Multifuse® PPTC Resettable Fuses – MF-RM Series


The Bourns® Multifuse® Polymer PTC (PPTC) Resettable Fuses MF-RM Series are the first of Bourns® Multifuse® PPTC devices designed to operate in mains rated AC circuits of 120Vac and 240Vac.

Traditionally, polymer PTCs have been targeted at DC circuits that operate at less than 72V, but the Model MF-RM Series opens up a whole new application segment for polymer PTCs.

Previously, only overcurrent protection devices such as one-time fuses and thermal switches were seen on the primary side of transformers. However, the new Model MF-RM Series now allows AC circuits to gain the benefits of resettable fuse protection. Resettable fuses bring reliable overcurrent and overtemperature protection at values close to the circuit operating current. This allows for tighter protection without the problems associated with nuisance trips.


  • 240 Vac rated
  • Allows the device to be used in AC circuits
  • Ihold values from 50mA ~ 550mA
  • Select the MF-RM device with a hold current greater than the operating current of the circuit
  • UL listed
  • Allows for UL rating of end user equipment
  • Resettable device
  • When a PPTC trips, it will then reset which reduces the cost of repair associated with fuses. Since the PPTC resets, it means a PPTC can be selected with an Ihold close to the operating current. This enables tighter protection unlike fuses that are usually selected with higher trip values to prevent nuisance trips
  • Fast time to trip and reset
  • Allows for quicker recovery after a trip event
  • Overtemperature and overcurrent protection
  • PPTC resettable fuses will help protect the circuit from damage that can occur from a short circuit as well as from overheating
  • RoHS compliant


  • Food blenders
  • Coffee machines
  • Washing machines
  • Powered garden tools
  • AC adaptors
  • Electric fans/blowers
  • HVAC
  • CCTV equipment
  • Powered by DIY equipment
  • Inverters
  • Electric fans/blowers
  • Set-top boxes