JWR –
The article written by Tom H. contains some dangerous advice and overlooks some important issues. He wrote:
“Next, cut the receptacle end (female) off the 120 VAC extension cord and install the replacement 120 VAC plug (male) to the cord. Make sure it’s wired correctly. (Black to black, white to white and green to green). You will now have a cord with a [male] plug on both ends.”
Such a modified power cord [commonly called a “disaster cord” or more aptly a “suicide cord’] is extremely dangerous, and should never be made. If one end is plugged into a power source, the other end now has exposed electrical contacts and anyone touching them is in danger of electrocution. Don’t take the chance of killing your child, spouse, or even yourself by having such a cord around where someone could try to use it.
Tome also wrote: “After making sure the main power disconnect is off, plug in one end of the extension cord to the inverter and the other end into any 120 VAC outlet in your house.”
Most homes in the USA have what is known as 120/240 volt single phase power coming into the house from the electrical company. A few may have 3 phase power.
Back feeding a 120 volt outlet with power will only energize 1/2 (or 1/3 if you have 3 phase power) of the 120 volt loads in your house. If your furnace, refrigerator, deep freezer, or other critical load is not on the same “leg” of your power panel as the outlet you are back feeding, it will not get power and will not run. Worse, if a load such as a furnace has motors that run from 240 volts, single or 3 phase, and power is applied to only one leg of the motor, it could damage or destroy the motor.
JWR added this advice: “The best and safest solution is to have a qualified electrician install a proper bypass circuit breaker panel that will eliminate any risk of a back feed!”
This is certainly true, and may be the only easy way to be both safe and meet electrical code when providing backup power to a furnace. There are some other solutions that are safe, however.
Here is an easy solution if your furnace only requires 120 volts AC at some reasonable amount of current. If you are competent to work on your own electrical panel (a working knowledge of electricity is a useful survival skill), you can determine which breaker powers your furnace, and disconnect the wire to the furnace from the breaker. Mount a small electrical box with a single 120 volt outlet on it next to your breaker panel, and feed it from the breaker that former fed the furnace. Drill a hole in the box next to the outlet and bring a short power cord with a male plug on the end out through a grommet (to protect the cord from damage as it exits the box). Run the other end of the cord into the breaker box and wire it safely to the power wires going to the furnace. When the short power cord is plugged into the new outlet, electrically the furnace is hooked up just as it was before you started.
If you unplug the cord from the outlet, and plug the cord into an inverter or generator, you can safely power the furnace with zero danger of back feeding the power lines. Back in 1999 I made such a modified power feed to my furnace, and tested it with an inverter powered from a pair of golf cart batteries. Because the furnace was a low power consumption type (hot water heat) I was able to get around two days of power for my furnace before the batteries needed charging. A large 50 amp battery charger would recharge the pair of batteries in a few hours. Therefore, I would only need to run my generator when I needed to recharge the batteries, or when I needed more power for appliances such as the deep freezer or refrigerator. If I kept the doors shut on the deep freezer and refrigerator, a hour or so of power
twice a day from my generator would keep them cold.
Tom wrote “A car that is quietly idling, parked in the driveway, is not going to stand out. … As long as you have gas for the car, you are in business.”
While most inexpensive generators make more noise than an idling car, they also use far less fuel. If you spend the extra to get a very quiet generator such as many of the modern inverter/generator sets, you can have both the quiet and low fuel consumption.
Blessings on you and your family! – RAR
Jim:
I think that Tom presented a very inventive idea, but I have personal reservations about it. I haven’t actually tried this in a real world test scenario, so these are just theoretical observations:
1.) Under normal circumstances, the higher the load placed on the alternator, the more energized it becomes. As the current draw on it increases, the mechanical resistance required to turn it becomes higher. The engine RPM increases to compensate. Higher RPM, more sound. (If you ever want to see the max amount of power your alternator can put out, try to find instructions on how to “full field” it. I would not recommend doing this on a vehicle with computer controlled anything!)
2.) Power loss because of clip on jumper cable connection will be high. A secondary effect of this will be high heat problems in the DC side of the wiring, possibly enough to melt the insulation off the wire.
