Schneider Electric RM35HZ21FM Harmony 5A 1CO+1CO 120-277V AC Over/Underfrequency Control Relay

The Schneider Electric RM35HZ21FM is a Harmony RM35-HZ frequency control relay, monitoring a 120-277 V AC supply for over and underfrequency conditions across a 40-70 Hz measurement window. It switches two separate 5 A changeover contacts with an adjustable 0.1-10 second fault delay, in a 35 mm wide DIN rail housing.

Technical Specifications

Certifications & Standards

• CE
• GL
• UL
• CSA
• IEC 60255-6

Selection Notes

The two independent 1 C/O outputs on RM35HZ21FM let an over-frequency trip and an under-frequency trip drive separate downstream circuits - useful for generator or wind-turbine protection where over-speed and under-speed events need different responses rather than a single shared alarm contact. Its 120-277 V AC supply range covers both 120 V and 230/277 V control circuits without a separate SKU, and the -2 to 10 Hz and -10 to 2 Hz threshold settings let each output be tuned independently around the 50/60 Hz nominal. Rated for up to 360 operations per hour under full load and immune to supply microbreaks as short as 10 ms, RM35HZ21FM tolerates momentary disturbances without a nuisance trip, a relevant spec where the monitored source is a diesel genset or inverter with a noisier frequency output than utility mains.