We are putting stall kits into our 40x40 pole barn, which was used as a shop/garage by the previous owners. The entire building is insulated and covered in plastic sheeting and electrical wires are run vertically along the support beams, all outlets and light switches are in weatherproof boxes with lids. I had an electrician out to inspect everything and he said everything was in good shape and we didn’t NEED to change anything unless we wanted to add or move outlets. So, are we good with this set up? Our county doesn’t require anything for outbuildings, no permits, no inspections, so no real help there info-wise. Ideally, everything would be in conduit, but for whatever reason that’s not something you see a ton of around here and electricians look at me like I have three heads when I mention it!
Do you have a local firehouse?
Hopefully experts will post here, but if my area didn’t have code I’d look at other counties or states for basic codes and why they have them.
some like hurricane latches won’t be applicable, but if you’re in a swampy flood prone state look at other flood prone states regulations etc.
where do you live and what is your weather pattern (earthquakes, floods, fires, volcano eruptions, dust storms, extremely high/low temps, snow ice,hurricanes etc).
Any place you may have mice, bugs and possible exposure to the elements, that is not in an enclosed, tight building, as horse barns are not, you really want wiring in conduit for electric and fire safety.
Every electrician here will insist any wiring in barns and shops that will be open part of the time be in conduit.
I would think the cost of rewiring would be whatever it is, for peace of mind, times cheaper than if and when there is a problem from exposed wiring.
BX cable is acceptable. BX is a metallic sheathed cable. ( also known as armored cable)
We have that in our attic.
Critters ate it right where it attached to where it was connected to what it was servicing, security cameras.
Impressive how mice disconnected them right there and ate the wires into the back of them flush with the covering.
Were told by electricians, some wire covering is tasty to rodents and they will hit it any place they can find to get to it.
Seems that was a weak spot that should have been better protected.
Beware, security camera installers are not electricians.
Critters ate it right where it attached to where it was connected to what it was servicing, security cameras.
BX cable is supposed to be run into metallic boxes that have clamps to hold the cable in place… the outer metal shield can be part of the grounding if installed correctly
I think they just ran it into the back of the cameras.
When they were checking them out, the cameras just fell into the serviceman’s hands.
The wire had been completely chewed off the Romex cable I think they called it, could have caused a fire if it had shorted out.
We didn’t go there in the barn, we asked for conduit, perhaps more mouse and idiot proof.
Have you asked the county if they could send someone out just to have a look at it? They may have an inspector for commercial electrical inspections that could come out and at least give you a second professional opinion. You never know until you call. 
OP, you could abandon the existing wiring and have what you need installed as the way you want. There is no need to rip out the existing, just disconnect it from the main panel. Have the disconnected conductors marked/tagged as intentionally disconnected
Great suggestion! Ran that by an electrician and he said that would be easier than putting the existing in conduit, so I think we’ll go that route.
It is called the National Electric Code for a reason - It is not governed by state or county - State and counties can add to it but not disregard what is written. Assuredly, if you are doing electrical work, there is a permit that you are required (many don’t) to pull. That being said, I do all of my own electric work and pull permits for a small portion of it.
A few bullet points for buildings with animals:
- If the wire is buried in insulation or behind a wall/partition it needs to be in conduit of some type (My understanding is there is an assumption that the walls will have mice in them.) The easiest method for this is using a flexible metal type such as Clanter mentioned (It goes by different names in different parts of the country - MC stands for Metal Clad, I believe BX is a generic brand name)
- If the wire is exposed on trusses, girts, etc. it can be direct bury cable commonly referred to as UF-B (Underground Feeder)
- NM-B (Non-Metallic Sheathed Cable) is NOT allowed.
- All boxes and switches need to be in dust proof housings
- In my less-than-humble opinion the best balance between installation cost and safety is to use UF cable and run it exposed if it is higher than 10' (out of reach of the horses) When the wire comes down below the 10' reach - put it in conduit.