On a side note, when looking at jumper cables to carry with you, buy the larger cables (Lowest number AWG). Trying to jumpstart one of my vehicles in 25 degree cold that had been sitting for three months took me two pairs of “el cheapo” 12 gauge cables. Larger diameter cable = lower resistance and heat buildup = more electrons streaming into your dead battery
One way to decrease this would be to replace your vehicle battery cable connectors with marine style terminal ends (The ones with the wing nut and post on them) and securing the inverter to the battery with actual ring terminals. The more surface area you can get in the connection, the better. Be warned however, most marine style terminal ends I have used have a noticeably smaller inside diameter than regular automotive terminals. They will require some force to go over your auto battery terminal posts.
3.) If a running generator will make you a target, a running vehicle will as well. – A.R.
Dear Sir,
As someone who has both solar photovoltaic/battery bank and multiple generator standby power options at home, and at a remote airfield location without grid power, I would like to offer my opinion on the article “Covert Home Power for When The Grids Go Down” offered by Tom H on Thursday December 17th 2009:
The use of a vehicle based generator system does offer a number of potential benefits, most importantly the regular running, maintenance (hopefully?) and fuel replenishment aspects, not to mention a large and safe fuel storage capability – you do always keep your tank at least half full? Without these important activities the author is correct that small gas powered generators become nothing more than “garage queen’s” – and expensive ones at that after a year or more in storage.
As with all things in life there are also unfortunately an equally if not larger number of negatives/limitations associated with vehicle based generator methods. The relative fuel economy of a small gas or diesel powered engine, compared with a typical car/pickup engine (and its’ 12V electrical generation capability) is vastly different. The much larger vehicle engine capacity and all of the accessories attached to it (water pump, air conditioning pump, power steering pump, and all of the associated drive trains/belts for these etc.) take power, and this comes from the engine and the fuel, increasing consumption. When was the last time you had a vehicle with a pull cord “re-coil” style starter option found on most small gas engines?
There are other issues too, such as leaving your vehicle engine running (not overly covert?) and the risk of vehicle theft as most modern engines will need the key in the ignition to run (especially bad if someone is looking to G.O.O.D. and needs functioning transport with available fuel). If you do choose this option, do you have a spare key to lock the car with the engine running? You may want to consider fitting a wheel clamp or similar to deter someone driving off – you may already have one if you own a larger trailer or caravan/camper?
Connecting to the vehicle battery with jumper cables often stops you from fully closing the hood, or risk a short circuit if you do, so a raised hood may be another give away and can increase the noise signature of the running engine too. The longer the cables (and I agree that thicker is better) the greater the power loss, so shorter cables are better, but this then places the inverter at greater risk of being stolen – you also need to protect the inverter from any water/moisture ingress – even next doors dog relieving itself! Consider permanently fitting a high power 2 pole connector to your battery (e.g. Google “Anderson SB connector”) under the hood and a matching end on your jumper cables. This can then be used to jump start other cars, power your inverter (winch, any other 12V appliance), and stops people from borrowing your jumper cables as they only work on your car now! This method also reduces any risk of polarity reversal/short circuit accidents.
One option seldom considered when using a vehicle based generator is the “extra battery method”. Take a large car or truck battery (or leisure battery) and connect this using the jumper cables to the vehicle battery. This can be located inside the (ventilated) garage and you can use slightly longer and/or thinner jumper cables with this method. Connect the inverter (also now in the garage) to this second battery and it provides a “reserve of power” for heavy starting loads – recharging from the running vehicle once this is passed. Remember that 2,000 Watts of power from the inverter is around 200 amps at 12 VDC (there are losses in the inverter) so you are placing a considerable strain on the vehicles electrical system – how many vehicles are capable of continuously producing this amount of 12v power from their alternator system, and even if they are the considerable heat generated will not be so easily dissipated as there is little if any air movement that would come from a moving vehicle in normal operation? The radiator fan will cool the engine, but by doing so will blow hot air into the engine bay where the alternator is housed, right next to a really hot engine too. You may want to check the continuous rating of your vehicle’s alternator output, and factor in the cost of repairing/replacing it verses the costs of a separate generator?
