Common failures in access control doors

July 2015 Access Control & Identity Management, Editor's Choice

Most institutions, parastatals and larger business premises have access control in one form or another, and after passing through gates, booms or turnstiles, visitors or staff are eventually confronted with locked doors, which can only be opened after certain criteria have been met.

Just as we cannot build a sturdy wall without a proper foundation to support it, the electronics used in access control need to be supported by a proper physical foundation. We sometimes lose sight of the objective of keeping the premises secure, and concentrate on monitoring, or reacting to the number of alarms raised. The electronics can monitor the status of the door, but it is the mechanical items such as the door, the lock/striker and the door closer that make it close and lock every time, and to achieve this the door itself has to be in good shape.

Very often, the door is thought to be locked, but is in fact, only closed.

Physical malfunctions

It is the experience of this writer that many access control systems become ineffective because of physical malfunctions of doors, locks, door closers and door hardware, and poor delivery of power to the lock or striker. Often the latch of the lock is not properly inside the electric striker, or the electric lock, motorised lock, magnetic lock or other device is not properly aligned or able to fully engage, with the result that the door can be easily opened. Staff, cash, assets and information become more vulnerable because staff assume that they are working behind locked doors, and they are not as careful as they would be if there was no access control at all.

The trend towards cutting the up-front cost has led to a serious deterioration of standards – clients are forcing contractors to compete fiercely with cheaper equipment and cheaper labour. Lighter aluminium sections and lighter timber doors, lighter ironmongery and lighter door closers offer relatively small initial savings, which are quickly exceeded by the repair and ongoing maintenance costs which ensue.

Doors need to be properly hung on sturdy frames to ensure that they close and lock every time. This means using the correct hinges or pivots, and in the case of timber doors, the right paint and weatherproofing. A damp door or frame will swell and cause the door not to close or open properly, because it can no longer fit into the frame. In dry weather, unprotected timber can become dehydrated and crack, with similar results. Routine maintenance of external timber doors is therefore also a security issue.

Electronic malfunctions

An electric released locking device.
An electric released locking device.

Apart from failure of readers and other electronic equipment, frequent causes of electronic failure are cable which is too light and power supplies that are too small for the job.

The power supply installed with readers and other low-current-drain electronics is often not big enough to support locks as well, and this is particularly so of magnetic locks. Magnetic locks are electro-magnets and require power 24/7 to remain locked (as do fail safe strikers – explained lower down). During power outages, these devices are constantly draining the battery – usually by between 0.25 and 0.5 of an amp per device, each hour. Light 0.2 mm cable as used in the alarm industry is too thin to carry power for most locks.

It is often wiser to have a separate power supply for the locks, and use the access control system to trigger them. Just as a thin hosepipe will deliver less water than a thick one will, from the same water source – the thinner (and longer) the cable – the more voltage will be lost. Cable thickness must be determined by the initial voltage at the power source, the length of wire between power source and locks, and the current drain of each of the locks used. Card and tag readers, face and fingerprint readers and digital keypads are generally ‘always on’ and will be using usually between 30 and 150 milliamps per hour, day and night – even when there is no activity. Some modern devices lower their power consumption after a certain period of no-activity, and come alive again when activated. All such devices, and intercoms which have displays, must be factored into calculating the total amount of power required.

The most common faults experienced at doors, and their causes, are examined in more detail below.

Failure to lock

Often the latch of the lock is not properly inside the electric striker, or the magnetic lock or other device is not properly aligned or able to fully engage, and the door can be easily opened from the outside.

Door closers: People do not lock doors, door closers do. Every access controlled door must close and lock automatically – every time – to be effective. Floor mounted door closers are usually not suited to access control applications as they do not have the dual-action necessary to ensure that the door closes and locks completely. Better quality surface mounted overhead hydraulic closers such as Dorma are equipped with a dual-action, allowing for separate adjustment of the closing speed, and of the last few degrees of closing, thereby ensuring that the lock or latch is ‘clicked’ fully into the locked position. To achieve this every time, the door must be correctly hung and properly aligned with the frame, and the closer must be fitted correctly.

An error of 10 mm in fitting a door closer is a huge error.

Other common problems are:

• Poorly hung door – affects closing and opening

• Wear and tear on hinges or pivots – affects closing and opening

• Poor quality hinges / screws missing – affects closing and opening

• Door has dropped since installation – affects closing and opening

• Door frame bowed – affects closing and opening

• Door warped or twisted (dampness) – affects closing and opening

• Poor installation of lock or striker – affects closing and opening

• Door closer incorrectly fitted (extremely common) – affects closing/locking

• Door closer too light for door size – affects closing/locking

Magnetic locks: Besides being entirely power dependent, magnetic locks rely heavily on the whole of the striking plate making contact with the lock body. This is achieved by means of a ‘wobbly bolt’ which is deliberately loose, to allow the striking plate to get ‘sucked’ completely onto the magnet. Bad fitting, in particular making the ‘wobbly bolt’ too tight, or welding this plate to a gate, will prevent the striking plate making full contact with the lock, and reduce the locking power immensely.

