We have an oven system consisting of a PLC5 interfacing to 6 Honeywell RM7890B BMS and each BMS has about 7 interlocking relays that are wired in series into the BMS as well as individually into the PLC for status. My question is there a way I can clean up the relays and replace them with some sort of multi channel safety relay or a Guard PLC without effecting FM or code? I just want to reduce the wiring and maintaining of the relays. The relays are for the typical combustion air pressure, high/low gas pressure, high temp, and an exhaust damper open switch and pressure. There’s a purge timer as well.
Replacing Relays in BMS system
- Thread starter DaveW
- Start date
If you are using relays only to feedback BMS status, you may replace it with anything you want. If relays are part of safety interlocks, i don't think you may do it with PLC, even safeguqrd PLC.
What we do in our company - we do not use relays in Honeywell interlocking circuit, but seriously connected sensors (pressure switches, valve positions switches etc. all connected in serious). All of the sensors have C-form contact, so we are using NO contact to energize corresponding relay or PLC input in case of a sensor alarm.
What we do in our company - we do not use relays in Honeywell interlocking circuit, but seriously connected sensors (pressure switches, valve positions switches etc. all connected in serious). All of the sensors have C-form contact, so we are using NO contact to energize corresponding relay or PLC input in case of a sensor alarm.
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