The Ohm Symbol
I regularly hear complaints about electric strikes, cylindrical locks or mortise locks that are hot to the touch. When I ask, I am always answered that, yes, the device is being used in a continuous duty application.
Continuous duty means that the electric lock or strike is powered continuously, usually for several hours a day. Most fail safe locks and strikes are run continuously, since they are usually locked part of the day and they require electric power to lock. Whenever a door is kept unlocked by using an electrical timer, the lock or strike that is controlled by the time is run continuously for part of the timing cycle.
Heat in an electric lock or strike is caused by resistance in the electrical circuit as it passes through the coil of the solenoid inside the device. Often this heat is sufficient to “burn out” the solenoid. The solenoid does not actually catch fire, usually. The term, “burned out” refers to a solenoid that has been ruined by excessive heat so that it no longer functions.
Heat from electrical resistance is exacerbated when there are problems with the supply of power. For example, if the power supply provides less than sufficient amperage to constantly power the solenoid, the solenoid will ‘run’ hotter. Similarly if there is a current drop because of a long wire run with inadequate wire gauge, the solenoid will not get sufficient current and will run hot. Also if the voltage supplied is significantly higher than the solenoid is rated to accept, that could create a heat problem as well.
Often, however, there is no detectable reason for the solenoid to run hot. Sometimes, it seems, they just do.
A great way to mitigate the problem of the hot lock or strike (when all power supply problems have been solved) is to use an electrical device in line with the electric lock or strike that provides it with a full inrush voltage and current upon activation and then reduces the voltage and/or current to a holding level, allowing the solenoid to run cooler.
Several companies offer these units. Here are some examples:
- HES: Model 2005M3 Smart Pack controller
- COMMAND ACCESS: CRU-2 current reduction unit
- TRINE: LC-100 line conditioner
access control, electric locking, electric strike, electronic security, power supply, security hardware
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