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Front View Inside View User Interface Remote Detector Unit Block Diagram Lightning Sequence & Detection Technical Paper

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Intelligent Lightning Disconnect Controller
120Vac, single phase


Introducing a new controller for protecting valuable equipment from lightning damage. Rather than attempting to absorb the lightning surge after it has arrived at your critical equipment, this controller anticipates the lightning surge and disconnects your equipment before it arrives! This technology, which has been available to industry, government and the military, is now available to small businesses and homeowners. Perfect for protecting any vital and high-value equipment such as:

  • computers
  • servers
  • modems
  • routers & switches
  • phone systems
  • entertainment systems
  • radio communications
  • ethernet networks

It can also be used to isolate systems that are frequent targets of lightning such as irrigation systems and well pumps.

If the cost of down-time can exceed the replacement cost of damaged equipment this system is the solution.

Our Experience

Here at LLC we had never seen any problems resulting from lightning. Then in the summer of 2010 we experienced the loss of computer equipment during a thunderstorm even though surge suppression was in place. There was no direct lightning strike. And it seemed that the lightning at the time was a safe distance away. Yet there was a bang in the office and several computers went blank, some remained functional but their Ethernet ports were fried, and the network router/switch and modem were damaged. After enduring the down-time and the painful process of repairing and replacing equipment we began designing a controller that would sense and automatically disconnect vital equipment during lightning storms. It was during that process that we found such a device had already been developed and patented. We worked with the manufacturer to come up with this new version of their controller. We now have device installed here in our office and it is operating successfully and are making it available to you, our customers.

Operation Summary

Lightning rods, surge suppressors and good grounding are all important for protecting against fire and injury but they are not enough. This controller senses when a bolt of lightning is about to strike and temporarily disconnects vital, sensitive and high-value equipment from external connections. This isolates the equipment from the pathways that can carry the destructive lightning-induced surge. Two types of isolation are performed when lightning is eminent: (1) power circuits are disconnected for up to 16 minutes and transferred to a UPS system, (2) communication circuits are disconnected for 0.2-0.4 seconds. Equipment powered by the UPS continues to operate. And communications are not lost because the interruption is brief. Spare contacts are available for starting an optional standby generator or for remote monitoring and indication.

Lightning Damage

Lightning is a major source of voltage spikes that can damage or destroy your investment.  Don't risk the damage and outage time by not installing adequate protection!

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Note that no device can guarantee protection from a direct hit of a lightning strike.  But this product when used in conjunction with surge protection and proper system grounding will reduce consequences of such a strike.  And it will virtually eliminate damage from other (non-direct) lightning strikes. 

Frequently Asked Questions

Q1: Won’t my properly installed and maintained electrical grounding protect my facility?

A1: Grounding meeting NEC Article 250 only addresses the danger of fire and personnel safety. It is not intended to maintain the reliability of equipment.

Q2: I have surge suppressors at the service panel and downstream where valuable equipment is used. Aren’t these effective against lightning?

A2: Probably not by themselves. They may not respond fast enough to prevent lightning damage. MOV type suppressors degrade over time. And if ground potential rise occurs these suppressors can actually become the pathway for damaging high voltage to enter sensitive equipment.

Q3: We have been operating for years with no apparent damage from lightning. Doesn’t that mean we are safe?

A3: No. It is estimated that 95% of all electronic system failures are due to repeated degradation from transients, many of which are caused by lightning.

Q4: My facility is insured against lightning damage. What incentive do I have to incur the cost of better lightning protection?

A4: Insurance usually covers only the direct costs of system repair or component replacement due to a catastrophic event. But 95% of electronic system failures are nearly impossible to positively attribute to lightning. The indirect costs of system down-time, staff overtime, lost data, and lost business may not be covered. And insurance premiums often increase with payouts.


** Response time is measured from completion of stepped leader EMP to when contacts open

Control voltage 90-264VAC, 127-370Vdc
Battery Backup 12VDC, 7Ah SLA (provided by installer)
Power Switching Relay Contacts (2) form C, 1500Vrms dielectric
15A@120VAC 50/60Hz resistive
12A@277VAC 50/60Hz resistive
12A@28VDC resistive
Response time: 20 msec**
Communications Switching 10kV isolation
(1 pair) RJ11 phone jacks - in & out
(1 pair) RJ45 ethernet jacks - in & out
(1 pair) F coax connectors - in & out
Response time: 8 msec**
Control Interface Backlit LCD display, 4 lines x 20 characters
numeric key pad & function keys
resettable strike counter
User Adjustable Settings
    - time delays 0-16 minutes
    - time periods 0-16 minutes
Switching delay before disconnect
Switching disconnect period
Detector sensitivity
Background EMI indication
Alarms LED indicator - RDU failure
LED indicator - strike alarm active
LED indicator - UPS alarm active
LED indicator - backup battery/charge failure
audible strike alarm
audible UPS alarm
Connections barrier terminal block for hardwiring (standard)
pigtails for plug-in connections (optional)
cable to Remote Detector Unit (optional)
Sensor Remote Detector Unit (RDU) with whip antenna 51" high
Enclosure NEMA 1 indoor, gray finish
12”W x 18”H x 6”D

This product is designed and Made in USA  


Customers who purchased this product also ordered:
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Surge arrester for service entrance panel such as the hardwired Delta Arresters at this link.

Extended run-time UPS system (>30 minute run-time recommended).  This can be achieved by using a UPS with the capability of adding external battery packs such as the Eaton/Powerware series 5125, 5130, 9130 or Toshiba series 1000.  Size will depend on your actual ac electrical load.  Note that the cheap $100 UPS systems usually sold at local retailers have very limited battery run-time and do not have the capability for external battery packs.


Ordering Table
Optional items can be provided by installer if hardwiring unit

LDrdu.jpg (11707 bytes) Lightning Disconnect Controller with Remote Detector Unit -
internal terminal block for hardwired connections
LD-pp.jpg (13083 bytes) optional Pigtails for power connections -
#14 ga 3/c SJ cord with plugs, connectors, cord grips and terminals, 25' total
LD-rdc.jpg (12964 bytes) optional Remote Detector Cable -
#18 ga 3/c shielded (order by the foot)
SD-50-1289.jpg (16008 bytes) High Current Contactor - for switching power over 15 Amps (optional)




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