Facilities rely on automatic transfer switches (ATSs) to start emergency engine-generators when utility outages occur. But that cannot happen if an engine start circuit is damaged by work activity inside a facility or a backhoe excavating soil between a transfer switch and an outdoor generator. This Application Note explains how the ASCO 5101 Engine Start Monitoring System helps facilities avoid this outcome and comply with code requirements.
ChallengeA National Electrical Code® (NEC®) compliant engine-generator starts automatically when it receives a start signal from an automatic transfer switch. If signaling wires are damaged, an engine will not receive the start signal needed to begin supplying mission-critical power. Without a means to monitor the integrity of the start signal circuit, facility personnel will never know when wiring is compromised, placing the facility at risk for an outage.
To mitigate this risk, requirements to monitor the integrity of the engine start circuit were first promulgated in the 2017 Edition of the NEC. Article 700.10(D)(4) of the 2020 Edition states:
disconnected, or shorted wires. Loss of integrity shall start the generator(s).
SolutionThe ASCO Power Technologies Engine Start Module System brings new and existing backup power systems into compliance with NEC requirements. It consists of two UL-listed electronic modules, which are shown in Figure 1. At left, a transfer switch module mounts inside each automatic transfer switch. At right, a generator module mounts on inside of a generator set. One generator module can communicate with up to eight transfer switch modules.