One of our readers wrote us about replacing some T8 Motorola 3 lamp series-parallel ballasts (first image below). I suggested he replace them with 3 lamp parallel instant start ballasts. Unfortunately, this involved removing (or replacing) and rewiring the lampholders. He was looking for a solution that did not involve replacing or rewiring lampholders.
He was able to locate a 3 lamp series ballast (second image below). Just to see if it might work, he wired the new ballast to the fixture lampholders while matching colors (third image). As it turns out, the lamps lit up and are still on.
This reader David is a retired electrician and doing volunteer work at the local library.
3 Lamp Series-Parallel Ballast
3 Lamp Series Ballast Wiring Diagram
6 Individual wires, 2 common wires
After 3 Lamp Ballast is Replaced
As seen below, the wire colors on the ballast match the wire colors on the lampholders. Orange wire connectors are preferred for joining 4 ballast wires (18 AWG).