You should put one disconnect switch on the back of the wall with the transformers and one disconnect switch should have been installed on the exterior near the channel letters.

It is likely that each transformer could have a different load. So you will have to determine whether a single 20 amp circuit or a 30 amp circuit or double 20 amp cicuits should be used.

In either case use just one switch arranged so that once disconnected their are no live conductors in ANY of the transformer cans.

There are exceptions that allow a lockable disconnect to be located elsewhere but that kinda of circumvents the purpose of the switch in the first place.

Hope that helps. [Linked Image]