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Comment by tw04 | Hacker News Reader

>I don't think any lost heat (most have gas) but at least one person found their gas fireplace they were hoping would heat them up when out of power didn't really work that well.

I'm curious how they didn't lose heat. Any furnace built in the last 30 years, even gas, has an electronic control board in order to ensure it doesn't accidentally turn on the gas without a functioning pilot light and/or heating element (which would blow up your house).

No electricity = no heat, regardless of natural gas supply.

I've got about a dozen coworkers in Texas, they've all been without power (which means no heat) for two days now. The power comes on long enough to at least warm their houses up to 50ish degrees before dropping back out so they're not completely screwed but I know they're scared.

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The big issue isn't just the control board-- most forced-air furnaces (at least, of the type used in the southern US) use an electric blower to actually distribute hot air to the rest of the house.

End result's the same, though-- no electricity = no heat, regardless of natural gas supply. (But, at least in this case, a relatively small generator can provide enough power to get the furnace up and running and heat the house; the electric furnaces and heat pumps that are most common in places like Texas would need something quite a bit beefier to run without grid power).

This is one reason why a gas fireplace is a great thing - even without electricity, you can at least heat half a room.

My gas fireplace still requires electricity to run. I know I can start it with a match if needed (and it has a pilot of course) but I'm not 100% sure if I can manually override the gas valve to open. It opens when I flip an electric switch.

Does it? Mine opens when I flip an electric switch, but it's self-powered via a thermopile on the pilot-- no AC connection whatsoever.

Some other models (from the same manufacturer as mine) don't have a standing pilot, but either use a battery as the primary ignition source, or use AC power but take batteries as a backup.

I've seen both styles. If it is a regular switch in the wall it uses mains to open the valve. If it has a switch on it, or a thermostat on the wall it probably is thermocouple powered. Though there are exceptions both ways.

Even with the switch on the wall nothing is certain. See my sibling post to parent. We had a wall thermostat but all it did was send a trigger current. If the thermo pile wasn't generating enough current nothing would happen :)

Sooo many different systems and many are just not well thought out. Especially in climates where it usually doesn't matter.

Here in Quebec it does matter so the one we have works in all conditions with various levels of manual intervention. We don't even have the one with a battery operated fan but even that exists.

Try it. I was confused the first time I used ours when the power was out. That switch still worked.

My gas fireplace has a valve mounted flush with the floor. You use a special key-like wrench to turn it on.

Even with the valve barely open you have maybe 3 to 5 seconds to get it lit in a normal fashion. Heh mess around too long and you’re in for a big woosh and plenty of singed arm hair.

Being close to the gulf a lot of people have generators that are likely big enough to power at least their fridge and one or more window/portable AC units. (For hurricanes.)

That size is usually big enough to run a blower and control board (and maybe a few other circuits), but it wouldn't come close to powering an electric heating element. But having a gas heater makes it all doable.

That's what we do, anyway.

Though with a generator that big and some ingenuity you can plumb the radiator into the house and get heat from the engine. The more load on the genererator the more heat.

Schemes like that are generally how CO poisoning stories start. Or fires. A door gets cracked to run a hose through... etc.

Besides, at some point, you're just reinvinting an overly complicated combustion heater.

Which I already have, is already hardwired for fuel, and only needs to be plugged in.

Very much true. I didn't touch on safety which is a real issue.

That doesn't make the idea bad though. There have been attempts to do this in commercial furnaces before, but the details are hard, and ultimately of questionable value in general. In this particular situation it might be useful, but that is a lot of complexity for something that only makes sense for a week every 10 years.

Maybe not a heating element, but heat punp?

Heat pump efficiency drops a lot when the temperature goes significantly below zero celsius

It's more an explanation of how you can have gas heat without power. Also, even heat pumps use a heating element at some point below 28~30 degrees. If you rely on the pump only below that, it'll start to freeze up into an ice block itself at some point.

Plus having a continuous plug-in (natural gas) fuel source is a big advantage over refilling a gasoline generator, which most portable generators are.

> No electricity = no heat, regardless of natural gas supply.

You're confusing furnaces and fireplaces.

A fireplace is soemthing that sits in a living space usually with a visible flame behind glass and is designed more for aesthetics than function. They typically run using a millivolt valve for the gas supply, with the voltage generated from a thermopile sitting in the pilot flame. They're often controlled by a regular light switch or a simple two-wire mechanical thermostat.

There's natural gas and propane models, and they'll run so long as you have gas flowing.

I upgraded mine to use an older wifi thermostat, but kept a light switch on a small cable underneath so I could always use it in case of a power outage, and it's come in handy a couple times. [1]

Mine also has a mains-powered blower fan built in (that's the plug on the left), but electrically it's completely separate and controlled by its own thermostat. It turns on when a certain temperature is hit -- usually about 5-10 minutes after the fireplace is on -- and stays on for some time after the flames are off. Obviously the blower doesn't work when there's a power outage but the fireplace still generates a usable amount of heat for the room.

On the other hand, my gas forced-air furnace -- which distributes heated air via ducts around the house -- is, as you describe, entirely useless without electricity. Even if it was running without the main blower fan, it would just be heating up the air sitting in the duct coming out of it. At best it might get some heat into the house via convection but I suspect it would cut out on thermal overload before actually doing anything useful.

