Free-standing outdoor panelboard: mount, pad and height

Short answer: pour a concrete pad, stand the panelboard on double galvanized strut columns or a frame of 2 in [51 mm] rigid conduit, keep the top of the cabinet 5 ft [1.5 m] above grade, and plant bollards anywhere a car can reach. The NEC gives you a ceiling and a clearance, never a floor. NEC 240.24(A) keeps the center of the highest breaker handle at or below 6 ft 7 in [2.0 m] above the surface you stand on. NEC 110.26(A) holds 3 ft [900 mm] of clear working depth in front of a 120/240 V panel. The 5 ft top is the field value for parking-lot and right-of-way installs: handles land near chest height, and the bottom clears plow windrows.

Height: the code sets a ceiling, practice sets 5 ft

Two numbers in the NEC fix the layout. NEC 240.24(A) requires overcurrent devices to be readily accessible. It caps the center of the grip of the operating handle, in its highest position, at 2.0 m [6 ft 7 in] above the floor or working platform. Grade is your platform on a free-standing panel.

NEC 110.26(A) sizes the space in front of equipment likely to be serviced while energized. It needs at least 3 ft [900 mm] of depth for 0-150 V to ground in Condition 1, which covers a 120/240 V panelboard. Width runs at least 30 in [760 mm], or the equipment width when that is larger. Headroom is 6.5 ft [2.0 m] or the equipment height, and the door must swing open 90 degrees.

Height itself has no floor in the code for this equipment, so practice sets the working value: put the top of the cabinet at 5 ft [1.5 m] above grade. Breaker grips land near 4 ft 6 in [1.4 m], a comfortable work height without a ladder. The bottom stays above plow windrows and trimmer debris. Where winters stack snow against the stand, raise the top to 5 ft 6 in [1.7 m]; the highest grip still sits under the 79 in [2.0 m] cap. Grips near the top of a cabinet start to break that cap around 7 ft [2.1 m], so treat that as the practical ceiling.

Read the table from the top down. A 48 in [1220 mm] cabinet lands its bottom 12 in [300 mm] above grade, where splash and plow spray live, so rinse it and keep its drains open. A wall-mounted control box follows different height logic; the outdoor control enclosure mounting-height article walks that case. When the gear inside grows wider or deeper, the enclosure sizing guide carries the width, depth and bending-space numbers.

Worked example: a stand for a 36 x 36 x 12 in cabinet

The cabinet is a 36 x 36 x 12 in 316L stainless wall-mount enclosure. Work the layout like this:

• Top of cabinet at 60 in [1.52 m] above grade. Bottom: 60 - 36 = 24 in [610 mm] above grade.
• Pad surface 4 in [100 mm] proud of grade. Column height above the pad: 24 - 4 = 20 in [510 mm].
• Highest breaker grip 8 in [200 mm] below the internal top: 60 - 8 = 52 in [1.32 m]. That clears the 79 in [2.0 m] cap by 27 in [690 mm].
• Working zone: 36 in [900 mm] deep by 36 in wide, clear to 6.5 ft [2.0 m].
• Bollard face: 36 + 6 = 42 in [1.07 m] from the door, tops 42 in [1.07 m] above grade, footings 3 ft [900 mm] deep.
• Pad 6 in [150 mm] thick, damp-cured 7 days before it carries steel.
• Feeder overcurrent device at 60 A: equipment grounding conductor 10 AWG [5.3 mm²] copper under NEC Table 250.122.

What you need

• Columns: two 1-5/8 x 2-7/16 in [41 x 62 mm] galvanized strut channels welded web to web, which makes a 4-7/8 in [124 mm] post. A frame of 2 in [51 mm] rigid galvanized conduit does the same job and doubles as raceway.
• 1/2 in [M12] stainless wedge anchors, two per column, about 2-1/4 in [57 mm] embedment.
• 1/4-20 stainless hardware for the strut slots.
• Gasketed conduit hubs matched to the stub-ups, typically 1 in [25 mm] to 2 in [51 mm].
• 4 in [100 mm] schedule 40 steel pipe for the bollards, concrete filled.
• Anti-seize for the stainless threads, a level, and a tape.

