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Author Topic: Selecting a generator  (Read 43484 times)
KA3VEZ
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« on: June 19, 2013, 01:23:03 PM »

Here is a dumb question.  Determining how many watts a generator should be? I know you do volts * amps but do you do it for the power supply(115 * 20) or for the rig itself(13.8 * 20 in my case) Sorry if this seems like a simple thing but just want to make sure. Thanks for any input.

~Kirk, KA3VEZ
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AA4PB
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« Reply #1 on: June 19, 2013, 02:11:27 PM »

First, the power supply doesn't draw 20A at 120V. It supplies up to 20A at 13.8VDC. That is 276 watts out of the supply, maximum. Assuming the supply is 80% efficiency, that's 331 watts going into the supply on the 120VAC side. 331W div by 120V = 2.76A being drawn at 120VAC.

Be sure to add in wattage for all the other accessory equipment plus plenty of extra capacity in determining the generator capacity.
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K1CJS
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« Reply #2 on: June 19, 2013, 03:03:04 PM »

It might also be a good idea to think about whether or not you want to use that generator for other uses.  If all you want is to use a generator for field day, depending on your field day setup, all you may need is a Harbor Freight special, priced sometimes at $80 to $100.
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W8JX
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« Reply #3 on: June 19, 2013, 09:21:44 PM »

It might also be a good idea to think about whether or not you want to use that generator for other uses.  If all you want is to use a generator for field day, depending on your field day setup, all you may need is a Harbor Freight special, priced sometimes at $80 to $100.

It is easy to up-size and buy more than you need. I would get something in 1000 to 1500 watt range. Easy to carry and easy on fuel too. Bigger units can get thirsty for fuel even on light loads.  
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KB2FCV
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« Reply #4 on: June 20, 2013, 10:20:33 AM »

It all depends on what you're using it for. What needs to run on it? What are the possible uses?

Something to consider.. if you are looking at a generator for home backup you'll want to look at fuel consumption. I saw this first hand here in NJ. During the aftermath of Hurricane Sandy many gas stations were without power for well over a week and also many weren't getting fuel deliveries. I think I only had to wait in line one day to get gas for my generator. The other folks? They had to stand in long lines every day for hours and their biggest complaint was fuel consumption. Many of the bigger generators will drink 5 gallons in 8 hours. I picked up a little honda that will sip 1 gallon in 8-10 hours.. big difference. With maybe 15-20 gallons I can go a week.. and more if I can ration.

Be sure to calculate what you need to run. If using as a backup for the house... really take a look at what is critical. My needs are: sump pump - heat - refridgeration (in that order). Anything else is a non-essential luxury... even light (although I do run a CF bulb here and there.. you can get away with LED battery powered stuff) The Honda I picked is just enough to run the essentials and it works great. I took the time to calculate starting current of the items I need to run.

Just some food for thought based on my experience..
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W8JX
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« Reply #5 on: June 20, 2013, 11:15:24 AM »

I have used several generator sizes over the years and a 3 k model I have is most useful by far. It is a Honda clone from china and 6 years old now and very reliable and easy on fuel. (on light loads about a quart of fuel a hour). Its only drawback is size/weight.  It weighs about 100 lbs plus 25 lbs more when full of fuel and not easy to carry. When you look at 1200 to 1500 watt units, they weight 50 to 70 lbs and are far easier to move and some will run 8+ hrs on a gallon of fuel too. 
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K9YLI
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« Reply #6 on: June 22, 2013, 08:17:03 AM »

The people  of N J  on tv were  nutso..
you only need to run a freezer  every  3 days if you dont open it..
run fridge every  4 or 5 hours  during normal use, with careful  planning before you open it.
if you need to run a sump pump  that changes a bit.
5 gallons of fuel should  easily last over a week..
You  cant  watch  Tv or  be on the computer.. its an emergency  situation.
you get to use  candles or  coleman lantern,  for light.
go to bed when it gets dark.,charge  cell phone when  re cooling   fridge.
battery  radio.....
If you expect to run your house  just like normal with a back up  generator,
you need a 30 KW with  100 gallon  tank..

back up  means  keep your food cold and  your  basement  pumped out.
 
