Pique the Geek 20110619: Recovering from Trouble

A comment thread on Friday evening’s Popular Culture installment got me to thinking about this, and I decided that it would be a good topic here, and some Geeky stuff that can be used by a wide range of the public.  Thus, I write this as a public service.

There are several situations that people can find themselves in due to circumstances beyond their control.  Many of them involve interruptions of utility service, but some other eventualities can also require fast attention to mitigate further damage or even personal injury.  We shall discuss a few of those this evening.

Probably the most common situation that occurs is electrical service interruption.  This can be more serious than one might think.

Electrical service can be interrupted several ways.  The most devastating ones are the ones that affect very large areas for a long time, usually caused by adverse weather.  People who depend on electrical service to survive (mostly folks with medical conditions that require electricity to power their life preserving medical devices) should have a back up generator and enough fuel to carry them for at least a week, if not longer.

For those of us fortunate enough not to depend on electricity to live, there are steps that can be taken to mitigate any damage that might result from an outage.  The problem (except for heating and food in the refrigerator for prolonged periods) is not that the power goes off, but what happens when it is restored.  Think about what happens when power is restored after a significant (larger than, say, a group of ten or so houses) outage is restored.

Usually, everyone leaves their electrical equipment as it was when the power failed.  When power is restored, all of those devices (some of which, like an electric water heater or HVAC equipment) use a LOT of power.  When the power comes back on, essentially EVERYTHING tries to restart at once.  Many of these loads are capacitive, meaning that they draw an unusual amount of current at first, then level off to a lower requirement after starting.  HVAC, refrigerators, and freezers are like that, as are other things with large electric motors.  Others are resistive, like incandescent lighting and water heaters.  They may have a bit higher initial requirement, but not by a lot and it falls off fast.  In any event, the result is that the electrical service, once restored, is subjected to incredible loads instantly, and neither voltage nor frequency of the restored power from the mains can cope with such a huge, instant load.

The result is that the supply voltage (nominally 120 or 240 V in North America) drops for some time, depending on the number of customers affected and can also spike to values well over nominal as the load becomes equilibrated with the supply.  In addition, the frequency (in North America, 60 Hz, extremely closely controlled by the utility company) fluctuates because of induction from the many new loads being added, and the waveform of the power (normally a really nice, well controlled sine wave) becomes distorted.  These factors combine to have the potential to cause real damage in electrical devices.

Capacitative devices and electronics are particularly sensitive to these distortions.  Purely resistive devices are more resistant, although voltage spikes can burn out incandescent filaments.  Here is what to do to prevent as much damage as possible to your devices.

First, keep a torch (I like the British term, but most of us call them flashlights) in a place that you can get to easily even in the dark.  For some reason, perhaps Murphy’s Law, power outages tend to occur after dark.  You will need it, if it is dark, to do the first and most important step.  Go to your power panel and shut off the main breaker (for older installations, remove the main fuse).  This will prevent any surges from getting into your house.  Next, turn off all of the secondary circuit breakers (or unscrew the fuses) to disable each individual circuit.  Assuming a total electric house, one will service the HVAC, another the range, another the dryer, another the water heater, and several more for lighting and small appliances, including electrical outlets that service pretty much everything else.  This is important for an orderly start up later.  Then go around the house and turn off or unplug all devices.

Do no open your freezer!  In normal conditions, unless you have put a lot of warm things inside recently, an unopened freezer will keep its contents frozen for 48 hours, give or take depending on the ambient temperature.  If you happen to have a gas range, cook any perishables from the refrigerator within a day or two and eat them.  If not, drink that milk and juice pretty quickly and plan on discarding the rest.  If you have a gas or charcoal grill, then that chicken or other meat can be cooked and eaten even if in a total electric house.  Use your judgment.  For something like an ice storm or hurricane or tornado, it is likely that the power will be out for a long time. For a lightening storm, a couple of hours is likely.  But still do the electrical things that I recommended.

Once the power has been restored, to the following.  How do you know when it is back?  I recommend that you take an incandescent light bulb and make sure that the circuit into which it is plugged is active.  You do that by turning back on the main breaker (or replacing the main fuse) and activating the single circuit that controls that lamp.  I used the lamp in my clothes dryer, since it was on a dedicated circuit and with the door open there was no chance of the dryer itself starting.  Begin restarting your equipment one item at a time.

Wait at least 10 minutes for the electricity supply to stabilize.  That will assure that it is fairly clean by then.  Do not get into too much of a hurry.  Remember, this is as important for a five minute outage as it is for a five day one.  Begin by closing all of the secondary circuit breakers (or screwing the fuses back in) slowly and one at a time.  The chances are that you missed at least a couple of loads when you were unplugging or turning them off, so go slow.  Do the biggest loads first, like the water heater and HVAC (one exception:  NEVER try to restart HVAC equipment until it has had at least 10 more minutes down time, so for a five minute interruption it is the last to go back on, and the same with refrigerators and freezers, because the compressors in them need time to release pressure.  You can trip breakers, blow fuses, or even damage the compressors if you do not wait long enough.)

