1771 -> 1756 Wiring Converstion

[Bob O]

Good morning,
I'm looking for opinions on the 1771 wiring solution offered by Rockwell when upgrading from PLC 5 to ControlLogix.


Thanks and Happy Fathers day to all the dad's out there.


https://www.youtube.com/watch?v=x6D2LCPdtsY

 

[Doug-P]

Rockwell's solution looks pretty slick. Avoiding the wiring error problem by itself would be a big plus. It wasn't shown but using the conventional method you'd also have to factor in the time to print up new wiring labels.

Does the conversion accommodate the different 1771 physical rack sizes?

There might could be an issue with the labels/wire numbers if the 1771 was from the PLC-2 octal addressing days.

 

[Bob O]

Thanks for the reply!
I agree about the slick wiring and reducing errors but my first concern/thought was do I really want to mount the new controller over the 1771 swing arms. Wouldn't this make future troubleshooting more difficult? I see the controller mounts to a plate that swings up but just thinking out-load.
Great question on rack size!

 

[Doug-P]

do I really want to mount the new controller over the 1771 swing arms. Wouldn't this make future troubleshooting more difficult?

If you're speaking of troubleshooting field devices wouldn't it be the same? You just put your meter/voltprobe on the 1756 point instead. However, you have now added a connection (failure) point which didn't exist before - the cable from the 1756 to the adapter. Now, it probably will never fail but if there's a problem it'll have to be checked.

If using this conversion at the very least I'd torque all the 1771 terminal screws before buttoning up. Over time they can get quite loose.

 

[Bob O]

Doug,
Thanks for you insight, much appreciated. Always good to get another point of view to help point out the obvious.
Have a good weekend,
Bob O.

 

[Doug-P]

No problem. If you go this route would you post back and let everyone know how it went?

 

[Bob O]

Yes I will!

 

[JohnCalderwood]

We have so far tried one conversion using the 1771-1756 rack.

It went very well, and over a year down the line, still no issues.

The panels we have from the past tended to come as the German standard, where wires to digital I/O are all the same colour and have no wire numbers. So a rewire would entail a lot of investigation to tag all the cores going to the 1771 wiring arms...

The conversion kit for a full 16 slot rack took just over half a day to carry out, whereas an adjacent site went for the rewire for a PLC rack and it took them over a week to do.....

So impressed are we that we have 2 other PLCs requiring upgrade from PLC5 to ControlLogix this summer, we will utilise the same procedure and kit.

 

[JaxGTO]

We have used it twice. Works real well for io where all points are wired to terminals. If not it is very hard to get to the original plc5 swing arms in the back. Last one we did 3 16 slot racks in 7 hours.

 

[Bob O]

John and Jax thanks for the feedback!
I have a couple things to verify…


· My rack [A3B] isn’t list but maybe the conversion for the [A3B1] will work.
· I have 4 1771-OBD cards rated at 2A per point and the 1756-OB16E is only rated at 1A. I can install two 1756-OC8 for each 1771-OBD card but then I’m out of room in the new 1756 rack [A13] with all the other cards. I would need custom length cables to extend to a remote rack which are not listed. Physical space is also tight in this panel.
· I also have eight 1791 block I/O modules communicating over the remote I/O scanner that need addressed.

In addition to the outputs, I have an AI, AO, three DI and a prosoft card.

 

[Paullys50]

Just offering another opinion, a few years back I looked at using this system and after seeing the price of the components it was a hard pill to swallow. Turned out that I actually couldn't use the system because the control panel in question was not deep enough to accommodate the staking of the logix rack onto the conversion plate, the logix power supply hanging off to the left also had clearance issues so I needed to figure out an alternate solution.

I was able to use PointIO. Within the same footprint of the PLC5 rack I was able to build a PointIO rack with all of the IO the previous PLC5 had, and had room above the PointIO rack for the power supply, fusing and power terminals. Installation labor was not all that much more since the wiring just needed to be disconnected from the old, re-labeled and re-terminated to the PointIO. Wiring was plenty long enough as I had the PointIO rack mounted at the bottom of the previous PLC5 rack.

Results will vary depending on the PLC5 IO density, IIRC the PointIO material cost was 1/2 to 1/3 the cost of the conversion system. Even with the additional labor to wire up the PointIO rack it was still cheaper than the conversion system. The electricians had it all complete in about 1/2 day.

Looks like I will have a number of PLC5 obsolescence projects on my hands over the next few years, a quick audit of some of the panels shows I'll have clearance issues w/the conversion system. Looks like PointIO will become my go to.

 

[RonJohn]

Paully's5.0, I like your solution. I take it you used a 4-slot 1756 rack with just the PLC and comm cards?

Recently, we had a PLC5 conversion containing two 16-slot racks (1771-A4B?). One of them had a ton of spare slots, so we purchased a 1756 rack and IFMs to take the place of the old 1771 I/O.

I've been wary of the additional terminal connections buried underneath the 1756 rack with the conversion option. Glad to hear others have had good success with the conversion kit.

 

[Paullys50]

Paully's5.0, I like your solution. I take it you used a 4-slot 1756 rack with just the PLC and comm cards?

To clarify, the PLC5 rack in question was a remote rack which had previously used a 1771-ASB. There was a central PLC5 rack w/processor in a central control panel which remained, albeit we scrapped 75% of the original functionality. The project consisted of new equipment and the reallocation of old equipment due to cost considerations. Hence the need to migrate 3 PLC5 IO racks. We did use a 7 slot CLX rack with multiple Ethernet cards for IO, SCADA, and PLC comms. We also had to continue to use 1 RIO network to support some weighing systems which used Rice Lake controllers VIA RIO. We also had to use DH+ communications to existing PLC5 systems for data exchange to ancillary systems.

 

[alan_505]

One thing you can do to get some space is use a redundant Power supply and mount the actual p/s away from the rack and connect with a cable, there are new cables that have right angles at the rack end.


Alan