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How do you configure and activate ERMS (arc flash reduction) on a Masterpact MTZ?

Published date: 21 May 2020

Can you use a smart phone to put a Masterpact MTZ breaker into ERMS maintenance mode?

Product Line:
Circuit Breakers

Masterpact MTZ


The ERMS function is used to reduce the LSIG protection settings in order to trip faster when an internal arc fault occurs. It is one of the recognized solutions to improve  the protection of workers against arc-flash. It complies with the recommendations issued by NEC Section 240.87, NFPA 70E, IEEE 1584, and EN 50 110-1.  The ERMS function provides an additional LSIG tripping curve in addition to the dual settings available on the MTZ control unit.

As soon as the ERMS digital module is installed on MicroLogic X control unit, the ERMS function is available, but not engaged. Additional steps are required to set the appropriate ERMS LSIG settings and to engage the ERMS function.  ERMS LSIG settings can be customized on site by means of a smartphone via Bluetooth, or with EcoStruxure Power Commission software running on a PC. Customization using either method is password-protected.

ERMS can be engaged/disengaged by a smart phone using the Ecostruxure Power Device App app. ERMS can also be engaged/ disengaged through an external lockable selector switch with the additional dedicated ESM hardware module (ERMS Switch Module).  As soon as ERMS is engaged, the ERMS LSIG factory settings are automatically replaced by the ERMS LSIG customized settings.   When ERMS is engaged, the corresponding  information is made available as follows:
  • the MicroLogic X front face with the ERMS blue LED
  • the MicroLogic X embedded display with the blue backlight
  • an external light with the additional dedicated ESM hardware module
  • a PC with EcoStruxure Power Commission software
  • through the customer communications network (Ethernet or Modbus SL)
NOTE:  The ESM module for an external switch is incompatible with the M2C contacts--can have one or the other but not both.
NOTE:  Factory default ERMS settings are on the attachment.

ERMS Switch Module (ESM)
  • The ESM is basically a special IO module dedicated to the ERMS function, and it is required in order to engage/disengage ERMS mode on the Micrologic X with a selector switch. The ESM is not required if you are only planning on engaging/disengaging ERMS using the smart-phone app.
  • If an ESM module is connected, its default condition is to be in ERMS mode.  A switch must be connected and turned OFF or 24 Vdc must be applied to ESM terminals 484-471 in order to turn ERMS off (484 +).
  • If neither of these conditions are met, the control unit will be in ERMS mode, and the app will not be able to disengage it. Similarly, if the ERMS mode is engaged with the app, using the ESM module switch will not be able to disengage it. ERMS must always be disengaged by the same method (and the same phone, in the case of the app) that it was engaged in.
  • The only way to bypass that (in the case of the phone getting damaged or the person with the phone not being available) is to get a level 4 password from the site admin (they should be given it when they receive the breaker) or from level 3 support.

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