How To Replace A House Service Electric Box

If you lot're a GC and you lot inquire clients what they would similar to accept in their newly remodeled dwelling house, they'll probably mention things like additional windows, granite counters, and new hardwood floors. I item they are unlikely to ask for is a new electrical service. Merely that doesn't mean they're non going to discover if y'all neglect to advise them to replace obsolete or overburdened equipment.

They might not notice right abroad, simply eventually they will — if breakers are e'er tripping, if in that location's bereft chapters to add a spa or major appliance, or if their reckoner gets fried because the surge protector was plugged into an improperly grounded circuit.

And they will definitely notice if someone gets electrocuted or the business firm burns downwardly.

Every bit an electrical contractor, my visitor works by and large on existing buildings, and we never do anything without get-go checking the service panel.

The existing service could be so former it's completely unsafe, or it could exist so shut to chapters that adding whatever new loads — even modest ones — could push information technology over the brink. Either condition would crave a service change (see sidebar), which about always means increasing the capacity of the service in amperes, and if the firm is actually old, taking information technology from 120 volts to 240 volts.

The "service" refers to all of the equipment between the utility splice and the principal means of disconnecting power to the house — including the neutral double-decker and the grounding electrode system.

Changing the service involves removing the old meter socket, the main disconnect, and oftentimes some distribution equipment, such as a fuse or breaker panel. This is followed by the installation of a new meter-master, which is a single metal enclosure containing a utility pull section, a meter socket, a main disconnect, and — in nigh cases — a distribution section.

Service Driblet

In areas with above-footing power lines, the service drib is a twisted triplex cable that runs between the ability lines and the firm. It ends in a utility splice at the weatherhead, a helmetlike cover on top of a conduit. The wires on the house side of the splice — called service conductors — travel through a service conduit to the meter socket.

On older homes, the meter socket is in a separate enclosure, but on newer homes it'south usually in the main panel.

In areas where the power lines are buried, at that place is a service lateral — an surreptitious feed — running to the pull section of the meter-main.

The Local Utility

The NEC (National Electric Code) has a very specific prepare of requirements for the service. Just strict as those requirements are, the utility's rules are oftentimes even more than stringent.

For example, whereas the NEC allows the use of exposed service entrance cable and EMT for the service conductors, our utility requires 1 ane/4-inch or larger rigid metal conduit.

Utilities besides have rules governing allowable distances from doors, operable windows, metal gutters, communications drops, gas service, and metal railings. In addition, they prescribe the height of the service driblet above walkways, stair landings, and other areas of pedestrian access; higher clearances are required over driveways and streets.

It's important to understand what the utility expects. If there's anything unusual about the installation, we go a service rep to come out and approve the programme in advance.

The concluding thing we want is to consummate an installation and have the utility people pass up to hook it up because they interpret the regulations differently than we do.

A Example in Point

Most of the photos in this story are from a projection in which we replaced the original service on a house built in the 1920s. The drop contained iii wires, just but two (a neutral and a hot) were connected, so the service was 120 volts rather than the usual 240 volts (a neutral and 2 hots).

This blazon of service is archaic simply not uncommon in the older homes in our expanse. We replaced it because it was of insufficient capacity and was clearly unsafe: Live metal parts were exposed in a footing-level outdoor wooden enclosure. A curious child could have opened the door and touched something live, and even an developed would take chances electrocution by changing a fuse in the pelting.

The author's company was hired to supervene upon this original 1920s electrical service; it posed a hazard considering it was old, undersized, not grounded, and in an outdoor ground-level wooden enclosure next to the driveway.

The service drop was connected to knob-and-tube wiring, which entered the edifice through holes in the wall. One of the hots was bent back and not connected, so the firm had only two-wire 120-volt service.

Most of the wiring was knob-and-tube. The unabridged business firm ran on two twenty-amp circuits that, given the historic period of the wiring, should accept been fused at xv amps. They were actually fused at xxx amps; it's a wonder the firm hadn't burned down.

Locating the New Service

The erstwhile service was on the side of the house next to a narrow driveway, but we couldn't put the new service there considering there wasn't room to install protective bollards (3-inch steel pipes set in concrete) in front of the equipment, as required by the utility.

Instead, we decided to install the new service on the opposite side of the house; a utility pole was nearby and the outside wall was far enough in from the property line to give us 36 inches (the code minimum) of clearance in front of the equipment.

An electrician verifies that at that place will be the required 36 inches of clearance in forepart of the new panel within the belongings line.