Failure to release

If the door fails to release when triggered electrically by the reader /access control system, (i.e. the lock clicks or the reader shows a successful transaction) the causes are very often those in the list above. In addition, if the reader ‘allows’ access but the door does not release, the following are likely causes.

Lack of power at the door

• Not enough power at source

• Power supply too far away and / or:

• Cables are too thin (causing voltage drop)

• Broken cables

The voltage needs to be measured at the lock, under load (while it is being operated). This is usually vastly different to measuring at the transformer or power supply, where readings are mostly deceptively higher.

Understanding power for locks

• AC = Alternating current (usually about 240 V AC) which comes from a socket in the wall, or an inverter, or a UPS.

• DC = Direct current as derived from a battery, or a battery backup system. DC is the most common today in access control systems.

• Most electric locks and strikers used in South Africa are designed to work with 12 V – to plus/minus 10%. Some use 24 V because they are intended to work with USA designed 24 V fire systems.

• Over voltage will shorten the life of the coil.

• Under voltage will lead to poor performance – generally a reluctance to unlock.

• Reputable brands will have a label indicating the power requirements – for example 12 V AC. If AC is specified as the only power source, the lock or striker is not intended to use DC (battery) power.

• Note that AC power can be converted to DC using a bridge or other rectifier and a diode – however this increases the voltage by 30% to 40%. It is therefore necessary to start with a lower voltage.

• If the voltage is too high, or ‘switched on’ for too long, it will burn out the coil of a lock or striker.

• Electric locks require momentary power (usually only a fraction of a second) to unlock. Most card or tag readers and keypads usually have outputs of several seconds, which is too long and shortens the life of the coil.

Electric Strikers can be fail-safe or fail-secure:

• Fail-safe means the striker fails to the life safety default – it requires power to stay locked, and opens in the absence of power (the same way a magnetic lock does).

• Fail-secure means that in the absence of power, the striker remains locked. This is the most common type. It uses power momentarily to unlock and does not use any power to stay locked.

A simple test of door security

Disconnect the door closer (usually the arm of the door closer can be easily disconnected at the ball-joint) before attempting the following simple test.

1. Try to push or pull the door open without using the handle, key, pushbutton or access control equipment. If it opens when pushed, it is not locked.

2. With the door closer still disconnected, open the door fully and try to push it into the locked position using only your little finger. Difficulty in completing this task means the door cannot be relied upon to lock itself and such difficulty is often attributable to poor alignment of the door and frame, a badly fitted lock, door closer etc.

This article is intended as a general guideline based on the author’s experience of more than 40 years in the industry. It is not intended to cover every lock and door, or every situation. There is no substitute for expertise when installing and troubleshooting access control. By far, most of the problems encountered in the field are caused by price-cutting, incorrect specifications and poor installation.

Battery backups

This is a very general guide to understanding battery backups as generally used in the security industry.

A battery backup stores low voltage power (usually 12 volts) in a battery or batteries to operate electronic security devices like electric locks, electric strikers, magnetic locks, readers as well as fire and intruder alarms so that the user is not constantly dependant on the availability of Eskom.

Like water evaporates, so your battery discharges slowly, even when you are not draining it. This is why battery backups should be connected to a 24/7 power source, so that the battery / batteries are charging all the time when electricity is available. Backups must not be powered from lighting and other circuits which could be switched off at night or over weekends.

The battery can be likened to a farmer’s dam, which receives water when there is rain and the river is flowing into it, and stores the water until it is needed. The bigger the dam, the more water you can store. Similarly, the bigger the battery, the more power can be stored and / or used.

The bigger the inflow of river water to the dam, the longer the farm can survive without rain, and the more water can be piped to the fields. Similarly the bigger the charging capacity of the battery charger, the more power can be drawn from the battery, and the quicker the battery can recover the power drained from it when charging power is restored.

When deciding on the size of batteries and chargers remember to factor in not only all card, tag face and fingerprint readers and digital keypads, but also allow a margin of at least 40% for safety. Every device with a display or LED lights is drawing some current even when not being operated.

For more information contact David Miller The Lockshop, +27 (0)21 555 1720, lockman@lockshop.co.za, www.lockshop.co.za


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