Who actually specified that motor? Did they keep the entire system in mind or were they simply specifying one component at a time? And will that spec require over-speeding the motor?
Often, an HVAC system is designed by the selection of individual components and not by a whole-system approach. This has become common practice for mechanical engineers, usually resulting in poor system performance and very inefficient HVAC systems. One of the disadvantages of the component approach manifests itself in the equipment manufacturers selecting motors for pumps and fans to operate at speeds in excess of the rated 60 Hz, without consideration of the effect on the whole system.
Manufacturers are selecting pumps and fan motors sized at up to 25% less than the basis of design at times in order to reduce the first cost of their equipment. In some cases, manufacturers are selecting fans and pumps to operate at frequencies up 100 Hz. In order to meet load, these motors must operate at higher-than-designed frequencies. Often, only a detailed review of the equipment submittals during the construction administration phase reveals this less-than-ideal selection. Engineers are faced with the difficult decision of whether or not to approve these submittals without fully understanding the effects on the performance of the designed HVAC systems. They must also deal with very difficult questions, such as, “How does running the motors at higher frequency affect the current, voltage, torque, durability, efficiency, and long-term performance?”