Hello,

I have a circuit that runs 28.4 volts AC (no ground). I would like to change the toggle switch to a programmable timer switch (mechanical of digital). Does anything exists that would work with this voltage?

 

Just about every mechanical switch I have come across would switch 28.4 volts.

 

The current is not mentioned, but the big challenge will be getting a timer switch that will operate on 24/28 volts AC. A mains powered timer switch with isolated contacts will work, assuming that mains power to drive the motor is available.
But if the timer is to be an electronic programmable device, finding one for that voltage range will be a bit more challenging.

 

Mains driven mechanical timer switches take very little current so you could use almost any 110V to 24V transformer in reverse to drive one..

 

The application is actually very unclear. The TS wants to have some sort of timer switch controlling an isolated ciircuit with a no-load voltage of 28.4 volts. We have no hint as to the current that would be switched, nor if there is any additional connection to the system available. MOST timers require power in both the off state and the on state, and so for any advice to be useful we need additional information: load current, and power availability. I have seen a spring wound time switch once, but not recently. A battery powered electronic time switch may exist, possibly.
So really we need a bit more information about the application.