wmartin@brl-tgr.ARPA (Will Martin ) (02/02/85)
In the light of the recent postings about automatic thermostats, I have a question about the operation of gas-fired furnaces when there is no electricity due to power interruptions. At this time of year, we often see or read news stories about this or that area losing electrical service due to storm or ice damage, and the loss of heat in the homes in that area forcing people to community shelters or emergency relief centers. I would think that anything that can be done to reduce vulnerability to such failures would be desirable. For those with electric heat, or hot-air gas or oil heat requiring electrically-powered blowers to distribute the warmed air, or for those with forced hot water heat, where an electric pump is necessary, or for oil burners that require electric oil pumps, there is no question that the loss of electricity destroys the capability to heat the residence. Only a temporary generator or restoration of electricity will help in those cases. However, for gas-fueled hot water or steam systems which do not use a pump, the ONLY function of electricity is to run the thermostat. This is a trivial usage, yet the system will not work if there is no electricity. I would think that there should be a method of "working around" the loss of electricity for these heating systems. My first thought is to simply attach a car battery in place of the transformer connections that link the heating system to the electrical mains. This would only be a temporary expedient, though. That battery would have to be recharged somehow, not an easy task when there is no power. What I would think would be a better backup system would be a completely mechanical one. It would not have any thermostat, but operate on a time basis. For example, an air-delay dash-pot unit would allow gas to flow for 15 or 30 minutes after manual setting. If the residence has warmed enough by then, you simply don't re-set it until some time passes and the house begins to cool again. If it hasn't warmed up enough, you re-set it and get another 15-30 minutes of heat. Yes, this requires constant manual attention, but that is also a safety feature. The idea is for it not to run unchecked and get too hot. It's no different in principle from having to stoke the coal furnace (which I recall doing as a child). Does anyone know if such a non-electrical system is available, either as a stocked item, or could be assembled from stock parts? Could such a backup system be installed for swich-over use without violating building codes? It would require parallel gas connections to the furnace, one going through the electrically-controlled normal path, and one going through this separate manual-control system (since the elctrically-run path shut-off valve would be closed by the lack of power to hold it open). If this is infeasible, how about a method of bypassing the electrically- controlled portion of the heating system in emergencies? Is there a way to force open an electrically-controlled valve without damaging it, in the abscence of electricity? This hasn't happened to me yet, but it might. I'd like to be prepared, and it is galling to think that such a trivial thing as a control circuit being unpowered would render the entire heating plant useless. Regards, Will Martin USENET: seismo!brl-bmd!wmartin or ARPA/MILNET: wmartin@almsa-1.ARPA
brian@sdcc3.UUCP (Brian Kantor) (02/03/85)
> In the light of the recent postings about automatic thermostats, I have > a question about the operation of gas-fired furnaces when there is no > electricity due to power interruptions. > > However, for gas-fueled hot water or steam systems > which do not use a pump, the ONLY function of electricity is to run the > thermostat. In many systems in which the gas burner is near the thermostat (internal thermostats such as in water boilers, pool heaters, etc), there is a thermoelectric generator running off the pilot flame which provides enough power to operate the gas valves. If the thermostat were at some distance from the burner, the electrical resistance of the wires to the thermostat would play a significant part. And if your furnace is one of those that uses a high-voltage spark to ignite the burners instead of a pilot light, you're out of luck with the power off. Brian Kantor UC San Diego decvax\ brian@ucsd.arpa akgua >--- sdcsvax --- brian ucbvax/ Kantor@Nosc ``You unlock this door with the key of imagination...''
rib@cord.UUCP (RI Block) (02/03/85)
The system you descibed, one that requires no external source of electricity to maintain temperature already exists. The source of electricity is a thermocouple heated by pilot flame; the trade name for this is "Power Pile". There are also special versions of thermostats available with contacts designed for switching the 75 - 300 mv developed.
