ELK Fireplace Control

[dutchyn]

We're installing two natural gas fireplaces, both for ornamentation and as redundant heating for our electrical geothermal system. The fireplace needs a 3-volt battery backup -- I figure the HA system can supply that on 2 wires, and the fireplace control offers a rocker switch attachment. I'm planning to wire an Elk relay in parallel to that switch, so that if the heat drops too much (based on the thermostat), the Elk can turn on the fireplace(s) and report the difficulty.

Comments? Suggestions?

Chris Dutchyn

 

[mustangcoupe]

Yes this will functionally work, and I believe has been discussed before. Just be careful, as to the ratings of current as you would with any other device. Also be secondly careful because you are working with fire in this case, and a fuel source.... what happens if the fire place does not ignite? does it have overrides for the fuel source?. If something should go wrong it could be fire and possibility loss of life should something go wrong while sleeping or not paying attention to the fireplace.

 

[dutchyn]

Just be careful, as to the ratings of current as you would with any other device.

Apparently it carries only 3V, and acts as an advisory input to the actual natural gas ignition controller.

Also be secondly careful because you are working with fire in this case, and a fuel source.... what happens if the fire place does not ignite? does it have overrides for the fuel source?

Good notes! I would hope that the natural gas fireplace controller would handle any of that. But, I will check with the manufacturer.

Chris D.

 

[dutchyn]

Also be secondly careful because you are working with fire in this case, and a fuel source.... what happens if the fire place does not ignite? does it have overrides for the fuel source?

I would hope that the natural gas fireplace controller would handle any of that. But, I will check with the manufacturer.

The manufacturer says that if I run their wiring through a relay on the ELK board, all is well. Now I need to ensure I can supply 3VDC to keep the fireplace controller running in case of power failure. The fireplace control has a plug for a 3VDC battery pack (2 "D" cells) that I intend to replace with 3VDC off the ELK battery. Can anyone suggest an appropriate transformer and circuit?

Chris D.

 

[BraveSirRobbin]

The fireplace control has a plug for a 3VDC battery pack (2 "D" cells) that I intend to replace with 3VDC off the ELK battery. Can anyone suggest an appropriate transformer and circuit?

You can use an LM317 Voltage Regulator if you are into some soldering and bread-boarding. I found this schematic which I modified below for converting 12 volt to 3 volt.

You can also use some board kits and possibly even this adapter (complete unit, but more expensive). (Look closer for these two suggestions as I just quickly Googled and glanced at them).

 

[dutchyn]

You can use an LM317 Voltage Regulator if you are into some soldering and bread-boarding. I found this schematic which I modified below for converting 12 volt to 3 volt.

It's been ages since I did any soldering! It'll be fun!

Thank you,

Chris D.

 

[BraveSirRobbin]

Just check the circuit out with a meter before hooking it up to anything first

Also, don't forget the TO-220 heat sink. I used this setup in one of my How-To's (shows some pics) although it was regulating a different output voltage.

 

[PaulD]

.... The fireplace needs a 3-volt battery backup --

Chris Dutchyn

I would assume the battery is for backup in case the electricity is off. If true, supplying the 3V by alternative means powered by electricty defeates the purpose of the battery.

 

[dutchyn]

.... The fireplace needs a 3-volt battery backup --

I would assume the battery is for backup in case the electricity is off. If true, supplying the 3V by alternative means powered by electricty defeates the purpose of the battery.

Your assumption about the 3VDC powering the fireplace ignition controller during a power failure is correct. Your apparent premise about the alternative means being supplied by mains voltage (120VAC) is incorrect. I need a 12VDC to 3VDC convertor (not 120VAC to 3VDC) because I intend to draw the 12VDC from the ELK-1280 battery that will keep the rest of the home automation running for several hours during a mains outage, and automatically recharge when mains is restored. So, I believe this approach is actually beneficial, compared to worrying about whether the "D" cells are charged.

But, this does lead to another question: typically how long will an ELK-1280 keep an M1, one M1RB, one M1XOVR, three M1XIN, an M1TWI with two speakers, and three M1XSP running? Since we're in a low population density, semi-rural area, we'd be low on the "restore power" priority list.

Chris D.

 

[BraveSirRobbin]

I didn't realize the three volts was 'just' for backup and not continuous draw. Is it really worth the trouble and effort to have this backup off of the Elk battery?

As far as your battery backup time you can do a guesstimate, or more accurate measurement calculation.

The battery supplied with the Elk is eight amp hour. This means it can supply an eight amp output draw for one hour. If you know your total draw you can simply calculate the backup time in hours by 8 amphr/amp draw. I really don't like to take a battery under 50% of its total capacity (so it will be able to recharge/recover).

You can get a 'good guess' of your current draw by simply adding up all the component's current draw attached to the Elk (include the Elk unit itself). This should be listed in their manuals under 'specifications'.

Another method would be to measure the current off of the battery while the Elk is unplugged from its AC source. If you have a lot of sirens/strobes/etc... you may want to measure this current in an alarm condition. Be aware though your 'alarm condition' draw would depend on the timeout of the siren feature via the Elk's settings.

An easy way to increase the backup would be to get a larger battery. Another would be to purchase a UPS unit and plug the Elk M1 into that.

 

[dutchyn]

I didn't realize the three volts was 'just' for backup and not continuous draw. Is it really worth the trouble and effort to have this backup off of the Elk battery?

It's just two wires, and because of redundancy, they're already there. In addition, our heat comes from geothermal and it gets cold here (-40 or lower) in the winter. We want to press the fireplace into service as emergency heat in case electricity fails.

As far as your battery backup time you can do a guesstimate, or more accurate measurement calculation.

So 8 Ah = 96 watt hours @ 12 volts. I estimate nominal usage for all of the items (I/O devices, smokes, motion sensors, keypads) is 18 watts (1.5 amps), and maximum (speakers) is 104 watts (8.6 amps). That means I should expect nominal battery backup to be more than 5 hours, and worst case to be almost an hour. With the larger battery I get 16 hours and 3 hours respectively.

I really don't like to take a battery under 50% of its total capacity (so it will be able to recharge/recover).

So, if it discharges more than 50% it won't recharge!? Really?

Chris D.

 

[Lagerhead]

Another method would be to measure the current off of the battery while the Elk is unplugged from its AC source.

The M1G has a built-in voltage and current readout accessible from the keypad. I know this does not help your planning, but it is a handy feature after you have the M1 installed.

 

[Lagerhead]

it gets cold here (-40 or lower) in the winter

Is that Fahrenheit or Celsius?

 

[gatchel]

it gets cold here (-40 or lower) in the winter

Is that Fahrenheit or Celsius?

It's funny. I actually think that -40 F and -40 C are the same thing. (If I am remembering correctly from HS science...)

 

[Lagerhead]

it gets cold here (-40 or lower) in the winter

Is that Fahrenheit or Celsius?

It's funny. I actually think that -40 F and -40 C are the same thing. (If I am remembering correctly from HS science...)

Exactly, that's why I thought the question was funny. The answer of course is "both."

I have a close female relative, who shall remain otherwise unidentified, who having this information, then asked "And where are they equal on the positive side?" :lol:

Ok, ok -- not everyone's an engineer or quick with math.