I Have The Power…Or Do I? A Simple Example of How a Small Error Can Cause a Potential Large Impact

“My circuit is not working. My strobes are not flashing. What happened?”

You are on site observing a pre-test for a fire alarm system. You’re working with a general contractor who is scrambling to finish their project by the due date. There is no float left and the stakes are high. Your vendor assures you that the system is laid out in accordance with the approved submittal. It will function and you’re ready to begin your pre-test.

You begin testing your visual devices for the proper candela, synchronization, flash rate, etc. As you reach the 3rd circuit from a power supply, you find a portion of it flashing, but several toward the end of the circuit are not working. There are no trouble indications on the fire alarm panel, no readily apparent cause. What could have happened?

Forensics

You cut your installing contractor/vendor loose to begin troubleshooting and then tell the owner that there will be delay. That afternoon, your installing contractor/vendor calls and tells you that the circuit you were testing is pulling more current than the power supply output is rated for. How could this be? All of the calculations show adequate supply, proper circuit loading, etc. The strobes candela settings matched the approved submittal drawings. After a longer deep-dive from the vendor’s shop drawing designer, you find out that the power supply output capacity of the circuit in question was rated for 3 amps, while the value used for that output in the submittal was 4 amps. The culprit? A copy/paste error. That’s it.

This was a real-world example and all-too-common. In this case, installing contractor/vendor needed to add several Notification Appliance Circuit (NAC) power supplies and split several of the existing circuits into more total circuits, install new cabling and conduit, and recalculate all of it before being able to begin again.

Impact

This project ultimately missed its target completion date by only a few days, and while liquidated damages were not assessed, they easily could have been. The installation contractor/vendor had cost overruns for overtime, the general contractor was impacted similarly, and the engineer of record had travel cost impacts due to delays in completion. The owner’s overall schedule was only slightly impacted, but it could have been much worse.

Mitigation

Much of this, and similar problems, can be mitigated through a third-party review. At Precision Alarm Review, this is one of many scenarios we look for. When comparing submitted material to calculations, it is extremely common to find a misplaced value for a component or device. Many times, you’ll an error like that “carried forward” into other similar circuits in larger projects. It’s an example of how a very small error can create a much bigger impact than expected.

Contact us today to find out more about how we can help you avoid this type of scenario.