Bulletin 1492 I/O Wiring Conversion Systems

Has anyone used the 1771 wiring arm conversion hardware to convert to 1756 RTBs ?

Is it as simple as it sounds?

Is there anything to be wary of?

TIA

Simple, yes. Once you get past ordering all of the correct pieces. So many part numbers that run together if you're not careful. Some of the combinations are confusing, especially where you are combining two 1771 modules into one 1756 module (6 and 8 point modules) or where two 1756 modules are required to replace a single 1771 module (8 point isolated analog). When the 1756-IF8I module becomes available that will alleviate that problem.

Snapping the swing arm adapters into the 1771 chassis replacement frame takes a little practice.

A couple of drawbacks that I see are the fact that you're introducing extra components and connections between the field device and the I/O module and the fact that your 1771 swing arm connections are covered up once you mount the 1756 chassis. If all of the I/O points are wired down to terminals then you're fine, but if you have modules with few points in use you pretty much give them up unless you make provisions during the conversion.

We did one conversion where all of the 1771 I/O was cabled to IFM modules and we thought about just replacing the IFM cables, but there are some differences in the field wiring to the IFM between 1771 and 1756 modules. Using the conversion kits was quicker, and did not require any rewiring or disturbing of cables in the panels.

We always pre-assemble the chassis and swing arm adapters, and put matching labels on the the adapters and cables that connect to them. Then place all the parts for each chassis in a separate box so everything for each chassis is in one place and parts do not get crossed up during installation.

Thanks for the useful info danny.michael...

i've got to specify the hardware needed for an upcoming job, and i guess i've got to spend some time deliberating the options, as the 1756 chassis isn't defined yet..

My gut feeling is to go for 32-bit 1756 modules to replace 2x16-bit 1771 modules, and 16-bit 1756 modules to replace the 8-bit 1771 modules - that should leave 1756 chassis space to double-up analog modules where 8-channel 1771 modules were used.

I only have to replace the "local" chassis, but obviously need a slot for a 1756-DHRIO (DH+ is needed as well as RIO to the remote chassis. I don't think there is the physical space for anything bigger than a 1756-A13 chassis.

Yes, space is also a consideration. A 17 slot 1756 chassis with power supply is wider than a 16 slot 1771 chassis, especially if the 1771 power supply is in the rack. If the 1771 external supply is present then the entire 1756 package is about the same width.

The racks that will be replaced all have in-chassis supplies...

I'm working on a similar project and I'd recommend using the 1771 Migration Wizard in IAB software from A-B. You input the processor and I/O you are replacing, and it will output a BOM for the migration. I was impressed when I began using this for laying out large systems and also recommend it for these migrations from PLC and SLC platforms.

Also see the attachment for dimensions on migrating from the 1771 16 slot rack to the CLX 17 slot rack. It shows three mounting options - left, center or right justified. Don't forget to figure in depth for the processor key if it will be left in the switch.