The Holm Park outfit, however, made life difficult for themselves following a series of glaring missed chances during the second-half.
The visitors started strongly and City ‘keeper John Daly twice had to make smart saves to keep the opposition at bay before they deservedly opened the scoring on 10 minutes.
An initial shot was parried by Daly into the path of the onrushing Heaney who made no mistake with a decisive shot.
But the lead was short-lived as Philip Donnelly levelled the score on 13 minutes when he fired a superb 15-yard shot past outstretched Limavady stopper Matthew McGraw.
Armagh now began to dominate and went in front on the half-hour when Stephen Murray outpaced the visiting back-four to slot home past the advancing McGraw with aplomb.
City made the score 3-1 on 55 minutes when Paul Carville and Donnelly combined to set-up Murray once again and he dispatched a low shot into the net.
Armagh were in rampant mood at this stage but Murray was disappointed to miss three clear-cut chances with the United defence at sixes and sevens.
These misses gave Limavady encouragement and, with 15 minutes left, they reduced the arrears when Friel cut in from the left and fired a powerful 20-yard angled shot past the dispairing Daly.
City faced a torrid finish with Limavady having two penalty shouts turned down in the final minutes but, in the end, the home side held on for a deserved win.