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Power Budgeting for Sensors

jmistler

Member
This is my first Elk install. Working on power planning.
 
My setup:
 
Elk-M1G
Elk-M1XEP (P1216 power supply)
Elk-M1XSLU (.031A)
Elk-M1XOVR (.33A)
Elk-M1DBH (0A)
Elk-120 (1A)
Elk-M1TWA (1A)
Elk-WSV2 (1A)
(10) GRI-2600 water sensors (.01A)
​(1) Sentrol garage door sensor (.25A)
(9) Tane Pill, SBT10 window / door sensors (.5A)
 
The current draw worksheet has me at nearly 9A. I thought my setup was pretty small compared to what I had been seeing from others on this forum, so I was scratching my head. Some questions:
 
1. Those door sensors seem like they draw a HUGE amount of power @ .5A each.  Is that what everyone else is finding with door sensors?
2. In order to stay under 1A for my main board, it seems like I will have to put the Elk-TWA, Elk-120, Elk-WSV2 on aux power (which seems in line with what everyone else is doing) but will I also have to power all of my sensors from aux power?
3. If I do have to power the sensors from aux power, does that mean I need to add an M1XIN and hook them all up to that, leaving the M1G inputs empty?
 
Thanks!
 
 
 

RAL

Senior Member
The door and window contacts that are connected to zone inputs do not draw any power.  You are mistaking the current handling limit of the switch contact for power draw.  It's just the maximum current that the switch contact can handle.
 
Things like motion detectors, glassbreak detectors and the GR2600 sensors do draw power.
 
If you are powering the M1XEP off of the P1216, you do not need to count the M1XEP in your power calculation.
 
You SHOULD include any keypads in your calculation.
 
Still, from the other items in your list, you will be needing an aux power supply.  I'd recommend something like from the Altronix AL400 series. This should be just enough to power the XEP, Elk 120, TWA and WSV2.  If you think you might be adding more in the future, you could add a second AL400.
 
One other thing to be careful with is sizing the backup batteries.  You want the M1's battery to run out of power before the aux batteries.  The M1 won't be happy if the aux batteries die before the M1 does.
 
You do not need to connect sensors powered by aux power to an M1XIN.  They can connect to M1 main zones without any problems.  But you should connect the NEG/-12V terminals of the M1 and aux power supply together.
 

jmistler

Member
Thank you so much. A few related questions. First...
 
Am I thinking correctly that, in order to install the TWA (using J16) and have two or more relays also connected to the system (beyond output 3), I would need to add an M1XOVR?  An M1RB would have no way to physically connect to the main board, right?
 

RAL

Senior Member
jmistler said:
Thank you so much. A few related questions. First...
 
Am I thinking correctly that, in order to install the TWA (using J16) and have two or more relays also connected to the system (beyond output 3), I would need to add an M1XOVR?  An M1RB would have no way to physically connect to the main board, right?
Yes, you would need to add a M1XOVR.  That will give you 8 more voltage outputs plus 8 more relay outputs. If you wanted them all to be relay outputs, then you would connect a M1RB to convert the 8 voltage outputs to relays.  Another way to convert the voltage outputs to relays would be to use the voltage outputs to drive individual relays, like an Elk 912 or 924.
 

jmistler

Member
Regarding the Altronix AL400ULX...
 
If using that to power the XEP, Elk 120, TWA, and WSV2, would I need to add an Altronix ACM4CB to distribute it to out to each one?
 
What about this low battery cutoff issue I have been reading about?  Altronix LPD necessary?
 
Any other devices or connectors to make that auxiliary power work smoothly?
 

RAL

Senior Member
Adding a LPD to cut power from the batteries is a good thing to do.  Otherwise, nothing prevents the batteries from being drained below 10.5V, where it can cause damage to the batteries. I've wondered why Altronix didn't build that into the design of the power supply.

There are a whole bunch of AL400 models, which are mostly based on the same power supply board - the AL400ULXB2. They then customize things by adding output distribution boards for particular functions.

The ACM boards are meant for access control applications, such as electronic door locks. You don't really want an ACM model.  But if you can find one at a bargain price on eBay, it might be worth it, as you can disable the ACM functions and use it as a simple distribution board. It just takes more effort to understand the configuration options.

Rather, you should get a power distribution model, which has a PDx or PDxCB suffix. The plain PD boards have 4, 8 or 16 outputs, each of which has an individual fuse. The PDxCB boards use PTCs instead of conventional fuses. It might seem like a nice idea to have a PTC that resets itself without having to replace a fuse. But blown fuses are easy to spot, while it takes a bit more work to find which PTC is having problems. Overall though, blown fuses should be a rare occurrence.

So, I would recommend one of the models below, with the CB models as a second choice. The ULX models have a larger/deeper enclosure which can accommodate larger batteries as well as the additional PDx board.