There are some very special instances with hybrid vehicles where they are capable of generating much larger amounts of electrical power (e.g. Toyota Prius), but these are the exception rather than the norm. If you have a Prius/Lexus then Google “Prius UPS” for details on these systems – they can even automatically start/stop the engine as power is used from their onboard battery systems, increasing fuel efficiency and running time. These really are the best vehicle based generator systems if you already have such a vehicle.
There have been many articles on the use of back feed “suicide cables” to power to grid down locations, and whilst these are functional there are considerable risks associated with this method. The best option would be in install a power inlet and transfer switch if at all possible. If you are going to use a back feed cable I would advise you to set up a check list of actions (for both connecting and disconnecting/returning to grid power), and follow these in strict order to ensure you do not cause a dangerous condition – remember it may be dark/cold when you are doing this and you may not remember exactly from memory what is needed – pilots (amateur and professional) use check lists, and they regularly practice their emergency actions, so take a hint from people who really need to get things right first time! I would also attach a brightly coloured plug or label/streamer to the “live” end of the back feed cable as a reminder not to touch this when the system is back feeding power. The location you choose to plug this in must consider risks from people tripping over the cable and pulling it from the receptacle – exposing the live pins. Anywhere that children may be able to access it is not even considered in my opinion!
A couple of options not considered are small diesel and propane powered generators. Diesel fuel stores for much longer than gas (especially with anti fungal compounds added) and once warm the engine can run on a variety of different “fuels” including cooking oil, heating oil, even clean engine oil at a push, but if you do not have anything else that is diesel powered it can prove difficult to “rotate” your fuel supply” (even if that is only every 2 – 3 years) and they can be much harder to start in cold climates. Propane stores almost indefinitely, you can use it on your gas grill in the summer and this can also provide standby heat and cooking facilities all year. A few medium sized propane bottles (a minimum of 2 – use one, plus a full spare) can be safely stored in a garage or shed, and far more safely than gas (petrol) IMO. The down side for both of these being that the generators are typically more expensive to purchase initially.
Please do not think that I am being negative with my comments. Any system is better than none, and vehicle based systems can and do work so long as you acknowledge their limitations in running time, security and power available etc. (I would not aim for much more than 800 to 1,000 watts continuous, even if you do buy a bigger inverter [~1,500 Watts] to allow for “start-up” surges). The components required for vehicle based systems can also be “recycled” into a more permanent fixed solar/battery/generator system as time and funds permit.
Whilst “modified sine” inverters are much cheaper than the “pure sine” variety, you should be careful with electronics/motors working from modified sine power. Ordinary filament light bulbs work fine, but some compact fluorescent lamps can flicker or make high pitched noises on modified sine power. Some items such as cell phone chargers and other “transformer-less” wall-wart power cubes can fail quite spectacularly on modified sine power, as can some satellite/cable boxes in my experience – if you can afford a pure sine inverter then this is the choice to make.
Finally it should be remembered that any small engine (gas/diesel/propane) can also provide considerable distraction when trying to get them to work after periods of storage, when after a few minutes it should have become obvious that it isn’t going to start and that you should abandon it for now and implement plan B, only returning to it when this is working. (You do have a plan B, right?)
My thoughts and prayers are with you and your family at this time, and I hope and pray that the true meaning and message of Christmas will support you all over the holiday season following your loss of the Memsahib. Kind regards, Ian H. – NSoB (Nanny State of Britannia)
Jim,
The Army sent my organization a cheap generator several months ago as part of a bigger system. About a dozen of them went out to various Army posts to be used by civilian trainers, some of them have no military background. This week, several of our sites tried to start their little generators and were shocked that they were inoperative. (I am just as guilty as they are. We have all ignored our generators since September.)
There are basically two types of internal combustion generators out there, main power generators and backup generators. The difference in cost between the two types is substantial. Heavy duty power plants are more than ten times the price of a backup generator, so as a compromise, many of us wind up owning a backup generator of some kind. There are lots of little micro-generators around 1 KW, but I am not talking about those. They are really too small to be much help, but the larger ones can be very useful for keeping refrigeration or pumping water or any number of tasks when the grid is down.
