This should fix your problem, I have also added a line so that you know the bot has started your timer.
on *:text:!on:#: {
if ($nick !isop #) { return }
else {
msg # Announcements are starting
.timer.timername 0 1500 msg # test
}
}
on *:text:!off:#: {
if ($nick !isop #) { return }
else {
msg # Announcements are stopping
.timer.timername off
}
}
You could also change it from using
if ($nick !isop #) { return }
to
if ($nick != YOURNICKHERE) { return }
So it will respond to only your name even if you aren't OP.