AL400ULPDx
AL400ULXPDx
AL400ULPDxCB
AL400ULXPDxCB
 

RAL

Senior Member
jmistler said:
Regarding the Altronix AL400ULX...
 
If using that to power the XEP, Elk 120, TWA, and WSV2, would I need to add an Altronix ACM4CB to distribute it to out to each one?
 
What about this low battery cutoff issue I have been reading about?  Altronix LPD necessary?
 
Any other devices or connectors to make that auxiliary power work smoothly?
Just to add one more option... if you just get a plain AL400ULX, without any power distribution board, you can simply connect the output of the power supply board to all your device wires with wire nuts, Wago connectors, or terminal strips.  This won't give you any fused protection, and if one device fails, it will take them all down, rather than blowing a single fuse.  
 

jmistler

Member
If I went with an Elk-P412, could I connect each of the three devices (Elk 120, TWA, and WSV2) to an individual power terminal?  Are these power terminals functioning exactly like a distribution board, or is there some limitation?
 
Can the Elk-P412 be recess mounted or does it have to be surface mounted (like the Altronix AL400ULX)?
 

RAL

Senior Member
jmistler said:
jmistler, on 18 Sept 2020 - 01:20, said:
If I went with an Elk-P412, could I connect each of the three devices (Elk 120, TWA, and WSV2) to an individual power terminal? Are these power terminals functioning exactly like a distribution board, or is there some limitation?

Can the Elk-P412 be recess mounted or does it have to be surface mounted (like the Altronix AL400ULX)?
The P412 is similar to the Altronix AL400 in that it has a power supply plus a separate distribution board. The P412 distribution board has just 3 outputs vs 4 on the AL400. Each output is protected by a PTC.

It's designed to be surface mounted, like the AL400.

One advantage of the AL400 is that it has AC Fail and Battery Fail outputs that allow it to be monitored by the M1 using zone inputs. That will let the M1 know if there is a problem with the aux supply. The P412 has no equivalent outputs.

The closest thing that Elk offers is the P212S, which can be monitored via the data bus. But its only a 2A supply.

The AL400ULPD8 can be had for about $25 less than the P412.

https://www.zoro.com/altronix-power-supply-8-fuse-12dc35a-or-24dc3a-al400ulpd8/i/G6570846/

https://www.homecontrols.com/Elk-DC-Power-Supply-Battery-Charger-ELKP412


Here's one on eBay (brand new) for under $155. $60 less than the P412.

https://www.ebay.com/itm/Altronix-AL400ULPD8-Power-Supply-Charger/333671843089?hash=item4db0644511

And here's a used AL400ULPD8CB for under $45 that looks to be in very good shape: I rarely see them for such a low price.

https://www.ebay.com/itm/ALTRONIX-AL400ULPD8CB-12-24vdc-POWER-SUPPLY-CHARGER-8-OUTPUT-UL-LISTED/202900713944
 

jmistler

Member
Thanks for the detailed response.
 
I am safe to assume that there is no code-compliant way to recess mount either the AL400 or the P412?
 
Could I mount 2 P212S boards inside the Elk enclosure to achieve the recess mount I am looking for? (and pay extra vs. the other solutions)
 
Does each P212S need its own battery, or could I connect more than one P212S to one battery?
 

RAL

Senior Member
The covers for both the AL400 and P412 are hinged on the side.  To recess mount them, you would need to come up with a way to mount the enclosure so that about 3/4" protrudes from the wall to allow the cover to open and close.  

The power supply generates a modest amount of heat.  The AL400 enclosure has ventilation holes on the side to allow the heat to dissipate.  The Elk enclosure provides no ventilation.   I guess Elk thought it wasn't significant enough to worry about with a surface mount enclosure.  Recessing either one could make it more difficult for the heat to escape.  I can't say for sure whether that would violate any building or electrical codes.  
 
The P412 comes with a traditional power cord.  If you recess the enclosure, you would have to run part of the cord behind the wall.  That would be a violation of the NEC.  Looks like the supply has screw terminals where wire from a romex could be connected instead, so easy enough to make that change.
 
You can't share batteries between power supplies.  Each supply has its own charging circuit and wants to be in control of the batteries.   If you connect two supplies to the same battery, they will fight each other.
 
I don't think it would be possible to mount two P212S boards in the standard 14" M1 enclosure along with the M1 board.  You would need 3 batteries, and there just isn't room.  It would be a tight fit to add just one P212S along with its own battery.   You might be able to do it in a 28" enclosure, depending on what else you need to put in the can.   But even that would get crowded with at least 3 batteries in there.   Another option would be to get a On-Q/Legrand or Leviton 42" structured media enclosure to give yourself even more room.  The downside of those is that you lose the pre-drilled mounting holes that the Elk has for the circuit board glide brackets that allow you mount boards on edge. And I'd recommend a mounting plate like the Legrand  364715-01 to mount the M1 in the those enclosures.
 
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