CSLB C-10 Electrical ContractorEquipment and InstallationMedium
A journeyman is installing a 277/480-volt panelboard against a grounded masonry wall. The front of the panelboard will have exposed energized parts when the dead front is removed, and the opposite wall is grounded masonry. What minimum working clearance in front of the panelboard does the CEC require?
- A6 feet
- B4 feet
- C3 feet
- D3.5 feet
Show answer & explanationAnswer & explanation
Correct answer: D. 3.5 feet
This is Condition 2 (exposed live parts on one side, grounded parts on the other) per Table 110.26(A)(1). For voltages 151–600V nominal to ground under Condition 2, the required clear working space is 3.5 feet (1.0 m).
Why the other options are wrong
- A. 6 feet applies only to Condition 3 (exposed live parts on both sides) at this voltage range.
- B. 4 feet is not a value used in Table 110.26(A)(1) for this condition.
- C. 3 feet applies to Condition 1 or to lower voltage ranges, not this scenario.
Working Space Clearances
Table 110.26(A)(1) sets minimum depth of clear working space in front of electrical equipment based on voltage and condition (1, 2, or 3).
- Condition 1: exposed live parts, grounded parts not on opposite side
- Condition 2: exposed live parts, grounded parts on opposite side
- Condition 3: exposed live parts on both sides
- 151-600V Condition 2 = 3.5 ft
Memory trick: More danger on both sides means more distance required.