NXT 2D/4D Hardware Installation Guide

NXT 2D/4D Hardware Installation Guide

1.0 Introduction

The following information explains how to install the NXT-2D or NXT-4D controllers and peripherals that connect to those controllers. Other wiring diagrams and additional NXT installation information can be found in the NXT-4x4, NXT Reader and NXT-RM3/WI+ installation guides.

 

2.0 Important Note:

Keri Public Statement on the Amazon Key

 

Keri Systems, Inc. has updated its policy regarding the integration of Amazon devices

with Keri Systems controllers.

 

We are pleased to inform you that Amazon has now provided official installation
documentation for Keri products within their installation app. As a result, Keri Systems
will allow Amazon devices to be installed alongside Keri controllers when following
the guidelines and best practices provided by Amazon.

 

This change reflects our commitment to supporting secure and flexible access solutions
that enhance customer convenience, including use cases such as Amazon delivery access.

 

Please note the following:

  • Installers must follow Amazon’s official documentation and procedures for
    installing Amazon devices with Keri hardware.
  • Keri recommends that all installations be performed by trained professionals
    familiar with both Keri and Amazon device requirements.
  • Any damage caused by improper installation or failure to follow approved
    documentation may still void the controller warranty.
  • Responsibility for any security concerns or access control changes introduced
    by the integration rests with the Building Owner or Manager.

 

Keri Systems remains dedicated to providing robust access control solutions.
We will continue to monitor and evaluate integrations to ensure the safety
and satisfaction of our customers.

 

 

3.0 Controller Wiring Diagram

3.1 NXT-4D Controller Installation Drawing

 

 

Notes:
  • This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy, and if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a residential area may cause harmful interference in which case the owner will be required to correct the interference at the owner’s expense.

    • PCBs revision M and later only have 2 x Ethernet activity LEDs (A and B).

    • This controller uses a CR-2032 3 volt backup battery that retains all controller configuration and cardholder records if the controller is down-powered. The voltage level of the battery should be checked annually.


3.2 LED Definitions Table


LED Definition
Purpose
LED Name
                     
    Ethernet Comms [a]



10/100
a (D21)
Link
b (D22)
Utility LEDs
Standard Firmware Config Reset
c (D48)

Host Channel Active
d (D49)

Firmware Upgrade
e (D50)

Event Channel Active
f (D51)

Unused
g (D52)

Mercury Firmware Config Reset
h (D53)
RS-485 Bus
Bus 1 Tx
 i (D1)

Bus 2 Tx
j (D6)

Bus 3 Tx
 k (D11)

Bus 4 Tx
l (D16)
Relay State
Relay 1 active
m (D3)

Relay 2 active
n (D8)

Relay 3 active
o (D13)

Relay 3 active
p (D18)
Power
Controller power indicator
q (D26)
Thermal Fuse [b]
Fuse indicator
 r (D23)
RS-485 Bus Overcurrent [c]
Controller bus RS-485 overcurrent LEDs
 s (D54


 t (D55)


 u (D56


 v (D57)





[a] - PCBs at revision M or greater have only 2 Ethernet communication LEDs (D21 and D22). PCB revisions earlier than M also have the D33 (Activity) LED.

[b] - If thermal fuse LED is green, the power wires are reversed; if the LED s is red, the unit is drawing too much current.

[c] - PCBs at revision F or greater have the RS-485 Bus Over Current LEDs t, u, v, and w. PCB revisions earlier than revision F do NOT have these LEDs. These LEDs will be solid red if the associated bus is drawing too much current.



4.0 Lock Wiring and Installation

4.1 Wiring a Fail-Safe Lock

 


4.2 Wiring a Fail-Secure Lock

 


4.3 Lock Port Protection

Transorbs are provided with the controller ship kit. They are used to protect the controller from voltage spikes induced on the port wiring by absorbing the excess voltage and slowly releasing it back into the circuit. Keri strongly recommends wiring in the transorbs provided with the controller ship kit. Refer to the Transorb Wiring Diagram below.