Also, at that place was enough room nether an existing window for us to install the panel and notwithstanding comply with the utility's requirement that the centerline of the meter be no lower than 36 inches and no higher than 75 inches higher up form.

We used a standard meter-main with distribution — a metal enclosure containing a meter socket, a main disconnect, and buses for co-operative circuit breakers. The plan was to bring the service conduit in from above and have conduit for the branch circuits out the bottom and into the crawlspace.

Mounting the panel. Since the equipment is heavy and supports a length of steel conduit, information technology's disquisitional that the panel exist solidly attached to framing members — not just siding. We typically fasten panels with iii/8-inch-by-3-inch lags or Simpson SDS structural screws. If the holes in the panel don't line up with framing, we drill new ones.

To prevent h2o intrusion, we run a bead of quality caulk across the top of the enclosure and downwardly both sides.

Service Conduit Clearance

The service drop for this particular projection could not hang over the neighbor'south grand, and so the periscope (the part of the mast above the roof) had to exist at the forepart corner of the building.

With the new meter-main firmly bolted to framing, the electrician installs a vertical section of the service conduit.

To avoid running the service drop over the neighbor'south holding, it was necessary to run the conduit to the forepart corner of the building earlier turning it upwardly and passing information technology through the roof overhang.

To get the conduit there, we ran it up from the panel, turned information technology 90 degrees toward the street, then turned it 90 degrees upwards before passing it through the eaves. We extended the conduit 24 inches in a higher place the roof; if nosotros had needed more clearance for the drop, we'd have made it higher.

In areas of pedestrian-just access, the NEC requires 10 feet of clearance between the baste loop and form; our local utility requires 12 anxiety. If information technology'southward possible to meet this acme requirement without penetrating the eaves, we extend the horizontal run of the service conduit virtually eighteen inches past the building corner and install the weatherhead at that place.

In this case, nosotros needed the height, so nosotros penetrated the eaves and installed a roof jack over the conduit to forestall the hole from leaking. The utility required us to spike the conduit to the wall within 3 feet of the hub at the top of the enclosure, once every x feet afterward that, and twice where it left the building wall. To clear a slice of trim, we spaced the service mast — conduit — off the wall past installing it over pieces of Unistrut.

Service Conductors

Once the panel and service conduit were in, we pulled the service conductors into the conduit. Since this was a 125-amp service, we used 1 ane/4-inch conduit and #2 THHN (thermoplastic high-heat-resistant nylon-coated) copper conductors.

Copper vs. aluminum. The electrical code allows us to use aluminum service conductors, just nosotros always use copper considering it's more than reliable.

Aluminum has more resistance than copper, and it as well tends to oxidize, which creates fifty-fifty more than resistance at connections. When the flow of current encounters resistance, the wire heats upwards and expands. When the menstruation drops, the wire cools and contracts. Over fourth dimension, this activity stresses the connections between the service conductors and the lugs on the panel — sometimes enough to loosen them.

Applying an antioxidant compound to the connections tin mitigate the problem, but in my view the added cost of using copper service conductors is a minor toll to pay to avoid future headaches.

Color-coding. Before pulling the wires, nosotros typically mark them at each end with colour-coded tape.

In a single-phase service, the phase legs are black and blood-red; the neutral is ever white. And when we install the wire, we leave enough extra at the weatherhead for the utility to form a drip loop and make the service splice.

Inside the panel, the hots terminate at the upper — or line side — lugs of the meter socket, and the neutral at its own lug.

Gravity makes information technology easier to "pull" service conductors by pushing them into the conduit from higher up.

The electrician uses colored tape to color-code conductors and so the utility knows which 2 to connect to the hots and which i to connect to the neutral.

One time the conductors are in the meter-main, the electrician connects the hots (crimson/blackness) to the line-side lugs, and the neutral (white) to a lug that ties to the neutral motorcoach in the distribution section.

Grounding Arrangement

Our side by side footstep was to build the grounding electrode system, which consisted of a copper footing rod wired to the service chief and h2o line. Although nosotros're immune to use 1/ii-inch rod, we use 5/8-inch rod considering it's less likely to bend when we drive it.

The electrician uses a rotary hammer with a ground-rod-driving attachment to bulldoze a grounding rod into the soil.

He then runs a single grounding wire that connects to a clamp on the water primary.

An acorn clamp on the ground rod.

The neutral bus in the main service.

The rod is driven into the earth near the panel and is supposed to go 8 feet deep. In some jurisdictions nosotros're required to drive ii rods 6 feet apart. Nosotros always add a 2nd rod if we hit something and have to drive the first one at an bending.

