Idemitsu Australia Resources chief operating officer Steve Kovac said that - at the request of the Construction Forestry Mining and Energy Union - Boggabri Coal mine and the union would enter into a three-week cooling off period on any industrial action.

"Boggabri Coal will therefore facilitate an orderly return to work from Wednesday," he said.

"We are hopeful of constructive dialogue with the union and other workforce representatives in this period."

The lockout started at 6pm on November 22 and was expected to continue until 6am on December 2.

CFMEU Northern Mining and NSW Energy District President Peter Jordan said workers had been taking rolling industrial action for two months trying to secure pay and conditions in line with Idemitsu's other coal mines at Muswellbrook in the Hunter Valley and Ensham in Queensland.

After voting this week, workers overwhelmingly rejected the company's proposed EA with an 88% "no" vote.

Workers' concerns include pay rates that are $30,000 to $40,000 a year lower than permanent rates in Hunter Valley coal mines, with unfair bonus structures and no provisions to support skills training for workers.

"Workers at Boggabri are not asking for anything that isn't already provided to workers at Muswellbrook and Ensham," Jordan said.

"Boggabri produces top quality coal and there's no reason why these workers should be treated differently, with worse pay and conditions, just because they are in the Gunnedah Basin.

"The 88% no vote sends Idemitsu a clear message about workers' views."