When the Rev. Thomas C. Kelly got a promotion earlier this summer, it meant he had to move from the place where he had been living for the past 12 years.

Moving day was considerably less of a hassle for him than for the average American working his way up the corporate ladder. All of Father Kelly's belongings fit neatly into two suitcases.

Friends say that this disdain for wordly goods is one of the hallmarks of Father Kelly, 46, who on Monday will be consecrated a bishop, one of the most influential in the American branch of the Roman Catholic Church.

Bishop-designate Kelly has been serving since last March as general secretary of the National conference of Catholic Bishops and its service arm, the United States Catholic Conference.

It was assumed that his designation as a bishop would follow, as it did on July 13.

"To be effective as a general secretary one needs to be a bishop among bishops," explained the Rt. Rev. James S. Rausch, who held the post for nearly five years and with whom Father Kelly worked as associate.

It is characteristic of Father Kelly that he tried, unsuccessfully, to convince the Vatican that he could do the job effectively as plain old Father Kelly, without elevation to the episcopacy.

As the date for his consecration approached, he circulated a memo through his office saying that if anyone had thoughts about getting him a gift - a common custom on such occasions - he would be pleased if instead they would make a charitable contribution in his name.

In a church which, though changing, still puts great store by its trappings of medieval aristrocracy, its watered silk vestments and its episcopal palaces. Thomas Cajetun Kelly will be a different kind of bishop.

For example, one of the symbols of the bishop's office is the crozier, derived from the Shepherd's crook and signifying his role as keeper of his flock. An ornamented, gold-worked crozier can run into four figures.

The crozier that will be handed Father Kelley at his consecration at the Shrine of the Immaculate Conception Monday afternoon will be an actual shepherd's crook, made of ash, manufactured for export to sheep farmers of New Zealand. It cost $7.

One key to Father Kelly's simple life-style is his membership in the Dominican order. Being a Dominican defines much of life for him.

His face lights up and his black eyes snap as he talks about it. He became a priest, he said, because "to become holy is one of life's great possibilities. The Dominicans offered me the most congenial approach to that."

Entering the order, which he did at 17, is, he said. "the most smartest move I ever made. I have never for one moment regretted it."

"He thinks of himself as a Christian, of course, and as a Catholic and priest. But "being a Dominican is my primary identification," he said.

His countenance glows as he talks about the close fellowship of living in the order, the "witty conversation", the internal dedication to the truth," the joy of the shared liturgies. It would not occur to him to complain of how much he misses this close brotherhood of 28 years, now that he has moved from the Dominican House of Studies to the NCCB Staff House in the Northeast.

Collegues note that on the rare occasions when he has an hour he loves to slip back to catch up on the news of those who knew him as Father Cajetun, the religious name he has taken as his own middle name.

If Father Kelly follows the ascetic life-style of a monk, he is no simple friar. He holds a doctorate in canon law from the University of St. Thomas in Rome in addition to his licentiate in theology and has done graduate work at the University of Vienna and at Cambridge University.

A New Yorker by birth, he was a secretary in the office of the provincial of the Dominicans' New York province for three years. He served on the staff of the apostolic delegate here in Washington for six years before he moved over to the headquarters of the American hierarchy.

As general secretary of the dual organizations of the heirarchy, he directs a staff of about 300, most of them at the headquarters at 1312 Massachusetts Ave. According to one colleague, he knows every one of them by name, even the people who come in at night to clean.

He makes "rounds" once a day, keeping in personal touch with all the offices in the eight-story building. At the same time his staff describes him as a highly efficient administrator with a mind for detail, one who sees to it that requests are dealt with promptly.

Something of a workaholic, Kelly works straight through the lunch hour, taking only a mug of tea, a couple crackers and maybe an apple at his desk. Work that isn't finished by closing time goes home with him. Fellow residents of the staff house are accustomed to hearing his typewriter clattering away far into the night.

Kelly believes that the Catholic Church "is alive and well in the United States." That is not to say that there are no problems, "but we're dealing with them as well as we can," he said.

He has no "platform" for his administration as general secretary. "I feel it's up to me to find out what the bishops want and then to do that as well as possible," he said.

Even though, as he points out, "90 per cent of the job is laid out for me" in job descriptions. Father Kelly, like his predecessors, will put his own stamp on the job, growing out of his concerns for the church.

He talks about the problems he sees in the church - the whole area of family life ministries; tensions between the bishops, who are the church's officials teachers, and the scholars, who sometimes move out ahead of the bishops in refining and updating church doctrine; the need to developtechniques of "shared responsibility" that will involve lay men and women in the church.

The problem he keeps coming back to is what the church is going to do with its women. "One of the biggest challenges in the church today is to release the energy women have and bring it to full potential," he said.

Not ordination to the priesthood. For Father Kelly, that question has been "resolved" by last winter's "no way" from the Vatican.

"But there are only a few ministries in the church that are ordained," he argues. "There are so many other ways women can serve. But it is the women themselves who must give the definition to what their role will be."

The church, he adds. "will be infinitely better place when women have reached their full potential."

Within his own bailiwick, he has established an in-house committee of staff women to monitor and review the work of the U.S. Catholic Conference as it relates to women.

If, as a part of middle-management for the world-wide Catholic church, he is bound by the Vatican's position against women priests, he is on the friendliest of terms with those Catholics who challenge that ruling.

When his designation as bishop was announced last month, one of the first to offer congratulations was Sonya Quitslund, a longtime friend and a leader of the local proordination caucus.

"She asked me to ordain her," he recalled with a pleased smile. "It was one of the nicest calls I got that day."