Generator/Inverter question

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The primary question, as always, is "What do you need to power, and how much power will you need to run it vs. the larger amount of power it takes to START it."
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Excellent advice. We have been through four power outages here in the Ozarks this year -- the Super Tuesday Tornado (6 days), the Big Snow Storm(3 days), the Big Flood (6 days) and most recently Hurricane Ike (4 days).

Our survival plan is well-tested now!!

I use a generator to keep my freezer and refrigerator from thawing -- you can lose several hundred dollars worth of food in a 2-day power outage. My generator is a 1.35 W Coleman that I picked up for about $150. It more than paid for itself during the first outage. But don't expect to power the house -- the fuel costs will shock you!
 
I have a powermate 1350, and two 80 minute sessions (a full tank of gas) keep the freezer cold, and the same for the refrigerator.

I have been tempted to get a 5KW, but portability is an issue -- the generator needs to be moved from a storate site to a place where it can be run, and the cord reach the appliances.
 
Pilgrim hit it on the head. While inverters are handy for limited use, when you start getting into the bigger one it starts to get very expensive very fast. Also, car alternators are not meant to be battery chargers per say. While they do charge the battery that is not what their job is, I have seen alternators burn up because they were pressed into battery charging duty.
If you have long term power requirements, more then an hour or two you would be best served by a portable generator.
 
700 watts runs my microwave (heats my coffee, or cooks me a meal), and/or provides compact florescent lighting, digital camera monitoring and computer networking just fine. I can eat the ice cream in my freezer and cook up the beef therein for jerky in the two days mentioned by folks, so I see no real need (a nice to have for sure) for a generator ... just me and the dog.
 
In our case, we had four power-outages that lasted longer than 2 days -- a couple of them lasted almost a week.

And the problem is, it doesn't matter what you do with the contents of your freezer -- even if you eat five or six times as much as you usually would, at the end of a few days, it's all gone and has to be replaced.
 
I just ordered a Kill A Watt electric meter, which should tell me how many watts our refrigerator / freezer uses when it's running, and how many watt-hours it uses per day.

Armed with this information, I should be able to price out an inverter, batteries and a charger. I won't be surprised if a small generator turns out to be cheaper, at least in the short run, though.
 
Talked to a guy I know in Houston, who prepared well for the storm and bought a Honda generator. Long story short, it was stolen the second night he had it running.

He ran out and got the license plate number of the truck. Cops caught the thieves, but generator had already been sold. Guy is out of luck.

He owns a Dawoo (sp?) .223 rifle (Korean made, sort of like an AR-15 but not a clone) - that he totally forgot in the event. Not a "gun guy" - does not think about guns or make it to the range frequently; may have shot the rifle a few times when he got it, probably not since. Gun as talisman, not tool.

Cop told him that he could have shot the thief, but only while the thief was on his property - not once he was in the street. This is incorrect - I'll post the relevant 9.3.whatever statute if y'all want - but it is interesting that the policeman told him this. Wonder if he believes it or was just trying to give a short explanation that might keep the guy out of hot water.

Makes me wonder whether, in an urban/suburban setting (i.e. potential for "collateral damage"), I would shoot to prevent theft of a generator.

If a family member depended on a medical device that required electricity (e.g. an oxygen concentrator or something like that), it would not be "just a generator" and the consequence would be more serious than loss of a freezer-full of food. I hope I would have the courage and clarity to take the shot (and *make* the shot!) in that circumstance. If the consequences of the theft would be less than life-threatening, I'm afraid I would hesitate to shoot. That's just my take on it, from the comfort of my computer chair, with no adrenalin.

Hook686, I agree that solar is better for charging batteries than for running equipment. And whoever mentioned propane-fueled refrigerators and freezers - I owe you. I need to look into that!

Regards,
Andrew
 
I read folks talking about the inverter size. It is my understanding that the inverter size is secondary. What is important is the load placed on the inverter. If I only place 700 watts on the inverter, the 90 amp alternator is not over taxed because only 58 amps is being drawn. The car will not be overloaded, and this inverter will work fine with 700 watts.
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You need to match the inverter to the load. Inverter efficiency increases as it approaches its rated capacity. Most inverters operate at highest efficiency somewhere around 2/3rds their rated capacity.

Another consideration in sizing your inverter is the start up load, or surge. Inductive loads have higher surge requirements than resistive loads. Check to see if the inverter you choose can handle the start up load of anything with a motor in it.

As you have probably noted, using an automobile engine/alternator set up to run a 800 watt inverter is a bit of overkill/waste. 745 watts is one horsepower. To keep your engine idling requires more horsepower than you are realizing out of your inverter. That's why most people posting on this topic are recommending portable generators that are sized to handle the task.

Choosing an Inverter.

