Wet stacking generators

[TractorGuy]

From what I've read if you haven't had a problem with the MEP-003A wet stacking you shouldn't have to worry about one of the newfangled units.

I would like tighter control on the frequency on my MEP-803A but I set it around 61 with no load and it remains between 60 to 59 loaded. When I crank my load bank to 50 amps it will get down to 58.8. (I converted mine to digital meters) I set my voltage to 246-248 to match what it is at my panel from the power company. The voltage remains steady at any load. I originally had some voltage drop under load on one leg but that went away with some contact cleaning and recrimping.

 

[Industrial Toys]

I have said it before. Frequency is not very important. Most switching computer supplies could not give a darn. In fact (I believe) many even work 50 or 60 cycle without changing over anything.

Frequency is only useful to give an indication of how well the generator is keeping up to the load.

 

[Gcorron]

frequency is important to non-linear loads, like computers and radios, etc.. If you are far off frequency, it can cause shut down (most of these items have shut down circuits now days) and overheating, shortening the life span.

When buying a gen, especially in the little fellas, it is important to check the harmonic distortion number if you have any intention of using electronics. The lower the harmonic distortion, the better. Not real sure about the newer TV's, but I'm guessing being off can effect them greatly. Sine wave is also very important for evaluation, lots of the little fellas put out square wave. Look for one with a true sine wave for critical electronic loads.

I've had friends who thought they got a terrific deal on a gen to find out that it would not allow them to use their radios, and would not work with their battery chargers. If light bulbs, refrigerators and sump pumps are your big target, these things are not nearly so critical.

George

 

[buickanddeere]

If the unit is water cooled and operating at 195-210F, don't worry about it. If the unit is air cooled then yes she will operate too cool for fuel efficiency and low emissions.

 

[bdog]

From what I've read if you haven't had a problem with the MEP-003A wet stacking you shouldn't have to worry about one of the newfangled units.

I would like tighter control on the frequency on my MEP-803A but I set it around 61 with no load and it remains between 60 to 59 loaded. When I crank my load bank to 50 amps it will get down to 58.8. (I converted mine to digital meters) I set my voltage to 246-248 to match what it is at my panel from the power company. The voltage remains steady at any load. I originally had some voltage drop under load on one leg but that went away with some contact cleaning and recrimping.

I have put about 400 hours on it since I got the MEP. It burns a quart of oil about every 50 hours. Not sure the cause or if it was like this when I purchased it.

 

[jenkinsph]

I use a 5.5kw Onan CMQD on my service truck works great for the last 12 years or so. Mine is hooked up to my F550 fuel tank so fuel is always fresh and no hauling cans of diesel for it. Very quiet with a Kubota diesel engine running at 2800 rpms. With belt drive the engine can run at its optimum speed while the generator turns at 1800 rpm. Mine is a fixed speed 120/240v 25a 60 cycle model. The new models are rated for 5kw now. These are available in 120v and 3phase models too.

The 8kw CMQD is variable speed to compensate for light loads. I suspect since you will have 40 hrs at a light load (half of the time) that this generator would be a good choice for your uses. Colorado Standby Generators sells this unit for $8,740 with weather proof housing.

These are not cheap but I never experience any problems with sensitive loads and mine has been bullet proof since new. Only expense has been fuel and filters and have about 950 hours on mine.

Here is a link Diesel Generators for Sale - Cummins Onan Commercial

 

[100 td]

Sine wave is also very important for evaluation, lots of the little fellas put out square wave. Look for one with a true sine wave for critical electronic loads.

If you are purchasing a true rotating field 1800 rpm 4 pole generator like the OP is looking at, it produces sinewaves.
If you wish to purchase some elcheapo variable or high speed inverter generator, it could produce a modified sinewave (which is like a square wave with a zero time break between the cycles). Good quality inverter generators produce sinewaves.(well close to sine waves and I don't know of any producing square waves or saw tooth waves), but there is always the possibility that someone is selling junk.

As mentioned previously, most electronic switching power supplies these days are multi-voltage/multi frequency input so frequency variation should not be a problem. Frequency output of generators affects the running speed of electric motors, so if your motor it expected to run at 3450 rpm at 60Hz allowing for losses, it will run slower if the frequency being supplied is less than 60Hz. When it gets way out of whack it can lead to heating etc.
A lot of cheap AC alarm clocks are frequency dependent, so if your frequency is low, the clock will be slow.

 

[buickanddeere]

60Hz equipment has to be operate at 60hz so anyone thinking of throttling hack and reducing the frequency, lets forget about that idea.

 

[jenkinsph]

60Hz equipment has to be operate at 60hz so anyone thinking of throttling hack and reducing the frequency, lets forget about that idea.

I agree with the need to maintain 60hz but that does not mean you can not adjust the engine speed in all cases. The better quality small inverter generators today can provide clean modified sine wave power that is good enough for most uses.

Square waves would be very hard on most loads and I consider this unacceptable. A good modified sine wave form that both my Honda generators produce looks pretty good on a scope. Good electronics and technology today can make a difference.

 

[Industrial Toys]

I just happened to look at a particular computer PSU. Yup. Good for 50 or 60 hz. That doesn't mean EXACTLY one or the other. It will probably be happy deviating from either quite a ways. Even new ballasts go practically from DC to light and a HUGE voltage range.

I was not aware that a rotating alternator could put out square waves. Not saying it can't, but I would wonder how.