Due to costs of pulling I decided to try a used transformer as of infrequent usage of the GFCI and more of lighting. I opened the mobile home's 200 amp breaker box at the pole. It has a double breaker for both hot legs, 90 amp double breaker for the heat pump package unit. It also has the 20 amp pump double breaker.
The pump uses 12-2 cable with ground. I added a 20 amp double breaker with 12-3 with a ground uf cable in conduit out to two sheds. One 110v leg to one shed and the other to the shed beside it. There was no neutral white wires except the one from the new uf cable.
The neutral from the pole is bonded to the bus bars on either side. My white neutral to the sheds is the only one there. There in no ground rod for the box but the ground wire is going into the meter box. The connector between the meter and the breaker box is pvc so I'm not sure if the neutral is electrically bonded to the power pole neutral to the meter case.
Thanks for all that. Looks like it might be less hassle/expense to just put the gfi at the front corner of the house which is about 30 ft from the pump house. Yes is is a structure that I can stand up in as I wanted to store some yard tools in it. I guess it is easier to just add a light. Here is what's out there. First there is a waterproof box with the 12-2 with ground from the breaker box, and 12-2 with the ground going to the pressure switch.They are seperated by a double pole switch to disconnect the pump to work on it. The bare ground wire is attached to the metal box ground lug and a ground lug in the pressure switch with the ground coming up from the pump. I added a waterproof box for the switch above (rather than smash it all in tha single box) and the gfi. That box has a tap in the rear to receive the x-former out for the gfi/light. The boxes are connected by a metal nipple but no actual green wire from ground lugs in each box. Out the top of that box using the "load" connections goes a green, white and black through conduit to an octagon box at the ceiling with a porcelin lamp holder that has an outlet and pull switch. I replaced the old douple pole switch with a new 30 amp one. Ok, so switching to just a light in there I have an extra porcelin single lamp holder for two bulbs in series. I can easily change things around as I have extra electrical parts. If I can get a 220 v lamp with a regular base, do I use the bare wire connected to that green ground going the the light for ID purposes or the white ?