1.0 — Electric Strike does not buzz.
Is the strike getting power? Is it an AC model electric strike, which inherently buzzes? Are you applying AC current, that causes the buzz sound? Have you checked that the transformer is rated at the proper voltage and amperage for the strike to operate properly?
DC electric strikes on the other hand do not buzz on direct current. Their operation is silent.
1.1 — Strike is getting power but does not release.
Check that the strike is receiving the proper amperage, that it is rated at the required voltage. Too low an amperage will not deliver the voltage at a force to operate the strike. Typically a strike without the proper amperage at the rated voltage will often create a weak or erratic buzz sound on AC power.
Is the strike a fail-safe (lock with power) or fail secure (unlock with power) and are you properly applying or removing power to the unit? If the transformer is not new, check that it is still putting out the rated voltage.
Make sure there is no binding of the latch of the lock set within the cavity of the strike. Weather stripping, bowed doors, misaligned locksets, and sagging hinges, all can contribute to a door bind. This will pre-load some strike models and not allow for them to release properly. Is the button or power on/off control working properly?
1.2 — How to stop strike from making a Buzz
Typically a DC electric strike is selected for silent operation. When using a plug in or hardwire AC transformer the use of a rectifier can be added to the circuit, at the strike or transformer. This will convert the AC voltages to DC, allowing for the use of a DC electric strike, which will not make the buzz sound. AC electric strikes will burn out if DC voltage is applied, as the coil resistance can not handle the constant current.
1.3 — How to make a silent DC strike Buzz
By adding a Piezo DC voltage buzzer, matching the voltage of the electric strike
The DC buzzer is added to the circuit, across the wire leads of the strike, in parallel. This allows for tucking the buzzer into the frame with the electric strike.
The use of a buzzer is generally added to DC strikes, on intermittent duty. This is a fail secure, power to unlock application, where as the buzz announces that the door is released.
1.4 — Intermittent Duty
With regards to electric strikes this generally means that a magnetic coil design is not intended to be energized for periods longer than one-minute intervals. The AC coil resistance (Ohms) is not high enough to withstand the heat generated by constant electric current. The heat build up can short and burn the coil windings, leading to failure. As well, if the coil does not short, the life cycles of the strike can be reduced, due to damaging the coil. Usually AC model strikes are fail secure action, meaning momentary power is applied to open.
1.5 — Continuous Duty
This type of electric strike coil usually has a higher resistance (Ohms) as compared to AC coils. They are designed to handle the constant electrical, direct current, of DC voltages. Allowing for a DC electric strike to operate for prolonged periods of time in the energized state. In this case a DC model strike may be available as fail secure or fail safe action. The fail-safe action requires constant power to be locked, and opens when power is interrupted. Fail secure DC models can be used to allow for a strike to be kept in the open position, for extended periods of time, by keeping the strike energized.
Some units are rated for AC/DC operation. These units inherent the limitations of an AC strike, as they have too low a resistance, to be operated at continuous duty.
1.6 — Pre-Load (See 1.2)
This is a condition where upon the electric strike latch (keeper) has pressure upon it, in the opening direction. Generally it is due to a misaligned strike and lockset, allowing the latch bolt to apply outward pressure to the strike latch. The pressure can be so great that in some model electric strikes the coil may not have the ability to mechanically release the strike keeper, while the pre-load pressure binds against the latch. Check for strike to lockset alignment, with the door open and closed. The hinges on frame should not allow the door to sag. The door closer should hold the door to the frame stop and not partially ajar. Electric strike cavity, depth and width, should be of the proper size to accommodate the latch bolt, with an allowance for some play. Weather striping that is installed in front of the frame “stop” does not allow for adjustments to maintain door and frame alignment. A sealer, which mounts on the soffit of frame, often can be adjusted to door alignment, from the top to the bottom of frame. This type of stripping prevents undue pressure against the door. Badly bowed door or frames need repair or replacement in some cases. An electric strike that buzzes erratically or opens only intermittently could be a sign of preload condition. If the strike keeper can be opened (remove or apply power) with finger pressure, while holding the door opened, the strike is then functional.
