1734-EP24DC and 1734-FPD

TijanaJ

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Join Date
Mar 2016
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Belgrade
Posts
18
Hi,
we have a Point I/O rack configuration which consists of some input cards, then a couple of output cards after them, and in the end a couple of IT2I cards. This is the configuration that the customer wants to keep, but now they want to drop power to the output cards when Estop is pressed.
So, I will add a 1734-FPD before OB8 cards, but since I don't want to drop power to the IT2I cards, is it enough to put EP24DC after OB8, or should I put another FPD after the outputs cards for some reason?
Which one of these configurations is the correct one:
input cards, FPD, output cards, FPD, IT2I card, EP24DC, IT2I cards
or
input cards, FPD, output cards, EP24DC, IT2I cards

Thanks in advance 🍺
 
Great question !

Do you already have a 1734-EP24DC because you need the extra PointBus logic power ?

Because your rightmost modules are 1734-IT2I, they do not participate in the Field Power Bus. The only terminations on a 1734-IT2I are for the millivolt/thermocouple and shield. Like all POINT modules, they get their microprocessor power from the PointBus, not the Field Power Bus.

You can add a 1734-FPD Field Power Distribution module to the left of the Output modules to allow them to be switched by the E-Stop. It will not affect the Thermocouple input modules.
 
@spartacus06 - that's what I would have done, but our client insists on keeping this configuration (with OB8 before IT2I), because these are some modifications made on the existing system.

@Ken Roach - we have 5 IT2I modules, and according to IAB I have to add EP24DC (regardless of the FPD). But, you want to say that if, for example, I had one IT2I module, and bus had enough power to supply it, I could put FPD before OB8 and IT2I, and IT2I would work with no problem, even if the power was cut from the FPD? I didn't realize this is really how it works, THANKS A LOT, this is really helpful! :D 🍻
 
if, for example, I had one IT2I module, and bus had enough power to supply it, I could put FPD before OB8 and IT2I, and IT2I would work with no problem, even if the power was cut from the FPD?

Yes.

Modules like the 1734-IT2I that don't participate in the Field Power bus just pass it through to the right.

Those modules will still get their logic power from the POINTBus (the upper set of contacts) and will not be affected by the cut-off of 24V DC power on the Field Power bus (the lower set of contacts).
 

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