We have to purchase a inline safety switch(for our ac unit) which isn't covered under our warranty,is this part associated to our heating unit?

What kind of safety switch? Is it in the drain line or on drian pan?

An inline safety switch could also be called the outdoor disconnect.

Never heard it called that... thanks

It has multiple meanings:

Safety switch (http://www.electronics-manufacturers.com/products/relays-switches/safety-switch/)

The word "inline" could mean series here, so the question is inline to what? Water, power, control circuits

Safety could mean water, a disconnect, smoke, door safety switch.

The terminology is way to vague.

AC disconnect or the outside disconnect is a safety switch.

A water alarm for the pan can be wired to shut off the AC if the drain stops up.

Overpressure and underpressure switches are safety switches

All are for the AC unit.

That was why I was confused earlier as to what safety switch they wanted to discuss.
Guess we will wait and see if they ever answer.