Four tries for the home side ensured they grabbed a bonus point as well and they were the only one of the three promoted teams to taste victory on the opening weekend of the season.
Having cruised to the Division Three title last season without dropping a point at home, Penallta ensured it was business as usual on their own patch as wings James Powell and Shaun Robson flew in for tries. Back row men Chris Harries and Geraint Thomas followed suit and Karl Rees weighed in with three conversions and a penalty.
There were tougher starts for Newport HSOB and Llanishen, who also climbed a rung of the WRU National League ladder last season. The old boys went down 31-17 at home to Abercynon, who also left with a bonus point, while Llanishen were hit for six in 32-6 defeat at Ynysybwl.
Bwl's livewire skipper John Reed scored one of his side's six tries and there were also two from Jamie Richards.
Ystrad Rhondda ran in seven tries in their 46-20 home win over Pill Harriers, with wings Nathan Rees and Gerwyn Davies grabbing two each. Pill picked up a bonus point thanks to pack tries from Dai Tovey (2), Andy Grant and Lee Hussain.
There were losing bonus points on the road for Tredegar at Builth Wells, where they lost 13-7, and Rhydyfelin at Mountain Ash, where they scored the only try in a 9-7 defeat.
In Division Three East, Abergavenny won the battle of the two relegated teams from last season as they ran in three tries in a 17-8 triumph at Croesyceiliog. There was also joy on the road for newly promoted Garndiffaith, who squeezed passed New Tredegar 31-27.
Pontypool Utd topped the scoring in the division with an eight-try 55-11 home win against Blaina. Wings Joel Griffin and Rob Morgan grabbed two apiece as did No.8 Steve Thomas.
Gwernyfed also hit a half century in Division Four East as they ran out 50-0 victors while in the new Division Six East Beaufort were 65-8 winners over Whiteheads.