Short answer
A door release pulls back a latch as soon as it gets power, so the door can open. With fail-secure the door is closed when there is no power, with fail-safe it opens instead. Which you choose depends on the function of the door: escape routes have requirements. The voltage is usually 12 or 24 volts and comes from its own transformer.
Who this article is for For anyone who wants a door release or has one that is not working. On escape doors and communal entrances it is always work for a professional.
What it does
The door frame has a strike plate with a moving latch. When the release gets power, that latch lets go and you can push the door without using the handle. When you let go, the latch drops back again.
Fail-secure or fail-safe
This is the most important choice, and it is about what happens when the power fails.
| Fail-secure | Fail-safe | |
|---|---|---|
| Power on | door opens | door stays closed |
| No power | door stays closed | door opens |
| Use | homes, offices | escape doors, fire situations |
| Power consumption | only when opening | continuous |
On an ordinary front door you want fail-secure: no power simply means closed. On a door that must be able to open in a fire, fail-safe may be required. That follows from how the building is used, and I always involve the building manager or the fire safety adviser.
The power supply
Usually 12 or 24 volts AC, with its own transformer. Watch the power: a release briefly draws a lot more when it pulls in than at rest. A transformer that is too light gives a release that hums but does not open, and that is by far the most reported complaint.
With a fail-safe release there is power on it all the time, so that transformer runs all day and must be rated for that.
If the door does not open
- Can you hear the release buzzing or clicking? If so, power is getting through and it is mechanically stuck: the door is under pressure from the lock or the strike plate has sagged.
- Do you hear nothing? Then no power is getting through. Measure at the release, measure at the transformer, check the push button.
- Does it hum heavily without opening? Transformer too light or at the end of its life.
A door that has gradually got heavier is usually a hinge and lock problem.
A door that suddenly gets heavier after years is often a door that has started to drop. Then the hinges and locks are the problem, not the electrics.
At a communal entrance
There is more involved: several indoor stations, a door entry panel, sometimes a key switch for the postman and an emergency button. That is an installation in itself. See intercom in a block of flats.
Safety and burglar resistance
An electric release is a weaker point than an ordinary strike plate, unless you choose a version designed for it. On an outside door of a home I pay attention to that, certainly if the door is on a back path. A release with locking or a motor lock is then the better choice.
From my own work
At an owners' association (VvE) in Sittard there was a fail-safe release on the main entrance. So during a power cut the front door of the block stood open, all night. That had once been chosen because of the escape route, but the building had a separate escape door. After discussion with the board it became a fail-secure release with an emergency button, which fits how the building works.
When to call an electrician
- The door release hums but the door does not open
- It is an escape door or a communal entrance
- An access system with codes or badges needs to be added
For escape doors I work out with the building manager what is allowed and required. See business and request a quote.
Frequently asked questions
My door release hums but the door does not open, what is that?
Usually a transformer that is too light or a door under pressure from the lock. If it hums, power is getting through, so the problem is the power rating or something mechanical.
Which release belongs on an escape door?
That follows from how the building is used. On a real escape route fail-safe may be required, so that the door opens when the power fails.
Is an electric release vulnerable to burglary?
An ordinary release is a weaker point than a fixed strike plate. There are versions with locking, and a motor lock is the alternative.
Further reading
Doorbell transformer: what it is for and why your doorbell is not working
If your doorbell is not working, it is usually the push button and not the transformer. Search in this order and you will usually have it within a quarter of an hour.
The intercom is not working: troubleshooting in four steps
If it does not work in one home, the problem is in that home. If it works for nobody, the problem is at the entrance or the power supply.
Intercom in a block of flats: how it is put together
In a block of flats the work is in the riser cable and the door entry panel, not in the handsets. That decides whether replacement turns out easier or harder than expected.
Questions and comments
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