The typical backup generator is about 6 HP gasoline rated for something like 3,500 watts and costs from 300 to 600 dollars. The following is specifically written about a “All Power” AGP3002D 3,500 watt gasoline generator, but since it’s is a typical survival generator this will also apply to many different models and sizes. I am talking about any generator too big to carry but small enough to wheel (and has wheels). If it has convenience outlets instead of a wiring collar, and it’s big enough to to run a freezer, I am talking about your generator. These are not top-of-the-line generators, but they are a pretty good if you take care of them and use them within their limitations. They are basically backup generators intended for short duration events. They should be fine for short duration crisis and in a total collapse, unless you have made a substantial commitment to storing fuel, your cheap generator will easily outlast your fuel supply.
There are two basic approaches to backup generator maintenance: You can maintain it constantly ready for action, or you can mothball it between missions. Most people don’t really need to be able to push a button and have their generator come to life. In fact, if they can get their generator up within about half an hour, that’s probably just fine. Also, most people need a backup generator very infrequently. Maybe less than once a year.
Mothballing is probably the best choice for most people.
To mothball a generator, drain out all the gasoline. You can let it run dry or drain it from the fuel filter (or disconnect the fuel line). Be careful. Gasoline is explosive. When you try to start it later, you will have to keep pulling the starter rope until you suck fresh gasoline though the system….be patient and keep pulling.
You can leave the oil in the engine (and probably should) but if it sits for a year without starting, you will need to drain the oil and replace it with new stuff before you use it. Look at the oil before you use it and use common sense. If your oil is ever black for any reason, it needs to be replaced immediately. The engine only holds a little over a half a quart (.6 liter for the model I have). Use regular 10W30 oil. No need to get fancy.
Protect the generator from the elements while in storage. You can leave it in a garage and haul it out when needed. If you must store it outside, you are risking weather damage and theft. Most of these things are not really made to sit outside in the weather, so try to store them in some kind of shelter.
When the grid power goes off and stays off long enough for you to use your generator, Oil it, fuel it and start it up. Plug in your stuff and smile smugly at your own cleverness. You should start it up at least once a year and it should work when you need it. That’s pretty much all there is to mothballing.
Or, you can maintain your generator ready to use on short notice. That requires more work. Regular maintenance requires you to run it under load for about an hour per month. You will need to follow some steps to do it safely.
You should follow this procedure whenever you run the generator for any reason.
- Put in fresh gasoline. For maintenance run-up, about a pint of any kind of unleaded should be enough. Don’t use much because gasoline has a short shelf life and turns into varnish (or technically….gunk) in a few months. You ideally want to burn through all your gasoline every couple of months, so only add a little and then run it almost dry every month. I think old fuel may be the most common cause of failure in small engines. Don’t leave old gas in your tank or you will be sorry. I don’t know much about fuel preservatives, but they seem to be unnecessary unless you are storing a lot of fuel. If you have only a few containers of fuel for emergencies, you can rotate them and burn the fuel in your car or truck. I only keep about 20 gallons and rotate my fuel every month. On my model, there is a fuel filter (glass bowl type) in the back. It has a drain plug for removing water. If you have a fuel filter bowl you really need to check this when you refuel and drain out the water if you see any. (it will be the lower layer…duh). My tank is sized to run the generator about 8 hours under a 1,500 watt load. It holds 4 gallons, so I can expect to need about a half gallon per hour of use.
- Check the oil level, You will need to change the oil after the first 20 hours of operation and then every 100 hours thereafter. There is often no oil filter so this is really important. You may need to siphon or pump the old oil out if there is no drain. The oil level is usually checked at a cap or plug at the bottom of the engine. There is no dip stick on cheap gas engines. The oil plug is slanted into the base of the engine so that when the generator is level, the oil level should be exactly as much as it will hold with the oil plug out. (like a lot of lawn mower engines.) If a few drops spill out when you open the plug, that’s perfect but basically, if you can touch the oil with your finger without inserting it past the first knuckle, (an inch or so below the top) you have enough. Even dirty oil is much better than no oil. If you ever run it without oil you will be very sorry.
- Check the air filter periodically and wash it with soap and water when it’s dirty. (if it’s a replaceable filter, you will need spares). The manual on mine says to clean it every 60 hours, but in a smoky or dusty environment, you may need to clean this filter every time you refuel.
