Surface-mounted, frame to door edge
UL 294 · NFPA 80 · NFPA 70 (NEC)
Maryland, DC & Northern Virginia
A door power transfer loop is a flexible, armored cable that protects wires as they cross from the frame to a moving door. It lets electrified locksets, electric exit devices, and request-to-exit switches on the door receive power and send signals. The steel armor resists cutting and pinching every time the door swings. Two mounting boxes, one on the frame and one on the door edge, hold the loop in place. It is a budget-friendly way to electrify an existing door without major frame changes.
Add power to an existing door without replacing hinges, so upgrades are quick and less disruptive.
Heavy steel armor shields the wires from cutting, pinching, and vandal attacks at the hinge side.
Exposed design makes inspection and replacement simple, cutting downtime when wires wear out over many years.
King Locksmith And Doors Inc. installs and services door hardware for businesses, government agencies, healthcare facilities, and hotels across Maryland, Washington DC, and Northern Virginia. Our technicians wire power transfer loops for electrified locks, exit devices, and access control systems. We match each loop to your door, frame, and wire count, then test every connection before we leave. From one office door to a full campus rollout, we deliver clean, code-aware work you can trust.
The right loop depends on your door, the devices it powers, and how often it opens. Use these five factors to pick a loop that lasts and keeps your access control system reliable every day.
Loop length must fit how far your door opens. A loop that is too short pulls tight and strains the wires. A loop that is too long sags and can snag on people or carts.
Doors that swing past 90 degrees often need a longer loop. Typical sizes run 12 to 24 inches. We measure the gap between frame and door at full open before choosing a size, so the cable moves freely every cycle.
Every electrified door needs a set number of wires. A lock may need two wires for power, while a request-to-exit switch and latch bolt monitor add more. The loop’s inner opening must fit them all without crowding.
Overstuffing a loop causes friction and early wire failure. We carefully count every conductor, plan for future devices, and choose a loop with room to spare. That keeps your door ready for added monitoring or lock upgrades later.
Hollow metal, aluminum storefront, and wood doors each mount loops differently. Hollow metal doors need prepared openings or surface boxes. Aluminum stiles are narrow, so mounting boxes must fit the space without blocking glass or hardware.
Wood doors need solid backing for screws. Fire-rated doors add rules about drilling and field changes. We review the door label and construction first, then choose mounting parts that hold firm and keep the opening compliant with NFPA 80.
A side office door may open a few dozen times a day. A hospital corridor or hotel entrance may open thousands of times each day. Each swing flexes the loop and the wires inside it.
High-traffic and public doors need heavy-duty armor and secure end fittings. Mounting the loop on the less exposed side reduces tampering and accidental damage. We size the loop and its fittings for your traffic so it keeps working for years.
Exposed loops are affordable and easy to service, but some sites want a cleaner look or more protection. Concealed electric power transfers hide the wiring inside the door and frame when the door is closed.
Electrified hinges are another option that routes wires through the hinge itself. These choices often need more door and frame preparation upfront. We explain the cost, security, and look of each option in plain terms so you can choose with confidence.
Both options carry power to an electrified door, but they install and wear differently. This quick side-by-side view shows where a power transfer loop gives you a clear practical advantage.
Consideration
Door Power Transfer Loop
Electrified Hinge
Lower parts and labor cost overall
Hinge and wiring prep cost more
Mounts on existing doors with minimal prep
Requires swapping hinge and frame wiring
Larger opening fits more conductors easily
Limited to the hinge’s fixed wire count
Visible loop is quick to inspect
Hidden wires are harder to diagnose
Works on metal, wood, and aluminum doors
Needs compatible hinge size and frame prep
Most loop problems start small, with a lock that works some days and fails others. Watch for these warning signs before an electrified door stops working or leaves you exposed.
We mount power transfer loops on new or existing doors, sized for your devices and door swing.
We replace worn, kinked, or vandalized loops and rewire damaged conductors to restore steady lock power fast.
Turn a mechanical door into an electrified opening with a loop, new lock hardware, and clean wiring.
We wire loops into your access control panel so card readers and keypads release the door reliably.
Upgrade exposed loops to concealed power transfers or electrified hinges for cleaner looks and stronger tamper resistance.
We trace intermittent faults with continuity and voltage tests, then verify the lock, exit device, and signals.
Get a free site assessment for power transfer loops across Maryland, DC, and Northern Virginia. Our team will respond fast.
