Confusing behaviour from gas fireplace

Question

I recently moved into a house with a gas fireplace. The fireplace did not turn on when I flipped the wall switch, so I started poking around to try to figure out what’s going on. I have absolutely no info on the fireplace and can’t really make out any model number or anything.

Most of the fireplace internals are blocked by brick unless I start taking things apart, but I was able to pull out the “Command Center”, pictured below.

This takes 4x AA batteries, all of which were missing. I added those, and when I click the “ON” button, everything seems to mostly work. The fireplace immediately beeps, I can hear the igniter ticking and I can see the pilot and main burners ignite. Everything stays lit.

However, things are more confusing when I hit the “OFF” button. When I first hit it, a few things happen:

• The fireplace immediately beeps
• I hear a ticking noise as if it’s trying to ignite
• The fireplace stays lit

Aside from the beeping and ticking, nothing actually changes with the flame.

If I hit the “OFF” button again, I see this instead:

• The fireplace beeps (like before)
• The fireplace ticks (like before)
• The fireplace goes off
• When off, the LED on the Command Center blinks red every 10 - 15 seconds

This behaviour is repeatable. When the fireplace is off, I can consistently turn it on and then back off, but only after hitting the OFF button twice.

It seems fishy that I need to double tap the OFF button to turn off the fireplace, but this at least tells me that the fireplace is functional in some basic way.

What’s confusing me now is how the wall switch fits into any of this. All of the behaviour above is completely identical regardless of the position of the wall switch. However, the wall switch does seem to do something:

• The LED on the Command Center lights up solid green when the switch is on and stays off when the switch is off.
• The LED still blinks red every 10 - 15 seconds, but the position of the wall switch just changes the state of the LED during the rest of this interval
• Flipping the switch on does not ignite the fireplace if it’s off
• Flipping the switch off does turn the fireplace off if it’s lit, although the behaviour is slightly different than shutting it off from the Command Center. The flame goes out and the fireplace ticks, but it beeps after the ticking stops, unlike the button on the Command Center which triggers an immediate beep.

None of this makes much sense to me. The LED on the Command Center always reflects the state of the wall switch, so I don’t think there’s a wiring issue between the two, but it doesn’t seem like the switch is doing what it’s supposed to.

Just to confuse things further, all of my googling suggests that fireplace wall switches use low voltage signalling to control the fireplace. However, I took off the wall switch plate and see some things that would suggest otherwise:

• The switch wiring uses pretty thick wire (maybe 14 AWG?)
• My non-contact voltage tester goes off when I put it near one of the switch terminals. The tester is configured to it’s less sensitive mode (supposedly >70V)

That’s as far as I want to take things with the switch since I don’t want to electrocute myself. But I can’t find any references to a high voltage fireplace wall switch, so this is just confusing things further for me.

At this point, I’m probably just going to call a fireplace technician to come and take a look. But if anyone knowledgeable about fireplaces have any ideas, any help is appreciated.

UPDATE

I found a few metal plates under the fireplace with a bunch of extra information. Here's information about the fireplace itself:

I also found these operating instructions for the Command Center:

These instructions don't describe the behaviour of the wall switch, but the beahviour of the fireplace is correct if I follow these instructions.

Finally, there's this pretty vague wiring diagram:

This at least shows the optional wall switch, but it doesn't provide much in the way of details. It shows a connection between the wall switch and...the cable between the Command Center and main control board? There's nothing spliced into the cable between the Command Center and control board, so I don't think this wiring diagram is particularly accurate.

The diagram does label the ON/OFF buttons as "ON/HI" and "OFF/LO" though, so that might be a hint as to why I'd need to double-tap the OFF button to turn things off. Maybe the controller supports a two-stage burner but the fireplace only has one connected.

Answer 1

After finding the model number and looking through the manual, I think I've figured this out. This probably won't help anyone else, but here it is.

The manual included instructions for an RF remote control for the fireplace. The previous homeowners had left this little touchscreen brick behind in a drawer with no information, and as it turns out, after putting batteries in it, I saw that it was actually the remote for the fireplace. I can turn the fireplace on and off using it.

As for the wall switch...

Normally, this fireplace expects you to connect a wall switch to the Command Center, which remotely toggles the pilot/main burner on and off. This is what the wiring diagram suggests. However, this doesn't match the wiring I can see on the control board or the voltage levels I saw on the switch terminals.

It turns out that the wall switch is completely unrelated to controlling the main operation of the fireplace. Looking at the wiring diagram, the fireplace has an AC module, which is connected to 120V power. It seems like the main purpose of this AC power input is to turn on some light bulbs inside the fireplace when it's lit. I'd guess that the valves and igniter also use AC power if it's available, but it looks like like batteries in the Command Center provide enough power for the fireplace (without lamps) to still work if mains power is off.

I'm pretty sure the wall switch just toggles this AC input. The lights can be configured on or off through the remote, but when I wrote the original question, they were configured to stay off even when AC power is available. After reconfiguring this through the remote, the fireplace works fine with the switch in either position, but the light bulbs only turn on when I light the fireplace with the switch in the on position. The green LED on the Command Center is just a status indicator for whether or not AC power is available.

The only remaining mystery is why turning off the wall switch stops puts out the fireplace if its lit. I'm guessing this is a safety / electrical thing (e.g. you can't light the fireplace using AC power and then switch over to the DC battery backup without turning it off in between) so I'm not too worried about it.