Port protection

 

Note: The transorbs that Keri provides are non-polar; they can be
installed in either orientation.

 

4.4 Using Isolation Relays

For locking devices that may induce heavy voltage spikes – Mag Locks and devices with heavy-duty solenoids such as turnstiles, vehicle gates, and overhead doors – Keri recommends using isolation relays.

Keri has an Isolation Relay Kit (p/n IRP-1). The transorb should be installed as close to the lock as possible.
 
Please refer to the IRP-1 Isolation Relay Installation Guide (p/n 01833-001) for further detailed information.

 

5.0 Reader Wiring

5.1 Keri Systems Proximity Readers

  • six conductor, shielded, stranded, AWG 24 wire (Belden 9536 or a larger gauge).
  • four conductor, shielded, stranded, AWG 24 wire (Belden 9534 or a larger gauge)
    for the MS-4000 only (there is no beeper or LED in the MS-4000).

 

MS Reader Specs

 

5.2 Wiegand Compatible Readers

Four to seven conductor, shielded, stranded, wire – depending upon the Wiegand reader’s requirements. A minimum gauge of AWG 24 is required for data transfer with a 500-foot maximum run length per Wiegand specification.

 

5.3 Keri NXT Readers

When using NXT readers, these are wired directly into the controller ports and are powered from the controller. The NXT readers use 4 wired (power, ground, Tx+ and Tx-). As shown in the following diagram, the shield drain, for the reader cable, is connected to the earth-ground point on the controller.

NXT reader extension cable type is: Belden 9841 or equivalent (one twisted pair) for data combined with Belden 8461 or equivalent for the 18x2 power cable or Belden 8723 or equivalent (two twisted pairs in one jacket).

 

Note: CAT5/CAT6/CAT7Ethernet cable should not be used - this type of cable is prone to excessive voltage drops and as is a solid wire which is more susceptible to breakage.

  1. RS-485 bus runs can daisy-chain together an NXT-4x4 and NXT-Reader on one line. The total cable run distance should be less than 500 feet from the NXT controller for runs with two readers or one reader and one 4x4, and less than 1,000 feet for single reader runs.
  2. Cable resistance causes a drop in voltage at the end of long cable runs. Ensure the appropriate power and current for your device is available at the device at the end of the cable run. Heavier gauge cable reduces this effect.
  3. Keri does not recommend hot-plugging a Reader, RIM, or 4x4 into an NXT controller. Remove power from the controller prior to connecting these devices.

6.0 Controller, Reader and 4x4 Cable Options

Connection TypeMaximum Cable
Run Distance		Cable Requirement
Controller Power [a]250 feet (75 meters) maximum length
Two conductor,
stranded AWG 18 wire.
Controller Earth Ground [C]N/ASingle conductor,
AWG 18 wire
(or larger gauge).
Input Connections - Used to connect the RTE or the Door Contact to the controller [d]500 feet (150 meters).Two conductor,
stranded,
AWG 18 wire.
Lock Output Relay Connections - Used to actuate devices such as Mag Locks or Door Strikes [d]500 feet (150 meters).Two conductor,
stranded,
AWG 18 wire.
RS-485 cable - When only connecting to
NXT readers		Up to 1,000 feet (300 meters) for a single NXT reader. Up to 500 feet (150 meters) for two NXT readers on the same bus.- Power - Two conductor, stranded,
twisted pair,
AWG24 (or larger).

- Data - Two conductor, shielded, stranded, twisted pair, 
AWG24 (or larger).
RS-485 cable - When connecting to NXT readers and either 4x4 modulesUp to 500 feet (150 meters) for
each device on the bus.		- Power - Two conductor, stranded,
twisted pair,
AWG24 (or larger).

- Data - Two conductor, shielded, stranded, twisted pair, 
AWG24 (or larger).
Keri MS-Readers via RIM 
Used to connect MS readers to
NXT controllers		Up to 500 feet (150 meters).Two conductor,
shielded, stranded,
twisted pair,
AWG24 (or larger).
Wiegand Readers via RIM 
Used to connect Wiegand readers to NXT controllers		Up to 500 feet (150 meters).Seven conductor,
shielded, stranded,
twisted pair,
AWG24 (or larger). 