The grounding electrode usher is #half dozen bare copper wire. It should run as a continuous single slice (no splices), and it should connect to the following items:

• the neutral motorcoach in the console;

• a lay-in lug on the grounding bushing on the conduit that goes to loads;

• an acorn clamp on the footing rod;

• a footing clamp on the water main located within 5 feet of where the piping enters the firm.

By code we're required to bail the water pipes in the house to the gas pipe. This creates a larger grounding arrangement and ensures that any existing circuits mistakenly "grounded" to a gas pipe are connected to something that actually is grounded.

If the house has a gas line, the water pipes must be bonded to it. This is usually done at the water heater because both pipes are accessible in that location. A single length of grounding wire is connected to clamps on the water lines into and out of the heater, then to a clamp on the gas line.

The electrician installs a grounding clamp on the gas line after scraping off paint to ensure metal-to-metallic contact.

We normally bond the gas and water pipes at the h2o heater (if it's gas) because all of the pipes are accessible in that location.

The wire runs between the gas line and the water lines at the heater; it's necessary to connect to both the common cold-water inlet and the hot-water outlet, considering if dielectric unions were used, the pipes downstream from the h2o heater might not be grounded.

Identifying Circuits

Earlier shutting down power, transferring loads, and demoing the quondam service, it's critical to check the existing circuits. If something isn't working, we desire to know about information technology before making whatever changes; that mode, information technology's clear we didn't cause the trouble.

We also want to find out which wires are neutrals. Wires often aren't color-coded in old knob-and-tube systems, so when nosotros find the neutrals, we marker them white. If nosotros forget to identify them and accidentally hook upwards a hot and a white (120-volt) as 2 hots (240-volt), nosotros could fry whatever is plugged into that circuit.

When changing out an one-time 240-volt service, nosotros mark the phases black and red, based on testing before we shut off the power. Never rely on somebody else's colors. That person could have run a black to a red phase on a multiwire circuit. If, at the new console, you connect both of them to the black phase, you could be loading the shared neutral with twice as much electric current equally it tin handle — which could torch the house.

Transferring Existing Loads

This house had only a couple of circuits, so when nosotros removed the original service we were able to reroute the wires from the existing loads to a junction box within the crawlspace. In that location we connected them to Romex, so ran the Romex to the other side of the house and fed it through a conduit into the service panel.

The electrician transfers the existing loads past disconnecting the knob-and-tube wiring from the fuse "panel" and running it to a junction box in the crawlspace, where information technology's connected to Romex.

From there, the Romex runs to the other side of the house, exits the wall through a piece of conduit, and enters the bottom of the service console.

Since both circuits served more than than 1 room and included bedrooms, nosotros wired them to AFCI (arc fault circuit interrupter) breakers, which we and then installed in the distribution section of the panel. Eventually, more circuits will be added, and simply the bedroom circuits volition exist on AFCI breakers.

If nosotros had been replacing a newer service — one with a metal enclosure — we would accept stripped out the interior and treated it like a giant junction box. We would have run Romex between breakers in the new panel and existing loads in the one-time enclosure.

Final Steps

One time the quondam loads were transferred to the new panel and nosotros'd labeled the panel to indicate which rooms the circuits served, we reinstalled the cover and called for an inspection.

Sometimes, if we're lucky, nosotros can get the utility people to show upwardly, install the meter, and reconnect the business firm on the mean solar day nosotros call.

One time the loads take been transferred to the new panel, the electrician labels the circuits and installs the cover.

Since the business firm was occupied and it was going to exist some fourth dimension before the utility could show up and make the final connection, the author's crew supplied temporary power by running Romex between the existing service drop and the new service conductors.

Later, the utility came out, removed the jumpers and existing service drop, and connected the new service drib.

But frequently it's difficult to make this happen, and then if the domicile is occupied and the homeowners need the ability interruption to be curt — they work from dwelling, say, or have medical equipment — we may leave the old service continued and temporarily estrus up the new i with a jumper. That way, we can motility branch circuits ane at a time, which means the only ane that'due south off is the 1 we're working on.

Nosotros also might use a jumper to ability the business firm until the utility is able to show up and make the permanent connection. Keep in mind, though, that non every utility will allow y'all to install jumpers, because doing so requires connecting to a live service drop.

Peitsa Hirvonen is a licensed electrical contractor and the owner of SESCO Electrical in Berkeley, Calif.

How To Replace A House Service Electric Box,

Source: https://www.jlconline.com/how-to/electrical/replacing-an-electrical-service_o

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