We understand the desire for HVAC and the electrical box to be tamper proof. As commercial property managers, we are allowed to put disconnects and overcurrent devices behind a locked door to prevent access by unauthorized persons as long as all tenants have a key. The definition of readily accessible does not preclude the use of a locked door for service equipment or rooms containing service equipment, provided those for whom ready access is necessary have a key (or lock combination) available.
However, unless there has been a theft issue, we do not recommend adding any additional complexity to access for those that need access.
HVAC Lock and Cage