1.7 — Checking electrical condition of strike
Testing the Ohms reading of a coil can tell you whether the coil winding are in good condition. The windings are what creates the magnetic field, that manipulates the mechanical mechanism to be open or closed. If the winding have been damaged the strike may not lock or unlock. When resistance “Ohms” goes up, the amperage goes down and the coil may not have enough power to develop the proper magnetic field. If resistance goes down the coil may draw more amperage than the power supply is rated to deliver. This could possibly burn out the transformer.
By reading the Ohms with a meter, you can compare to the rating of the electric strike. Usually the voltage, amperage and or Ohms rating can be found on the product label or the manufacturers catalog. Voltage divided by Amperage will give you the Ohms. (V / A = Ohms)
1.8 — Checking Transformer
Transformers are used to step down the high voltage to a lower voltage to operate low voltage devices such as electric strikes. There are basically two types of transformers, plug in and hardwire. The hardwire type is often mounted to an electrical box through a 1/2 inch knock out. The plug-in version is connected to a wall receptacle power outlet. The hardwire most often are AC current outputs. The plug-in type can be available in AC or DC current output. The AC hardwire type can be converted to DC, by use of a rectifier with an equivalent amperage rating.
The transformer should be matched appropriately to the device load. Meaning that the voltage, current and amperage all have to be accounted for to operate the load properly. Often transformers may not show the amperage rating as amps, but give a VA rating. The Voltage times the Amperage equals the VA, (V x A = VA). To figure the amperage when given a VA rating, divide the VA by the voltage, (VA / V =A).
Use a meter to read voltage at the transformer and then at the electric strike. Do this by placing the two meter probes; first on the transformer connector, then at the two strike connections.
DC transformers have a positive terminal and should be checked with positive polarity, in mind. Compare the voltage reading of the wire leads in frame to the transformer. This will confirm that the strike is receiving the proper voltage and that the transformer rated output is sufficient to operate the strike, both at the transformer and after passing through the wire run to strike. If the voltage at strike is significantly different than the transformer output, then check the wiring.
1.9 — Wire Runs
Should be kept to a minimum distance from power supply. Wire runs of less than 100 feet, are at best. Doing so avoids adding resistance on the power output to electric strike, creating a voltage drop.
Wire resistance (Ohms) can be changed in three ways, length of wire, diameter of wire, and by heat.
The longer the wire, the longer the voltage has to travel. If the wire diameter is thin, then the voltage has to squeeze through the wire. If the wire is exposed to excessive heat, then the wire builds resistance. Look to locate power supplies not far from strike location. Wire size should be a minimum of 20 gage, for short runs. Avoid hot attics with black tar roofs, or running wires close to hot water and steam pipes.
Stranded insulated twisted pairs of wire are recommended. The solid core jacketed phone wire should be avoided. Especially when snaking wire over ceilings, behind walls and into doorframes. The stiff wire is prone to breakage and the insulation is easily damaged. Twisting wire and screw connectors tend to crack and break solid wire in small gages.
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2.1 — Checking voltages (See Checking Transformers)
All devises in an electric strike circuit should be rated at equal voltages. Meaning all electrical components should have the same voltage rating. A magnetic coil is designed to perform at a certain power, to operate the strike. When the strike coil does not receive the appropriate voltage, a proper magnetic field is not created to operate the strike. As the voltage lowers, so does the amperage, further reducing the power.
Selecting components of the same voltage rating will help insure the coil does not run hot, and possibly lead to coil failure, as well as being able to mechanically operate the strike. Of equal importance is a strike that places a burden on a under rated transformer, causing it to fail.
Transformers have their voltage rating affixed by a label or can be checked with a voltage meter. Determining voltage of electric strikes can be accomplished in a few possible ways. The label on the box or the strike, more often gives the electrical characteristics. Some manufacturers use color coded wire leads or print specs on coil tape. The Ohms of the coil could be checked and referenced to a manufactures catalog or data sheet. Knowing the resistance (Ohms) of the coil will reflect a specific voltage and confirm whether the coil is in good condition. (See 1.7 Checking electrical conditions of strike).
2.2 — AC vs DC (see 1.4 & 1.5) Quick Hit List
AC DC Intermittent Duty Intermittent or Continuous Duty Buzz Silent (or separate DC buzzer or LED) Lower Coil Resistance Higher Coil Resistance Higher Current Draw (AMP) Lower Current Draw (AMP) AC Transformer DC transformer or rectifier on DC of equal voltage Burns out on DC of equal voltage Often fails to operate on AC of equal voltage Fail Secure Duty Fail Safe or Fail Secure Duty
2.3 — Strike Burns Out Coil (See 1.4 & 2.2)
AC coils could burn out when operated at there rated voltage on DC current. The lower resistance of the coil is unable to handle the constant direct current. The power builds up as heat and may short or fuse the coil windings.
