I am not sure I can explain the wiring. I did it myself a few years ago. These units are meant to be installed on houses and hardwired into the house. They do not come with plugs or any external wiring. I wired using a 30amp plug with the same configuration type used for outlets in most RV parks. These may not be available in Mexico as they are not what you might call a standard plug. On the outlet side of my ISB I mounted a 50amp outlet that allows me to plug my normal 50amp plug from our RV directly into the ISB. Again - this 50amp configuration seems to be made specifically for RVs and may not be available in Mexico. I do not know where you would get one. Be sure you can get all the wiring needs before you buy the ISB unit - or any other unit.
Besides the plugs and outlets you need the correct wire. I used stranded flexible wire like extension cord wire but it has to be at least 10 gauge wire for 30amp. I think I have about 10 feet so I can place the ISB wherever I might need to. I also made all my connections to the ISB weatherproof with outdoor conduit and caulk. But of course the outlet can still be exposed to weather. You could put longer extensions to/from the ISB but I figure it has to be near the park pedestal and then use my regular hookup cord to run to the ISB. Many wiring configuration are possible depending on your rig and your requirements.
I forget exactly how I did it by my incoming to the ISB is obviously only the standard 3 wire type used for up to 30amp. But I wanted my outlet to be for a 50amp plug in so I can just plug my standard 50amp service cord directly into the ISB. So inside the outlet box I had to splice the one wire from the 30amp type wire to two wires going to each hot leg of the 50amp outlet. This would also depend on your rig and you requirements. You need to understand electricity pretty well to do this - it is not a job for amateurs. I can't draw a diagram. Hopefully you will understand what I am trying to say here.
I have my ISB mounted on a board so I can take it in and out of our RV as needed. Since we do not use it all the time it is not hardwired to our RV. We only use if for 30amp or lower plugins. When we have 50amp we cannot use it as that would require two ISB units. The other reason ours is not hardwired is we do not have appropriate space for it near our other power connections. So I just take it out and lean it up against whatever we are plugging into and the plug it in. I cover it with plastic in case of rain but the box itself is made to be outdoors and the covers are sealed with gasket material - it is weatherproof but my plugs may not be.
I think just about any ferreteria can order these things but they may not carry them in stock as they are a high dollar item. ISB has distributors all over Mexico according to their website so ferreterias should be able to get them quickly. You might want to go on the ISB website to get the details of what it is you want and also who the nearest distributor is in case the ferreteria does not know. I think in Mexico all you would need is the 4000 unit.
I think the biggest problem you might run into in Mexico is finding the plugs and outlets that match the plugs and outlets used for RVs. They could be hard to find in Mexico. The 30amp plugs may be available as all the RV parks seem to have the same type 30amp outlets that we see in the US. But the 50amp outlets are RV specific and not easy to find even in the US - though I think Home Depot has them in the states.
I'll try to post a snip of the ISB specs here........
