Bonding a metal cover on a non-metallic handhole enclosure

Short answer: bond the metal cover with its own jumper to the circuit conductor. A non-metallic handhole body is an insulator, so cover-to-rim contact carries no fault current, and an unbonded lid can sit at line voltage waiting for a hand. When the handhole carries service conductors, the NEC requires the cover bonded to the grounded service conductor. On a feeder or branch circuit, NEC 250.96(A) requires metal parts bonded so they can safely carry the fault current imposed on them — to the EGC with the circuit. Size the jumper from the breaker ahead using NEC Table 250.122; a 60 A breaker takes 10 AWG copper, the 100 A row steps up one size. Ten feet [3 m] of that copper adds single-digit milliohms; the whole job is milliohms.

The bond follows the circuit, not the box

Polymer concrete, fiberglass and HDPE handhole bodies do not conduct. The lid floats above live splices on an insulating rim, so the only path off it is the one you bolt on. NEC 250.4(A)(5) draws the line: the effective ground-fault current path is low impedance, and the earth is not part of it. Soil under a buried lid measures tens of ohms. The 25 Ω figure long used as the benchmark for a single made electrode passes 120 V ÷ 25 Ω = 4.8 A, and a 20 A breaker holds 4.8 A forever. The breaker never sees that fault, and the lid stays hot.

The touch numbers explain the urgency. A lid floating at 120 V to ground, touched by a worker in wet gloves, meets about 1 kΩ of body resistance, the conservative wet figure from the IEC 60479-1 shock studies. That is 120 V ÷ 1000 Ω = 120 mA, some 7 to 12 times the 10-16 mA let-go range. Bonded, the lid sits a few volts off the EGC, and the breaker clears the fault in cycles.

Which conductor takes the jumper is set by what runs through the box. Service conductors: the NEC's bonding rule for services ties metal parts of the service to the grounded service conductor, and it wants a bonding jumper around any concentric or eccentric knockout ring left without full metal contact. Feeders and branch circuits: NEC 250.96(A) requires raceways, cables, equipment and enclosures to be bonded so they safely conduct any fault current likely to be imposed on them, so the lid lands on the EGC with its circuit. The NEC's handhole article carries the same cover rule; the page on handhole metal cover grounding requirements goes through it in detail.

The same logic reaches any non-metallic enclosure with a metal lid, not just handholes. A fiberglass control box with a stainless door takes the same jumper, as the article on grounding a fiberglass enclosure sets out. The fundamentals sit in the enclosure grounding and bonding guide.

What you need

• Green insulated copper for the jumper — match the EGC color convention; NEC 250.119 requires green or green-yellow insulation on insulated EGCs 6 AWG and smaller.
• A crimped lug at each end, matched to the jumper and to the cover's bonding hole.
• External-tooth lock washers, stainless hardware on stainless lids.
• A file or sandpaper; NEC 250.12 requires nonconductive coatings such as paint removed from threads and contact surfaces at bonding connections.
• A crimp tool, wrenches, and a meter that resolves 0.01 Ω.

Take the jumper size from the rating of the overcurrent device ahead of the circuit, the way NEC Table 250.122 sizes the EGC itself:

The sizes look generous next to load rules — the NEC ampacity tables carry 8 AWG copper at 50 A at 75 C — because a bonding jumper is sized to survive a fault long enough to trip the breaker, and the table is written for exactly that job.

Installing the bond

1. Set the case first: service conductors in the handhole bond the lid to the grounded service conductor; feeders and branch circuits bond it to the EGC.
2. De-energize, lock the source, and verify absence of voltage before the lid comes off. Buried handholes collect water; treat the interior as live until it is proven dead.
3. Find the bond point at the splice: the grounded conductor on the service side, the EGC on everything load-side. On a feeder, land on the EGC, not on the neutral — NEC 250.6 exists to keep neutral current off metal parts.
4. Cut the jumper with about 12 in [300 mm] of slack beyond the straight run, so the lid lifts for splicing without pulling a crimp.
5. Crimp the lugs and bolt one end to the cover's bonding provision. Strip paint, galvanizing or anodizing to bright metal under the lug, as NEC 250.12 requires, and let an external-tooth washer bite that bare metal. On a stainless lid use stainless screw, nut and washer, and keep bare copper out of direct clamped contact with galvanized steel; that pair corrodes in a wet box, as the article on stainless and galvanized metal contact explains.
6. Land the other end on the splice with a listed connector sized to the conductors in the handhole.
7. Check the entry hardware too. When metal conduit feeds the box, the rules in metal raceway as the equipment grounding conductor decide whether the conduit itself carries the fault path. The fitting at the wall matters as much as the jumper, which is why grounding conductor entry: connector and bond pairs the two.
8. Dress the jumper clear of standing water and snags, and tag it as a bonding jumper so the next splicer leaves it alone.

Checks that prove the bond

• Null the meter leads first; a normal pair of probe leads alone adds 0.1-0.3 Ω and buries the milliohms you are hunting.
• Measure from lid to splice. A 10 ft jumper of the table size with two good crimps reads about 0.01-0.02 Ω. Anything above 0.1 Ω points at a crimp, a washer riding on paint, or a corroded thread — redo that joint.
• Tug-test each crimp; a bad one slides off by hand.
• Walk the details that make the bond: washer teeth on bright metal, green insulation on the small sizes, slack for lid removal, tag on the wire.

Mistakes that break the bond

• Counting on the rim. The body is plastic or polymer concrete; that contact carries zero amps. The jumper is the bond.
• Bonding to a driven rod. A rod at the handhole is an auxiliary electrode under NEC 250.54: it may be connected alongside the conductor, and it replaces nothing. Its 25 Ω of soil passes 4.8 A at 120 V; no breaker trips on that.
• Landing a load-side lid on the neutral. Only the service cover bonds to the grounded conductor. Past the main disconnect, the whole point of NEC 250.6 is keeping neutral current off metal, so the EGC is the only correct target.
• Sizing from the load. NEC Table 250.122 reads the breaker ahead: a 100 A breaker feeding 30 A of load still takes the 100 A row, not the 30 A row.
• Coating under the lug. Paint or galvanizing left in place adds ohms exactly where NEC 250.12 sends you with a file. Strip to bright metal.
• A jumper too short to lift the lid. The next splicer cuts it, and the bond is gone by summer. Leave the 12 in [300 mm] of slack from step 4.

Which bond to run, by case

A metal handhole body that is itself bonded needs no lid jumper at all: contact through the rim and hinge does the work, the same way a metal junction box bonds its cover through the box, as covered in bonding a metal junction box with spliced feeder conductors.

So: pick the conductor by case, take the copper size from the table row behind your breaker (10 AWG behind a 60 A feeder), crimp both ends, strip the coating, and prove the joint with a milliohm reading under 0.1 Ω. That turns a live lid back into a dead one.

Catalog dimensions to compare

Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.

Questions