De acordo com o National Electrical Code, a proteção contra sobrecorrente não pode estar nos banheiros. Então não, você não pode colocar o painel no banheiro.
National Electrical Code 2014
Chapter 2 Wiring and Protection
Article 240 Overcurrent Protection
240.24 Location in or on Premises.
(E) Not Located in Bathrooms. In dwelling units, dormitories, and guest rooms or guest suites, overcurrent devices, other than supplementary overcurrent protection, shall not be located in bathrooms.