Just go slowly and you can restore normal function in under a half hour without doing damage to your electric and electronic devices.  I have done this for decades, and NEVER have lost a device to a power failure, although neighbors have had to replace freezers (not to mention the lost food), TeeVees, refrigerators, and in the worst cases, entire HVAC compressors.  For HVAC and refrigeration, five minute outages are much worse than five day ones.

Another problem that is common is a water heater failing.  Prevention is the best way to avoid this situation (you have no control on the power coming into your home, but you DO have control on the location of the water heater, at least to some extent).  Water heaters fail in four ways, two harmless and two that can be unmitigated disasters, at least economically.  Electric water heaters often have an element burn out, and that is just a nuisance.  Gas ones sometime have burner problems, once again a nuisance.

The next more serious failure is for the thermostat to fail, causing the water heater to overheat.  All modern ones have a relief valve that is supposed to be connected to a drain to divert the boiling water and steam safely.  Make sure that the relief valve is connected with reliable piping to a clear drain, or you will flood.  Sometimes the relief valve fails open, dumping water anyway even though nothing is wrong with the heater itself.  You will still flood unless good connexions betwixt the valve and the drain are maintained, so make sure.

The most catastrophic failure is for the tank itself to fail.  This dumps water from the bottom of the tank (the relief valve is on the top), and because the tank has a continuous supply of feed water, it will keep dumping until the feed water is interrupted by the supply valve, usually on the top of the tank.  But there are still from 40 to 60 gallons of water in the tank, even if you close the valve, and there is no way to stop it from draining, and it is HOT!  By the way, except for the innocuous failure of a heating element in an electric water heater, this is the most common failure mode for any water heater.  If you have one long enough, it WILL get a rupture in the tank, so plan for it.

There are two strategies to deal with this.  The first is to have your water heater on the lowest level of your house.  In that way, when the tank fails, the water can not damage a lower floor.  That is not always feasible, and many multi level homes have water heaters on an upper floor.  Let that puppy rupture and you are looking at thousands of dollars of damage!

The way to counteract that is to set the water heater in a catch pan (a piece of galvanized steel of sufficient diameter to allow the water heater to sit inside) with a drain stub connected to a reliable, open drain.  If the tank ruptures, and it will given enough time, the water from the tank will be contained by the catch pan and vented harmlessly to the drain, unless the rupture is so severe that the pan is overwhelmed.  Remember, the water in the tank is under pressure, so it does not really run out, it shoots out of the tank.

The best strategy is to combine the two.  Put your water heater on the lowest level, if possible, and use a tall (12 inches or more) catch pan connected to the drain.  I promise you that given long enough, the tank in your water heater WILL fail.  There is no easy recovery from water damage, except for restoration.  In this case, preemptive action is much more effective than reaction after the fact.  Please be warned.  Fast action in shutting off the supply to the water heater is about the only action that you can take after a leak in the tank.

Interruption of water service is less common, but does happen, usually because of a broken main.  Depending on where it happens, it can take hours to weeks to repair it.  There is nothing that a homeowner can to to prevent this, and once again only preemptive actions can mitigate the effects except for a couple of sort of weak approaches.

Usually, there is no warning about such a thing, but in the rare cases that warning are given, fill up the bathtub!  That is a good reason to keep your bathtub clean.  A full bathtub ranges from 40 to 100 gallons of water, so that can keep you drinking and cooking for a long time.  Even if a boil order is given, that water is useful, if you have electricity or gas.  In an emergency, you can also use household bleach to kill pathogens in that same water, but that is a poor long term solution.  Eight drops of good bleach in a quart of water, shaken rapidly and allowed to stand for 15 minutes will kill most pathogens, rendering that water fit to drink.  I would recommend pouring it from container to container with a long stream to allow the air to remove most of the chlorine before drinking.

If you do not have any warning, you still have potable water in the house.  Personally, I keep a gallon or two in the refrigerator just because I like to have cold water to drink.  But short of this, you STILL have fresh, uncontaminated water to drink, and you will not believe the source!

A regular household toilet has a reservoir that contains several gallons of water.  I am not talking about the bowl, which is likely heavily contaminated with bacteria that you really do not want to drink, but the tank above it.  This water comes from the same supply as your taps, and is fine to drink or to use for cooking.  In addition, your water heater has 40 to 60 gallons of potable water in it.  Just be sure to turn off the water heater before you tap it, not only for personal safety from burns, but also to prevent burning out the top element (for electric ones) as you tap out the water.  All modern water heaters have a valve near the bottom that also has a connexion that fits a garden hose to use to flush the bottom of the tank from hard water scale.  You can, after allowing the heater to cool, use this device for potable water for a long time if your water supply is interrupted.

These are just a few of the more common troubles in which we can find ourselves.  There are more, but these are both common and difficult.  Please respond in the comments for other situations that you have encountered and how you dealt with them, and I will try to offer suggestions to you and others about possible alternatives.

