Forced-air Furnaces: The What, Why, and How

Tech connections has what you're looking for: ▶ this video Efficiency wise, the comparison between a heat pump and a furnace depends on the outside temperature. Heat pumps lose their efficiency for high ∆T, so for winter in a Russia, a furnace is likely the better option

For a full on description of how a good portion of furnaces, tech connections made a video not long ago: ▶ this video

Yes, they do need need electricity. Source: I live in Ontario, Canada, and am currently being kept warm by one. Most (gas) furnaces are forced air, and how exactly would the fan run without electricity? How do you think the thermostat runs its thermistor (and probably LCD display) without a power? The Technology Connections YT channel has a recent good overview, "Forced-air Furnaces: The What, Why, and How": * ▶ this video As for efficiency, you can get units that are 99% efficient (AFUE): * link * link

Technology Connections did a video (because of course he did) on how gas furnaces work. The short of it is that the flame is contained inside of metal tubes and never mixes with indoor air. No exhaust gases can leak into the breathable air. ▶ this video

> It's not supposed to be sealed, it's just supposed to have draft. It depends on the model. High (>90%) efficiency, condensing furnaces are completely sealed off from the house: they take in air from the outside (via PVC pipe), combust, extract the heat, and exhaust the results (via PVC pipes). * ▶ this video Older lower efficiency (<85-90%) furnaces suck in air from the house, exhaust into metal pipes (PVC would melt because not as much heat is extracted from the fumes), can be back-drafted and you have to worry about CO. Basically: if the furnace has vents in which you can see a pilot light, it's the older style.

Modern gas furnaces use the outside atmosphere for combustion. It helps get them high (for gas) efficiency levels! ▶ this video