any issue with multiple surge devices on solenoid coils?

Westom-I didn't mean to invite another dissertation that has nothing to do with the original poster's question. He never asked, and doesn't seem to care, about if he needs surge protection or not. The question is will it hurt to double up on it given the unique situation he is in. Rupej answered the question directly.
 
As stated previously, there are both AC annnnnnnnd DC coils. Sizing of said surge suppressors is completely irrelevant for the topic 'multiple surge suppressors'. Help for sizing was never asked for nor needed, which is why the specs needed to do so were not given... quantites again, do not matter here...many of the other BS/opinions in this thread is relevant in any way to the topic...

If there are any technical answers to why or why not we can use multiple surge suppressors on a device, I'd love to hear it!!!
 
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To answer the original question Stacking surge suppressors
By that question I assume you mean parallel them
While you could stack them, but the question is why would you there in nothing to be gained by doing it.
As the old saying goes the strongest chain is only as strong as it’s weakest link this is true on all surge suppressors or any electronic component.
Even with the same suppressor there will be slight differences in the voltage level that they start to conduct. It is not possible to manufacture then to be exactly the same. Even with only .001 voltage difference them the lowest one will conduct first. The first one to conduct will dissipate the surge up to it’s limit and burn up the other devices will do nothing until the first one is destroyed.
If you think the device is not able to dissipate the surge then you should consider getting a higher wattage device.
Normally for 120VAC coil as 130V MOV is used and all DC coils a simple diode connected across the coil works best
Do not put a diode in series with the coil.
To be the most effective all surge suppressors should be located as close to the coil as possible.
When considering any surge suppressor you have to ask what at you trying to protect?
In most cases you are trying to protect the PLC output card from the voltage spike from the collapsing magnetic field when the power is removed from the coil, that surge can be very large normally they consider that voltage level to be over 10X coil voltage. If you are trying to protect the supply voltage to a device or panel then you should look at supplying a better power supply with surge suppression built in.
You can get MOV’s with very large power dissipation ratings if you feel you need them.
Just to be clear Fuses or Breakers are not surge suppressors they are current limiting devices by the time they open the damage has already been done they just isolate the damage to the local device.

For you application I would install inter-pole relays with a 6 Amp or more contact rating in your panel, have your PLC outputs control the relays. That would provide you with total isolation between the PLC and the real world devices. Simple and easy to trouble shoot and cheap to replace if necessary. You still should use surge suppressors in the outputs of the relays and to the solenoid coils to help extend the life of the relays. That surge can damage the relays contacts even with the correct current ratings.

I see here that some are recommending Zener diodes or avalanche diodes they are both old school attempts but they will not work. Back when they first came out zener diodes were called avalanche diodes before they settled on zener
They are always used with a series resistor to limit the current through them. The way they work is with the voltage in forward polarity they act like any standard diode and pass current with the normal .7v voltage drop across the diode but with the voltage in the reverse polarity they block current until the threshold voltage is exceeded then all current is passed through the diode “Avalanche” without a resister to limit the current the diode would burn up in about 1 second or less, not much protection to be had there.
For an AC coil an RC suppressor can be installed and they do work very well, the problem is they are difficult to size for each coil, there is no universal RC for coils the only way to select the correct one it trial and error using a scope to see what works for each coil. Not something you want to do in the field.

Great details, thanks! The valves for this project are custom made, and huge. And often times this mfgr sticks surge suggestion into the coils themselves on custom valves (Not in the din connector that screws onto it) hence the reason for POSSIBLE doubling of the Surge suppressors
That being said they are pilot operated hydraulic solenoid valves, so I have a pretty good idea on the sizing, the wattage won't be anything crazy. Standard premade cordsets should be fine. If they are my wires will be big enough to handle the amperage and i will address the 'o-$#it' factor out in the field for the wattage requirements on the surge devices themselves. Plc will be isolated with relays
 
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IMO, the answer, in general is that doubling up on surge suppressors is fine, provided they are MOVs or diodes. Doubling up on RC snubbers may provide worse results than a single snubber, but certainly better than none.

Westom, you've mentioned a few interesting stories of non-engineers making poor engineering decisions. Would be curious to hear more about those.

Agreed! Thanks for the advice
 
Westom, you've mentioned a few interesting stories of non-engineers making poor engineering decisions. Would be curious to hear more about those.
This problem often continues unnoticed. For example, why do so many domestic auto executives not drive cars? DeLorean discussed how these people would criticize him for constantly driving competitor's products. Sometimes a different one every two weeks. Because he was rare - he wanted to learn.

Columbia was a disaster waiting to happen. A Flight Director, Linda Ham, did not bother to even learn who wanted information to avoid it and why they wanted it. Apparently she was more concerned with relationships to other organizations.

Richard Feynman (his books are classic on these topics) discussed how others on his school board would recommend text books that were poor, incomplete, and sometimes contained bad science. He read the books. And believes other did not bother.

Operators in Three Mile Island knew they had lost control at 4 AM. They called for help from senior Met Ed management. And were told they had everything under control. Only Met Ed executive who know anything about nuclear power was on National Guard duty.

Three Mile Island operators could not even make outgoing phone called because all phone lines were clogged. When Jimmy Carter stepped in, all Three Mile Island phones were connected directly to the White House switchboard so they could call for assistance. MetEd management could not even ask Bell of PA for priority phone lines.

Notice who made decisions to create a Flint water crisis. All except one were MBAs. Those had no training in anything related to water, utilities, or anything related to human health or government services.

None of that is relevant to the topic. But it does demonstrate a common thread for why bad decisions are made. People who make decisions because, somehow, they are experts who never came from where the work gets done. Business schools, in particular, create this problem and the resulting failures.

They could not even ask for phone lines so that nuclear operators could call out for assistance - for three days. They are called accidents so that guilty top executives do not get blamed.
 

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