Anything wrong w/ using PLC and contactors to control exterior lighting?

[Todd0x1]

I need to spec some hardware for a project, is this a bad idea?

The project has four separate structures all spaced 100 feet or so apart, additionally there is a small utility building with the electrical service in it. There is a desire for centralized control of all the exterior lighting, both on the buildings and outdoor lighting on the grounds. There is existing ethernet infrastructure. I was thinking I could use a PLC located in the utility building which would drive one or more local contactors to switch the lighting circuits that originate from that location plus a Modbus I/O module driving a contactor at each of the four structures. I suppose a 508 shop would have to make the panels up.

 

[sameguy]

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[Hv&Lv]

You wanting to monitor something?
Photo eye controlling a bank of contactors is one common and easy way

 

[kwired]

I need to spec some hardware for a project, is this a bad idea?

The project has four separate structures all spaced 100 feet or so apart, additionally there is a small utility building with the electrical service in it. There is a desire for centralized control of all the exterior lighting, both on the buildings and outdoor lighting on the grounds. There is existing ethernet infrastructure. I was thinking I could use a PLC located in the utility building which would drive one or more local contactors to switch the lighting circuits that originate from that location plus a Modbus I/O module driving a contactor at each of the four structures. I suppose a 508 shop would have to make the panels up.

508 shop shouldn't have to do it. They might be able to make an assembly that you technically can not make though because you have to design yours to NEC and they can make theirs in accordance with 508.

 

[Besoeker3]

OK. Ignorant Brit strikes again...
What is a 508 shop?

 

[kwired]

OK. Ignorant Brit strikes again...
What is a 508 shop?

A shop that is qualified to build industrial control panels in accordance with UL508 standards.

 

[Besoeker3]

A shop that is qualified to build industrial control panels in accordance with UL508 standards.

Thank you, sir. Still had to look that up...............

 

[kwired]

Thank you, sir. Still had to look that up...............

Won't go into details of the standard since I'm not qualified and don't really know much about them. But for most part if I want to build a control panel I have to follow NEC requirements when building it. 508 might allow some things that NEC does not. A 508 panel is not individually evaluated and given a listing though. Most 508 panels are probably custom made for an application where an actual listed panel is probably mass produced and every one of them is the same other than some options that are included in the listing.

 

[Besoeker3]

Won't go into details of the standard since I'm not qualified and don't really know much about them. But for most part if I want to build a control panel I have to follow NEC requirements when building it. 508 might allow some things that NEC does not. A 508 panel is not individually evaluated and given a listing though. Most 508 panels are probably custom made for an application where an actual listed panel is probably mass produced and every one of them is the same other than some options that are included in the listing.

Appreciated. We just have BS7671.

 

[ptonsparky]

Appreciated. We just have BS7671.

Wow, I thought BS standards were only becoming prevalent in the good old USA.

 

[Todd0x1]

You wanting to monitor something?
Photo eye controlling a bank of contactors is one common and easy way

Control would be by photo eye + time clock, plus some manual override.

With how spread out everything is, and with the existing ethernet infrastructure, the savings on wire pays for the whole PLC + remote modules setup.

 

[ptonsparky]

We've used similar strategies in the past. Put a couple HMIs on there and you're good to go.

 

[jim dungar]

I suppose a 508 shop would have to make the panels up.

I believe you are talking about a panel built to '508A', and not one of the other UL 508 standards.

Why does your panel need to be built to the NEC? You probably just need to a 'listed' panel that can be installed under the NEC, like one built by a UL508A shop. Just include whichever NEC requirements you want them to meet, like no conductor smaller than #14 or no breaker smaller than 15A.

 

[Todd0x1]

I assumed the panel with a PLC, power supply, and contactors would need to be listed and could not be field assembled by the electricians right?

 

[kwired]

I assumed the panel with a PLC, power supply, and contactors would need to be listed and could not be field assembled by the electricians right?

