t have it on a maintenance plan it could use some attention.
When the outdoor temperature and humidity are mild, economizers save energy by cooling buildings with outside air rather than using refrigeration equipment to cool recirculated air. A properly operating economizer can cut energy cost by as much as 10 percent of a building’s total energy consumption.
Economizers are designed to save energy, and that’s good. The bad news is that about half of all unmaintained economizers don’t work properly, and their problems increase as they age. To make matters worse, there’s a good chance that malfunctioning economizers waste much more energy than they are intended to save. If an economizer breaks down when its damper is in a fairly wide-open position, peak loads shoot up as cooling or heating systems try to compensate for the excess air entering the building.
To increase the likelihood that an economizer will not turn from an energy saver to an energy waster you have a few options.
1. Specify upgraded components, such as stainless-steel dampers, direct-drive actuators, and enthalpy control.
· Stainless-steel dampers resist corrosion much better than the galvanized steel and aluminum dampers typically used in economizers. Though stainless-steel dampers cost about twice as much as galvanized-steel dampers, in the long run they are cheaper than the total cost (including labor) of removing and replacing a failed damper repeatedly.
· Direct-drive actuators have fewer moving parts between actuator and damper, and therefore fewer parts that can fail. They are also much easier to install than typical linked actuators. Since their introduction in the 1980s, a company named Belimo has dominated the market, but increased competition is narrowing the price gap between direct-drive actuators and the more failure-prone linked actuator. In many cases, direct-drive models now cost the same as or less than their linked counterparts.
· Modern sensors that use solid-state electronics to measure enthalpy are much more reliable than older-technology sensors.
2. Have economizers on a maintenance plan right from the start with at least bi-annual testing.
3. When all else fails, lock the economizer in minimum-outside-air position, some economizers cannot be cost-effectively maintained in working order. They may be:
· Located in an especially corrosive environment;
· Made from seriously inadequate materials;
· Even in top condition, capable of producing only inconsequential energy savings;
· Installed in a building with undersized outside and exhaust air openings.
The biggest choice faced by economizer owners and operators is whether or not it is worthwhile to invest in upgraded components and testing for a particular unit. To make this decision, first estimate how much energy an economizer is likely to save. Then, choose upgraded components and testing procedures accordingly. For example, a functioning economizer installed on a 30-ton rooftop unit might save about $1,000 a year, and so it is probably worth maintaining. An economizer in a unit one-tenth that size saves only $100 a year might be better off locked in minimum position. The biggest challenge you’ll face is estimating the savings associated with a given economizer. Because those savings vary widely by location and building type, check with your technician to learn what savings are typically produced by your economizer and discuss recommendations.
Toby Sweeney
Service Manager