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2.2 Installation do's and don'ts
It is vital to observe anti–static precautions when working inside the ACU cabinet.
Suppressors MUST be fitted across all inductive loads as close as possible to the device itself.
These devices include (but not limited to) motors, locks, auxiliary relays and sounders. Suitable
suppressors are included in the installation kit supplied with this controller.
Solder and tape all connections. DO NOT use crimps or B–connectors or wire nuts or punch–
down blocks.
Each ACU must be grounded to a good mains ground. This can be achieved via the ground
wire (cable shield) from the power supply or by a separate wire to mains ground.
All cable runs must be in shielded cable. The shield of each cable must be grounded at one
end, and at one end only. This will usually be at the ACU chassis plate. However, if the
peripheral equipment (lock releases, card reader's etc.) is grounded then the shield of the
cable must be grounded at the peripheral end and not at the ACU end.
Cable runs must be at least 2 meters long. This allows induced static to dissipate before it
reaches the electronics.
The braid of the cables (or the drain wire or ground wire) must be terminated to the earthing
clamps which are mounted to the chassis plate (unless the peripheral is connected to ground -
see below). The "pig tails" of the screened cable should be kept as short as possible to reduce
the radiating length.
The lengths of un-shielded wire should be kept to an absolute minimum. This will reduce the
chances of noise pick up. They must not be allowed to protrude into the area of the
electronics.
Where metal-cased peripheral equipment (lock release, card reader etc.) is to be mounted on
a metal surface (e.g. a metal doorframe) ensure that the metal surface is grounded and that
the cable ground wire is connected at the peripheral end and in this instance the cable
ground wire must not be connected at the ACU end, because the metal surface where the
peripheral equipment is connected should be providing a good ground.
Where peripheral equipment (lock releases, card reader's etc.) is to be mounted on a non-
metal surface, the peripheral must not be grounded independently and the ground wire must
not be taken to a local ground but connect back at the ACU chassis which should be connect
to a good ground (earthed). If the peripheral is metal-cased then the ground wire can be
connected to the metal case, but this still needs grounding via the wire screen back at the
ACU chassis.
When using RS485 communications, attention must be paid to the special earthing
requirements detailed in the section titled "Communications".
In addition to these general principles, it is vital to follow the specific requirements for installing
peripheral equipment (readers, lock releases etc.) These requirements are explained in the
relevant places of this manual
Please note that in all recommendations for wire, minimum gauge requirements are listed. It is
the responsibility of the installing company to follow all local and national electrical codes as
they apply.
Never install any access control system until approval has been obtained from local fire
authority. In particular note that the use of an exit (egress) button may not be legal. Single–
action exit may be required.
The use of shielded cable, and adherence to correct grounding procedures, is necessary for every
connection to the controller.
EXcel4 Controller
Page 8
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