unsigned long will work for 300000 and longer and causes less confusion.
So simply change:
const int led_A_Interval = 15000; // number of millisecs between humidity checks
const int blinkDuration = 3000; // number of millisecs that pump is on
to...
const unsigned long led_A_Interval = 15000; // number of millisecs between humidity checks
const unsigned long blinkDuration = 3000; // number of millisecs that pump is on
Will do the trick so I can increase duration to 300,000? Currently using in application during test phase so not keen to make adjustment unless it's the correct one.
Appreciate help cheers.