I am seeking clarification on the necessity of using external grounding wires for ionizers in an ESD-controlled environment. Our team has installed ionizers equipped with 3-pin plugs, which are already connected to the facility’s electrical grounding system. A customer has raised a request to connect an additional external ESD grounding wire to the ionizers to ensure compliance with ESD grounding standards.
Here are a few specific questions I’d like to address:
Is the electrical grounding via the 3-pin plug sufficient to dissipate electrostatic charges from ionizers effectively?
Under what circumstances would adding an external ESD grounding wire be required for ionizers?
Are there any industry standards or best practices that explicitly address grounding requirements for ionizers?
I want to ensure we comply with ANSI/ESD S20.20 standards and meet customer expectations. Any guidance, references, or experiences you can share would be greatly appreciated.
I believe that the grounding prong on the ionizer should be attached to the chassis of the ionizer, thus effectively grounding it. If this were not the case then the ionizer should be treated as an isolated conductor per ANSI/ESD S20.20 section 8.3.2. In this section it says that if an isolated conductor comes in contact with ESDS items, it has to be less than +/- 35 volts. It also says that if the isolated conductor does not come in contact with the ESDS items, section 8.3.1 on insulators applies. Since an ionizer will not likely come in contact with your ESDS items, you should treat it like any other insulator you have in your ESD protection area and ensure the electric fields from the ionizer are not greater than 5000 V/m (125 V/in) at the location where the ESDS item is handled.
The response that Andy gave is absolutely correct, and I would like to offer some additional comments.
The third prong ground wire on the power cord of the ionizer equipment is primarily for equipment/personal safety, not ionizer operation. I came across a similar scenario a few years back.
A couple of questions:
Is your power cord permanently installed or is it a type that can be removed (like a computer power cord?) If permanently installed, there is very little chance of you losing ground connections, if it is of a removable type then there is a possibility that the connection points in the plug could wear over time and multiple disconnections and reconnections.
My units had removable power cords so here is what I did.
plugged in the power cord to the unit and took a resistance reading from the ground pin on the cord to the chassis of the ionizer. My expected reading should have been 1 ohm or less. If I got that reading, I epoxied the cord into the unit power connection point.
If I did not get that reading, I purchased a new power cord, connected it to the unit, did the same test to verify proper resistance, and epoxied the cord to the unit connection point.
If your unit has a permanently installed cord, do the same test. if your resistance is 1 ohm or less, then you are fine and document it. If not, then you need to troubleshoot the power cord and internal ground connection.
If you want to install an external ground, that is up to you and your management. In my opinion, there is no need for it.