What is the Fuse Control Module in transfer switches?

This article explains what a Fuse Control Module (FCM) does inside Generac automatic transfer switches, how it protects sensing, charging, and control circuits, and which switch models include integrated brownout protection. It clarifies the FCM’s role as a fused interface for utility sense, battery charge, and low-voltage signals. Use this to understand capabilities and to identify compatible transfer switches for installations.

  • Mar 2, 2026
  • Knowledge

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What is the Fuse Control Module in transfer switches?
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What-is-the-Fuse-Control-Module-in-transfer-switches

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Fuse control module (FCM)

In plain terms, the FCM is the transfer switch’s “fused junction box” for sensing, charging, and control—routing the critical signals while adding overcurrent protection.

The below image shows a typical connection in a fuse control module. This image comes from an automatic transfer switch installation guide which can be found on Generac.com.

Typical FCM connections diagram

The fuse control module in an automatic transfer switch is essentially a protected power-and-signal interface between the switch’s controller and the “field” wiring (utility legs, neutral, and low-voltage control circuits).

What it does

  • Provides fused utility sensing: It brings in N1 and N2 (the two utility hot legs) and routes them through fuses so the controller can monitor utility voltage/presence without exposing the control electronics to an unfused fault. (Shown as N1 (fused) Utility Sense and N2 (fused) Utility Sense.)
  • Provides fused feed for battery charging: It routes T1 (fused) Battery Charge along with a dedicated neutral (00 / Dedicated T1 Neutral) to support the battery charger circuit (commonly used to keep the generator’s starting battery maintained).
  • Distributes low-voltage control power and signals: It provides +12 VDC (194) and DC ground (0), and passes the transfer control signal (23) used by the transfer switch controls.
  • Protects the control system: If there’s a short, wiring error, surge, or component failure on any of those circuits, the module’s fuses are intended to open first, helping prevent damage to the controller board and limiting fault energy in the control wiring.

Which Generac transfer switches have a FCM?

 

ModelCoverageSE TypeIntegrated Brownout Protection
RXG10EZA1W: 50A, 10 CircuitsEssential LoadsNon-Service Entrance RatedNo
RXG16EZA1W: 100A, 16 CircuitsEssential LoadsNon-Service Entrance RatedNo
RXG16EZA3: 85A, 16 CircuitsEssential LoadsNon-Service Entrance RatedNo
RXG24SHA1: 100A, 24 Space, 40 CircuitWhole HomeService Entrance RatedNo
RXG42SHA1: 100A, 42 Space, 60 CircuitWhole HomeService Entrance RatedNo
RXGW20SHA1: 200A, 20 Space, 40 CircuitWhole HomeService Entrance RatedNo
RXSC100A3: 100AWhole HomeNon-Service Entrance RatedNo
G0099530: 200A*Whole HomeNon-Service Entrance RatedYes
RXSC400A3: 400AWhole HomeNon-Service Entrance RatedNo
RTSC600A3: 600AWhole HomeNon-Service Entrance RatedNo
RTSC800A3: 800AWhole HomeNon-Service Entrance RatedNo
RXSW100A3: 100AWhole HomeService Entrance RatedNo
G0099550: 150A*Whole HomeService Entrance RatedYes
G0099520: 200A*Whole HomeService Entrance RatedYes
RTSW300A3: 300AWhole HomeService Entrance RatedNo
RTSW400A3: 400AWhole HomeService Entrance RatedNo
RXSW100A3SPD: 100AWhole HomeService Entrance RatedNo
G0099540: 150A*Whole HomeService Entrance RatedYes
G0099510: 200A*Whole HomeService Entrance RatedYes
RXSW100A3CUL: 100AWhole HomeService Entrance RatedYes
RXSW200A3CUL: 200AWhole HomeService Entrance RatedYes
RXUW150A3: 150AWhole HomeService Entrance RatedYes
RXUW200A3: 200AWhole HomeService Entrance RatedYes
RXGUW200A3: 200AWhole HomeService Entrance RatedYes
RBU150A3: 150AWhole HomeService Entrance RatedWith Upgrade Kit
RBU200A3: 200AWhole HomeService Entrance RatedWith Upgrade Kit

*Indicates a transfer switch has been updated to include brownout protection. All models have a FCM; however, newer versions have an updated FCM that includes brownout protection.

See also

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