I live on an island off Honduras in an American Style home that was wired by a local "electrican" and I use the term loosely. I have sever power surge problems and decided to install a TVSS on the main panel and I have encountered some challenges and need advise.

First, the 2 hot phase wires and the neutral come from the pole and are then split, yes I said split in a box with these split wires going to two different electrical Square "D" breaker boxes.

It is obvious that at some time later the owner decided to add a ground wire and brought in a 4th wire (green) from the opposite side of the house, that is tied to a 5' grounding rod driven into the ground and then it also is split at a floor joist with green wires going into both of the breaker panels.

The square "D" panels have two verticle ties on each side, one sticks out more than the other. Whoever attached the grounds and neutrals put a ground and it's neutral into one hole on the deeper bar.

Now, to my real problem. Where do I attach the neutral and ground wire for the TVSS. In every box I have ever wired I have all my grounds down one side and all my neutrals down the other side so I simply attached the ground to the ground and neutral to neutral but with these boxes they look like they are all tied together.

Hope I have explained this well enough. I think the wiring is a real mess.

I'd bring the service box up to code first. The easiest way may be to install a service disconnect ahead of the two circuit breaker boxes, make the two panels "Sub-panels" with separated ground and neutral connections, then properly ground and bond everything.

You also said the ground rod is on the other side of the house? It should be as close as possible to the panels to prevent objectionable ground currents.

If you still have surge problems, then install the TVSS at the service disconnect.

In addition, I would believe the local electrical system be in poor condition or reliability may call for UPS protection for critical equipment such as computers, medical equipment. Will help greatly with filtering also.

You don't say where you experience surges, through the entire house due to the utility, lightning, or only branch circuits.

UPS and whole house surge protection will help with the utility and lightning.

Local surge protection at the devices being affected help with internal causes. Loose connections or circuits with motors are typical causes.

For any TVSS to work properly when needed, it must be grounded properly, as so for the entire wiring in the home, and especially the service.

Ground resistance should be 25 ohms or less, lower the better. Can't speculate with how soil conditions are there, but I imagine sandy and dry due to good drainage,If so more that one 8 or 10 foot ground rods will be needed.

When you say the incoming splits, does that mean one wire one way and the other another way?

If the Main breaker is in the panel, then grounds and neutral can be connected together on the same bar, not in the same hole unless it is rated for more that one wire.

I think you need to a have a real pro look at this. You carry the freight and expenses, I can be packed tonight.