dwl@hou4b.UUCP (D Levenson) (02/05/85)
I have gas-heated fan-forced air heat. Electricity opens the gas valve when the thermostat decides heat is needed. Electricity also operates the blower motor, which is switched on by another thermostat, that senses sufficient heat in the furnace itself (generally about 30 seconds after the main burner has lit). Without electrical power, the furnace defaults to an off state. There is, however, a manual override control on the gas control valve, allowing me to light the main burner with a manual control. As the furnace heats, the air within it rises, into the hot-air plenum, and into the house via the normal distribution ducts. The old-fashioned "gravity-flow" hot air systems worked this way by design. It is less efficient than using the fan. Also, the safety devices which shut off the burner when the temperature goes too high are bypassed. In practice, it means standing by the furnace and watching it carefully (feeling it, smelling it, etc) for about ten minutes. Then turn off the gas. Hot air will flow slowly from most of the air registers for the next half hour or so. Then go downstairs and repeat the cycle. This works if the furnace is below the living space (in the basement) and if the furnace uses an upward air flow internally. Not terribly convenient, but far more convenient than being evacuated to a shelter while your house freezes and your pipes burst. I can maintain a temperature close to the normal set-point of the thermostat with only a few minutes per hour devoted to the job. It automatically lowers the temperature at night (which my old-fashioned thermostat only does if I turn it down) because I get up and run it less often! Dave Levenson AT&T-IS, Holmdel
dan@digi-g.UUCP (Dan Messinger) (02/05/85)
In article <7946@brl-tgr.ARPA> wmartin@brl-tgr.ARPA (Will Martin ) writes: ... > However, for gas-fueled hot water or steam systems >which do not use a pump, the ONLY function of electricity is to run the >thermostat. This is a trivial usage, yet the system will not work if >there is no electricity. I would think that there should be a method >of "working around" the loss of electricity for these heating systems. ... >What I would think would be a better backup system would be a completely >mechanical one. It would not have any thermostat, but operate on a time >basis. ... >If this is infeasible, how about a method of bypassing the electrically- >controlled portion of the heating system in emergencies? Is there a way >to force open an electrically-controlled valve without damaging it, >in the abscence of electricity? My house is heated by a gravity feed gas furnace. One of those old coal burners with a gas conversion unit stuck into it. (commonly known as the "octopus") Sticking out of the side of the control unit is a small knob, which when turned opens the gas valve, and low and behold, I have a warm house. Its not quite as safe as what Will suggests... Once turned on manually, it stays on. Its only safety feature is that the manual control will not stay in the 'on' position if the electricity is on. So yes, Will, such things do exist. Although I must admit that I have only seen such controls on OLD OLD furnaces. During several blizzards I have been thankfull for having an old furnace and a warm house (while my neighbors huddled around their fireplaces, or came to my house). (You say there are hot water and steam heaters that don't use a pump? Give me a brand, Will. I want to get rid of that octopus in my basement!) Forcing the valve open is no problem. For most furnaces, the valve is held closed by a spring, and the solenoid pulls against the spring to open the valve. The solenoid is not actively holding the valve closed. (It doesn't actively do anything without power :-) ) The big problem is moving the heat. It seems to me that the modern furnaces have a few inconveniences. As much as I would like to get rid of the octupos that occupies half my basement, I also rather like to stay warm. And it is not uncommon to lose power during a heavy snow in my neighborhood. So I would be interested in hearing recommendations on new home furnaces that can be manually controlled during loss of power. Dan Messinger ihnp4!umn-cs!digi-g!dan
djw@lanl.ARPA (02/06/85)
> And if your furnace is one of those that uses a high-voltage spark to > ignite the burners instead of a pilot light, you're out of luck with the > power off. > > Brian Kantor UC San Diego > OK NOW, I've had a 30K btu heater in my cabin for 15 years. It uses a thermocouple to power the propane ( really butane at this altitude ) safety shutoff valve. The pilot heats the thermocouple and the electricity generated energizes a magnet just enough to keep the gas shutoff from closing and shutting off the 4-12 oz gas flow. Recently I decided to look at one of those new-fangled Piezo-electric start ovens and wanted said starting mechanism for my wall heater. There must be a solution other than a $400.00 solar panel, so I propose to the net, and all the GE, White Westinghouse/GMC, etc. engineers out there, 1) No flame >> no gas through the safety valve or 2) No electricity >> no gas through the safety valve. I want a wall heater with piezo start and no pilot flame. It would be nice if it worked off a battery backup from thermocouple power/thermostat... Where is such a beast? My heater in the cabin is probably 25 years old, certainly unsafe, and has no thermostat. I will give up the thermostat if I can have the gas safety shutoff and the piezo electric start. These things are available on gas ranges, why not on wall heaters?