NVQ Masterclass [Part 3] - Doors...the key to choice

On a typical door, the door contact senses whether the door is open or closed and generates an alarm. For example, if the door opens and an ID device has not been presented, the system will generate a door forced alarm. If the door has been left open longer than a specified time, the system will generate a door left open alarm (All alarms are sent to the PC via the master door controller.)

Fitting access control hardware to a door
An access control system is only as good as the locks and doors to which it is fitted. For a system to be reliable, the doors have to be sturdy and well maintained, fitted into solid door frames and, most importantly, close properly every time.

3cf:Some manufacturers supply doors that close automatically. Where doors do not close automatically door closers should always be fitted so that the door closes securely after someone has passed through.

Types of doors and door terminology
There are a variety of different door types and many different ways of locking doors. There are six basic ways of describing the opening operation of a single leaf door:

1. Left hand (open in)
2. Right hand (open in)
3. Left hand reverse or left hand open out
4. Right hand reverse or right hand open out
5. Left hand swing
6. Right hand swing

Determining which of these six categories a door falls into may seem obvious. A correct description will assist a lock manufacturer or installer when advising or quoting on a system.

Left and right handed doors
When standing facing a door is the lock on the left or right hand side of the door? If the lock is on the left, it's a left hand door and if it's on the right it's a right hand door. Unfortunately, door manufacturers take the reference point as the hinge and this can cause confusion. Please take note of the diagram (Fig 1) as it uses the hinge as its reference which is the complete opposite.

Door and door frame construction
The construction of the door and door frame is of considerable importance when specifying an access control system. A thin hardboard door isn't much use barring access to a high value installation whilst over-spec heavy steel doors are not appropriate for indoor use.

In high security applications you may wish to give careful consideration to the fabric of the building in which the door frame is set.

The material a door is made from and the space available may restrict the choice of lock. Locking mechanisms for wooden doors are usually different from those for metal or glass. The proximity of metal construction can limit the performance of some proximity readers.

The installation of the cables supplying power to the lock and reader also need to be taken into consideration. Closing the door securely is as important as opening the door. Doors failing to close properly are a common problem. Usually, the better the quality of door the less likely the problem.

Door closers
For a door to lock securely it must first close properly. Although it's obvious that a door needs to close before it can be locked, this requirement is often overlooked. People using the door should never be expected to close a door manually. If a door is not of the self closing variety then a door closer should always be fitted. There are a huge choice of door closers available including pneumatic, electrical and mechanical. There are varying speeds of operation, durability and price. Door closers should conform to EN1154 the European standard for door closers.

Fire doors
Fire doors are specially constructed to withstand high temperatures. If any work on fire doors is required when fitting locks, always seek assurances from the door manufacturer that the performance of the fire door will not be compromised.

Audio/Video door entry
These systems are the most common type of access control used in residential applications and consist of a front panel mounted on the exterior of a building next to the main entrance. When a visitor presses a button to call for attention, the person receiving the call can press a switch to release the lock. Larger systems are used in local authority residential applications where many flats can be linked to the front panel. These systems can incorporate audio and or video modules and can also be integrated with access control systems so that tenants can gain access. (PAC, for instance, produces a special Panel Mount Reader designed to fit into most makes of entry panel.)
When a valid key or card has been presented to a specified reader, a Visual Verification window containing a photo image associated with that key or card automatically appears. This allows an operator to compare the person's appearance with the image stored on a PC.

Air Lock
An air lock is a special type of access point usually used in high security or safety applications. An air lock consists of two doors but only one door will open at once. Usually the airlock will allow only one person in at a time. The second door will not open until the first door is secure. Presence in area: This is a report generated by the access control system giving the names of the system users in an area at any given time. If this is required then turnstiles or special gates that only allow one person in at a time should be fitted. This ensures that no-one can leave or enter an area without the systems' knowledge. No set-up is totally foolproof but this prevents accidental tailgating (when a person gains access through a door directly behind someone with an authorised ID card).

Door locks and locking
All access control systems have to lock and unlock doors electronically. Basically all locks operate in one of two modes 'Fail Safe' and 'Fail Secure'. The 'Fail' means total loss of power to the lock. 'Safe' means that the door remains unlocked until power is restored. 'Secure' means that the door remains locked until the power is restored.

All doors on fire escape routes should be 'Fail Safe'.

The specification of electronic door locks is NOT a simple task. Industrial sites, offices and residential properties will have a large number of different types of door.

The way that the doors open, the material that the door and its frame is made from, the type of door (e.g. fire door, emergency exit), the ease of installing the cabling will all have a bearing on the type of lock and fittings that need to be specified.

Alterations may need to be made to the structure of the door or the door may be unsuitable and have to be replaced.

Lock types
Electric strikes or door releases: These are easy to fit but are a low security option.

Electro magnetic locks or mag-locks: These are powerful, but require power all the time to keep the door locked.

Electro magnetic Shearlocks: These work like magnetic locks, but offer the added advantage of mechanical interlocks.There are many different types of locks in the categories listed above each with varying characteristics. The locks must be married with the types of door and the customer's expectations.

Frequency of use
Most lock manufacturers will give a number of operations per given time period that the lock is rated to provide. There are many different types of electronic locks on the market. The choice of lock is often left to the installer. Lock manufacturers publish detailed guidelines on the huge array of locks available and are usually happy to give detailed specifications and help when specifying locks.

In an emergency, the access control system must be able to release the door locks automatically. Alarms, such as fire alarms, can be also integrated into the system.

IMPORTANT NOTE:
Where an ID device is required to exit a building or secured room, a break glass emergency exit switch or a mechanical means of exit – ie: electric lock with mechanical override – must be installed.