Being that AC strike coils are intended for intermittent duty cycles (no longer than 1 minute), a stuck button or shorted wire run could cause the coil to fail. Holding a door open for extended periods of time, by energizing the strike will reduce the life of the coil. AC coils require more amperage and as a result generate more heat to the windings.
Transformers with overly rated voltages can also cause the AC coil to burn, as also true with DC coils.
Some strike models that are burden with a door preload, may cause an AC coil to over heat. As well as someone continuing to hold the button as an individual attempts to take the load off the door, for the strike to open, when entering.
2.4 — Matching the grade (See 1.6)
Lock hardware is graded by standards that are developed through the BHMA. These standards when independently tested are granted a grade level recognition. Electric strikes are also graded and non-graded, not only locksets carry a certain grade level. When selecting an electric strike many of the hardware configurations and features are taken into account by the design, to be compatible with locksets of similar grade level. Strikes that have no grade level will often accommodate like locks, also without a grade.
Often an inappropriate non-grade electric strike is selected to accommodate a Grade 1 heavy duty lockset. Typically you will find the lockset, in a high traffic heavy duty application, is a tremendous burden on the strike. In short time the lockset damages the strike beyond being operative.
A heavy duty mortise lock with a steel three piece anti friction latch and an auxiliary dead latch feature, matched with a light duty electric strike with a narrow style zinc cast faceplate, zinc cast latch keeper, shallow cavity depth or height and designed for wood applications, very commonly leads to a malfunction.
2.5 — Auxiliary ramps
Mortise locks with any auxiliary latch feature that make the latch bolt a dead latch, require electric strikes with an auxiliary ramp configuration. Narrow style strikes will not accommodate an auxiliary latch feature. The auxiliary ramp is required for allowing the auxiliary latch to ride up the face of the frame and be depressed into the lockset, making the latch a dead latch. Also the ramp section fills in the cut in hollow metal frames, not exposing a slight hole, that has been prepared to allow the latch bolt to have a clear path to the strikes latch keeper. If the auxiliary latch of the latch bolt did not have a path to follow, preventing it from hitting the frame edge first, the door may not completely close, due to the latch hanging up on the edge of the frame. In the case of the auxiliary latch, it will often break off or holds the door open. The latch bolt can get stuck between the strike keeper and the hole in the edge of the frame, possibly jamming.
Narrow style electric strikes are more suitable for wood frame applications where the frame thickness prevents breaking through into the hallow, of the frame. Typically the frames are 3/4 inch thick. The narrow style non-grade electric strike commonly has a cavity depth of 1/2 inch. This strike is acceptable for a nongrade lockset, cylindrical or mortise (without auxiliary latch) with a 1/2 inch latch bolt projection.
Thus, the installation requires the 1/2 inch of wood be removed where the rabbit area of frame meets the frame face, for a latch path. This allows for the strike keeper latch to pivot open properly when the door is opened.
2.6 — Door does not latch completely shut (See 1.6, 2.4 & 2.5)
Additional cause may be an electric strike faceplate, is not fully mortised into the frame. A lockset latch bolt that is not completely compatible and having a taper or bevel that does not engage properly with the strikes keeper face. This would be the area that the latch bolt comes in contact with the strike and depresses the latch bolt momentarily into lockset and then releases back outward into strike cavity. When the latch bolt meets the strike keeper the proper angles on both allow the latch to ride into the cavity and the door to close.
2.7 — Door closes but strike keeper does not lock
(See 1.6, 2.4 & 2.5)
This could be due to one or a number of causes.
There are some electric strikes available that are hand changeable. This generally requires that a mechanical part be adjusted or reversed in the mechanism. Some types of these strikes, if fail secure, (locked without power), may be in the opened position if installed upside down or in the reverse hand of frame.
(See additional 1.5, 1.7, 1.8, 2.1, 2.2)
Fail safe action (locked with power).
With fail safe action the strike requires power to lock the strike latch. Make certain the strike is receiving power.