Automatic Door Power Requirements: Supply, Wattage and Cost

Automatic door power is one of the first things an electrician, architect or facilities manager asks about, and one of the last things to be sorted out on many projects. An automatic door needs mains electricity at the head of the opening, a safe way to isolate it, and low-voltage cabling for sensors, push buttons, locks and access control. Get the automatic door power right before the ceiling closes and installation is simple. Get it wrong and the door arrives on site with nothing to plug into.

This guide explains automatic door power in plain terms: what supply the operator needs, how much electricity an automatic door actually uses, what it costs to run, what happens in a power cut, and what to agree with your electrician before we arrive. It uses the published figures for our MC-125 sliding door operator and MCW-100 swing door operator.

Do automatic doors need electricity?

Yes. An automatic door is driven by an electric motor under the control of a small computer, and both need power. Without power the operator cannot open the door by itself, the sensors stop working and an electric lock goes to whatever state it was set to on power loss.

That does not mean the door is useless without power. A sliding door on the MC-125 can be moved by hand with a force under 40 N on a single slide and under 50 N on a bi-parting door, and an optional battery backup keeps the door running for a period during an outage. A swing door on the MCW-100 remains a hinged door that can be opened by hand. Automatic door power, in other words, is about how the door behaves both with mains and without it.

Published automatic door power figures

These are the electrical figures we publish for our two operators, taken from the manufacturer’s documentation.

• MC-125 sliding door operator: power supply AC 110 to 220 V ±10%, 50/60 Hz. Brushless DC motor, 24 V, 60 to 70 W, with an integrated gearbox. Optional battery backup.
• MCW-100 swing door operator: power input AC 100 to 240 V. Brushless DC motor, 55 W, with a 24 V DC control output for accessories.

Both run from a normal South African mains supply, so automatic door power is rarely a special installation. The motor runs at low voltage inside the operator, which is one reason the drive is quiet and controllable. The figures that matter to the electrician are the mains input, the position of the supply and the extra loads described below.

What the electrician needs to provide

On almost every job, automatic door power is brought to the opening by the building’s electrician rather than by the door installer. Our quotations exclude the electrical supply to the entrance unless the quotation says otherwise. That is normal practice: the supply is part of the building’s installation and is certified by the person who installs it.

The usual automatic door power brief for the electrician is:

• A mains supply at the head of the door, terminated at a point we agree on the drawing, usually at one end of the header.
• A local isolator near the header, so a technician can switch the door off safely to work on it without going to the distribution board.
• Protection sized by the electrician at the distribution board. The operator is a small load, so the circuit is sized for safe installation rather than for the door’s demand.
• Preferably its own circuit, or at least a circuit not shared with equipment that trips. A door that loses power every time a kettle or a sign on the same circuit trips is a door that fails at random.

In South Africa the electrician works to SANS 10142-1, the wiring code, and issues a Certificate of Compliance for the installation. We do not certify electrical work. We tell you what the door needs, and your electrician designs and certifies the supply.

Automatic door power cabling: more than one cable

The mains supply is only one of the cables an automatic door needs. Most entrances also need low-voltage cables, and these are the ones that get forgotten.

• Activation devices: push buttons, no-touch switches and key switches away from the header need a cable back to the operator. Our guide to the automatic door push button covers placement.
• Access control: card readers, keypads and intercoms on each side, wired to the operator’s inputs and to the access-control panel.
• Electric lock: where the leaf has a powered lock, it needs power and a control signal, usually from the operator.
• Fire alarm interface: where the fire strategy requires the door to respond to the alarm, a signal cable from the fire panel. What the door must do on alarm is set by the fire strategy, not by the door supplier.
• Building management: on some projects a fault or status signal goes to the building management system.

All of these are easiest to install while the ceiling is open and the header is going in. Running cables later means chasing walls or surface trunking across a finished shopfront. Automatic door power and control cabling should be on the drawings before the builder closes up. See our automatic door specification guide for how to write it into the tender.

How much electricity does an automatic door use?

Less than most people expect. Automatic door power consumption has two parts, and only one of them depends on traffic:

• The motor, which only draws its rated power while the leaf is moving. On a sliding door that is a few seconds per opening and a few seconds per closing.
• The standby load, which is always present: the controller, the sensors, any electric lock and the battery charger where battery backup is fitted.

We publish the motor rating but not a standby figure, because the standby load depends on which sensors, locks and accessories are fitted to the particular door. If you need a measured figure for an energy model, we can take it on an installed door of the same build.

What automatic door power costs to run: an upper bound

The arithmetic below is an illustration to show scale, not a measurement. It deliberately overstates the cost by assuming the motor runs flat out all day, which it never does.

• The MC-125 motor is rated at 60 to 70 W. If it ran at 70 W for 24 hours without stopping, it would use 70 × 24 = 1,680 Wh, or 1.68 kWh a day.
• At an illustrative tariff of R3.50 per kWh, that is about R5.88 a day, or roughly R180 a month.
• In real use the motor runs only while the leaf moves. Even a busy entrance spends most of the day with the motor stopped, so the motor’s real share is a small fraction of that upper bound.

Use the rate on your own electricity bill rather than ours, because municipal and Eskom commercial tariffs differ. The point stands either way: automatic door power for the drive itself is a small line in a building’s electricity bill. The far bigger energy cost of an entrance is the heated or cooled air that escapes while it is open, which is why hold-open time and half-open mode matter more than motor wattage. Our guide to revolving door energy explains that side of the question.

