Installing a Wall Sconce With No Ground Wire in an Old House

A wall sconce with no ground wire in an old house will light the moment the breaker goes back on, and that is the trap: working and being safe are two separate tests. The green or bare lead coming out of the fixture is an escape route for fault current, and if it ends in a wire nut and nothing else, the painted metal shade is what your hand is on the day that route is needed.

What settles the answer is not the sconce. It is the box already in the wall, and whether that steel can is bonded back to the panel through conduit or armored cable or is just a lump of metal sitting in 90-year-old plaster. From the top of a stepladder those two look identical. Under a fault they behave nothing alike.

Can a wall sconce go up in an old house with no ground wire?

Yes, the connection can be made and the light will work. On a box with no grounding means at all, the fixture's green lead is capped and left unconnected, and the sconce runs normally on the two conductors that are there.

What it skips is what the fixture is made of. A moulded plastic body gives a fault nothing to energise. The Houseland bear sconce is the opposite case: the shade is 7.1 in (18 cm) across in painted iron, the ears are iron too, and the joint is a chrome swivel, so what a hand finds in the dark is metal. Writing for IAEI Magazine, inspector Randy Hunter reduces Part V of NEC Article 410 to one line: if a luminaire or lighting equipment has metal parts, it shall be grounded. He adds that the bare copper tails on a fixture are equipment grounding conductors and have to be connected properly.

So the question splits. Yes, it can physically be done; whether that lead should end in a wire nut depends on establishing that the box truly has no grounding means, which nobody can do by eye.

What is that green wire on the fixture actually for?

It is a fault path, and it does nothing at all until something has already gone wrong. Say a hot conductor works loose inside the canopy and touches the metal body. With a grounding conductor attached, that current gets a low-resistance route back to the panel, the breaker sees far more than its 15 A rating and opens in a fraction of a second. With nothing attached, the metal simply sits at 120 volts and waits for a hand.

Earth is not a substitute for that path. IAEI Magazine's grounding and bonding primer puts it flatly, citing NEC 250.4(A)(5): the earth is not to be considered an effective ground-fault current path. The same article calls grounding and bonding the primary protection against shock, and cites an estimate of 58 electrocution deaths a week in the US at the time it was written in 2005.

Body material is why the same missing wire matters more on one fixture than another. The accepted answer on a DIY Stack Exchange thread about a lampholder that ships with no ground lead makes the split plainly: in a metal fixture anything that can conduct has to be grounded, while in a plastic one there is no exposed metal for anyone to touch. A double-insulated fixture, marked with the square-inside-a-square symbol and supplied with two leads and no green one, is designed for this exact wall. A fixture with an iron shade and a metal swivel is not that fixture.

How do I find out whether the box behind the plaster is grounded?

Test it, or pay someone for the 30 minutes it takes, because the box will not tell you by looking. The checks run in this order.

1. Switch off the breaker, then prove both conductors are dead with a non-contact tester and a meter. The wall switch is not proof; it may be breaking the neutral.
2. Look at what enters the box from behind. Metal conduit or armored cable is often a valid grounding method on its own, so an old box with no green wire anywhere near it may in fact be bonded. That is the point the accepted answer makes on a Stack Exchange thread about grounds joined to each other but not to the panel.
3. Feel for a threaded hole in the back of the box. An 8-32 machine screw belongs there, and where the box is genuinely bonded that screw is where the fixture's ground lands.
4. Settle it on continuity, not appearance. A low-resistance reading between the box and a known ground at the panel is the only thing that turns a guess into an answer.
5. If the box is plastic or fibre, stop testing. There is nothing there to bond to.

Steps 1 to 3 are within reach of a confident owner. Step 4 is where most people should hand over, because a reading of a few ohms through a rusted conduit coupling is not the same as a bond.

Which of the three boxes are you actually looking at?

Three boxes turn up behind old sconces, and each one gets a different answer for the green lead.

