What is "dirty electric"?

[General Lee]

Alright, I didn't take a pic but basically the 120/240V receptacle is 30 amp capable of 5,500 watts at 22.9 amps for 240 volts or 2 independent 120 volt loads at 22.9 amps each. It is protected by a 2 pole circuit breaker.

I also have 4 120 volt (duplex receptacles) protected by a 2 pole breaker. I can use one of these for up to 2,400 watts at 20 amps of current.

So when I feed my panel to run a few breakers, can I only use 22 amps or 30 since I'm running off the 120/240V receptacle? I was figuring 30

I have a hard time understanding the inner workings of electricity.

 

[joshuabardwell]

So when I feed my panel to run a few breakers, can I only use 22 amps or 30 since I'm running off the 120/240V receptacle? I was figuring 30

I don't really follow your description of your 240 circuit. You say that it's protected by a 30A breaker, but then you say 22.9A at 240V. Where does the 22.9A number come from?

 

[daybreak1998]

Howdy,
As with any appliance, motor, pump, refrigerator, etc... you want the 60Hz cycle. The overall volts could be plus/minus some and not matter as much. All US electrical items need to pass a UL rating. The UL rating states that the item can withstand a certain tolerance in voltage input. They say the UL rating is around 5% difference, which most manufacturers will build in a fugde factor of around 7% tolerance.

As with any electricty in the US. You really are looking at keeping it at 60Hz at all times. At least with a variance of +/- 2%. If you look at the spec for larger generators, they will have either a mechanical governer, or a more expensive electronic governer to keep the tolerances close to 60Hz, either under load or not.

If a generator is a 5500 watt unit, I do not care if it has 6 20amp plugs on it. It can only power a absolute maximum of 5500 running watts. Even if you think you can use the 120/240 30amp connector to its full power and then still have your 20amp duplex supplying a full 20amps. It just does not work like that.

 

[General Lee]

I don't really follow your description of your 240 circuit. You say that it's protected by a 30A breaker, but then you say 22.9A at 240V. Where does the 22.9A number come from?

I made a mistake, reading my manual I need a 4-wire (which I have) cord rated for 250 volts at 30 amps. This is where I mistakenly got the 30 amps from. Here is the specs from the manual:

Starting wattage: 8,250
Wattage: 5,500
AC Load Current at 120 - 45.8 volts, at 240 volts - 22.9 amps
Phase: single phase 60 Hertz

However, the 120/240 volt receptacle description is as follows: 120/240 AC, 30 amp locking receptacle

So basically my home circuit breaker is getting a maximum of 22.9 amps, right?

 

[aczlan]

I suppose it wouldn't be out of the question to have a single-leg 240 circuit, with a single 240-volt breaker, but I don't know of anywhere that's actually done. Is there such a place?

Outside of the US and Canada that is all that they do, not seen here as our equipment isn't setup to use that system.

Aaron Z

 

[joshuabardwell]

However, the 120/240 volt receptacle description is as follows: 120/240 AC, 30 amp locking receptacle. So basically my home circuit breaker is getting a maximum of 22.9 amps, right?

I'm not an electrician, but that is my interpretation. You're using a 30-amp cord, because the cord needs to be rated for equal to or better than the amperage it's carrying. So to carry 22.9 amps, you use a 30-amp cord. The 22.9 amps comes about because it is the max capacity of the generator itself. 5500 watts capacity / 240 volts = 22.9 amps. Assuming the breaker(s) on the 240 receptacle can handle 22.9 amps (and, surely they can), then the generator can put its full capacity out the 240 receptacle.

Bear in mind that's 22.9 amps at 240 volts. Most of the stuff you are running in your house is probably running off of 120 volt, so that's 46 amps.

Here is something I'm not clear on, and maybe somebody else can answer it. When you backfeed a 240 line into your main panel, each leg of the 240 is wired into an individual 120 volt breaker, right? And then, somehow it feeds back into the house. I know that if you exceed the capacity of either leg of the 240 line, you will pop the breaker. When a 240 appliance is operating, it presumably draws equally from both legs. But when you are splitting a 240 line, the draw on one leg can exceed that leg's capacity while the other leg may not be being used much at all. Can that happen when you're backfeeding a breaker? What determines how the loads are distributed across those legs?

 

[joshuabardwell]

Outside of the US and Canada that is all that they do, not seen here as our equipment isn't setup to use that system.

Riiiight. Duh. People outside the US have electricity too, huh? How about that.

