Wire Cost
From Open Source Ecology
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'.
Breaker Integration
- We would like to use a 100A breaker for the Subpanel. Can the 100A handle 1/0 Aluminum?
- 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.