- Ground it! Generators are dangerous. You are supposed to ground it using a long grounding rod. You might be ok strapping it to plumbing, but a dedicated ground rod is usually safer. If you are in doubt, wet the ground around the rod with salt water (or any water)…about 10 gallons to increase conductivity. Sand is a terrible conductor. If you hit bedrock, drive it in horizontally for it’s full length instead of leaving it sticking out. This is potentially lethal, so don’t screw it up. If you get a kid killed, you are really going to feel bad.
- Turn on the engine switch (mine is on the control panel, but it can be anywhere. Push the choke as far as it will go if you have a manual choke. (Mine is hidden by the air filter. It will be on the same side).
- Pull the starter rope fast but smoothly until the engine starts. (crossing your fingers seems to help). When the engine catches, let it run a few minutes and then push the choke back to the run position. Let it run 5 minutes before attaching a load.
- Attach a load that draws at least 1,000 watts. An electric space heater or even an old steam iron will work for a load. I have always heard that running a generator without a load is bad for it, but I am not sure if this is just superstition or if it is fact. I have always used a load because I am a primitive, superstitious primate. If someone knows the definitive answer, I would love to hear it.
My generator is rated at 3,500 watts, but that’s a lie. That’s the start up surge capacity. My maximum rated load is only 3,000 watts, and it’s not really big enough to run that much. My system is designed to run for long periods at half load, which is only 1,500 watts. That still sounds like a lot until you start counting up the watts you need. To figure out wattage, multiply volts times amps and that gives you watts.
Example: a typical Mr. Coffee (drip coffee maker) draws 7.5 amps at 120 volts. 120 times 7.5 is 900 watts.
Get a heavy duty extension cord for safety. Thin, long cords add a lot of resistance and can heat up under a heavy load. Your cord will need to be pretty long to reach outside to the generator, so get a good one.
Your generator is going to be noisy. If you are hoping to hide a cheap backup generator, forget it. They are much louder than expensive power plants of the same size. You might even need to wear hearing protection if you are working near the engine. I do. Hiding any internal combustion engine will be even harder if everything else in the area is quiet.
Cheap engines are not overly efficient, so they stink. They also put out copious amounts of carbon monoxide. You may want to set it up downwind and far enough away to not be annoyed. Under no circumstances run this thing indoors. Without adequate ventilation \a gas engine can kill you in minutes. – JIR
Hi Jim,
Just a few additional caveats to the article: Covert Home Power for When The Grids Go Down.
Running the 120 VAC electrical system from your automobile may seem like a relatively easy thing to do, but there are some hidden issues one must be aware of.
One issue is called Power Factor which happens when a reactive load (such as a motor) is running. In simple terms you can not simply multiply the current and voltage to get an equivalent power draw from the system. Depending on how the output of the inverter is designed and protected, you can even destroy the inverter outputs. This may happen with a motor that is two large, or by simultaneously running multiple motors. It’s best to check the inverter users manual or contact the manufacturer for proper operation of inductive loads like motors.
Another issue that was already mentioned is inrush current on a motor when it is starting. The additional power is used to take a physical piece of material (the motor shaft and get it moving from a stopped position. Overcoming the inertia can take a bit of extra power. A good rule of thumb is 5 to 6 times the running current draw , keeping in mind that a 1 HP motor at 120 VAC will draw at least 6.5 Amps when running under a load. Motors may have this specified on the name plate as Locked Rotor Amps or LRA. A 1 HP motor under load can draw as much as 40 amps (4,800 watts) on startup. This can simply mean that the motor won’t start, or can mean you’ve destroyed your inverter.
Even an incandescent light has some inrush current, so it is better when using more than one at a time to turn them on separately.
Back on the DC side you can do the simple math, but there can be a problem here also. A 1,500 watt inverter at full output will draw about 125 Amps (1,500 Watts / 12 Volts). A typical automobile alternator is rated at 50-75 Amps and the higher output alternators can output 100 or more. Keep in mind also that when supplying the higher power, the automobile engine may be more than just simply idling.
The main thing here is to know the limits of your system, which will typically be your alternator and DC power source, and know those limits (preferably by testing) before you need them. – LVZ in Ohio