Pilgrim
 
just ordered a Kill A Watt electric meter, which should tell me how many watts our refrigerator / freezer uses when it's running, and how many watt-hours it uses per day.
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You need a clamp on ammeter with a peak hold function to find the starting current.

Is often a couple of times higher than the running current the watt-hour meter registers.

The generator or inverter must be able to supply the peak starting current with less than a ~5% voltage sag or starting will be prolonged and can damage the compressor (or any induction motor).

If you want AC power from a car, get a 120 V alternator.
They take some searching but they are out there.
You can also remove the rectifier module and regulate the field to produce AC, then step it up using a transformner.
Frequency is usually the hardest part without throttle feedback.

The alternator already produces AC, that gets rectified to DC, then you want it back to AC using an inverter.
That is a long way around and is wasting power (and fuel) at each step.
 
Or, to save yourself the expense of getting a 300 dollar multimeter, you can find out the amp draw with that and multiply it by .85/.15. Those are reasonable efficiencies (running/starting) for an induction motor. Then figure out how much money will be saved by getting it exactly right. The larger the draw, the more you should be getting a multimeter for it, but small stuff, a fluke meter would be insane to add to it if you didn't need that meter for your job.
 
Living in south east Florida, I have seen my share of power outages. The last was when Wilma came through. I lost power for 9 days. My 5500 watt Coleman genset was used about 8 hours per day to power the hot water heater, and refrigerator mostly. It used about 5 gallons per 8 hour run. My home does have a full auxillary load panel so I can switch over to genny power and operate virtually all of the electrical appliances in the house excepting the air conditioner and electric stove.
My experience has taught me an order of importance: 1, refrigerator, 2, refrigerator (yes its that important) 3, microwave, 3, hot water heater; 4, communication equipment, (TV, charging phones & other batteries, radios, computer); 5, fans; 6, lighting. Remember, at night, lighting is easy with lanterns etc.
After Wilma, I sold the 5500 and bought a 7500 Yamaha electric start. FAR quieter. The noise of inexpensive gennys is obnoxious to begin with. After 4 or 5 days, the noise is well beyond irritating. I cannot emphasize this enough!
My suggestion is to get the quietest genset you can find, at least 5500 watt output and preferably more. Electric start is nice, especially if the wife must start it or age / infirmity limits your ability to yank a rope (remember it is a 12 hp single cylinder engine and demands a FIRM yank to crank it.)
I store about 40 gallons of gasoline for the hurricane season in various manners. At the end of the season, I use the gas in the wifes car and replace it at the beginning of next hurricane season.
My genset is secured with case hardened steel chains / locks to eyebolts in concrete. (then & now) The owner is also armed.
My experience is that smaller gennys are better than none as are noisy ones. However if you wish to be self sufficient for a week or more, get yourself more and quieter power. One last suggestion, use high quality synthetic motor oil in the genny. They work hard and hot, you want them to last a long time.

Stay dry.
Roger
 
Generators are the best way to go.

Propane would be more reliable in the long term, simply because if a gas main is damaged, it would be cut off. You would still have your propane tank. Propane delivers more BTU also.

Gas or diesel would draw people looking to steal fuel. May lead to some tense situations.

A permanent installation type genny would hinder someone walking off with it.

Sound attenuation is a must, but it can be done by most homeowners. Simply purchase the the self adhesive sheets in bulk and cut with a razor knife. Or, by it in the package up front.

Bottom line minimum about 2000.00. Lotta commitment capital wise. But, I had a customer tell me his wife had complained about the cost of the genny... until they lost power for about a week during an ice storm.

He said she never said another word about it after that.
 
That would reduce the start current.

You divide by efficiency to find input power.
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Maybe you can explain how multiplying by 5.7 would reduce the starting current?

You multiply by .85, because that's the normal efficiency and you're reading constant current, to get a baseline to transfer it a scale of 100, and then divide by the starting efficiency to get the starting current.
 
My parents just went a week without power and living off a 5500W cheap generator. It got kind of tense 4 or 5 days into it because it used so much gasoline and the stations weren't open yet.

I'm looking at getting a Honda EU2000i or a Yamaha EF2400is because they are much more efficient, quiet, and can be converted to propane/natural-gas. I've been putting it off for a couple of years because they are expensive, but Hurricane Ike was a wake-up call for me.
 
http://cgi.ebay.com/GENERATOR-PROPANE-GAS-CONVERSION-KIT_W0QQitemZ140268408677QQcmdZViewItem?hash=item140268408677&_trkparms=72%3A1205|39%3A1|66%3A2|65%3A12|240%3A1318&_trksid=p3286.c0.m14

converts em to dual fuel and can switch while running
 
"Maybe you can explain how multiplying by 5.7 would reduce the starting current?

