getting a backup generator?

castilloj · February 2013

Hello i have a sdmo 11kw generator that needs and engine rebuilt. im 2 weeks from getting the parts to rebuilt it. so ive been using small backup generators just to keep fridge and freezer cold. But The generators keep breaking. They are cheap chinese made dgm generators.
Ive been looking at the 7 kw Kubota generator and i noticed that actually has 2 30 amp receptacles. im only getting up to 40 amps on my sumo.
My question is how is that posssible that a 7000 w generator would offer more power than a 11000w?

Cariboocoot · February 2013

Re: getting a backup generator?

It wouldn't. 7kW is less than 11kW. Unless you are in the marketing world.

You can put as many outlets of whatever current capacity you want on a generator. That doesn't change its output, it only makes it easier to overload. I've got one with a 30 Amp 240 VAC outlet and four 15 Amp 120 VAC outlets. Can't use all of them at once, though; it's a 5kW gen.

Stay away from cheap generators too. Some of that stuff doesn't last for a tank of gas. They usually are the ones with the peak power ratings emblazoned boldly on them too. Continuous power rating gets buried in small print somewhere in the manual.

BB. · February 2013

Re: getting a backup generator?

Need more information--But a couple of things.

If the generator is a 120/240 VAC unit--Many will only output 1/2 power per 120 VAC circuit or 100% power on 240 VAC circuit.

A few generators allow the connection of the two 120 VAC coils in parallel so they can supply 120 VAC at 100% of rated load.

Another issue... Most "consumer" generators rate their maximum kWATT output--Where kWatt = kVA rating (i.e., PF=1.0). Commercial units may rate kVA > kWatt (i.e., kVA*PF=kW). So the PF rating may be 0.67 or 0.80 or so--for kVA=KW/PF.

And--there are Surge, 5 minute, 30 minute, 1 hour, etc. ratings...

Lastly, there are ambient and altitude deratings too... So, there are lots of ways for "Marketing" to "adjust" their output ratings to meet a market point.

Chris Olsen has "played" with lots of generators and has found some that exceed their ratings (his Honda 4000SX is "good", off brand gensets tend to be not so good), and others that may have problems trying to reach 60-75% of their name plate ratings.

Regarding the 7kW and 2x30 amp outlets.. Is that 2x30 amps at 115 VAC?
2x30a*115 volts = 6,900 watts

And there is the typical (US) NEC derating of 0.80--No circuit should operate at over 80% of rated output (circuit breakers will not trip at 80% of rated current and will trip--eventually--at 100% of rated current).

-Bill

solarvic · February 2013

Re: getting a backup generator?

Chris olson also has a champion generator that he thinks is good for the price. Chinese built with a honda clone engine It just outputs 110v and is rated 4000watt surge and 3500 running. They can be had with electric start for around $500 with remote electric start. Also if you want to spend less tractor supply sells one with pull start for $330 but is not for sale in california.

castilloj · February 2013

Re: getting a backup generator?

BB. wrote: »

Regarding the 7kW and 2x30 amp outlets.. Is that 2x30 amps at 115 VAC?
2x30a*115 volts = 6,900 watts

-Bill

Yes I just noticed it is 2x30 amps at 115VAC.

I just wonder if I need lower the charger on the Mate so that it does not overload the generator.

westbranch · February 2013

Re: getting a backup generator?

probably... what is the continuous output rated at? a bit less than that (30 Amp) would be best for the generator. No overload and no shutdown say to ~ 85% load.

getting a backup generator?

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