Surge Protector on Every I/O

Every I/O Analog and Discrete needs a surge protector in my control panel.
We have alot of I/O and the Cost for the Phoenix Contact Plugtrabs is ridiculous.
Is there a better design that can save cost and real estates in my control panel
to meet this spec?

Why do you need them and what is your application?
I have never had the need or even seen an application with them.
Not saying they are out there, just trying to understand you application.

james

The Engineer has a boiler plate spec and I'm being called on it.
It states every I/O Analog and Discretes must have a surge protector.

I looked into it and Phoenix Contact has a PlugTrab. They are not cheap. I'm hoping for a better solution, product, or technical reason that can get me out of this.

Application is a Waste Water Treatment Plant.
My control panel controls a bunch of Valves, a couple of Influent Pump, Grinders, and Transmitters Flow, Level, and Pressure.

RRoc said:

The Engineer has a boiler plate spec and I'm being called on it.

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We deal with this often. Sometimes it causes us to make more money, other times we just don't bid.

Depending on the quantity, you might get in touch with your Phoenix rep and plead for a big price break. The devices in use are very different for analog versus discrete I/O, and again different for AC and DC inputs and outputs.

I think the Phoenix devices are very good and might be worthwhile on analog signals, but for 24vdc, something like this:

https://www.digikey.com/product-detail/en/kemet/PMR209MC6100M047R30/399-7512-ND/3459468

And for 120vac:
http://www.auberins.com/index.php?main_page=product_info&products_id=238

Those are just examples, and may not meet the spec depending on the exact wording. When in your situation, I generally find the least expensive device that meets the wording of the spec. Occasionally the spec will list something that is a good idea, so I don't go cheap if I am going to have to stand behind its performance.

a MOV, TVS, diode or transvorb may be appropriate as well.
https://en.wikipedia.org/wiki/Surge_protector#Primary_components

Plug the entire panel into a ISOBAR. Boom, now every point on the system is surge protected.

RRoc said:

I looked into it and Phoenix Contact has a PlugTrab. They are not cheap. I'm hoping for a better solution, product, or technical reason that can get me out of this.

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Every IO port already has effective protection. Your concern is a rare transient - maybe once every seven years - that can overwhelm that already robust protection.

Anything adjacent to the IO port must already be inside that IO port. The tranient that can cause damage must exist when transients enter. First and foremost is single point earth ground. Second, every wire inside every incoming cable must make a low impedance (ie less than 10 foot) connection to single point ground. Any wire that does not is then the incoming path that subverts all protection.

TV cable must already have that best protection. A hardwire must connect a coax cable low impedance (ie less than 10 feet) to the one and only earth ground. Then a surge incoming on cable need not be inside hunting for earth destructively via all electornics.

Telephone cannot be connected directly to earth. So the telco installed a 'whole house' protector for free. And again, it is hardwired low impedance (no sharp bends or splices) to what defines all protection - earth ground.

AC electric is not required by code to have effective protection. You must connect every AC wire (again low impedance) to earth. AC wire cannot connect directly. So a 'whole house' protector (from manufacturers known for integrity - Isobar is not) does that earth ground connection.

Lightning can be 20,000 amps. So a minimal 'whole house' protector is 50,000 amps. Because effective protectors do not fail and remain functional for decades. And because 20,000 amps must connect to an earth ground so that it does not overwhelm superior protection already inside all electronics.

This is what they mean by all IO ports must be surge protected. A surge must not enter a structure. Otherwise that surge will hunt for connections to earth destructively via electronics. That Isobar may even make surge damage easier. Obviously. Its best connection to earth can be destructively via nearby electronics.

Any incoming wire (security alarm, radio antenna, etc) must connect to that single point earth ground - directly or via protector. Then tens or 100 times less money is spent on what actually provides protection. Provided by over 100 years of science and experience.

Manufacturers of integrity include Intermatic, Square D, Ditek, Siemens, Polyphaser (an industry benchmark), Syscom, Leviton, ABB, Delta, Erico, General Electric, and Cutler-Hammer (Eaton). However THE most critical item in every protection 'system' is THE item that harmlessly absorbs hundreds of thousands of joules.

Protection is always defined by an answer to this question. Where do hundreds of thousands of joules harmlessly dissipate. A protector is only as effective as its earth ground. A protector without that low impedance (ie hardwire not inside metallic conduit) connection to earth does not claim to protect from these potentially destructive surges.

The least expensive 4-20mA loop surge protection I've found is L-COM.

They have a quad channel 4-20mA surge protector at $67.
http://www.l-com.com/multimedia/datasheets/DS_AL-CL4W-XX.PDF

Their designation of "weather-resistant" housing deserves some skepticism - nowhere is a NEMA or IP rating mentioned.