You multiply by .85, because that's the normal efficiency and you're reading constant current, to get a baseline to transfer it a scale of 100, and then divide by the starting efficiency to get the starting current."

Just divide the running current by 0.15 then.
The running current IS the running current, regardless of efficiency.
 
Then you have an overly inflated number. The efficiency is Work Out / Work In which would translate to I theoretical for that power output / I line. If you simply divide by .15 then you leave the Work in line from the running level in, which lowers your efficiency well beyond what the startup will be.
 
Laying assumption on top of assumption is a good eay to start damaging equipment.

Ammeters are not that expensive
Seehttp://www.mouser.com/catalog/634/2024.pdf

If you are planning on running induction motors from a generator it pays to know what the starting load is since it can damage both the generator and the load.

Smaller induction motors often pull many times the running current.
Larger ones are actually a little better , but 3-4 times is not uncommon.
On an A/C condenser the LRA (Locked Rotor Amperage) is a good indicator of the initial starting surge.

For POCO power it is a little more forgiving most of the time, since even a 100 A load is small in their scheme of things.

There used to be a company making smaller turbine generator sets (`10 to 20 kW), but the Chicom cheap piston engine powered units appear to have run them off.
 
Living in south east Florida, I have seen my share of power outages. The last was when Wilma came through. I lost power for 9 days. My 5500 watt Coleman genset was used about 8 hours per day to power the hot water heater, and refrigerator mostly. It used about 5 gallons per 8 hour run. My home does have a full auxillary load panel so I can switch over to genny power and operate virtually all of the electrical appliances in the house excepting the air conditioner and electric stove.
My experience has taught me an order of importance: 1, refrigerator, 2, refrigerator (yes its that important) 3, microwave, 3, hot water heater; 4, communication equipment, (TV, charging phones & other batteries, radios, computer); 5, fans; 6, lighting. Remember, at night, lighting is easy with lanterns etc.
After Wilma, I sold the 5500 and bought a 7500 Yamaha electric start. FAR quieter. The noise of inexpensive gennys is obnoxious to begin with. After 4 or 5 days, the noise is well beyond irritating. I cannot emphasize this enough!
My suggestion is to get the quietest genset you can find, at least 5500 watt output and preferably more. Electric start is nice, especially if the wife must start it or age / infirmity limits your ability to yank a rope (remember it is a 12 hp single cylinder engine and demands a FIRM yank to crank it.)
I store about 40 gallons of gasoline for the hurricane season in various manners. At the end of the season, I use the gas in the wifes car and replace it at the beginning of next hurricane season.
My genset is secured with case hardened steel chains / locks to eyebolts in concrete. (then & now) The owner is also armed.
My experience is that smaller gennys are better than none as are noisy ones. However if you wish to be self sufficient for a week or more, get yourself more and quieter power. One last suggestion, use high quality synthetic motor oil in the genny. They work hard and hot, you want them to last a long time.

Stay dry.
Roger
Click to expand...

Sounds a lot like me except my first and only generator purchase was for my Honda 11,000 Watt model. I had talked to our maintence director at the hospital where I work and got a lot of good advice. The electrician there also helped me install a double throw switch to disconnect from utility power and go to generator input( one big cable using 6/4 wire)

With this setup I run everything in the house except for hot water heater( and could do that on selet time basis by turning off other things). This includes running the 4 ton heat pump. Once I needed to make a sharped stake to hold up a small tree that had blown over on the house and fired up the 3hp Delta table saw while the wife was cooking breakfast while ac was running, and it bogged generator down but it caught( will never try that again)

For Hurricane Ike I had 50gal of gas ready but only used a bit less than 5. We only run generator when we need it, for cooking, and periodically to keep freezers and refrigerator cold. I bought it because of outages we sometimes get due to ice storms but have only had to use it in hot weather, so at night we will run the ac for a couple of hours to cool house down then shut generator off and go to bed. It's amazing how cool and comfortable you stay all night with everything off in a well insulated house, nothing in the house generating heat except for myself , the wife and two dogs.

Like you I run synthetic oil and change yearly and after each use with no reguard to number of hours on the unit. I replaced the battery on the 20hp Honda Friday before the hurricane on Sat, just in case the wife needed to start it. I can start with recoil starter. Choke, one long slow pull( cannot pull that thing fast) and it starts near end of that first pull.

Basically I baby that thing, I keep it in a storage shed, which I insulated and keep a small radiator type electric heater there in the winter to keep everything dry and not allow to get too cold in case I need it. I also made a detachable trailer hitch with a 6' long drawbar so I can pull it behind my lawn tractor if yard is wet( this sucker weighs a little over 400 lbs)

The bottom line is think ahead so you can be prepared. That way you do not have to try to finda generator when everyone else is scrambling to get one also. This way you can plan on what you need and will probably get a better price on a bigger more reliable unit.
 
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