The middle row catches the most people, because a steel box feels like a ground. On a thread about a metal junction box with no ground screw, the advice for a bonded box is specific: pigtail the fixture ground, the supply ground and a lead to the bracket together, and if you want it better than that, drill and tap a 10-32 hole in the back of the box and use a green screw there.

Lighting branches were not required to carry a grounding conductor when much of this wiring went in, which is why a 1930s hallway can have grounded receptacles and an ungrounded sconce box on the same floor.

From the shop

Bear Nursery Wall Sconce, Adjustable Iron Wall Lamp with Wood Base, 8 Colors

Houseland's bear sconce is hardwired to a standard wall box with no visible cord, and stands 8.3 in (21 cm) tall with a painted iron shade on a rubberwood backplate. The E27 socket takes standard US E26 LED bulbs; a warm-white one around 2700K suits a bedroom.

View the bear nursery sconce — 8 colours & current price

Why is landing the ground on the neutral the one thing never to do?

Because it turns the fixture body into a current-carrying conductor. The rule with no exceptions is that the sconce's ground lead never goes on the white wire. The writeup that describes the 8-32 screw method sets this out in capitals: never connect the ground wire to the white wire, because doing so greatly increases the chance of the fixture becoming electrified.

A neutral is a return conductor, so it carries the same current the hot does, and there is voltage along its length. Bond the metal shade to it and the shade sits at that voltage above true ground all the time the light is on, not only during a fault. Reverse hot and neutral anywhere upstream, which happens constantly in houses that have been rewired in pieces, and the shade goes to a full 120 volts with the switch off.

A related version of the same mistake is joining grounds to each other without joining them to the panel. The Stack Exchange answer above calls that an island of grounds: a fault gets shared out to everything on the island rather than cleared, so the metal desk lamp, the appliance chassis and the sconce all rise together. Two ungrounded things bonded to each other are not grounded, they are just connected.

What should you ask an electrician to do about it?

Ask for a verdict on the box, in writing, before anyone buys a fixture. The list is short and an electrician will recognise every item on it.

• A continuity check on the outlet box against a known ground at the panel, with the reading reported rather than a yes or no.
• An answer on whether a grounding means can be brought to that box, and what it costs: a new home run, or a ground extension permitted by the local code adoption.
• If a ground is landed, that it goes on a screw used for nothing else. The IAEI primer is explicit that a metal box needs a listed grounding device or a grounding screw not used for any other purpose, and that where several grounding conductors enter a box they are spliced together under NEC 250.148.
• Enough free conductor left in the box to work with. The convention quoted on DIY Stack Exchange is roughly 6 in of ground wire from where it enters, with at least 3 in past the front edge.
• Whether your jurisdiction wants a permit. In many places an owner-occupier of a single-family home may do the work, and an extension of a circuit still needs one.

Ask a second question while they are on the ladder: is the box itself sound and rated for the fixture's weight. A backplate that screws to a box is only as good as the box's fixing into the framing, the same judgement call as choosing between a stud and an anchor for anything else that hangs on a wall.

What I'd do

Book the continuity check first and choose the fixture second, because the check costs a call-out and the wrong answer costs a wall. If the box turns out to be bonded, a metal sconce is a straightforward swap and the ground lands on a green screw. If it turns out to be a genuine two-wire box, my order is: price the ground extension, and if that is unreasonable, buy a double-insulated fixture for that spot instead of capping a green wire behind an iron shade.

Where the answer is that the wall stays shut, the honest fallback is a light that never needed the box. A plug-in fixture with the cord routed properly, or the battery versus plug-in trade-off that applies to lit wall pieces, gets light on that wall this week rather than after an electrician's schedule clears.

When the box is sorted, the rest is positioning, and that is a longer job than the wiring: our step-by-step for a hardwired sconce in a child's room covers box height and which side of the bed it belongs on. Every fixture in the Houseland wall lamps collection is hardwired to a standard wall box with no visible cord, which is the point of doing this properly rather than running a cord down the plaster.

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