I had my old fireplace damaged in a storm which resulted in its hasty removal and an ugly patch to cover the hole. I've been shopping for a replacement off and on since but it seems I'm running into difficulty in finding what I want because I don't know the names of certain features and parts. I'd like to do as much of the work as possible myself, or at least have the correct vocabulary when talking to contractors.
What I want is mostly what I saw in my brother's old house, a fireplace that can be turned on and off with a switch but required no power source to do so. The one change I would make is that instead of a manually controlled switch I'd put in a temperature controlled switch. Perhaps that's the first bit of vocabulary to discuss, a temperature controlled switch is a "thermostat" (obviously) but apparently there's no consistent naming convention on what it means to be able to add a thermostat of my choosing as opposed to having a thermostat bolted in. Or, is there a name for this but I haven't seen it yet?
There's two goals here. First is a matter of comfort, it would be nice to have supplemental heat on the north end of the house when the cold north winds blow. Second is a matter of safety, if the winds blow strong enough to take down power lines then I want a heat source that doesn't require electricity, batteries, or any other consumable but natural gas. I'd set the fireplace thermostat a few degrees below that of the furnace so that if the power goes out, or the furnace can't keep up for some reason, then the fireplace turns on all it's own. I'd still want to be able to turn the fireplace on with a manually controlled switch, temporarily overriding the thermostat, but I can figure that out easy enough.
The fireplaces with a thermostat in them will measure the temperature at the fireplace or where the remote control (which will need batteries) is placed. I want to put the fireplace thermostat next to the furnace thermostat so that the two are less likely to disagree on what the temperature is (or should be) in the place, and so I can control both without even having to think about where one or the other is located as they are both in the same place. This means finding a fireplace that can be controlled by a thermostat but has none already bolted in, or as part of a remote control with batteries, so I can add one of my own that doesn't require batteries, is there a consistent naming convention for this feature?
There's apparently three kinds of thermostats, 120VAC/240VAC capable or "line voltage", 24VAC or "low voltage", and "millivolt". It appears I want the millivolt kind of thermostat and fireplace as those are the kind that don't require batteries or utility power. I can find millivolt compatible thermostats all day but rarely any fireplaces. Is there another name for this feature other than "millivolt" I should be looking for?
The device that produces the millivolts is apparently called a "thermopile" or "thermocouple", but is there a distinction between the two or is it just two names for the same thing? It appears most fireplaces with a thermopile produce 750 millivolts but do all of them produce the same voltage? I suspect the voltage varies some but it looks like this is a nominal 750 millivolts, much like a 24VAC system is nominally 24VAC but could (like mine) actually measure closer to 28VAC.
Millivolts is not going to give a lot of margin for voltage drop so is there some ballpark figure on the maximum wire length? I realize this can vary by model but I would like to know if where I want the thermostat is even possible without resorting to something that requires external power. The "as the crow flies" distance between the fireplace and desired thermostat location would be less than 20 feet but with the wire running around corners and such under the floor and in the walls the wire could need to be twice that long. With such low power involved I assume typical 18AWG or 20AWG thermostat wire is acceptable, is that a safe assumption?
Since I want to avoid any need for power for the fireplace to run I want to avoid any need for a "power vent" like those seen on a high efficiency natural gas furnace. I'm seeing "ventless", "no vent", and "unvented", which I assume all means the same thing and indicates the exhaust from the flame is released into the home, is that a safe assumption or is there some distinction? I'm fine with not needing a vent since that should make installation easier and any humidity this adds to the home would likely be beneficial. There's "direct vent" but that might not work in my situation because of where that hole in the wall that used to contain a fireplace is situated. Other than "no vent", "direct vent", and "power vent" is there some other venting scheme I need to be aware about?
One last question, if there is a battery powered ignition built in to the fireplace does that mean I cannot light it with a match or something? I realize this will vary by model but the question is on if the presence of a battery powered ignition is generally a convenience or a necessity. My propane grill has such an igniter but it never works so I just use a match, I would think a fireplace is much the same. I don't want to be faced with losing the kingdom (as in freezing pipes causing damage) for want of a nail (no working alkaline cells to be found).
I know that's long but I've found that without plenty of background I get more questions than answers. I tried to give an answer to any question I'd expect to be asked so there's no debate on X vs. Y solutions and such.
