Use o método dual breaker - quem escreveu o manual precisa de um slap Code com 424.22 (B), já que o método single breaker não está de acordo com ele.
(B) Resistance Elements. Resistance-type heating elements in electric space-heating equipment shall be protected at not more than 60 amperes. Equipment rated more than 48 amperes and employing such elements shall have the heating elements subdivided, and each subdivided load shall not exceed 48 amperes. Where a subdivided load is less than 48 amperes, the rating of the supplementary over-current protective device shall comply with 424.3(B).
Se você tiver slots curtos, use um disjuntor de material duplo (quadruplex).