I really want a Honda EB3800 wheelbarrow style generator but don't have $2K to spend. I noticed this generator at the local HF:
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It has a nice Robin Subaru engine driving a Made in China generator. I realize this generator has two 2000W 120V circuits, instead of one 4000W
120V circuit. But I think that may be adequate for my needs--home backup and occasional use at the job site (aka yard). While I wouldn't be using it every day, I do want something that will last a long time. I have no doubt the Subaru engine is up to the task, but I wonder about the generator head.
I have a 20% off coupon burning a hole in my pocket (from harborfreightusa.com).
"AL" wrote: (clip) this generator has two 2000W 120V circuits, instead of one 4000W 120V circuit. But I think that may be adequate for my needs (clip) ^^^^^^^^^^^^^^^^^^ Aren't those two things completely equivalent?
Expensive generators like the Honda have a single 120V outlet (among other outlets) capable of supplying the full output current of the generator. This is useful for starting a table saw, air compressor, air conditioner, etc.
As I said, a cheap generator obtains 240V using a cost reduced method of connecting two 120V circuits in series. As a consequence of this cheap method of obtaining 240V, each 120V circuit is only capable of half of the max output of the generator.
I think you need to peruse the docs available on some of the major generator manufacturers sites (Onan, Kohler, Generac, etc.) as you seem to have a number of misunderstandings of the way alternators (generators) are constructed.
All 120/240V single phase generators are composed of two 120V windings in series which is the same as a 240V winding with a center tap. Some
120/240V single phase generators wind one of the 120V windings with heavier gauge wire or with doubled up wire to allow that winding to be loaded to the wattage capacity of the generator (the other winding must be unloaded or you overload the engine).
Suggest reading up on 2 pole and 4 pole alternator designs (6 + pole exist as well but are not usually found in small generators). Explore single and three phase winding configurations including the 12 lead reconnectible three phase design. Look at brush and brushless designs and the different excitation methods.
Pete, maybe you can help me clear up my confusion. If we have two windings that are in phase, then we can connect them either in parallel (getting entire capacity at 110v), or put them in series (getting entire capacity at 220v).
This is the way my Onan diesel generator is. I had a choice of either wiring it for 110V 7 kW, or at 220V 7 kW. I chose to wire it at 220v, with a center tap.
On an "expensive" 4000 Watt gen set, you can draw:
4000 Watts @ 240 Volts from one outlet, OR
4000 Watts @ 120 Volts from one outlet
On a "cheap" 4000 Watt gen set, you can draw:
4000 Watts @ 240 Volts from one outlet, OR
2000 Watts @ 120 Volts from one outlet x 2 outlets = 4000 Watts
When buying a gen set, you need to understand what you are going to do with it, and then make sure it has the capacity to supply enough power at the voltage you require to do the job. This means that you have to read the detailed specifications for each power outlet on the gen set that you will actually plug your load into, rather than relying on the overall power rating the generator.
You have ONE power cord coming out of your power tool that you plug into ONE power outlet on the generator supplying 120 Volts. How much power can that ONE outlet deliver? How much power do you need from that ONE outlet?
A 4000 Watt gen set supplying 2000 Watts per outlet from two outlets is not going to do the job if you need to draw 4000 Watts from one outlet. This is the difference between a "cheap" generator and an "expensive" generator. The "expensive" generator can deliver 4000 Watts @ 120 Volts from one outlet. The "cheap" generator delivers
2000 Watts per outlet from 2 outlets.
If you are planning to run a motor off your gen set, your gen set must be sized for the power required to start the motor, and not for the power required after the motor is running. The rule-of-thumb is that the generator power required to start a typical fractional horsepower induction motor is about 10 times greater than the nameplate horsepower rating of the motor converted into Watts. For example, 1/2 horsepower converted into Watts = 373 Watts. To start a 1/2 hp motor, your generator must deliver 10 x 373 Watts = 3730 Watts FROM ONE OUTLET. Can it?
That would be something of a 4 wire reconnectible. If the alternator was designed for it that is certainly an option. It's a lot like the two sets of input and output windings on various single phase step up/down transformers where you connect series or parallel depending on your needs.
Great answer- we used to sell gensets and customers would undersize them because they didn't figure inrush current. Our rule of thumb for motor starting was three times the running amperage, with the power source a high quality genset. We didn't sell cheapos.
-Carl (proud owner of a genuine Kohler Electric Plant)
You still haven't explained what this possibly has to do with being cheap vs expensive, which is *nothing*. It's just a matter of terminal configuration, and an efficient way to yield both 240 and 120 at the same time (which is why it is used for residential wiring). Cheap generators may be wired that way, because it is the best compromist, but that's not why they're cheap.
And just what utility generators provide a single 120VAC outlet at, what, over 30 amps you're claiming, and not 240? (As opposed to, say, RV gensets that are expensive for any number of unrelated reasons, and stuck with
It's a monster- Kohler K181 single cylinder cast iron engine and a Kohler generator section. The generator section has three windings- AC, starting, and a (IIRC) 200 amp 12/24 volt DC winding for jump-starting cars or trucks. The big DC circuit can, according to legend, be modified for use as a welder. The one in mine is tied off. The thing weighs about 300 pounds and the AC output is only 2200 wats, making less-than-portable. However, it has so much rotating mass it will pick up sudden loads smoothly (like the time I had it powering a fridge, halogen lamp. and a kerosene salamander and plugged in another fridge I thought was off. It wasn't and the entire genset jumped off the ground a couple of inches. The fridge started just fine.) The starter winding is neat- press the button and the engine quietly starts to spin up- no gear noise.
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