12F405 - 336.4 AAC 3-over-3 Double Circuit Tangent Underbuild (Obsolete - See 12F400)

Note: This standard has been updated with a fiberglass crossarm but the drawing has yet to be updated.

Notes:

1. 50’ minimum pole height without communication attachments. 60’ minimum pole height with communication attachments.
2. Engineer must specify the size & number of down guys and anchors depending on conductor design tension, line angle, available down guy lead and span length. Refer to T&D Guideline 4-6 and Compatible Unit Sections A and G.
3. To avoid accidental contact with jumpers, primary down guys must be equipped with 144" fiberglass guy strain insulators (MID 939267).
4. The upper circuit on 3-over-3 double circuit structures is an express feeder. Connect all transformers, risers and 1Ø and 2Ø taps to the lower circuit
5. Crossarms to be set to split the angle in the line. Guy should be set in the plane of the crossarm if possible.
6. This assembly is intended for primary conductors with a maximum working tension of 2,500 lb/Ø or less. For deadending conductors with a maximum working tension between 2,500 lb/Ø and 4,000 lb/Ø refer to Assembly Unit 12F415.
7. New overhead double circuit construction is allowed in rural areas only.

Material List

Compatible Unit	Description	Quantity
I0103	Insulator, 600V #2 Single Point Secondary Rack	1
I0387	Insulator, Sgl Polymer Vise-Top Insulator - 5/8" x 6-1/2" Pin Fiberglass Crossarm Mount	6
R1113	Split-Bolt Assembly, 5/8" x 6" Machine Bolts	2
X0301	Crossarm, 10' Single Tangent Fiberglass	2