NXT 2D/4D Hardware Installation Guide

NXT 2D/4D Hardware Installation Guide

1.0 Introduction

This document contains basic information for the installation of the NXT 2 door and NXT 4 door controller.

2.0 Product Specifications

2.1 Unit Dimensions

NXT 2D/4D controller PCB
- 6.75 inches high by 6.00 inches wide by 1.75 inches deep, including wiring connectors
- (17.15 cm by 15.25 cm by 4.45 cm)

- 13 inches high by 9 inches wide by 4 inches deep - (33.02 cm by 22.86 cm by 10.16 cm)

 Operating Temperature/Humidity Range
32°F to 150°F (0°C to 60°C) 
- 0% to 90% Relative Humidity, non-condensing

2.2 Controller Power Requirements

Input Power
• 12 VDC @ 1 A

Output Relay Contact Rating
• 1 Amp @ 24 VDC

Current Draw
570 mA typical

2.3 Input Device Configuration - 3 Inputs

• Door Sense - normally closed
• Request to Exit - normally open
• Global Unlock - normally open,
   or Auxiliary RTE A-Door - normally open

2.4 Controller Memory Retention

• 5 year lithium battery back up to support controller RAM and real-time clock

2.5 Buffer Capacity

48,000 Cardholders
10,000 Events

2.6 Reader Capacity

  1. 4 with NXT Readers *
  2. 2 with Wiegand or MS Readers
* 4 Reader capacity requires the Mercury Firmware option and NXT Readers

3.0 NXT Wiring Diagrams

3.1 NXT 2D/4D Controller Wiring Diagrams

See the table in section 4.0 for LED definitions.

Note: 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.

3.2 Wiring a Fail-Safe Lock

3.3 Wiring a Fail-Secure Lock

3.4 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.

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

3.5 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). Please refer to the IRP-1 Isolation Relay Installation Guide (p/n 01833-001) for detailed information.

4.0 Controller LED Definitions

5.0 Wiring Instructions

5.1 Terminal Blocks

PXL Wiring Instructions

Note: Screws on terminal blocks must be tightened securely.

5.2 Connecting the Earth-Ground and the 12VDC Power 

PXL Power Wiring

Note: TB2 is colored red to make it easier to tell it apart from the network connector

5.3 Controller Earth-Grounding

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.

Also, 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/peripheral drain wire may result in unreliable communication or operation of the attached peripheral.

6.0 Cable Requirements


  1. 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.
  2. 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.

6.1 RS-485 Cable Requirements

RS-485 bus runs can daisy-chain together an NXT-4x4 and NXT-Reader on one line. The total cable run distance should be no more than 500 feet from the NXT controller for runs with 4x4s and no more than 1,000 feet for Reader-only runs.

Recommended RS-485 Cable Type


Run Length





Twisted Pair


RS-485 from NXT controller to NXT 4x4 (with or without an NXT 1R/3R/5R reader)

Up to 500 feet (150 meters)








22 or 24

RS-485 from NXT controller to NXT 1R/3R/5R readers

Up to 1,000 feet (300 meters)








22 or 24

6.2 Controller Power, Inputs, and Outputs Cable Requirements

Total Run Length
# of Conductors
Controller Power
250 feet [a]
Earth Ground
Shortest path [b]
Inputs and Outputs [C]
500 feet
  1. To meet CE and C-tick regulations, the length of the controller power line can be no longer than 3 Meters (9.85 feet).
  2. 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.
  3. Values listed are minimums. Individual input and output devices may have more specific requirements.
  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.

6.3 Earth-Ground Cable Requirements

  1. Single conductor, AWG 18 wire (or a larger gauge).  Ground wire is green with or without yellow tracer.

6.4 Keri Systems Proximity Readers

  1. six conductor, shielded, stranded, AWG 24 wire (Belden 9536 or a larger gauge).
  2. 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).

6.5 Wiegand Compatible Readers

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

6.7 Keri NXT Readers

  • 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 9842 or equivalent (two twisted pairs in one jacket).

7.0 Controller Factory Reset

Keri recommends resetting NXT controllers the first time these controllers are powered on. Also, under certain circumstances NXT controllers may need to be reset. NOTE: Resetting a standard NXT controller will restore the controller to a factory default state. It removes all network configuration data assigned to the controller such as the IP Address, Subnet Mask, and Gateway address.

7.1 Reset a Standard NXT Controller

1. Remove power from the NXT controller.
2. Ensure a Jumper is across the J3 header (refer to the drawing on page 1). The Jumper can remain on J3 at all times.
3. Press the S1 switch and hold it down while applying power. Keep the button pressed until the Reset LED (D48) is lit. This indicates the reset routine has begun. Once the LED is lit, the button can be released.
5. The Reset is complete when the Reset LED goes off.

7.2 Restore Configuration Information to a Reset Controller

1. In Doors.NET under Setup > Hardware Setup > Panels, click on the controller that was reset.
2. When the Communication field shows the controller is Online click the Update Network icon on the ribbon bar.
3. Click the Live Events tab and watch for the Update Network Completed event message. When this message is posted the controller’s configuration information is restored.