Simply stated, door preload is pressure exerted on a door and in turn transferred to the keeper of the electric strike by the latch.
When pressure is applied to some models of electric strikes, the solenoid may not have the ability to mechanically release the keeper because the pressure binds it against the latch.
Even a small amount of this preload can cause problems in the functioning of some electric strikes. Door preload can prevent the smooth unlocking of the electric strike or even disable a strike – preventing a door from being opened.
Failure to release can prevent a door form opening, hindering safe passage or egress which could create a life-safety issue.
Additionally, a door left unlocked by a faulty electric strike leaves a building vulnerable.
A number of conditions can cause door preload including:
A strike that does not open or opens only intermittently could be showing signs of a preload problem. If preload pressure causes a strike or multiple strikes to malfunction, many access and security issues arise.
What to watch out for:
An electric strike failing to release when energized is not the only problem preload can cause.