midnite spd on load center

mahendra

hi can any one advise on how i can install a mnspd 300 on a 120v load center/sub panel.The panels does not have a main breaker .Main utility breaker shuts it off and i already have a spd on that but the panel id very far off so i want to put an spd dedicated to that panel.thankyou

Cariboocoot

Re: midnite spd on load center

If there's already an SPD on the main panel you shouldn't need one on any sub-panel connected to it. The surge will occur at the source of the power.

The exception to this is if you have a sub-panel for critical loads with a transfer switch so that it can be fed by generator or inverter. In that case a second SPD would be connected to the second power source input.

mahendra

Re: midnite spd on load center

what about whats was mentioned about long wires 100ft and over being surge antennaes. My sub panel is more than a 100 ft away thats the reason i want to add another spd to it.

Cariboocoot

Re: midnite spd on load center

Inside a structure is not much of an issue. But if you want to add one anyway it needs to go on the input of the sub-panel, where it is connected to the mains. Since it probably isn't set up for that the wiring gets a bit jerry-rigged, which is not good.

I assume there's neutral and ground bus bars in the box, with open slots you could put those two wires on. That leave hooking up the hot line (you did say this was a 120 VAC panel, right?) For that you have to be able to make a good connection between the small hot lead on the SPD, the larger hot wire from the main panel, and the terminal for the hot bus in the box. How you do this is going to depend on the wire sizes and what the hot connection is like.

niel

Re: midnite spd on load center

if you did put one in then it will need to travel to ground all the way back to the main panel and could induce a spike back into the wires you just despiked, if that's a word. also note that the tie point for neutral and ground cannot be done twice as it should only occur at the main breaker box.

vtmaps

Re: midnite spd on load center

niel wrote: »

if you did put one in then it will need to travel to ground all the way back to the main panel and could induce a spike back into the wires you just despiked, if that's a word. also note that the tie point for neutral and ground cannot be done twice as it should only occur at the main breaker box.

I wondered about that. I assumed that he had another ground rod at the sub box, but no neutral-ground bond at the sub box. --vtMaps

Cariboocoot

Re: midnite spd on load center

vtmaps wrote: »

I wondered about that. I assumed that he had another ground rod at the sub box, but no neutral-ground bond at the sub box. --vtMaps

And if there is another ground rod at the sub panel it creates the potential for a ground loop, unless it is properly connected to the main ground rod.

vtmaps

Re: midnite spd on load center

vtMaps wrote:

I wondered about that. I assumed that he had another ground rod at the sub box, but no neutral-ground bond at the sub box. --vtMaps

Cariboocoot wrote: »

And if there is another ground rod at the sub panel it creates the potential for a ground loop, unless it is properly connected to the main ground rod.

I assume that if there are two ground rods, they are connected by an insulated green wire. I don't know if the main and sub box are in the same building, and if they are in different buildings, I don't know whether the power line to the sub panel is above or below ground. Therefore I don't really know what is a proper connection between the ground rods.

Mahendra, how are these set up?

--vtMaps

mahendra

Re: midnite spd on load center

i already have a positive response from midnite solar thanks