Typographical Errors in 10 CFR Part 431 Energy Conservation Program: Test Procedures for Distribution Transformers NEMA has determined that there are two typographical errors in the April 27, 2006 Final Rule that have a profound impact on the distribution transformer efficiency and must therefore be corrected in the implemented rule. These errors existed in the July 29, 2004 proposed rule and were inadvertently carried forward in the NEMA Standards Document TP-2-2005, and the April 27, 2006 final rule. We regret any inconvenience in the lateness of our identifying these error, however, they must be resolved. Perhaps an errata to the Final Rule would be an approach The error detected in the Federal Register (FR) originates in equation 5-1, FR page 25007 with the formula for Pos, the specified energy efficiency load level. Please refer to pg 29 of TP2-2005, April 27, 2006 FR pg 25007, and July 29, 2004 FR page 45532 equation 5-1:

Plc = P1c2 [Pos/Por] = P1c2L2 And the explanation that follows: POS is the specified energy efficiency load level, where Pos = PorL2 Although, mathematically correct, the concept is not. The superscript "2" should be added the bracket quantity [Pos/Por] and removed from the explanatory note on Pos So that it reads Pos = PO1L Pos is the 'specified energy efficiency load level', which means it is the rated transformer output power times the load level, not times the load level squared. This is properly shown in TP 1-2002 page 3, Pos is shown to be = P x kVA x 1000 where P = per unit load. So, equation 5-1 is to be corrected to:

Plc = Plc2 [Pos/Por]2 = P1c2L 2 and Pos = PorL It is our belief that this error was not detected sooner because many of the manufacturers began calculating the efficiency based on the formula specified in TP- 1. For those who did not, by using the Federal Register and the formula for Pos, the resulting efficiency will be much lower than what it truly is (see TP2 p30 equation 5-3). If you have further questions, please let us know. 

# #6 Typographical Errors in 10 CFRPart431 Energy Conservation Program: Test Procedures for Distribution Transformers NEMA has determined that there are two typographical errors in the April 27, 2006 Final Rule that have a profound impact on the distribution transformer efficiency and must therefore be corrected in the implementedrule. These errors existed in the July 29,2004 proposed rule and were inadvertently carried forward in the NEMA Standards Document TP-2-2005, and the April 27, 2006 final rule. We regret any inconvenience in the lateness ofour identifying these error, however, they mustbe resolved. Perhaps an errata to the Final Rule would be an approach The error detected in the Federal Register (FR) originates in equation 5-1, FRpage 25007 with the formula for Pos, the specified energy efficiency load level. Please refer to pg 29 ofTP2-2005, April 27, 2006 FRpg 25007, and July 29, 2004 FR page 45532 equation 5-1:

And the explanation that follows: Pos is the specified energy efficiency load level, where Pos = PorL2 Although, mathematically correct, the concept is not. The superscript "2" should be added the bracket quantity [P

### osiPor] and removed from the explanatory note on Pos So that itreads Pos 

### =PorL Pos is the 'specified energy efficiency load level', which means it is the rated transformer output power times the load level, not times the load level squared. This is properly shown in TP1-2002 page 3, Pos is shown to be 

### = P x kVA x 1000 where P 

### = per unit load. So, equation 5-1 is to be corrected to:

and Pos 

### =PorL It is our beliefthat this error was not detected sooner because many ofthe manufacturers began calculating the efficiencybased on the formula specified in TP-l. For those who did not, byusing the Federal Register and the formula for Pos, the resulting efficiency will be much lower than what it truly is (see TP2 p30 equation 5-3). Ifyouhave further questions, please let us know.