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I want to install a HEPD80 whole house surge protector. Its on the main panel, but there is no ground bar in the panel. I live in Illinois where everything is in rigid metal conduit and grounding is handled by it.

So what do I do with the ground wire coming from the HEPD80?

Square D support is mystified and pointed me to their other SPD's that don't have the ground at all like the SDSA1175 (36kA) and HEPD25 (25kA), but even their own marketing materials say they aren't the preferred option for whole house protection.

Edit: I was asked to provide more information about the panel, but can't comment directly on the request because I'm a new user. I will add a picture of the panel, cover off when I can. In the mean time it is an old Square D Q0C30MW225. It has neutral bars, with only white wires going to them.

Edit 2: Edit to add a picture of the panel. It's not a picture of the whole box, but this seems to be the relevant part, its just breakers the rest of the way down.

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    Can we see the power panel
    – Traveler
    Jun 13, 2022 at 19:35
  • So you have metal conduit that is not flexible. There are 3 kinds of that: EMT (Electrical Metal Tubing), IMC (Intermediate Metal Conduit) and RMC (Rigid Metal Conduit). Don't use "Rigid" as a general descriptor for all non-flexible metal conduit. Any of these + FMC are legal in Chicagoland. Jun 13, 2022 at 20:59
  • You seem to have created two accounts here -- please visit the page on merging accounts to get that sorted :) Jun 14, 2022 at 2:35
  • Does that thick white wire exiting the top of the panel continue in a conduit, or as an exposed wire? Also, can you post a photo of the labeling on the inside right of the panel please? Jun 15, 2022 at 3:07
  • @ThreePhaseEel I've added a picture of the white cable exiting the panel through conduit as well as the other conduit coming into the box. (it will likely be pending review for a bit). I don't have a clearer photo of the the label handy, if memory serves it was listed the catalog part number again along with date of manufacture and inspection. Its also kind beat up being a 40+ year old piece of paper in a basement. If its is vital I will risk the ire of the family by turning off "the internet" again, albeit briefly.
    – Buck
    Jun 15, 2022 at 10:47

2 Answers 2

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If the conduit terminates in the panel, that means that the panel enclosure itself is what is tying everything to ground. If the main panel is technically a sub panel and there is a main disconnect elsewhere, there might not be a visible ground wire or bonding strap anywhere on the main panel. In that case you could get a ground lug and use a self-tapping machine screw to screw the lug to the panel enclosure and then attach the SPD’s ground wire to the lug, thereby bonding it with the grounded panel enclosure.

Edit: based on the photo, the neutral wire is the black with white tape, the ground wire is the all-white insulation wire. The grounded and grounding wires are bonded together via their bus bars. Put the SPD on either bus bar.

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    I thought the black cable with white tape might be neutral. So if all those screw terminals are neutral/ground bonded, should just find two empty spots and put in the HEPD80's neutral and ground into separate ones?
    – Buck
    Jun 15, 2022 at 11:00
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The enclosure metal is grounded.

So you can drill a #10-32 hole in the panel (or use an existing 8-32 or 10-32 hole intended to mount an accessory ground bar) and attach a lug there.

Or you can install an accessory ground bar in the sites provided for that purpose.

Or you can study the panel closely and see if any existing bars are bonded to the enclosure, and if they are, put the ground on that bar. (that might be the neutral bar). A green screw through a neutral bar usually is there to bond it to the panel.

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