In response to the ASHRAE 90.1:2007 mandatory requirements for the efficiency of 60Hz motors, some had used the European IE2 standard for 50Hz motors and demonstrated equivalency. The ASHRAE 90.1:2010 standard and user manual have however clarified that all 50Hz motors are exempt. The user manual states that the motor types that are exempted are due to the fact that they “serve a special purpose”, are “not appropriate for …” and “not common in … general building systems” or “have a small energy impact”. This is obviously not true in a country where nearly all motors are 50Hz, but they seem clear on the matter. Whilst we support and would advocate for the use of higher efficiency motors on projects, it seems like high-efficiency motors are no longer (or never were) a mandatory requirement we can enforce? For context, IE1 motors are the current minimum requirement in South Africa, although the implementation of the IEC standard is intended in the future.
If all the 50Hz electrical motors on a project are indeed exempted from the mandatory efficiency requirements, how would this be reflected in the modelling? In ASHRAE 90.1-2007, Table G3.1-'Modelling Requirements, sub-section 12 – Receptacle and Other Loads' states that "where no efficiency requirements exist……equipment" (incl. motors covered by section 10) "…shall be identical b/w the baseline and proposed…”. Would this clause be applicable in the case of a project where 50Hz motor is exempted for the reasons stated above? Or, the lowest efficiency for the 60 Hz electric motor as specified under Tabled 10.8B of Section 10 will be considered for baseline modelling whereas, the proposed will be as per the actual design?