Efficiency rules for the HVAC/R industry since 1975 have come from the DOE (Department of Energy). I think most of us have gotten used to the periodic changes in new equipment. Next year we will have another efficiency mandate to keep in mind. DOE rule 79 FR 38129 prescribes the minimum FER (fan energy rating) that is required for the blowers in new residential air handlers and furnaces. The rule takes effect July 3, 2019. The rules regarding how to test for fan energy ratings are still under discussion, so nothing is final. However, since the most significant improvement that designers could make to a blower is to improve the motor efficiency, the new standard will most likely require most manufacturers to start including ECM motors as standard equipment in all models.
Of course this new rule won't affect existing equipment, or repairs to older equipment. The rule doesn't have any requirements to replace existing PSC (permanent split capacitor) motors with new ECM motors during a repair. However, a good argument can be made for doing just that.
- Most manufacturers have been including many more ECM (read X-13) motors in their lineups. That's because of the efficiency standards changes in 2016 for cooling equipment. One of the ways to improve overall SEER rating was to use ECM motors in the blowers of package units and air handlers. The prices of these motors has begun to creep downward because of the increased production.
- There are more motor manufacturers making ECM motors than there were before. That makes for competitive improvements in quality and for lower prices, as well.
- Many replacement ECM motors have programming software available. As that becomes more common you may only have to carry a few motors on service trucks to cover a wide range of applications. That would mean fewer trips to the store.
- Some motors have Bluetooth programming abilities, making it possible to program fan speed while the equipment is operating. Faster set-up and better efficiency. There's no doubt that this type of intelligent control will become the norm.
- Many of the new ECM motors have built-in surge protection, eliminating one of the weaknesses of the older models.
- And let's not forget that the customer gets quieter, less expensive performance from ECM motors. Savings vary depending on fan usage, but there is always a positive payback for the customer.
There are some things to keep in mind when replacing a PSC motor with an ECM, or when installing new equipment that has an ECM blower on an existing duct system.
- Over the years the biggest complaint about ECM motors has been that the thermistor in the commutator fails too often. It's common to hear of installations where the motor module needs replacing two or three times during the warranty period. Failing thermistors are almost always caused by undersized duct work. Because these motors have some intelligence, they will try to match the static pressure or the torque that their programming calls for. Overcoming high-static pressure causes the thermistors to overheat (too much current flow) and eventually fail. Like a good dog they try to satisfy their master at any cost to themselves.
- Oversized duct work will also cause problems with ECM motors. It's that intelligence thing, again. By telling the motor how much air to move to satisfy the equipment needs it is easy to ignore the duct sizing. Moving air too slowly through a duct system can cause wasted energy, sweaty ducts, uneven distribution and uncomfortable customers.
- The manufacturer can program the 5 connections in an X-13 motor any way they want. High speed could be tap 1, or it could be tap 5. If you've ever tried changing fan speed on an X-13 and felt that there was no difference between one tap and another, it might have been because the motor was only programmed with one or two speeds. The point here is that you should read the set-up instructions carefully for good results.
With better motors, lower prices, and careful duct sizing these motors will be a real boon to your profits and to customers' satisfaction.