1734-IA4 Proper wiring

[phuz]

Could someone be kind enough to clarify this diagram to me on Page 53 of this PDF (http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1734-um001_-en-p.pdf)?

It shows the signal going into Ch0 but there is no connection for L1/N, only L1. So how does the module have a neutral reference? The module is on an AENT which is 24VDC power. I built this on Rockwell's IAB, too, and it doesn't mention a need for a 1734-FPD, so I really don't understand how sending a 120vac signal is going to trigger an input to this module. I am used to the 1756-IA16 where there are neutral points for reference.

Thanks.

 

[Ken Roach]

STOP !

STOP STOP STOP STOP !

Don't apply power to anything !

STOP !

 

[Ken Roach]

Okay, I've caught my breath. I was having a little flashback there to a customer who called up and unloaded on me when he connected AC POINT modules to a POINT assembly with out a 1734-FPD and smoked the whole thing. He was only reading the discrete I/O installation manual, and not the POINT I/O Selection Guide.

Don't rely on just the I/O Module user manual; it has a number of typos and ambiguities and focuses just on the modules, not on the assembly of the whole POINT I/O system. In my opinion the people responsible for writing it should have the Control-V on their keyboard disabled.

The 1734-FPD Field Potential Distributor module is your best friend when you're using AC modules with POINT I/O. It isolates the power bus from the devices to the left and establishes a new power bus for all the modules to its right.

That's how the 4-point AC Input modules get their L2/N reference; it's on the internal power bus. The 2-point AC Input modules have both L1 and L2/N available on the terminal block because they have enough terminals.

The wiring base connects the L1 conductor on the internal power bus to four of the terminals on the terminal block, so that you have convenient sources for the four inputs you're wiring into the module.

I don't know why the IAB software tool doesn't insist that you put in an FPD when there are AC modules in the assembly with a 1734-AENT. It should.

The 1734-AENT's DC power terminals that provide operational power to the adapter also connect to the internal POINT I/O power bus.

If you connect 120V AC power to those terminals, it will destroy the 1734-AENT.

If you connect 120V AC power anywhere on the bus system without also installing a 1734-FPD, it will destroy the 1734-AENT and any DC-powered or analog modules in the system.

 

[phuz]

Okay, I've caught my breath. I was having a little flashback there to a customer who called up and unloaded on me when he connected AC POINT modules to a POINT assembly with out a 1734-FPD and smoked the whole thing. He was only reading the discrete I/O installation manual, and not the POINT I/O Selection Guide.

Don't rely on just the I/O Module user manual; it has a number of typos and ambiguities and focuses just on the modules, not on the assembly of the whole POINT I/O system. In my opinion the people responsible for writing it should have the Control-V on their keyboard disabled.

The 1734-FPD Field Potential Distributor module is your best friend when you're using AC modules with POINT I/O. It isolates the power bus from the devices to the left and establishes a new power bus for all the modules to its right.

That's how the 4-point AC Input modules get their L2/N reference; it's on the internal power bus. The 2-point AC Input modules have both L1 and L2/N available on the terminal block because they have enough terminals.

The wiring base connects the L1 conductor on the internal power bus to four of the terminals on the terminal block, so that you have convenient sources for the four inputs you're wiring into the module.

I don't know why the IAB software tool doesn't insist that you put in an FPD when there are AC modules in the assembly with a 1734-AENT. It should.

The 1734-AENT's DC power terminals that provide operational power to the adapter also connect to the internal POINT I/O power bus.

If you connect 120V AC power to those terminals, it will destroy the 1734-AENT.

If you connect 120V AC power anywhere on the bus system without also installing a 1734-FPD, it will destroy the 1734-AENT and any DC-powered or analog modules in the system.

Exactly what I thought. Thanks for reassuring me, Ken.
I have the cards wired up, but the panel isn't powered yet nor are the 120vac pushbuttons wired, so I wasn't worried.

Good thing I just happen to have a FPD on my shelf.