PLC5 Migration w/ Flex I/O

I'm currently bidding a project and the customer is wanting to use the migration hardware kit to convert their existing PLC5 to Controllogix. Our engineer here is wanting to use Flex I/O with a small Controllogix rack with a new L71. Pros and cons of using Flex I/O versus using rack mounted modules? I realize with Flex you don't need to use terminal blocks but other specifics will be appreciated from a wiring, programming, etc standpoint.

I've not done the migration hardware kit path so I can't weigh in on that method but I do have a considered opinion about the Flex I/O. As an option, take a look at the Point I/O instead. It offers a wide range of flexibility and modularity that the Flex doesn't and it seems, IMHO, to have a better track-record. I use a lot of Point I/O with little or no issues.

Why don't you use terminal blocks with flex?

One thing I don't like about using the 1771 hardware kit is the old setup skipped terminal 8 and 9 (for IO). So your wiring will be offset after 7 compared to wire label (if they used IO numbering scheme). That is how I remember it at least.

That's a good point Van, I didn't know that. The conversion kit just seems like its the same amount of trouble to deal with versus installing a new CLX rack in its place. With FLEX we generally just situate them such that they lead directly into the wire duct because they can be turned vertically or horizontally. That to me is the biggest factor when trying to reuse someone's existing field wiring.

VAN said:

Why don't you use terminal blocks with flex?

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The terminations for FlexIO/PointIO are field wiring friendly.

OP, I've had considerable success using PointIO in place of a PLC5 rack. You can get the same IO count in the PLC5 rack footprint, and generally speaking the existing wiring will be long enough to re-terminate on a PointIO block. Flex doesn't make sense simply due to form factor UNLESS you have room from removing the field-wiring terminal blocks. Flex is pretty dated so I'd stay PointIO or the new 5069 Compact IO.

Recent discussion on migration here :

http://www.plctalk.net/qanda/showthread.php?t=111142

Hardware conversion depends on
- how complex the system is (for re-wiring etc)
- how much space you have in the panel (or a new panel..)
- what other installs are on the same site (spares etc)
- what the customer is comfortable with.

Yes, flex is older, but will still be around for some time. It does take up more length space per module, but you still have the 4/8/12/16 channels per module. Point I/O is the way forward, and you have to consider the lesser channels per module, and power requirements for so many slices.

We have done a lot of conversion from PLC5 to CLX. A path that has worked for us is using a Control or Compact Logix rack with 1492-IFM breakout terminal blocks and pre-made cables. It make the conversion fast and since the cards are local the maintenance guys do not have to deal with any confusion of remote IO in the local cabinet.
The biggest problem is when the wires are labeled with the PLC 5 octal (0-7,10-17) address and Control is Hex (0-15), what is worse if the PLC-5 is using two slot address then it gets really weird. It can created some confusion but all you can do is put a big note on the prints and deal with it (unless you want to relabel the whole machine.
Anyone with other thoughts?

I found with the hardware conversion is to make sure ALL of the IO points are wired from the swing arms out to terminal. Because once you put that conversion plate and cables on, it's really hard to get to them again. Especially while a machine is running.
Unless you don't care about unused/spare points.

If you do use the conversion kits make sure you start the job with spares. I've discovered a distressing number of open conductors on brand new cables. It seemed worse with the Modicon kits they used to sell, but the last 1771 rack I did I got a cable with two opens. Luckily I had extra cables.I typically ring them out beforehand but the customer had the parts and I didn't have access to them early.

So for those of you that have used the AB conversion hardware. How did check out go? What did you do? My thoughts are the you could verify that you had it wired to correct card in the correct slot. Then verity say point 0 and point 15 on each card to be sure your program wasn't wrong due to the octal/decimal addressing differences. I have been looking at this for a while now and the advantages of not having to check every point are huge on larger conversions. My philosophy is that if you lift and re-terminate a wire then it must be verified. Thoughts?

We always check every IO point. We quite often find in older systems IO points that have not been working for a long time. But on a newer system I would be fairly confidant to check a couple points on each card. But when it comes to any points that are safety related they should be checked 100%.