Panel Builder Rant (Profibus or 4-20mA)

I have a panel onsite that has a compact logix with a couple of profibus cards, PSU DI and DO modules in. Ofcourse now i need to add some 4-20mA inputs to this PLC. Trouble is there is hardly any room to the right of the PLC! I might just be able to shift the whole thing closer to the mains failure relay on the left and get the card on the right.
WHYYYYYY do panel builders not leave room like this, its not in a cramped area, they just havent left any room. Its a relativley new panel too, 2012/13!!

PLC


Panel

I wish I knew. We always specify a minimum of 20% expansion space. Space is cheap when you build a panel. Adding space after the panel is built is much more expensive.

I always plan for future expansion for my customers. 25%
My go to saying is that "panel space it cheap the first time". I hate small panels.

Do you not design the panel layout yourself? In general, panel builders build what I tell them to. Most specifications that I build to require 10-20% spare panel space for just this sort of situation.

No unfortunately I dont design the panels. We would give a "spec" to our capital delivery contractors who then subcontract the designing to panel builders. I wish I did have some input Although our specs do say the SI has to keep 25% spare IO which I guess they have done. But only 25% of the IO type that is needed, no analog needed from that project.

The easy fix here is to add your new analog to the Profibus network.
This is likely what was intended for add-ons by the designer too.

RussB said:

The easy fix here is to add your new analog to the Profibus network.
This is likely what was intended for add-ons by the designer too.

Click to expand...

I wish I had as much faith in the 'designer' as you do.

RussB said:

The easy fix here is to add your new analog to the Profibus network.
This is likely what was intended for add-ons by the designer too.

Click to expand...

It is, but i have very little understanding of profibus. Funny, our company policy now is for all instruments to be profibus instead of 4-20mA, but they wont send us (control system engineers) on any profibus training or give us the tools necessary to support / maintain profibus networks.

Out of interest what would be necessary to install a new insrument on a profibus network? The new instrument will be a Hach SC200. On those two profibus scanner cards are just two rotork actuators each.

I know exactly how this thing can happen. It's called budget. The designer gets pushed into working within an unrealistic budget.

Standard panel is nice and spacious. In walks the spec. PLC rack size doubles (because we only use CLX and 13 slot racks, even if you only need 4 slots), relay's turn into 3 pole ice cube, class CC fuses need to be class J, terminals go from 6mm to 8mm, the spec'd ethernet switch turns doubles in size.

The designer goes to the project manager and says the panel size is increasing because it's too tight. Project manager says: sorry, the customer only has room for this size panel. Designer says, but it it too tight. Sorry, a larger panel was not in the budget, we have to go with it. Designer inserts his face into the palm of his hand and folds like a lawn chair.

See the designer and you may often have the same thing in mind. However the salesman and the purchaser don't. So you get stuck with a panel with no spare space.

Not saying that this is always the case, maybe not even your case, but things like this happen.

Oceansoul said:

It is, but i have very little understanding of profibus. Funny, our company policy now is for all instruments to be profibus instead of 4-20mA, but they wont send us (control system engineers) on any profibus training or give us the tools necessary to support / maintain profibus networks.

Out of interest what would be necessary to install a new insrument on a profibus network? The new instrument will be a Hach SC200. On those two profibus scanner cards are just two rotork actuators each.

Click to expand...

To schedule ProfiBus, you need the software that came with the cards to program. It is a very similiar concept to programming DeviceNet. You can scan the profibus card's network through the backplane out through the selected ProfiBus port. Like DeviceNet with *.EDS files, ProfiBus use *.gsd files. Scan the network with unique node # for each device, schedule the new device and save configuration to the card. This assumes ProfiBus has the correct *.gsd file, if not you need to get that from the manufacturer.

Saving new configuration data requires the PLC to be in Program mode.

I think that possibly the wire ducts on either side of the PLC are underused.
You could cut the duct(s) and insert a narrower piece in its place.
That could leave space to expand the PLC.

Oceansoul said:

No unfortunately I dont design the panels. We would give a "spec" to our capital delivery contractors who then subcontract the designing to panel builders. I wish I did have some input Although our specs do say the SI has to keep 25% spare IO which I guess they have done. But only 25% of the IO type that is needed, no analog needed from that project.

Click to expand...

If you don't design the panel yourself you should at least approve the design before it's built. Changes in CAD are easy but changes once it's built are a PITA. Sounds like there are some fundamental flaws with the business model and management that need to be corrected.

Put sub-panels on the side walls.

If your company had a crystal ball you'd have specified the analog I/O when you bought the panel. If the builder had a crystal ball he'd have provided it.

Neither of you had that crystal ball, though, did you?

It is, in my opinion, unfair to criticize a builder for not predicting your future needs. Was he supposed to provide extra power supplies, terminal blocks, surge suppressors, and wiring too? If he did that would his bid still have been competitive or would another shop have gotten the project?

And before you get all carried away specifying all kinds of extra I/O and such for a possible maybe might happen future need, ask yourself what percentage of the time those extra goodies will sit there unused, just a waste of money? Is it possibly as cost effective to add some new remote I/O on the comm link in this case? A minor inconvenience, perhaps, but certainly a solvable problem!

Tom Jenkins said:

It is, in my opinion, unfair to criticize a builder for not predicting your future needs. Was he supposed to provide extra power supplies, terminal blocks, surge suppressors, and wiring too? If he did that would his bid still have been competitive or would another shop have gotten the project?

Click to expand...

It isn't fair to complain that no one saw this specific need. It is completely fair to complain that there is absolutely no space in the panel for expansion. As many others (and, I think the OP) have said, leaving space or an extra card or two in the main rack or an expansion rack further down would make this a moot problem.

Having to add an extra panel just for some remote IO is silly.

That said, IP65 analog IO does exist over Profbus, which might be cheaper than adding a small extra panel.