Disconnecting S5 connectors with Power On

Hi,

In a migration project from S5 to PCS7 we are going to use retrofit connectors from Siemens to do a Control Module IO test in a weekend.

The question I have is, we are going to disconnect the S5 connectors and connect them into the retrofit connectors that are connected to the S7-400 PLC.

After the IO tests during the weekend we are going to reconnect everything on the S5 for the production of monday...

Just wondering, disconnecting and connecting... I think we better do this with the power shutted off ? When disconnecting 4-20mA closed loops from an S5 IO card, are these old cards ok with that ?

But still, I think we need to shut off the closed...

What do you guys think how to retrofit test and return to old situation...

Thanks for tips,

Kind regards,
Combo

Switching off is always best, yes you may get away with it 9 times out of ten but can you afford it. Most faults occur when switching off or switching on probably due to a spike occurring at that moment in time, however, the poor contact as you insert a spade into a receptacle (plugging in) has a greater chance of causing flash over due to poor connection than powering off or on.

I believe the front connectors are designed to get connected/disconnected under power, as the power contacts for the electronics are disconnected first on removal.

I've used this S5/S7 adapters for PCS7 migration many times. Just a month ago for 2 full S5 racks switching every morning to S7 and in the evening back to the S5 for 7 days. I've got more fear that the S5 won't get into run when powering off/on, when it was constant running under power for about 10 years.

Combo said:

When disconnecting 4-20mA closed loops from an S5 IO card, are these old cards ok with that ?

Click to expand...

I dont think you can damage the cards that way.

I tend to agree that in most circumstances there should not be a problem I have done it myself a couple of times, however, we did a changeover from an old Ferranti system, the idea was to fit a new control cabinet alongside the old one. The new system Was an S5 155, the original system had Harting plugs & sockets connecting the I/O to the terminals, we wired the new cabinet to harting plugs & sockets so that for trials we could quickly swap the Ferranti system over to the S5, test & put it back. everything went well on a couple of trials, however, when swapping back to the Ferranti on one occasion, we lost a card. fortunately the company had spares. so yes hot swap of I/O connectors can be done but just be aware, if you can power down.

Before swapping, I would do:
1. Turn outputs off in the PLC that is to be disconnected. By forcing if no other way possible.
2. Disconnect the power supply from ouput cards when these have a dedicated power supply input to distribute to the outputs.