Task Group 3-1 met on Tuesday April 22, with 25 members and guests present.
The proposed addendum to IEEE 835 (Ampacity Tables) and the relation of the IEEE (Neher & McGrath) ampacities to the NEC ampacities was discussed.
A draft of a "Ampacity Table User Survey" prepared by the Chairman was distributed and a request for comments was made. This survey is proposed to be distributed (either by IEEE or by ICC) to users of the present IEEE tables.
A copy of the survey is attached as an appendix to these minutes along with the address for ICC member comments. (Filling out the survey is optional!)
The chairman presented a comparison of IEEE ampacities and those from the NEC tables which for buried cables do not allow for derating for multiple circuits, variable earth thermal resitivity or depth of burial. Users of the code need not use the optional NEC tables based on the AIEE "Black Books". This results in some "over-rated" cables in some instances.
The chairman is requesting that the ICC decide whether to take a position on this matter. Should this matter be discussed with the NEC code panel?
Task Group 3 -1 met on Tuesday morning Nov. 4, 1997 with 24 members and guests in attendance.
Summary: The need for an expanded version of the IEEE Standard Ampacity Tables and the methodology required were reviewed. A Survey of users of IEEE 835 was distributed for ICC members response and will be sent by IEEE to all those who purchased the standard. The deficiencies in the NEC ratings for buried cables and ICC input on this subject was discussed.
Review of Project: Initial response to the publication of the IEEE Ampacity Table document prompted there-convening of this task group. Some users are requesting a method of obtaining ratings for a wider range of ambient parameters and cable depth and spacing. The scope of and expanded standard was developed and reviewed at past meetings and was published as Appendix M - A of the ICC minutes for April 1996.
Survey: A user survey prepared by ~TG 3 -I chairman and reviewed at past meetings was distributed. The Draft survey is in the ICC minutes for April 1997. The survey will be posted on the IEEE/ICC Web site in January 1998. It is also expected to be distributed by IEEE to all users on record early in 1998 and results should be available for the Spring 1998 meeting. Based on the results of the survey a definite plan for expanded tables can be formulated.
Aerial Cable Ratings: The chairman reviewed the subject of aerial cable ratings as affected by ambient conditions (air temperature, solar radiation and wind speed and direction). The present tables provide ratings for only 4 combinations of wind speed and solar heating and one value of ambient temperature. It is impossible to interpolate or extrapolate to get ratings for other conditions based on the values tabulated.
NEC Ampacity Tables: Since the NEC ratings for low voltage buried cable do not consider the number of loaded conduits or variation in depth and earth thermal resistivity some ratings as applied according to the code are quite optimistic. At past meetings the question was raised as to whether and how ICC could bring this issued to the attention of the code panel. Subcomniittee 3 chairman Larry Kelly in attendance at the task group meeting plans to communicated with the IEEE liaison to the Code Panel. He would outline the problem and offer to provide input on how to correct it.
