Did some searching and found that it is un grounded romex from the 1950's it looks similar to this photo

Here is a link that might be useful: photo

This cable you describe is feeding your detatched garage??? Is it buried? In conduit underground, or buried unprotected? Flown overhead? Please provide further details. Photos of your actual installation would help.

If it's really 14g as you mentioned on the other site there is *NO WAY* you can run 100A service on this stuff. Let alone that it is missing conductors needed to do this safely and legally by the current code. You need to use appropriately sized and rated conductors (for conduit) or cable (appropriate to whatever installation this is as alluded to by davidr)... which is going to be at LEAST #6 with four conductors.

I'm having difficulty reconciling the photo with your description, i.e., "two large gauge wires wrapped with an outer ground wire and then encased in some type of plastic casing."

Ignoring the photo for now, my hunch is that the cable is old-style "SE", not the type of "Romex" used for ordinary house branch circuits. And if it's typical of the time period you surmise, it most likely consists of two #6 conductors (one red, one black) covered with a braided neutral/ground under a plastic sheath or cloth sheath impregnated with a water-resistant binder.

In the past, outbuildings such as garages were very commonly fed by three-wire cables with the two insulated conductors used as hots and the braided bare wires serving as both neutral and ground. In fact, three-wire feeds to independent outbuildings were perfectly legal for new installations up until the 2008 code revisions (with a few specific restrictions, such as a requirement that there be no other metalic connections between home and outbuilding). This wiring method is no longer legal for new installations or major renovations.

In any case, I'd be quite surprised if the conductors are larger than #6 and, if that's the correct size, it could in no way carry more than about 55 amps safely, even under older versions of the code.

Terrible Tom's description of the wire is accurate it's probably about a #6 wire with a braided bare wire. Sounds like I'll need to replace all of it $$$$$$

Thanks for the replies

I would replace it.