Note that I did not say anything about an actual, outside flood.  It is almost impossible to protect against them, and mitigation of damage is costly to the extreme, if even possible.  I recommend that anyone who lives even near a flood zone to carry flood insurance (normal homeowner’s policies explicitly exclude flooding from the outside, but usually cover a water heater tank rupture) and to keep their precious possessions on the highest floor of their house, in the attic, or in a secure, out of the flood zone storage space.  I used to live by a creek that would get pretty lively during periods of heavy rain.

My house never flooded, but it was on the uphill side of the creek.  Over the course of several years I studied to topography and observed water flow during periods of extremely heavy rainfall, and decided that it was a poor use of resources to carry flood insurance, so I cancelled it.  Then one spring we had a REALLY big series of storms.  Sure enough, my studies paid off, and my house was never even close to flooding.  But the neighbors on the other side of the creek (the downhill side) had their newly redone basement (and most items in it) pretty much ruined when the creek came a foot higher than the outside entrance to it.

Fire is a real danger in most household settings.  The two major causes of fire in a home are cooking and smoking.  Keep a fire extinguisher in the kitchen and check the charge indicator when you change the batteries in your smoke detectors.  Most cooking fires are grease fires, and can easily be controlled by taking something like a large pizza pan and using it to cover the skillet.  I have heard the advice about throwing baking soda into a grease fire, but I strongly recommend that you do NOT do that.  Even though it IS carbon dioxide that is released when baking soda get hot, the rapid expansion of this gas is more apt to cause the grease to be forcefully thrown into the air, giving it MORE oxygen and thus increasing the intensity of the flame.  The same thing goes for water.  Water is fine for a trashcan fire, but NEVER put it into a grease fire or you will cause a minor incident to become an unmitigated disaster.

Update:  Here is a trailer from Mythbusters about what happens when you use water to attempt to put out a grease fire:

As far a smoking goes, you should not.  If you do, like I do, restrict the areas in your house where you smoke to ones that have been rendered safe if that cigarette falls off of the ash tray, there is no paper, carpeting, or other combustible materials for it to ignite.  A cigarette will not ignite a piece of plywood, so setting the ashtray on something like that, or a glass tabletop works.  NEVER smoke when you are sleepy or otherwise impaired, and NEVER smoke in bed.  Even though I have a waterbed, the bedclothes are still quite combustible.

ALWAYS keep your smoke detectors working.  There are two types:  a flame detector and a smolder detector.  You need one or more of each.  A flame detector works by detecting ions coming from a fast, bright fire, and those do not always produce a lot of smoke.  A smolder detector works by sensing the reduction in intensity of an infrared light beam in the detector.  They are good for detecting slow, smoky fires before they get really hot and bright.

Here is a personal story.  I have a total electric house, and in one of the bathrooms is an old (built in when the house was built around 1965) bare element electric heater in the wall.  After moving here, I was using that bathroom to store packing boxes as I emptied them.  I THOUGHT that the heater was turned completely off, but I was wrong.  One night it got quite cold, and the thermostat turned on the heater, igniting some empty boxes stored too close to it.  I awoke to one smoke detector blaring, and soon found the boxes.  They had not come to full flame yet, so the smolder detector caught it.  I threw the boxes into the bathtub and flooded them, no real harm done.

While of the subject of detectors, if you heat with anything other than electricity, get a carbon monoxide detector, too.  CO is an insidious toxin, and if a heat exchanger decides to have a seam fail whilst you are asleep, you may very well “wake up dead”, as they used to say over at home.

One final hazard:  lightening.  More people in the United States are killed by lightening than win big at the lottery.  When you hear thunder, get inside if at all possible.  Stay away from windows as far as possible, and use only cordless telephones.  Avoid bathing or even washing your hands until the cloud passes.  If you are in an automobile, stay in it.  The metal skin of a car forms an effective Faraday cage, so you are safe from the lightening as long as you are in the car with the doors closed.  If outside, find the lowest spot that you can and lie down or at least crouch to avoid being the tallest object nearby.  NEVER seek shelter under trees, since at the tallest objects nearby, they are the most likely to be struck.

Well, you have done it again!  Danggit!  You have wasted many more einsteins of perfectly good photons reading this soggy piece!  And even though Keith Olbermann has not responded to my offer to be his science adviser, I am confident it is just because he has not seen me write about it yet, since that blog, Popular Culture, just came out a couple of days ago.  I am confident that he will consider me for that spot when he becomes aware of my eagerness to do so.  The local NBC affiliate is only about half an hour from here.

Please remember that I always learn much more than I could possibly hope to teach by writing this series, so keep those comments, questions, and especially corrections coming!  That, with other feedback, keeps me going.  Remember, nothing about science or technology is ever off topic here, so comment freely!  I shall hang around as long as comments are coming, and shall return tomorrow, and for the first time in months can say, after Keith’s show.  It feels GOOD to be able to say that again!

Warmest regards,

Doc