I have a query related t duplex RTD. We are using duplex RTD for gear box bearing, i just want to know that, do we need to connect both the sensor to Junction box or one will be spare in the RTD head itself and no need to connect it to JB. Who will decide the philosophy, please guide me.
Presumably the 2nd RTD element is just a spare and there is no available analog input for the 2nd RTD for redundancy purposes?
If the 2nd RTD's purpose is just a spare and not redundancy, then I would not wire the spare element to the JB, unless the RTD is inaccessible and for the sake of convenience, re-wiring from RTD #1 to RTD#2 is best done at the JB than at the RTD head.
If I unscrew an RTD head cover and see both RTD's with outgoing wiring, I assume the wiring actually goes to its final destination. If I see one RTD wired and the other not wired, I figure one is a spare.
Any tech will understand moving the RTD-to-destination cable from RTD #1 to RTD#2 when the time comes that a switchover to the spare is needed.
The second RTD is just another RTD. It can be left not wired or even used on a second monitoring system if you want. It is entirely a design decision.
I don't see the point in duplex RTDs unless you are going to wire them to something like a dual input transmitter or two separate transmitters. If one RTD fails what's the chance of the second one being ok? Better to just have a spare that can be installed IMHO
Bearing RTDs should be wired as 3 wire, you don't need the accuracy of 4 wire connection.