 

[General Lee]

Here is something I'm not clear on, and maybe somebody else can answer it. When you backfeed a 240 line into your main panel, each leg of the 240 is wired into an individual 120 volt breaker, right? And then, somehow it feeds back into the house. I know that if you exceed the capacity of either leg of the 240 line, you will pop the breaker. When a 240 appliance is operating, it presumably draws equally from both legs. But when you are splitting a 240 line, the draw on one leg can exceed that leg's capacity while the other leg may not be being used much at all. Can that happen when you're backfeeding a breaker? What determines how the loads are distributed across those legs?

They way I currently set up my genny (Soon to change when I upgrade genny) is I had a 40 amp breaker installed in the panel strictly for the genny. The breaker is connected to a receptacle for my 30 amp genny cord. I'm feeding the panel through this breaker so to speak. However, I'm not operating any 240 appliances. Mostly just 3 or 4 breakers and if its my well or water heater its one at a time.

I'm with you, I assume its drawing equally from both legs but I read its possible to get uneven voltage across one or the other legs. Someone else that knows the technical side of this will have to chime in.

On another note, based on what you explained earlier in the thread on overloading a genny, its very possible that is why my microwave got damaged. I had 3 fridges going, several lights, TV and associated satellite box and a surround sound system going all while the wife was cooking in the kitchen. Gas stove so no electric being used but the microwave may have put the generator over the top. Thats why I'm trying to understand if I got 22.9 amps at the panel or 30. 22.9 isn't much when you start adding things up.

 

[joshuabardwell]

On another note, based on what you explained earlier in the thread on overloading a genny, its very possible that is why my microwave got damaged. I had 3 fridges going, several lights, TV and associated satellite box and a surround sound system going all while the wife was cooking in the kitchen. Gas stove so no electric being used but the microwave may have put the generator over the top. Thats why I'm trying to understand if I got 22.9 amps at the panel or 30. 22.9 isn't much when you start adding things up.

If you've got a generator rated for 5500 watts continuous, then you can't pull more than 22.9 amps at 240 volts, period. (This is ignoring the "surge" rating, of course.) The cable and the breaker might limit what you could safely draw, but since they exceed your generator's rating, that's not an issue. But that's 22.9 amps at 240 volts, which is double that at 120 volts, which is where most of your power draw is going to be.

Microwaves are real energy suckers. If you think about it, even a weak microwave is rated at 800 watts, and more powerful ones go up to something like 1500 watts. For some reason, my dishwasher and my microwave (built-in over the stove, so can't move it) are on the same circuit. If the microwave runs when the heating element in the dishwasher is on, the breaker trips every single time.

If your generator has a volt-meter, you can check for over-capacity simply by checking to make sure it's putting out 120/240 or thereabouts. If you have a Kill-A-Watt, you can do the same from any outlet that is fed by the generator. If you were running your home off of extension cords, it would be easy to plug the Kill-A-Watt into the cords and check the actual watt/amp draw of everything running off the cord, but since you're feeding the house via the main panel, that's not an option... unless you check every single appliance that you're running individually, which, to me, would be a PITA. I have looked to see if I could find a version of the Kill-A-Watt that would plug into a 3 or 4-prong 240 cord, but I don't think they make one. Maybe some other kind of meter that shows amp draw or watts could be installed near your main panel or your generator receptacle. This would make it easy to tell if you were nearing your generator's capacity.

 

[hr3]

Thanks from me too. I've always wanted to know more about those things.
Can you tell me how one determines when a generator is overloaded or how much of the rated watt output you can use before it becomes questionable? Furthermore, how would one go about sizing a generator?

You can start sizing with this..

Equipment Wattage* Equipment Wattage*
Broiler 1,400 Personal Computer 500-2,000
Central Air Conditioning 2,000-4,000 Planer 300-900
Chain Saw 1,000-1,800 Refrigerator/Freezer 600-800
Circular Saw 1,200-1,600 Router 100-1,300
Coffeemaker 400-800 Sanders (belt, disc, orbital) 250-1,500
Drills (depends on size) 250-1,200 Shop Vacuum 700-1,400
Electric Furnace 5,000-25,000 Space Heater 1,250
Electric Range (oven only) 5,000 String Trimmer 600-1,100
Electric Range (one element) 2,500 Sump Pump 1,500
Hair Dryer 1,200-1,500 Table Lamp (tri-lite) 150
Heater (radiant) 1,300 Television 100-350
Hedge Clippers 300-1,000 3/4 HP Paint Sprayer 1,800
Hot Plate 1,250 Toaster 1,100-1,700
Leaf Blower 1,000-1,400 Water Heater 3,000-4,500
Microwave 1,200 Water Pump 1,000-2,000
Miter Saw 500-1,000 Window Air Conditioner 600-1,500
Outdoor Lighting 500-1,000