Surge protection before a 24 VDC source.

Elcan · Mar 30, 2017

Hi all,
We stopped using 110 VAC surge protection when we started using 24 VDC PLCs, instead of the 110 VAC.
Never had a problem in almost 10 years, but recently a CompactLogix lost its program.
Aside from discussing what could have happened with the PLC, do you recommend to use a power conditioner (surge protector) between the 110 VAC transformer and the 24 VDC power supply?

Thank you!

JeremyM · Mar 30, 2017

I'm guessing you're using a L3x - have you replaced its battery?

Elcan · Mar 30, 2017

JeremyM said:
I'm guessing you're using a L3x - have you replaced its battery?

L33ER.
This processor has been in the field for less than a year...

Mickey · Mar 30, 2017

Do you have surge protection across inductive loads?

James Mcquade · Mar 30, 2017

We use corcom.

had a slc 5/04 that lost its program 2 times in 2 weeks.
plant had a brownout each time.

we installed one of these units and never had another issue.
its now standard on all panels I have built.

regards,
james

Elcan · Mar 30, 2017

Mickey said:
Do you have surge protection across inductive loads?

Could you be more specific, please?

Mickey · Mar 30, 2017

Elcan said:
Could you be more specific, please?

Outputs that control inductive loads ( solenoids,relays).

http://www.actsensors.com/custom-sensors/surge_protection.htm

Elcan · Mar 30, 2017

Mickey said:
Outputs that control inductive loads ( solenoids,relays).

http://www.actsensors.com/custom-sensors/surge_protection.htm

Thank you for the feedback, Mickey.
No, I don't use that kind of surge protection.
However, you are talking about the PLC digital outputs, aren't you? My problem is related to the PLC processor for a CompactLogix. Unless you are trying to say that the inductive loads could have affected this processor.

RDS · Mar 30, 2017

Have used these powerline filters before, never had any problems. https://www.automationdirect.com/ad..._Line_EMI_-z-_RF_Filters_w-z-Surge_Protection

Elcan · Mar 30, 2017

Thank you all for the input so far.
My question was more about your recommendation about whether using or not using a surge protection between the 110 VAC transformer and the 24 VDC power source.

Mickey · Mar 30, 2017

Elcan said:
Thank you for the feedback, Mickey.
No, I don't use that kind of surge protection.
However, you are talking about the PLC digital outputs, aren't you? My problem is related to the PLC processor for a CompactLogix. Unless you are trying to say that the inductive loads could have affected this processor.

If the 24vdc that powers the processor is also used to power the outputs then yes the inductive spike can cause the processor to lose its program.

Elcan · Mar 30, 2017

Mickey said:
If the 24vdc that powers the processor is also used to power the outputs then yes the inductive spike can cause the processor to lose its program.

Yes, it's the same power source...
In this case I guess the surge protector wouldn't be of much help, right.
If this was the reason of the issue, I wonder why this problem happened to us the first time in 10 years.

Mickey · Mar 30, 2017

We stopped using 110 VAC surge protection when we started using 24 VDC PLCs, instead of the 110 VAC.

Didn't you just make this change?

IMHO, its always good practice to use surge protection across inductive loads. It may or may not be your problem though.

Another is grounding.

James Mcquade · Mar 30, 2017

Elcan,

that is what i'm talking about.
we put a corcom filter after the 110 transformer feeding ALL control items.
we also used surge suppression on all ac valves and reverse diodes on all 24 volt valves.

james

Elcan · Mar 31, 2017

OK, it seems that, in addition to the surge protection between the 110 VAC transformer and the 24 VDC power source, I would need to use surge suppression, in my case mainly for the 24 volt valves.
Having said that, could you share more details on how you implement it? Schematics, part numbers and some photos will be greatly appreciated.

Thanks!

Surge protection before a 24 VDC source.

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