If all your components are listed and used according to listing instructions there is no reason it can fail a NEC inspection.

If you have components that are not listed you still might be able to use some of them, not everything needs to be listed, NEC does tell us what does need to be listed.

If you are using "recognized" components, you pretty much need to be replacing a like component or someone that is authorized to build listed assemblies as those recognized components are not listed individually but are recognized components for use in listed assemblies.

 

[petersonra]

If you are using "recognized" components, you pretty much need to be replacing a like component or someone that is authorized to build listed assemblies as those recognized components are not listed individually but are recognized components for use in listed assemblies.

Presumably if the code does not require a specific component to be listed it would be ok to use a recognised item.

There is no code requirement that industrial control panels be listed. But I think at least some states and localities require it. Pretty much any assembly of stuff you might put together with wires attached qualities as an industrial control panel.

 

[kwired]

Presumably if the code does not require a specific component to be listed it would be ok to use a recognised item.

There is no code requirement that industrial control panels be listed. But I think at least some states and localities require it. Pretty much any assembly of stuff you might put together with wires attached qualities as an industrial control panel.

That statement would include the wall switch in my bedroom wouldn't it?

Otherwise AFAIK "industrial control panels" need to either be listed or assembled in accordance with NEC rules, so basically if it doesn't comply with NEC then it must be listed as is.

 

[jim dungar]

That statement would include the wall switch in my bedroom wouldn't it?

Otherwise AFAIK "industrial control panels" need to either be listed or assembled in accordance with NEC rules, so basically if it doesn't comply with NEC then it must be listed as is.

Does the NEC mention how to mount a 4 position selector switch into the cover of an enclosure? These devices are typically UL Recognized not Listed.

 

[kwired]

Does the NEC mention how to mount a 4 position selector switch into the cover of an enclosure? These devices are typically UL Recognized not Listed.

Wasn't aware of those typically only being recognized, but even if listed NEC likely would depend on instructions included in listing to determine how to mount it I would think and does same for many other things.

 

[RumRunner]

I need to spec some hardware for a project, is this a bad idea?

The project has four separate structures all spaced 100 feet or so apart, additionally there is a small utility building with the electrical service in it. There is a desire for centralized control of all the exterior lighting, both on the buildings and outdoor lighting on the grounds. There is existing ethernet infrastructure. I was thinking I could use a PLC located in the utility building which would drive one or more local contactors to switch the lighting circuits that originate from that location plus a Modbus I/O module driving a contactor at each of the four structures. I suppose a 508 shop would have to make the panels up.

Allow me to get into this fray if it’s not too late. LOL
You have an existing ethernet infrastructure which is a part of a PLC system that is active. In essence, you want another “system” added to your PLC controller to control the exterior lights.
Is your existing system utilizing a network that is meant to be accessed from outside the premises? In other words-- are you having a Local Area Network (LAN) or Wide Area Network (WAN)?

In either case, both formats are a “mini” computers. The difference is; the WAN has its own IP address along with a MAC address. . . in order to be recognized from outside the network.
MAC Address (Media Access Control) should not be confused with Apple MAC computers. It is manufacturer ID number assigned to the device.
The LAN on the other hand only needs a MAC Address--for it to be recognized by other computers in a Peer-To-Peer Network (P2P) .
Computers in a common location.

They do have their own identifying addresses though.
You can add the new setup to your existing network but it would be a separate “NODE”. Although a separate set of data-handling-- capable of being manipulated-- but still a part of the “Tree” structure originating from a common root. This is a rather complicated approach. . . but it can be done.
What this means is, you are creating a different ‘MINI’ computer that will interface with an [already] active system.
I really don’t want this to be more complicated than it needs to be --but I’m just trying to point out the distinction.

To summarize:
You can use a wireless topology (WIFI) where you don’t have to tap into your existing PLC infrastructure.

If integrating this lighting control into your PLC sounds like too much of a hassle-- perhaps just photo cells, timers and drum switches would do.

All the best