Access control and power failures

tmontney · Jul 4, 2023

I need to handle power failure for my electric strikes in my house. Of course, I can leave the keyed entry on the knobs, but what if I wanted to get rid of physical keys all together? All equipment (more than just access control) is already on UPS, but that will last a short time. Odds are, if the power fails it will be while I'm at work (and when I get home the battery is dead). What I need is the ability to conserve battery until it's needed.

Main backup power will run its course in the event of an outage. When that fails, it transfers to a separate, fully-charged, switched-off UPS. This UPS is only connected to the access control system. A button is wired to the exterior that allows the UPS to be turned on temporarily so that doors can be opened.

Of course, some problems:

How to transfer from one UPS to another?
- An automatic transfer switch?
How to wire a button to turn it on?
- (Would have to find a UPS which supports this)
- Perhaps a different style of battery is more appropriate?
How to put it on a timer/protect it from external abuse?
- Like a NOPB timer

DPG · Jul 4, 2023

I wouldn't risk it. Keep a key as a backup.

plugsandsparks · Jul 4, 2023

With no key of course you are locked out for more than just a power issue, but any issue with the strike plate solenoid, wiring and control box. Unless you have an alternative access method (backdoor) which can be opened passively with a key i would not do it. Anyway, the access control box may already have a battery installed and they do tend to last a while, if you have one it is already in-line and will take over demand when the main UPS drops out. Just make sure that battery is in good condition and test it to see how long it runs, you can always increase this batteries capacity to get more time (limit will be the built in charger)
think the probability of a separate powered off UPS being any good when you need it is probably 50/50.
Sorry not answered questions you asked, just not something i have done, would do or would recommend doing.
cheers
P&S

tmontney · Jul 4, 2023

Somehow hadn't considered mechanical failure in the strikes, not sure how I would protect against that (aside from a physical key).

This discussion, as intended, is a good sanity check. However, still open to ideas if anyone else feels confident in suggesting it.

James · Jul 4, 2023

might be worth considering a mag lock on a back door that by default is fail safe in the event of a power failure instead of fail secure.
or even a mechanical code lock for it.
but i think you should really consider a fail safe way of entering the property in the event of everything going wrong.
its all about balancing security against the worst case of failure.
even if you keep a spare window pane in the garage for a ground floor window and a good size brick in the bushes it could work.

DPG · Jul 4, 2023

James said:
might be worth considering a mag lock on a back door that by default is fail safe in the event of a power failure instead of fail secure.
or even a mechanical code lock for it.
but i think you should really consider a fail safe way of entering the property in the event of everything going wrong.
its all about balancing security against the worst case of failure.
even if you keep a spare window pane in the garage for a ground floor window and a good size brick in the bushes it could work.

And put the brick behind an 'emergency break glass' pane. But a different pane to the spare window. I think.

SJD · Jul 4, 2023

As well as a fail-safe way of entering, make sure you have a fail-safe way of exiting in the event of a fire, e.g. if the proposed UPS goes up in flames!

freddo · Jul 5, 2023

Just today I attended a site where they couldn't get in as someone had set the electric doors to off mode from the inside, then left the building before the doors closed and locked permanently.