Q's about Back-feeding Electricity from Generator

[Jgray152]

If you need 30 amps to power the essentials in the house, that's around 3600 watts at 120v.

3600watts at 12v is 300 AMPS! Do you have a battery that will last long with a 300 amp discharge? Does your vehicle have a 350-400 amp alternator?

 

[AquariumNerd]

If you need 30 amps to power the essentials in the house, that's around 3600 watts at 120v.

3600watts at 12v is 300 AMPS! Do you have a battery that will last long with a 300 amp discharge? Does your vehicle have a 350-400 amp alternator?

i didn’t read it all, I just gave across my idea. I am sure that no house will require a 5000w generator just to get through a power outage. When we have power out, we just light a few candles, and I keep check on my fish. If you have power down for a few days, you might need a generator for the fish, but will you actually need to keep the washing machine running and power the dish washer, electric oven? how about a pillar drill?


To need a constant 5000w of energy makes me think that you would have a 15000 liter marine tank in the house.

 

[johnptc]

OUR GENI FOR THE TANK IS 100 KILOWATTS/ 220 3PHASE

DONT ASSUME HOW BIG THE TANKS ON MFK

WELCOME ABOARD

 

[Jgray152]

i didn’t read it all, I just gave across my idea. I am sure that no house will require a 5000w generator just to get through a power outage. When we have power out, we just light a few candles, and I keep check on my fish. If you have power down for a few days, you might need a generator for the fish, but will you actually need to keep the washing machine running and power the dish washer, electric oven? how about a pillar drill?


To need a constant 5000w of energy makes me think that you would have a 15000 liter marine tank in the house.

Why do you think its ONLY for someones fish tank? Electric water heaters can take major power. Furnaces can take a lot of power as well. Fridge, freezer, washer dryer if you need too, fish tanks and anything else someone may have that needs to run.

You don't buy a gen for a house and get the one that has the correct amount of wattage that you will be running. You get the one that has more potential incase you need the extra load.

Example. An electric dryer can be 4500-6000 watts by its self. If your out for days and you need to do laundry....well...a maxed out small gen will not do it. This is an extreme case since most of the time you will not be out for days and half the northern US will not be out the same time you are like this past winter.

You can easily rack up 700+ watts for a fish tank in no time. Add that to a few 60watt lights, fridge, freezer, heating, maybe a well pump, TV, stereo to keep you sane. Easily rackup 1500-2000 watts of power at any given time. 13-17amp draw on a battery and you will be looking at only a couple hours at most. Toss the battery afterwards cause it will be junk.

I am sure that no house will require a 5000w generator just to get through a power outage

YOU may not need it. Can you tell me the EVERYONE does not need it? Some houses require some decent amount of power that a simple car battery will not provide for as long as you may need it for.

Besides, car batteries are not designed to be drawn down as far as Power Backup Batteries.

 

[Jgray152]

Max Current Rating For household copper wires at 110v

Gauge ....... Current Rating
4 ............... 80 A
6 ............... 60 A
8 ............... 46 A
10 ............. 33 A
12 ............. 23 A

 

[Bderick67]

Max Current Rating For household copper wires at 110v

Gauge ....... Current Rating
4 ............... 80 A
6 ............... 60 A
8 ............... 46 A
10 ............. 33 A
12 ............. 23 A

Where did you reference this from? You are better of going with the National Electric Code(NEC) table 310.17. The amperage rating of copper conductors has to do with wire size, and insulation temperature rating. Voltage has no pertinence.

 

[Jgray152]

Where did you reference this from? You are better of going with the National Electric Code(NEC) table 310.17. The amperage rating of copper conductors has to do with wire size, and insulation temperature rating. Voltage has no pertinence.

I wanted to be specific since for those that may find that chart and want to use it for a different voltage such as 220v or 12v since the amperage for a specific voltage is much different at those voltages than at 110v.

5000 watts at 220v = 22.72 amps
5000 watts at 110v = 45.4 amps
5000 watts at 12v = 416 amps

I got the chart here.
http://www.rowand.net/shop/Tech/WireCapacityChart.htm

You can see that a specific sized wire, say 8 awg will not handle 5000 watts at 12v. Now I don't know what the hell you will want to run at 5000 watts on a 12v circuit but I just wanted to be safe thats all.

The amount of current the wire can handle also depends on the temperature of the wire so there is not exact science to it, at least if you do not want to get too specific. So that table is pretty close and is within the NEC ratings.

 

[Bderick67]

This is the author quote regarding his chart

Maybe I'm just not understanding this as well I as think I am. Who knows... At any rate, the chart below reflects the difference in 110V AC vs. 12V DC usage, even though I'm still at a loss to explain the details.

Amperage rating for the copper wire has to do with two things only gauge/size of the wire and temp of the insulation. Bringing watts or voltage into the mix is not needed.

That chart in the link provided is way off the mark. Copper wire has a current rating much higher then what that chart shows. This especially holds true for the larger wire #8 and above, while the smaller wire also has a higher rating(even #12 at 40 amps) it is limited by the code to what size over-current protection can be used(#12 at 20 amps),

 

[johnptc]

ok

voltage matters not in the correct ampacity but in using a large enough wire to provide acceptable voltage drops. hence the gauge will be different for 12 than 440 volts based on voltage


also ampacity ratings change for free air, a couple of wires in adequate conduit or derated if the conduit is over filled


a large diesel motor using an electric starter will draw way over 5000 watts to start such as on a boat..........bigger engine starters maybe 24 32 or 36 volts..........

be safe...........dont spark around

 

[Bderick67]

ok

voltage matters not in the correct ampacity but in using a large enough wire to provide acceptable voltage drops. hence the gauge will be different for 12 than 440 volts based on voltage

While this is somewhat true it has to do more with conductor length then voltage, have a look at the NEC. #12 copper thhn for example rated the same no matter, 120, 220, 277, 440, volts. Voltage does not have a bearing on the wire amperage rating. You may need to upsize the wire for voltage drop, but the wire you buy is rated per conductor size, insulation and I should include if it is copper or aluminum.

also ampacity ratings change for free air, a couple of wires in adequate conduit or derated if the conduit is over filled

Again there are calcutations for derating according to installion, I believe the NEC Tables 310.16 310.17 etc are rated as in free air. There are many factors that go into installation of the wire, but I am sorry voltage does not have a bearing on the wire amperage rating.


a large diesel motor using an electric starter will draw way over 5000 watts to start such as on a boat..........bigger engine starters maybe 24 32 or 36 volts..........

Not sure what this would have do with residential or commerial wiring and isn't really cover by the NEC. I'm sure it applies to the generator it's self but this is a totally different constructed conductor.

be safe...........dont spark around

This I will agree with you completely