(a) If a trustee makes or expects to make a principal disbursement described in this section, the trustee may transfer an appropriate amount from income to principal in one or more accounting periods to reimburse principal or to provide a reserve for future principal disbursements.
(b) Principal disbursements to which subsection (a) of this section applies include the following, but only to the extent that the trustee has not been and does not expect to be reimbursed by a third party:
(1) An amount chargeable to income but paid from principal because it is unusually large, including extraordinary repairs;