Automatic door power during load shedding

In South Africa, automatic door power has to be planned for the hours when there is none. When the mains drops, an automatic door does one of three things, and the choice is made for the building rather than left to chance:

• Keeps running on battery backup. The optional battery on the MC-125 keeps the door operating for a period, which suits busy retail and healthcare entrances.
• Goes to a set state. Without a battery the door stops. Depending on how it is set up and what the building needs, it can be left to open safely or to stay closed and locked.
• Is opened by hand. A sliding leaf on the MC-125 moves by hand with a low force, and staff are shown the manual release at handover.

Which state is right depends on whether the door is on an escape route and what the fire strategy requires. Our guide to automatic doors and load shedding covers each option in detail.

Inverters, generators and automatic door power

Many buildings now run essential circuits on an inverter or a standby generator. An automatic door can be connected to those circuits, and on busy entrances that is often the best answer. A few points are worth agreeing with your electrician:

• Put the door on the essential circuit if the entrance must keep working during an outage. It is a small load and rarely a problem for an inverter.
• Allow for the changeover. When a generator starts, there is a short gap in supply. The MC-125 runs a power-on self-check at every start-up, so the door resets itself and carries on.
• Keep the lock behaviour consistent. If the lock and the operator are on different circuits, one can lose power while the other keeps it. Decide this deliberately rather than discovering it during the first outage.

Automatic door power, surges and lightning

Highveld thunderstorms are hard on electronics, and an automatic door controller is a circuit board like any other. Power surges after an outage or a nearby strike are a common cause of controller and sensor faults. Surge protection at the distribution board is the electrician’s decision and is worth discussing on any exposed site. Our guide to outdoor automatic doors and the South African climate covers lightning and weather in more detail.

Swing door operators

Automatic door power for swing doors follows the same pattern, with two differences. First, the MCW-100 sits on the head of the door frame, so the supply comes to the frame head rather than to a long sliding header. Second, the MCW-100 supplies 24 V DC to its accessories, which keeps push buttons and sensors on low voltage.

On a swing door with an electric strike or other powered lock, the lock and the operator have to be sequenced so the lock releases before the operator pushes the leaf. That is a wiring and commissioning job, and it is easier when both are planned together. See the MCW-100 swing door operator page for the full specification.

Automatic door power on revolving and hermetic doors

Revolving and hermetic doors are quoted per project, and so is their automatic door power. A revolving door’s drive, control and safety devices are larger than a sliding door’s, and hermetic doors in hospitals and laboratories often tie into theatre or clean-room controls. We confirm the supply and cabling for these from the site assessment rather than from a table. See automatic revolving doors and hermetically sealed doors.

Where to put the supply

The position of the supply matters as much as the supply itself. The MC-125 is surface mounted and needs a solid, level header across the full span, carried by a steel structure. The supply should arrive at a point on that header we agree on the drawing, not wherever the nearest ceiling void happened to be. Our MC-125 sliding door operator page shows the header detail.

Leave enough slack to terminate neatly inside the operator, keep the mains and low-voltage cables apart, and label the isolator so the next technician knows what it switches. These small automatic door power details save a lot of time on every future service visit.

Automatic door power on existing buildings

When we automate an existing door, there is often no supply at the head at all. In that case automatic door power has to be planned from scratch: your electrician brings it to the opening, usually from the nearest distribution board, in conduit or trunking to suit the finishes. We look at the route at the site survey so the quotation and the electrician’s work line up. Our guide to automating an existing door covers the rest of a retrofit.

Common automatic door power mistakes

• No supply at the head on the day of installation, so the door is fitted and then waits for an electrician.
• No local isolator, so every service visit starts with a hunt through the distribution board.
• A shared circuit with signage, a fridge or a heater that trips and takes the door with it.
• Forgotten low-voltage cables for push buttons and readers, found only after the ceiling is closed.
• Lock and operator on different circuits, so they disagree during an outage.
• Battery backup removed at some point and never put back, so the door stops at the first load-shedding slot.

What we check at commissioning

At commissioning we confirm that automatic door power is correct before we set up the door: the supply voltage at the operator, the isolator, the earth, and that each low-voltage device works. We then test what the door does when the mains is switched off, with and without the battery, and show staff the manual release. The results are written down at handover. Servicing then checks the battery and the power-failure behaviour on every visit. Our standard service interval is six months, more often on busy entrances. See automatic door servicing.

What to send us

To plan automatic door power properly, send us the drawing or photographs of the opening, what sits above the head, where the nearest distribution board is, whether the building has an inverter or generator, and what access control and locking you want. We will mark up where the supply and cables need to go, so your electrician can price and install them before we arrive.

Automatic door power: quick answers

• Automatic door power comes from a normal mains supply brought to the head of the door.
• Automatic door power for the MC-125 is AC 110 to 220 V ±10%, with a 60 to 70 W, 24 V brushless motor.
• Automatic door power for the MCW-100 is AC 100 to 240 V, with a 55 W brushless motor.
• Automatic door power should have a local isolator and, preferably, its own circuit.
• Automatic door power consumption is small, because the motor only runs while the leaf moves.
• Automatic door power during load shedding comes from an optional battery, an inverter or a generator.
• Automatic door power is installed and certified by your electrician, not by the door supplier.

Automatic door power questions

Planning a new entrance or automating an existing door? Request a quote with photographs of the opening and we will mark up exactly where automatic door power and cabling need to go. Requirements for powered pedestrian doors are published by the South African Bureau of Standards. We are on 010 412 0062, Monday to Thursday 08:00 to 16:30 and Friday 08:00 to 14:00.