Short answer: Overhead service conductors have to stay out of reach. Open service conductors and multiconductor cables without an overall outer jacket keep 3 ft from windows that open, doors, porches, balconies, ladders, stairs and fire escapes, except conductors run above the top level of a window (NEC 230.9). Final spans near these places still have to meet the vertical clearances. Over a roof they keep 8 ft 6 in. of vertical clearance, with reductions to 3 ft or 18 in. for 300 V or less on steep, guarded or isolated roofs or short overhangs (NEC 230.24). Above grade the minimum depends on the conductors, the voltage to ground and the area below: 10 ft at the service entrance and drip loop for messenger-supported cable at 150 V or less to ground, 12 ft over residential driveways at 300 V or less to ground, and 18 ft over public streets and areas with truck traffic. The point of attachment is at least 10 ft above finished grade (NEC 230.26). A service mast has to be strong enough or braced, and only power service-drop or overhead service conductors are attached to it (NEC 230.28).
PSI lists Services, Service Equipment and Separately Derived Systems (6 scored NEC Knowledge and 4 scored Calculations questions) as a subject area of the Texas Journeyman exam. PSI does not name 230.24 or say how many questions cover service clearances. The Texas Journeyman Practice Pack has 1,000 original questions and 10 timed mock exams in the real two-part format, with step-by-step solutions for every calculation. Try free practice questions without signing up. Get the full pack for US$39 with one payment.
Tsai Electro is an independent learning site. Not affiliated with TDLR, PSI or NFPA. We explain the ideas in our own words and do not reproduce NEC text. Check every rule and table value in your own 2026 NEC, and follow your supervisor and the local inspector.
Where this fits
The utility’s service drop is held to the building at the point of attachment, which is a mechanical support. The service-entrance conductors leave the service head, connect to the drop and run down to the meter and service equipment. This page covers the overhead part: how high, how far from openings, and how the conductors are held up. The cable used for the run down the wall is on the SE, SER and USE cable page. In Texas, the utility sets its own rules for the service drop itself, so check the utility’s service standards along with the NEC.
230.9: distance from building openings
- 3 ft rule. Open service conductors and multiconductor service cables without an overall outer jacket keep at least 3 ft from windows that are designed to be opened, doors, porches, balconies, ladders, stairs, fire escapes and similar locations.
- Above a window is allowed. Conductors run above the top level of a window are considered out of reach, so the 3 ft rule does not apply there.
- No obstruction. Overhead service conductors are not installed below openings through which materials may be moved, such as openings in farm and commercial buildings, and they do not obstruct those openings.
230.24(A): clearance over roofs
| Situation | Minimum vertical clearance |
|---|---|
| General rule over a roof | 8 ft 6 in., kept for at least 3 ft in all directions from the roof edge |
| Roof subject to pedestrian or vehicular traffic | Same as the grade clearances below |
| 300 V or less between conductors, roof slope 4 in 12 or steeper | 3 ft |
| 300 V or less between conductors, roof area guarded or isolated | 3 ft |
| 300 V or less between conductors, not more than 6 ft of conductors pass above only the roof overhang, covering not more than 4 ft horizontally, and the conductors end at a through-the-roof raceway or approved support | 18 in. |
For the final conductor span attached to the side of a building, the 3 ft extension beyond the roof edge does not apply. The clearance above the roof itself still applies. Read the exact conditions in your code book; exam questions often hinge on the slope or the overhang distance.
230.24(B): clearance above grade
| Over | Minimum |
|---|---|
| Service entrance, lowest point of the drip loop and areas accessible only to pedestrians, only for cables supported on and cabled together with a grounded bare messenger at 150 V or less to ground | 10 ft |
| Residential property and driveways, and commercial areas not subject to truck traffic, 300 V or less to ground | 12 ft |
| The same areas, more than 300 V to ground | 15 ft |
| Public streets, alleys, roads, parking areas with truck traffic, non-residential driveways, cultivated, grazing, forest and orchard land | 18 ft |
| Railroad tracks | 24.5 ft |
230.26 to 230.29: holding the conductors up
- Point of attachment (230.26). At least 10 ft above finished grade, and positioned so the clearances from building openings in 230.9 and the vertical clearances in 230.24 are maintained.
