Wire Cost

About Service Entrance and SER Cable

• Aluminum Ampacity - 1/0 aluminum does 100A at 60C. Good chart of wire types and their T resistance [1]
• Copper Ampacity - 2AWG copper is rated for 95A at 60C, 1 AWG is rated for 110 at 60C [2]
• NM-B house wire is specified for 60C by the NEC, but it can withstand 90C. [3]
• USE-2, RHW-2 and RHH - sunlight, heat, moisture resistant [4]
• Terminations at panels must be rated at 60C - [5] - thus you must specify wire for 60C. For example, if you want 100A, oversize 100A 90C wire to something larger at whose 60C rating you get the required ampacity.
• THHN to subpanel - yes if in conduit - [6]
• Standard practice - individual THHN through conduit or NM-B through stud holes [7]
• Romex or BX wire can be run without conduit - [8]
  • Romex goes up to 2 awg [9]
• 1/0 is 0.32" diameter wire [10]

Subpanels

• Since 2008, 4-wire cable is required. [11]
• SER cable is preferred, no conduit needed [12]. XHHW and THHN can be used but require conduit.

Cost

• THHN 6 ga copper - $1/ft [13]
• 6/3 NM-B is $5/ft [14] or [15]
• 2/3 NM-B is $9/ft [16]
• 4/0 is same price - [17] or [18]
• 1/0 aluminum URD is 100A and $2.50/ft [19]
• 2/0 aluminum SER is $4/ft [20]
• Lowest cost option, easiest to install (holes, no conduit): 1/0 aluminum SER is 1.1" OD + $3/ft [21]. $4/ft after shipping for 32'.
  • $5/ft at Platt [22]

Breaker Integration

• We would like to use a 100A breaker for the Subpanel. Can the 100A handle 1/0 Aluminum?
  • Breaker: LB200 [23]
  • 1/0 should fit [24]
• 2 hots+ neutral; ground runs from subpanel to main panel and is separate from neutral wire. Neutral to ground bonding occurs at the main breaker panel.