Generator output question

[2cool]

I have a 7hp HF generator, the advertised output is 3500 watts surge and 3050 nominal. I was exercising it last week with two resistance heaters; one 1600w and one 800w. By my crude reckoning, that's almost 80% load. My questions are:
1.Why did the circuit breaker open after about 30 minutes?
2.Is it just cheap components that are over-rated?
3.Is it reasonable to expect the set to deliver 3050watts for hours on end?
4.Should I replace the breaker with a better part?
5. I need to power two sump pumps, 1/2 and 1/4 in case power goes out in a storm. Do I need a bigger unit?
I don't have natural gas or propane possible. So it's gas or diesel.
Thanks for your help in advance!!!

 

[AandPDan]

What is the rating of the circuit breaker? On a standard outlet, 20 amps is 2400 watts so at 100% load there is a good chance of it tripping.

Some generators split the outlet. 20 amps to each receptacle, sharing the neutral connection. You'd be able to pull 240 vac from both hots.

What model generator?

 

[cancov]

I have recently been looking at this size generator lately as well. If you don't mind, how much did you pay? I've been looking more and more closely at the Generac 3250, from Home Depot.com, for ~$399. When needed for emergencies, I would entend on powering (1) kitchen refridgerator with freezer, (1) small deep freezer, a few fans and a CFL light or two.

 

[JimPghPA]

If it has 240 Volt output, and two 120 Volt outputs you have to realize that each 120 Volt output is one side of the 240. If the load was 120 and you put both on one side (both connected to only one plug on the generator) then the current through that one side would be greater than the rating of the circuit breaker.

If you put each load on it own plug on the generator than it should be able to run non-stop without tripping the circuit breaker. If it tripped the circuit breaker when ran like that then either the load is more than you think it is, or the breaker is bad.

I do not know your level of understanding how 240 and the two 120 Volt circuits are related, and I do not want to insult you, but if you do not know the relationship of how the 240 and the two 120s are wired, then get someone with a background in electric to explain it to you.

 

[tomcat27]

that generator should be able to power your two sumps. each one will pull more power as it starts up, so you may to ensure that they are on separate outlets or legs.

motors also vary widely in efficiency: my previous sump was rated 9 amps. its replacement uses 5 amps running.

the generator SHOULD deliver 3050 watts continusously - depending how you spread the load. last summer were had an outage that lasted 7 days - and the generators around here ran continuously. so did ours at work. yes, we ran a 5000 watt generator in the parking lot to power our 5 servers, network, and communication gear.

 

[SrDriver]

One Horsepower = 746 watts. Figure a spike of 3 to 5 times of this when the motor starts.

You should be fine.

 

[Donald]

You can also measure the voltage between the HOT side of each 120V outlet to determine how they are wired. If its zero they are both on the same leg of 220V, if its 220V they are split across both legs. How many circuit breakers do you have? One or two?

 

[itguy08]

Which version do you have the New Predator one or the older blue Chicago one?

I've got the older 5.5kw Chicago one and on mine there are 4 outlets with 2 separate wall outlet types. Each set of 2 has its own circuit breaker. If you put both loads in the same vertical socket that's why it blew. Put the loads across from each other and you'll be fine.

I exercise ours with the following:
1x 1500 watt space heater
1x 1850 watt hair dryer
1x 500 watt halogen shop light
A box fan

I space the loads out on both sets of sockets and yet to have a problem. The generator just runs.

 

[2cool]

The generator is an older HF Chicago 7hp 3050rated/3500 surge watts. The outlets are a duplex-style like in a house and a round type like I use for my RV to get 30 amp/125v service at a campground. Both outlets are labeled 120v. There is only one 20Amp breaker.
I've had this for about 2 yrs. and paid $329 for it. Runs very strong and no problems as far as the engine goes. This last time was the first that the breaker popped with the same load.
I am not very informed concerning AC generation and control; so I'd get a real electrician to do anything on that side of it. I was just wondering if I had to or am I asking too much of it.
THANK YOU once again for your interest and answers. This must be the best place to hang your digital hat on the web. We are a wonderful community!!

 

[2cool]

No insult taken, Jim!!! One of my favorite quotes is from the Dirty Harry series. "A man's got to know his limitations". Thanks again for the care that is evident in your message. I do enjoy your posts.

 

[itguy08]

What you may want to try (if you have not already) is plugging 1 load into one of the duplex outlets and the other into the other one.

Something doesn't sound right as 3080 watts is 25.66 amps at 120v which is more than the 20a breaker you have. I wonder if the 20a breaker is for each duplex - 20a for each duplex outlet.

Since you have a twist lock plug you could also use something like this to help you distribute the load.
http://www.electricgeneratorsdirect.com/CableMaster-CMGACF3025/p8278.html

 

[The_Jeff]

Originally Posted By: cancov
I have recently been looking at this size generator lately as well. If you don't mind, how much did you pay? I've been looking more and more closely at the Generac 3250, from Home Depot.com, for ~$399. When needed for emergencies, I would entend on powering (1) kitchen refridgerator with freezer, (1) small deep freezer, a few fans and a CFL light or two.


You can go smaller. Get a Kill-a-watt meter that measures what YOUR fridge/ freezer draws-- you can borrow the meter from your public library or shell out $20. My fridge runs on about 250 watts and the start up surge is maybe 400-500. It's a modern fridge with a "soft start" capacitor that doesn't draw tons of power. And the odds of your fridge and freezer starting simultaneously are very small, provided you plug them in one at a time.

More generator is more noise and more weight. A 2000 watt running will do you fine, IMO. Fuel consumption is better at a bigger % of total output load and running off gasoline is 10-15x more expensive than grid-- I crunched the numbers.

 

[JimPghPA]

I took another look at the original post.

1600 Watts + 800 Watts = 2400 Watts

2400 Watts / 120 Volts = 20 Amps

If you pull 20 Amps through a 20 Amp breaker it is right on the edge of what will trip it. Kinda like balancing on the apex of a comb. Could fall to ether side, ie trip, or not trip.

It sounds like that generator is only 120 Volts, and does not have 240 Volts, therefore it would not have two separate 120 legs.

It is possible for one plastic plug with two outlets that looks like the ones normally found in most houses, to have two separate 120 legs, each being one side of the 240 because there is a metal link in the middle of where you wire many of these plugs, and if that metal link is removed it could be wired to have two separate legs. If the generator is 3500 Watts surge and 3050 Watts continuous wiring the 20 Amp breaker for only one leg would limit it to 2400 Watts, so it would seem that the two plugs could each have separate feed. How else could this generator output more than 2400 Watts?

Some of the other post talk about running motors. If you are running equipment that has motors the starting current can be really high for a few seconds at start up, and that can be enough to trip a breaker, especially if there is already several amps of load already on the breaker.