 

[a] To meet CE and C-tick regulations, the length of the controller power line can be no longer than 3 Meters (9.85 feet). Verify the input voltage at the controller is a minimum of 12VDC - as voltage drops over long cable runs.
[b] Keri recommends this cable type for best system performance.
[c] Use the shortest possible path from earth ground point to PCB. Connect the earth ground only to the designated pin on the terminal block. This is important as all transient protection for the unit is made through this earth ground connection. For unit protection, the earth ground connection should always be made first.
[d] Values  listed are minimums. Individual input and output devices may have more specific requirements.


Notes:

  1. The Lock Output relay may require a heavier gauge of wire depending upon the current demands of the lock and the length of the lock wiring run.
  2. Cable resistance causes a drop in voltage at the end of long cable runs. Ensure the appropriate power and current for your device is available at the device at the end of the cable run. Heavier gauge cable reduces this effect.
  3. Keri does not recommend hot-plugging a Reader, RIM, or 4x4 into an NXT controller. Remove power from the controller prior to connecting these devices.


7.0 NXT Controller Earth-Grounding

7.1 At the Controller's Metal Enclosure

To ensure optimum earth-grounding of the controller and its connected peripherals, you should make a quality earth-ground connection to the metal enclosure lug (which displays an adjacent earth-ground symbol).

 

This good-quality earth-ground at the enclosure lug will provide an earth-ground for the entire enclosure - and will therefore ground anything that is connected to the metal enclosure - (the four metal screws at each corner of the PCB) - plus, through circuitry on the PCB, this includes anything connected to the lug marked J6 or pin 3 of the TB10 power connector.

 

In addition, the enclosure itself must be earth grounded to a good quality ground point external to the enclosure for a complete path to ground.

 

7.2 At the Controller's Earth-Ground Lug

NXT controllers have Ground Lug J6 at the top of the PCB near the TB10 power connector. Make your NXT earth ground connection directly to this lug.


 

 

8.0 Grounding RS-485 Devices and Readers

The shield/drain wire of any reader/peripheral cables MUST be terminated to one of the following points: any corner screw attaching the controller to the enclosure, Pin 3 of TB10, the green ground lug (J6) on the controller, or the ground lug of the enclosure. Failure to properly earth ground the reader drain wire may result in unreliable communication or operation of the attached peripheral.

 

The following diagram illustrates correctly grounding an NXT reader at the controller.


 

 

9.0 Controller Maintenance

9.1 The 3-volt Lithium Backup Battery

 

The controller's backup battery retains all controller configuration, including cardholders and this information is completely cleared if the controller loses power - (when the battery is flat or low voltage).


The controller's battery backup voltage should be checked every 18 months-to-2 years... but this really depends on how often the site loses power.

 

Once the controller is powered back up, an update must then be performed on the controller - to re-send the controller configuration and cardholders.

 

Notes:

When changing the controller's backup battery you should do the following:

  1. Check that the controller is online - so you will be able to update it.
  2. Ensure that the controller is down-powered when you remove the 3 volt lithium battery.
    - failure to do so may permanently damage the controller.
  3. Perform an update on the controller after changing the controllers backup battery.
    - the controller will need to be configured again when the battery has been replaced.


9.2 The Power-Supply Backup Battery

 

Backup Battery

 

Many installations also use backup batteries connected to the power supplies - this will keep the
controller powered-up for a certain amount of hours if there is a power-outage at the site. Again,
these backup batteries should be checked every 18 months-2 years.

 

After a while, battery backups on the power-supply may develop a fault - often causing them to
draw more current from the power-supply. With certain power-supplies this may result in less power
being available for the controller and its connected peripherals - If you disconnect the PSU backup
battery, and the voltage is low, then it is likely that the battery needs replacing.