The Second Department explained that the arbitrator exceeded his/her powers by awarding more than the requested damages:
An arbitration award may be vacated if the court finds that the rights of a party were prejudiced by (1) corruption, fraud, or misconduct in procuring the award; (2) partiality of an arbitrator; (3) the arbitrator exceeding his or her power; or (4) the failure to follow the procedures of CPLR article 75 (see CPLR 7511[b]). In addition, an arbitration award may be vacated if it violates strong public policy, is irrational, or clearly exceeds a specifically enumerated limitation on the arbitrator's power … .
An arbitrator's authority “extends to only those issues that are actually presented by the parties” …, and an arbitrator exceeds his or her authority by reaching issues not raised by the parties … . Here, the arbitrator awarded the petitioner $43,000 in damages based on the amount due under the subject contract, although the petitioner sought only $34,920 in damages for work done above and beyond the contract. Accordingly, the Supreme Court properly vacated the award as issued in excess of the arbitrator's authority … . Matter of Slocum v Madariaga, 2014 NY Slip Op 09005, 2nd Dept 12-24-14