- Means of attachment (230.27). Multiconductor cables are attached with fittings identified for use with service conductors. Open conductors are attached to fittings identified for use with service conductors, or to noncombustible, nonabsorbent insulators securely attached to the building or structure.
- Service masts (230.28). The mast has enough strength, or is supported by braces or guys, to safely carry the strain of the service drop. Hubs used with a conduit that serves as the mast are identified for use with service-entrance equipment. The conductors are not attached to the mast between the service head or end of the conduit and a coupling located above the last point of securement or above the building. Only power service-drop or overhead service conductors may be attached to the mast; cable TV and phone lines go somewhere else.
- Supports over buildings (230.29). Service conductors that pass over a roof are held on substantial structures. Where the system is grounded, a metal support structure is bonded to the grounded overhead service conductor in the way the section describes.
Service head and drip loop
At the top of the service-entrance conductors, the service head is listed for wet locations and is located above the point of attachment. The conductors form drip loops so water runs off before it can enter the service head. Where it is not practical to put the head above the attachment point, the code allows it within 24 in. of the point of attachment; check the exact allowance in your code book (NEC 230.54).
Worked example: a mast on a low-slope roof
A house has a 120/240 V overhead service. The incoming service drop crosses a residential driveway, then crosses 10 ft of a roof with a slope of 3 in 12 before it reaches its point of attachment on a service mast. The roof is not guarded or isolated and has no foot or vehicle traffic.
- Voltage between conductors. 240 V, which is 300 V or less.
- Slope test. 3 in 12 is less than 4 in 12, so the 3 ft reduction does not apply.
- Overhang test. 10 ft over the roof is more than the 6 ft allowed for the 18 in. reduction, so it does not apply either.
- Roof clearance. Neither reduction applies, so the conductors keep at least 8 ft 6 in. of vertical clearance above the roof along the whole span over it, including the lowest point of sag. For a real utility service drop, also confirm the utility’s own clearance and attachment standards. That is a clearance for the conductors, not a height the mast itself must reach above the roof.
- Driveway clearance. The 120/240 V single-phase service has 120 V to ground, which is 300 V or less to ground: 12 ft over the residential driveway, measured at the lowest point of the span over it.
Check yourself
- How far must open service conductors stay from a window that opens? 3 ft, unless they run above the top of the window.
- What is the general clearance over a roof? 8 ft 6 in.
- What is the clearance over a public street? 18 ft.
- Can a cable TV line be attached to the service mast? No. Only power service-drop or overhead service conductors.
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Highlight the clearance numbers
NFPA 70, National Electrical Code, 2026 Edition (softcover). Highlight the 3 ft opening rule in 230.9 and the 8 ft 6 in., 10, 12, 15, 18 and 24.5 ft values in 230.24, and note the conditions beside each value so roof and grade clearances stay apart on exam day. The Texas exam is open book. PSI allows a soft-bound NEC with highlighting, underlining and notes made in advance. Loose-leaf, spiral-bound and ring-bound copies are not allowed, and only permanent index tabs made or supplied by the NEC publisher are permitted; homemade and third-party tabs are not.
FAQ
How high must a service drop be over a residential driveway?
At least 12 ft where the voltage to ground is 300 V or less.
What is the minimum height of the point of attachment?
At least 10 ft above finished grade, and positioned so the 230.9 and 230.24 clearances are maintained.
When can the roof clearance drop to 3 ft?
When the voltage between conductors is 300 V or less and the roof slope is 4 in 12 or steeper, or the roof area is guarded or isolated.
How far must service conductors be from a window?
Open conductors and cables without an overall outer jacket stay at least 3 ft from windows designed to be opened, unless the conductors run above the top level of the window.
Can communication cables be attached to a service mast?
No. Only power service-drop or overhead service conductors are attached to the mast.
Sources checked October 2026
- PSI Candidate Information Bulletin, Texas electrician examinations (updated September 15, 2026): https://test-takers.psiexams.com/api/content/bulletin/1682
- NFPA 70, National Electrical Code, 2026 Edition, Article 230 Parts I, II and IV