Steps from grade to energized

1. Mark the layout. Stake the cabinet footprint, tape the working zone in front at 36 in [900 mm] deep by the cabinet width, clear to 6.5 ft [2.0 m], and stake the bollard line outside it.
2. Check the stub-ups. Each feeder is already stubbed at its location; confirm the stub lands inside the footprint and stands plumb. Move the footprint now, while it is only stake work.
3. Pour the pad. Go 6 in [150 mm] thick over compacted base, surface 4 in [100 mm] above grade, base below the local frost line. Slope the surface about 1/4 in per foot [2 %] so water runs away from the stand. Sleeve the stub-ups so the pour cannot pinch them. Keep the slab damp for 7 days before it carries steel.
4. Set the columns. Cut them to the exposed height, 20 in [510 mm] in the example, anchor them to the pad, and plumb them both directions before the final snug.
5. Hang the cabinet. Bolt the feet to the strut slots with the 1/4-20 stainless hardware; bolt pattern and levelling for our wall-mount feet are covered in how to mount a wall-mount enclosure securely. Where a screw passes through the back wall instead of a foot, follow the sealing detail in mounting screws through an outdoor enclosure without leaks.
6. Land the raceways. Finish each bottom entry with a gasketed conduit hub; the choice between hubs and sealing locknuts for outdoor entries gets its own treatment in conduit hub vs sealing locknut. Leave the weep and drain holes open.
7. Bond the stand. Size the equipment grounding conductor from the overcurrent device ahead of it: 10 AWG [5.3 mm²] copper for the 60 A device in the example, per NEC Table 250.122. Bond cabinet, columns and raceway into one path. A rod driven beside the stand is an auxiliary electrode under NEC 250.54; it may join the conductor, never replace it. The details live in the grounding and bonding guide. New concrete gives you one more option: tie the rebar cage into the electrode system before the pour, and concrete-enclosed (Ufer) grounding compares it with a galvanized ring.
8. Set the bollards. Drive 3 ft [900 mm] footings, set the 4 in [100 mm] pipe, fill with concrete, and cap them. Tops finish 42 in [1.07 m] above grade, on the traffic side just outside the taped zone.

Checks when done

• Tape the highest handle: grip center at 52 in [1.32 m] in the example, under the 79 in [2.0 m] cap.
• Tape the zone: 36 in [900 mm] deep, empty, and the door opens a full 90 degrees.
• Sight each column plumb and pull the door edge; a rock calls for a shim, not more torque.
• Run a hose over the roof seam for five minutes on a stainless build and look inside for water paths.
• Drain holes open, bollard caps on, anchor hardware snug.

Mistakes that cost the rating

• Do not caulk the drain holes shut to cure a drip. A 3R cabinet sheds rain by draining, and NEC 314.15 allows drain openings of 3 mm to 6 mm [1/8 in to 1/4 in] in wet-location boxes for that job; find the gasket fault instead.
• Carbon-steel bolts on a stainless cabinet streak and seize; use stainless throughout. Galvanized columns under stainless feet are a benign pair, and stainless and galvanized metal contact explains where that pair turns risky.
• Steel on a one-day-old slab loads green concrete. The 7-day damp cure comes before the columns, every time.
• A bollard inside the working zone trades one code problem for another; keep the steel outside the taped rectangle.

What to put on the order

For the distribution point itself, order the box from our custom stainless enclosures: you set the grade, the width, height and depth, and every cutout, and the bottom arrives open with hub cutouts landed over your stub-ups. The 36 x 36 x 12 in 304 build and its 316L sibling both fit the worked example. Custom work keeps the same promise: delivered in 10 business days from your approval of the drawing. Where the job calls for a listed panelboard, its own 3R cabinet rides the same stand, and the pad, columns, height and bollards do not change. Every rating here is a manufacturer rating: the stainless boxes we build are rated NEMA 4X / IP66 by the manufacturer, not UL listed.

Enclosures in this article

Questions