Hardwired Power Supply for Elk

[felixrosbergen]

Hi All,

Is there a good alternative to the 'wall wart' power supply that comes with the ELK M1?

I understand that the Elk needs 16.5v (seems unusual voltage but ok).

Also does one typically need additional 12v power supply for the various Elk addon modules or do they all get powered from the Elk?

Has anybody used an industrial grade power supply hardwired to the breaker panel? I am concerned about the quality of the Elk power supply since it has such a critical role in the whole system.

Am i being overly anal? Have elk power supply failures occured?

Any way to make the power supply redundant?

Felix

 

[Sandpiper]

Am i being overly anal?

In a word.....YES.

All 12VDC (nominal) systems need 16.5 VAC, so this is not unusual at all. The AC is converted to DC so that it has enough voltage to charge a 12VDC battery. 12VDC batteries actually take around 13.9 VDC so there are many factors involved........

The AC power supply (wall wart) is very robust and not prone to failure unless it is overloaded, but for normal systems this is not a concern. You can supply your own AC source if you wish, it just needs to be 16.5 VAC at between 20 and 82.5 VA. The VA rating is important in order to provide the Class 2 rating necessary for "Power-Limited" circuits (NEC article 725). To maintain code requirements, you need to use a Class 2 transformer.

The ELK will provide 12VDC for additional equipment, but at a 1 amp maximum current. If you have additional needs, you can provide your own power supply to power these. Connect the "common" sides of the power supplies together , but not the "+" sides. You probably don't need this though, unless you have a large amount of devices. There are many other posts in this forum on this topic.

Redundancy is possible, but I don't know why you would want this. In effect, the battery backup is your redundancy, and you get notification if the primary supply is lost. Supplying redundant AC power seems to me to be overly complicated for this type of system. And my hunch is that the redundant system would actually cause more outages that it would ever prevent.

KISS..........Keep It Simple, ********

 

[BraveSirRobbin]

I don't own an Elk but let me address some of your questions.

The AC wall wart in the Elk feeds the system, but it also charges a large battery in case the wall wart or AC power fails. If you want you could also use a UPS in your closet and plug the AC wall wart in it for increased backup performance. The wall wart as far as my knowledge is really just a transformer and doesn't have a lot of parts prone to failure. The Elk can also be configured to give warnings in case of a power failure as well.

The on board Elk system has a limited amount of power for auxillary devices such as keypads, glassbreaks, motion sensors, etc... This maximum supply current is listed in the manual. Each external auxillary device will show it's current draw in their instruction manuals. Just add up the current and make sure you don't exceed 90 percent of the rated current output the Elk main board can supply.

If your auxillary devices exceed this supply current, you will want an additional 12 volt supply. Elk makes great auxillary 12 volt power supplies each having their own respective battery backup in case of power failure. I'm a big fan of these supplies as they have enough intelligence to shut down on a short, then turn the supply back on when the short is removed. Again, you can plug this system in your UPS for additional backup time.

You will also want to use a 12 volt distribution box that has individual fuses of their outputs so the "full current" capability of this additional supply is not allowed to each of your auxillary devices. This way if one device shorts, it will not draw down the entire supply and you will also not have that supply's full current going through its wiring.

Of course, these are only my suggestions as there are many ways to implement your needs.

Edit: Didn't see Sandpiper's reply, but he said basically the same thing as my post

Edit2: Here are some links for you to browse:

http://www.elkproducts.com/products/elk-p112_p124.htm

http://www.elkproducts.com/products/elk-p412.htm

http://www.elkproducts.com/products/elk-pd9.htm

 

[felixrosbergen]

Hi All,

Thanks for the swift replies.

I'd like to expand the question a little bit with the following information:

My plan it to have the Elk and a PC/Server for automation software (likely Homeseer) in the same area. The PC/server would have UPS to support it for several hours.

Does the Elk have full function when it's running on battery or are some things disabled? Also with the expected running time with the 8ah battery?

I guess i don't reall understand why the elk does just take 12vdc, but i guess it's because of the battery charging function.

It is possible to just not use the wal wart and connect a 12vdc power supply to the battery leeds? The 12vdc power supply would be conected to the same UPS as the PC/Server.

I'm just kicking around a few thoughts....for some reason i cant' stand wallwarts....

 

[BraveSirRobbin]

Yes, you can do this. Refer to THIS thread and look at the post by Elk's Chief Engineer "Spanky"!

FYI he quotes using a 13 VDC supply:

In reality you can power the M1 from a separate DC power supply. Run 13 to 14 volts DC into the battery leads. Run a +13 volt wire from the +Battery input to one of the AC inputs so that the M1 will startup when the power switch is turned on.
I suggest using at least a 2 amp or larger power supply.

I'm not sure of the merrit of this though as you now have a DC power supply to worry about failing. I guess you could use two and diode sum them together...

 

[Sandpiper]

Does the Elk have full function when it's running on battery or are some things disabled? Also with the expected running time with the 8ah battery?

Yes. The Elk maintains all functions when on battery power. When the battery charges gets down to about 10 volts or so, the ELK will shut down to prevent damage to the battery.

The battery running time will vary from system to system depending on the number, size and condition of the batteries, how much load you have on them and other factors. However, to get a rough idea you can calculate it.

Batteries are specified by voltage, type and size in AH (Amp-hours). AH is battery load in amps times the duration of the load in hours. For example, an 8 AH battery will provide 1 amp of power for 8 hours, or .5 amp for 16 hours. This is nominal, of course, and is not exact. So depending on how many devices you have on the system you can calculate the hours.

For a typical system, the Elk controller uses .13 amps, a keypad .1 amp, and 2 motions at .025 each. Zones with contacts take about .003 amps each. So the total load would be .13 + .1 + .025 + .025 + 16* .003, for a total of .328 amps.

So 8 AH / 0.328 A = 24.4 hours...................this is typical. Yours may vary.