Photo © BigStockPhoto
Creating consistent comfort
ECM motors are high-efficiency, programmable, brushless direct-current (DC) motors, with integrated controls utilizing a permanent magnet motor and built-in inverter. ECMs are significantly more efficient than the permanent-split-capacity (PSC) motors used in most residential furnaces and are much easier to control.
Modern airtight houses, apartments, and condos require continuous circulation to distribute fresh air throughout the house, which is when the benefits of ECM motor technology are most apparent. The ECM motor continuously operates at a low level, keeping living spaces consistently warm. If there is a temperature drop, the furnace automatically modulates to a higher heat production until the programmed temperature is achieved, then it cycles back down to low.
Until recently, the major weakness of commercial fan coil units has been their low fan motor efficiency. PSC motor efficiency drops off dramatically—by at least half—when turned down; their installed motor efficiencies are typically in the range of only 12 to 45 per cent. ECMs operate with as little as 80 watts of electricity and use up to 75 per cent less energy than standard fan motors. Inherent variable-speed operation of the ECM matches the speed required by the heating and cooling application, enabling fans, compressors, and pumps to efficiently meet partial loads. The ECM operating constantly and ramping up occasionally equates to an 80 per cent reduction of electricity usage.
In addition to lower operating costs, recent advancements in ECM motor technology allow the fan airflow volume to be pre-set at the factory and provide an average 90,000 hours of operation (compared to 50,000 hours for a typical PSC motor). Further cost savings are realized in the wider operating range of the ECM, which allows one motor to replace two models using induction motors. This feature alone provides several benefits, such as a simpler product line from which to choose, little or no equipment changes when tenants change, more similar-sized units on the job, decreased spare parts inventory, and increased contractor flexibility. The ECM’s low operating temperature (i.e. essentially ambient) requires very little energy to offset the heat gained from the motor versus PSC motors, which typically run between 32 and 65 C (89 and 149 F).
As government regulations squeeze inefficient systems out of the market, newer HVAC assemblies with innovations like ECMs are reducing utility bills. Micheline Joanisse, a Natural Resources Canada (NRCan) spokesperson, points to two reasons for this—use of brushless DC motors and energy-efficient air-conditioning.
Built-in intelligence in ECMs enables the motors to run at many different speeds and react to changing duct pressure, saving 300 to 500 watts for a low-pressure duct system, according to the NRC. That means if a filter gets blocked it senses the blockage and automatically increases the fan speed to ensure there is air flow.
Photo courtesy Nailor
“In homes with a heat recovery ventilator (HRV) or energy recovery ventilator (ERV), it is common to connect the motor into the existing furnace ductwork,” says Joanisse. “So the furnace motor must run continuously to properly distribute fresh air through the house. Therefore, it is important residential customers know by reducing their overall electrical energy consumption, they will save an average of $130 per year.”
Energy-efficient air-conditioning can benefit residents in milder climates like Vancouver from new technology in cooling systems. A particular advancement is the multi-split air conditioner, which has indoor heads in several zone-controlled locations and concentrating cooling in warmer areas. Infrared sensors in the systems detect movement, sensing when rooms are unoccupied, and automatically setting the temperature back to reduce overall power consumption.
What to look for
The most economical heating and cooling systems will have a high heating and cooling efficiency rating. For central air-conditioning equipment, contractors should look for units with a higher seasonal energy efficiency ratio (SEER) rating; the higher the rating, the more efficient the system. The number represents the total output (in BTUs) of a central air conditioner or heat pump during a normal cooling season, divided by the total electricity (in watt hours) consumed during the same period; Energy Star requires a rating of 14 or more. More efficient heat pumps will rate between 14 and 18 SEER.
Heating season performance factor (HSPF) shows the system’s ability to heat spaces in the cooler seasons. The most efficient pumps start at HSPF 8 and top off at HSPF 10. However, heat pump efficiency ratings do not tell the whole story—features of the heat pump should also be investigated. As with efficiency ratings, costlier systems will include advanced features but they tend to pay off in the long run with improved home comfort and lower energy bills.
While lower-rated systems cost less to initially purchase, the savings in energy costs for a higher-rated system more than offset the initial expense. For example, while the initial cost of a 90 per cent plus furnace may be higher than mid-efficiency equipment, government subsidies in Canada help offset the extra cost of installing more efficient heating systems. (Information about grants and financial incentives can be found on the NRCan website at www.nrcan.gc.ca/energy/funding/efficiency/4947.) Those who upgrade to a 94 per cent efficient furnace with a brushless DC motor can take advantage of the incentives being offered.
Conclusion
Moving beyond residential and multi-family projects, there is considerable potential for energy savings in high-rises beyond MURBs. Energy-efficient fan coil units using ECMs are ideal for the rapidly advancing hospitality industry and retirement facilities—in new construction and the retrofit market—with incredible savings to the owners.
Rob McKenna, a strategic account manager with Regal Beloit Canada, has been involved with selling and supporting the energy-efficient motor manufacturing industry at the original equipment manufacturer (OEM) level for over a decade. He may be reached via e-mail at rob.mckenna@regalbeloit.com.