Dan

danw said:

They have a quad channel 4-20mA surge protector at $67.
http://www.l-com.com/multimedia/datasheets/DS_AL-CL4W-XX.PDF

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Again,

A protector is only as effective as its earth ground. A protector without that low impedance (ie hardwire not inside metallic conduit) connection to earth does not claim to protect from these potentially destructive surges.

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L-Com discusses its key and critical feature:

A ground clamp provides a tie point for earth ground.

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View its schematic. To what does each protector part connect to be effective? "Earth ground". If a low impedance connection to earth does not exist, then what does each protector connect a surge to? Nothing.

A protector is only as effective as its earth ground. Protector is used because that signal wire cannot connect direct to earth.

Best protection means a surge connects low impedance to earth so as to not enter a structure. Facilities that cannot have damage were doing it this way even 100 years ago.

The AC input modules have internal MOV's.
Have you looked at ZipLink transorb modules?

keithkyll said:

The AC input modules have internal MOV's.
Have you looked at ZipLink transorb modules?

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First, Ziplink uses semiconductors - not MOVs.

Second, protector capacitance is a concern on signal lines. MOVs and transorb may have excessive capacitance.

Third, that Ziplink is installed on a transient generator - not on its victims. Read its specifications. That solution would be inside any properly designed device. OP's concern is protecting potential victims - not suppressing a transient inside the source.

The OP asked for surge protectors. Transorbs are superior to MOV's. The capacitance of these devices are negligible in low impedance circuits.
It's best to suppress a surge as close as possible to the source. In the OP's case, that's not a consideration. His concern is within his control cabinet.

This really depends on what kind of protection you are needing. Do you want to protect the cabinet from transients coming up the line side? If so an isolation transformer will do the trick. You will feed the entire cabinet from the isolation transformer and this will prevent line-side surges. Emerson has a nice line of these in varying specifications:

http://www.emersonindustrial.com/en-EN/documentcenter/ControlTechniques/PDF/Transformers.pdf

I have used them and they work great. Now, as for your other types of transients, if you are dealing with a system that has a lot of metal piping then you may be trying to protect against lighting. I have had it surge up pipes, into a flow meter, to an analog card and into a com line. As far as protection against this type of damage, well, good luck. There are various means (such as lightning rod systems) to prevent the pipes from being struck.

There are a TON of different types of transients that may be worrisome depending on your application.

I have a surge protector on my Line Side From Phoenix Contact.

I'm stuck with the specification calling out every I/O in my panel must have a surge protector. I did see Surge Protector Terminal Blocks from Phoenix Contact but they are only for Analogs. For discretes Phoenix Contact recommends PlugTrab Surge Protector. I have over 200 discretes and 34 Analogs.

keithkyll said:

It's best to suppress a surge as close as possible to the source.

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Exactly. Facilities with a cabinet of electronics put no protectors adjacent to that cabinet. Put best (and also much less expensive) protection at the service entrance.

Impedance is critical to all protection. Every foot longer to earth significantly increases impedance. (Yes, wire length - not thickness - is critical.) Protection increases with increased distance between electronics and protector (increased impedance). Protection increases with decreased distance between protector and earth (decreased impedance). Then a protector is also closest to the source; not its victim.

Low capacitance is irrelevant to 4-20 ma signalling. It is significant with ethernet, telephone, and other high speed signalling.

Specification calling for protection on every I/O in a panel is about protection at a building's service entrance. Best protection at each IO port is already inside electronics. Sometimes protection at an IO port may compromise superior protection already inside on that IO port.

Isolation transformers are already routine inside electronics. Not just on AC. Isolation transformers are even routine on ethernet and coax (radio frequency) ports. More examples of best protection already inside systems.

These simple rules are well published by so many professionals. For example, "Planning guide for Sun Server room":

Section 6.4.7 Lightning Protection:
Lightning surges cannot be stopped, but they can be diverted. The plans for the data center should be thoroughly reviewed to identify any paths for surge entry into the data center. Surge arrestors can be designed into the system to help mitigate the potential for lightning damage within the data center. These should divert the power of the surge by providing a path to ground for the surge energy. ... It is also necessary to protect against surges through the communications lines. The specific design of the lightning protection system for the data center will be dependent on the design of the building and utilities and existing protection measures.

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Protection of IO ports is always a building wide solution. A most critical requirement is single point earth ground and low impedance (ie less than 10 foot) connections to that ground. Wall receptacle safety ground is not earth ground.

Protector is not defined by analog or digital. It is defined by current (protector life expectancy), threshold voltages, capacitance (signal speed), and of course, the impedance of that connection to single point ground. Best protection is a direct hardwire connection to any wire (cable) that can make a direct connection to earth ground (ie TV cable, satellite dish, radio antenna).