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W8JX
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« Reply #7 on: June 22, 2013, 12:09:12 PM »

The people  of N J  on tv were  nutso..
you only need to run a freezer  every  3 days if you dont open it..
run fridge every  4 or 5 hours  during normal use, with careful  planning before you open it.
if you need to run a sump pump  that changes a bit.
5 gallons of fuel should  easily last over a week..
You  cant  watch  Tv or  be on the computer.. its an emergency  situation.
you get to use  candles or  coleman lantern,  for light.
go to bed when it gets dark.,charge  cell phone when  re cooling   fridge.
battery  radio.....
If you expect to run your house  just like normal with a back up  generator,
you need a 30 KW with  100 gallon  tank..

back up  means  keep your food cold and  your  basement  pumped out.
 

I think somewhere in middle is solution. When we had long term power failure I would run a 3k generator about 14 to 16 hours a day. Used 3 to 4 gallons a day and kept food cold in a few fridges and an some lights as needed and powered TV and such. I would shut down at nite and go to emergency lights. No need to camp out in your house for days.
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KD0REQ
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« Reply #8 on: June 23, 2013, 10:54:53 AM »

our power was out for 15 hours this weekend.  when we woke up, I finally dragged out the generator to run the fridge, found a 4-cell Mag was corroded up, and replaced it with an LED 180 lumen flashlight from Rayovac.  refilled the gas cans 8 miles away, and just then power came back on.

I bought mine for winter heat, which requires 1800-2200 watts to run the fan and oil burner.  you can crank the heat until it shuts off, switch the cords and run the freezers and fridge for an hour, cycle back, then shut the genset down for a couple hours.  that'll stretch a 4 gallon tank well past a day.  LED lanterns and headlamps will go 2-3 days on one set of batteries or more, depending on whether you read in the dark.  cook on the Coleman, and this will last you a week.

and run whatever you want up to a full gallon on field day if you have thoriated filaments in the amp.
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ALCO141
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« Reply #9 on: June 24, 2013, 09:35:37 AM »

i have run generators over the years from 400 watt to 25 kw, it is improtant as has been stated that you size your generator properly, best to have an 85% power utilization from the generator that will give you best fuel economy and make no mistake these are thirsty beasts.  he honda 2000 is very fuel efficient and will run individual appliances as needed, one at a time.  other option is to go with a loarger whole house unit that runs from nat gas or propane, if you dont need it portable.

if you go with gasoline then you need to figure fuel storage and also how you will connnect to your house add this to the cost.

alex
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K7LA
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« Reply #10 on: June 25, 2013, 09:28:40 PM »

I would add one more item to the gasoline generator tips:
Use a fuel stabilizer additive like Sta-Bil if you are planning
on keeping the fuel in the genny for several months to a year.

The ethanol blends in use today break down the gasoline
components more rapidly than refinery blends used in the past.
Use of a stabilizer will ensure your genny fires when you need it most.
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W8JX
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« Reply #11 on: June 26, 2013, 05:49:22 AM »

I would add one more item to the gasoline generator tips:
Use a fuel stabilizer additive like Sta-Bil if you are planning
on keeping the fuel in the genny for several months to a year.

The ethanol blends in use today break down the gasoline
components more rapidly than refinery blends used in the past.
Use of a stabilizer will ensure your genny fires when you need it most.


Generally if you shut off fuel and run crab dry before storage you will be fine.
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AA4PB
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« Reply #12 on: June 26, 2013, 06:07:42 AM »

I'd recommend fuel stabilizer in the gas AND run the carb dry when you shut it down for storage. The stabilizer will help the gas that remains in the tank.
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KE4DRN
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Posts: 3734




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« Reply #13 on: July 02, 2013, 07:07:44 PM »

hi,

I would recommend you have at least one Carbon Monoxide detector
in your home if you are running any type of generator.

Few  years ago, an older couple had one running, it was too close to
the house and when the furnace cycled on the exhaust gases from the
genset were pulled into the home from an open window.

The OM died from CO poisoning and the only thing that saved his wife
was that she was on oxygen supply.

73 james
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W8JX
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Posts: 6654




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« Reply #14 on: July 02, 2013, 08:30:30 PM »

I'd recommend fuel stabilizer in the gas AND run the carb dry when you shut it down for storage. The stabilizer will help the gas that remains in the tank.


I do not think this is as much a problem today as far as needing fuel stabilizers.
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