The most likely problem is that the breaker has tripped. On some breakers there is a indication window that shows a red flag if the breaker needs resetting. On other breakers there is no indication but a slight misalignment of the breaker handle as compared to the other ones. On the distribution panel find the breaker number of the circuit that is off from the panel index. Push the breaker handle to the furthest off position that you can. As the handle is moved to the off position you will feel a bit of resistance. Push past it as that is the breaker resetting. Return the breaker to the on position to see if the circuit has re-energized.
The only other reason is that a wire has become disconnected in the circuit. If you have been doing any electrical work on the circuit start looking in that area. To troubleshoot these types of problems it will require the use of a volt meter to check to see if the circuit is "hot" from the breaker out. Then it is just a matter of finding where the voltage stops and locate the problem.
Check the circuit breaker to see if it tripped.
Breaker is tripped.
There is no reset button on a central air unit, there is a small breaker or fuse box outside next to the unit, it is possible the fuse is blown or breaker tripped.
If it's a GFCI receptacle and the button is not resetting then change the GFCI outlet.
It may have tripped a spark gap or GFCI breaker.
If the GFI outlet is tripped (the outlet, not the breaker) then it is telling you there is a ground fault which must be fixed. If the GFI outlet is not tripped, and the breaker is not tripped, but it is still not providing power, then you have a loose connection or a wiring error.
Some breakers can trip totally off. If the breaker is continually turning off without a wiring issue, then the breaker could be going bad.
It is a verb, the past tense of trip. It describes an action. "Mark tripped over the rug." Tripped is also an adjective. "Homeowners can reset a tripped breaker themselves."
If your thermostat doesn't have batteries, it may be hardwired into your HVAC system. Check the circuit breaker to ensure it hasn't tripped. If the circuit breaker is fine, there might be an issue with the wiring or the thermostat itself. Calling a professional HVAC technician would be the best course of action to diagnose and fix the problem.
disconnect beside unit may have blown fuse or tripped breaker,contactor in outside unit may be bad,or no coolant in system
It takes a finite amount of time to trip a breaker. The short you caused may not have tripped the breaker. If the dryer is no longer working there may be an internal reset that has tripped.
A breaker that still shows full voltage after it has tripped is definitely bad.