[1] https://i.imgur.com/secdqaR.jpg

They used go make furnances that didn't have a blower, hot air raises which gives circulation. You need bigger pipes and can never get high efficiency (went out of style before about 1960 is my guess ). If the furnace looks like it belongs in a horror film it might be this style.

For a full on description of how a good portion of furnaces, tech connections made a video not long ago: https://youtu.be/lBVvnDfW2Xo

I have a gas-only fireplace less than 20 years old that does not require power to function. There's a mechanical spark generator for lighting the pilot, but in colder months I keep the pilot on all the time. I believe the opening/closing of the valve for the gas to the main flame area is powered by a thermopile once the pilot is on.

Maybe it's changed lately, but most of the medium sized gas heaters (thinking fireplace inserts, fake wood stoves, etc.) have a feedback loop where the pilot light heats a thermocouple that opens the pilot light valve, plus a thermopile for opening the main valve when the thermostat switch closes. The fan won't run, but you'll still get radiant heat without main electricity.

Good question. I am unclear about heaters but I do think some of them are out for some team members and you may be right on that. Ovens also are commonly gas but ones since 1990 require an electric light. But... stovetops which are gas do not require electronic ignition. The risk is of course carbon monoxide poisoning; hopefully you have such detectors as part of your in-home fire detectors.

The problem is not so much the deliberate rotating blackouts who can get restored after a time, but large groups of people for whom power is out due to some other weather-related outage issue; there are large swaths of them in Houston at least according to the Centerpoint Energy outage map which distinguishes between the two (but does seem to be not the most timely updated data per various people I have talked to whose status has changed during today: http://gis.centerpointenergy.com/outagetracker/ )

My gas fireplace had a place you could put in D batteries to run it. Pretty cool feature if the power goes out.

Having grown up with wood fireplaces, the thought of having to change the batteries to turn it on is hilarious.

This seems to be a problem specifically with whole house furnaces. I don't quite get why but I'm guessing cheap companies. Our gas fireplace has no such problems. Piezo electric knob to start the pilot (like your Coleman camping stove but it actually works - ask me how I know) and the pilot generates the electricity needed to actually let the gas flow. If the pilot isn't able to generate the electricity to open the gas valve then no gas ever enters the burn chamber. Again ask me how I know - yes those things gunk up and then can't supply the current you need to open the valve. Easy fix tho. Zero electricity needed and the upstairs stays warm. Also no cold air sucked into the house. The whole system is closed off towards the house. Love this thing!

"No electricity = no heat, regardless of natural gas supply."

For the furnace yes.

The gas fireplace and gas ovens/stoves though probably don't need electricity.

I haven't seen a gas oven that can work without electricity. A gas stove, yes, you can simply turn on the gas and quickly use a kitchen lighter to ignite the gas manually and hope not too much poisonous gas escaped the stove. But ovens? How?

Many gas ovens (and stovetops) work just fine without electricity thanks to pilot lights.

Older gas ovens used a standing pilot light. They would work without electrical power. Really old ones you light with a match.

My kitchen has a gas range, the oven uses electical resistance/incandescent ignitors so it won't work without electrical power. The top burners have spark ignitors but of course I can light them with a match.

The gas oven in my apartment has a pilot light that is always on, no electricity needed.

It's not poisonous.

Gas heaters still require electricity for basic management.

I'd imagine heaters have batteries for specifically this case. If they don't, it's frankly a miracle if we don't lose anyone, and someone needs to get prosecuted.

gas furnaces do not have batteries.

That's a failing of gas furnaces. I don't know why you'd design a system without them except to breed dependency.

We're talking about forced air furnaces here, I think. Something has to force the air. A big blower motor that takes hundreds of watts.

Forced air heat is not great in terms of comfort, but in Texas you already have all the ductwork and the blower motor and so on for AC, so it's simplest just to add a gas burner to that.

Furnaces don’t come with batteries because a 12v 100Ah battery that costs $180 will run a 1/3rd HP (700w) fan for 2 hours. To sustain the fan for 3 days, you’d need 36 batteries. Lead-acid batteries have a limited lifespan. You would also need a transfer switch and enclosures and at that point you may as well buy a UPS or a natural gas generator to provide backup power.

One thing the NEC 2020 update allowed is bi-directional power between an EV and its charger, you can set up an EV to provide backup power your house, with a transfer switch and everything.

Radiant heating systems with boilers require electricity for the pump, even if they’re gas fired. Electric resistive heating needs electricity. Forced air heating needs electricity to run the fan. All heating systems require electric power, even if the heat is generated by burning natural gas.

The real question is why gas furnaces don't also have their own generators built in

I wasn’t aware, but these actually exist: https://en.m.wikipedia.org/wiki/Micro_combined_heat_and_powe...

Why would you use car batteries? Seems like a terrible fit for the job of daily charge and discharge.

What? A backup battery for a furnace doesn't do anything daily.

It is not feasible to run a gas furnace off a battery (short of a "whole house" battery like a Powerball). It's more than just basic management. You need to run either a blower or a pump to distribute the heat throughout the house. You'd need a substantial battery to run a 1/3 HP motor for any length of time.

Ahh, I see, power companies have simply failed their customers and certainly will receive their commupance.

A gas boiler furnace with steam radiators typically only requires power for the thermostat and solenoid valve, which can indeed be powered by a small battery. This is assuming you have a pilot light, which many older furnaces do.

Residential steam boilers are pretty rare these days. Generally hot water heat uses circulation pumps (which draw less than a forced air blower, but still have a non-trivial continuous current draw)

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