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Generator Load

06/18/2012 4:57 AM

What is the maximum & minimum safe Load for Diesel & Gas Generator? What are the probable problem if we run diesel or gas generator in low load and the reason for it?

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#1

Re: Generator Load

06/18/2012 5:14 AM

The maximum safe load is as stated in the original equipment manufacturer's data, or today's overcurrent protection setting, whichever is the lower.

The minimum safe load is zero, and there should ben no problem with this other than unneccessary fuel consumption as a result of not turning it off.

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#2
In reply to #1

Re: Generator Load

06/18/2012 5:29 AM

Thanks.

Most the manufacturer recommended that minimum load for generator is 25-30%, and they explain that without this load your machine piston, exhaust unit will damage! What are the causes for it?

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#3
In reply to #2

Re: Generator Load

06/18/2012 5:30 AM

Speak to the manufacturer, then. <Unsubscribes>

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#4
In reply to #2

Re: Generator Load

06/18/2012 12:00 PM

Haven't you just answered your own question, which we could not have answered anyway, due to your economy lack of information.

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#5
In reply to #2

Re: Generator Load

06/18/2012 5:21 PM

Maximum Safe Load is on the Specification plate on the machine.

Minimum Safe Load is Zero.

Economic and Operational Maximum and Minimum are as per Vendor Recommendations.

Petrol (Gas) Driven Small Generators will run happily at 10-15% for short periods, then they start to overheat.

Diesel Generators are recommended to run at a Minimum of 35-40% to prevent glazing of the cylinders and blowing seals and gaskets. Ideal is 50-60%.
Turbos have also been known to cook due to low oil flow at low loads.

Regards,
Sapper

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#11
In reply to #5

Re: Generator Load

06/19/2012 10:36 PM

Yes, That's it, what I am looking for. Wet stacking at the time of low load or less then 30% of rated load.

(We are using Diesel as Fuel.)

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#8
In reply to #2

Re: Generator Load

06/19/2012 1:50 PM

Minimum SAFE load/condition is zero (no load). A generator manufacturer must conform to safety guidelines in the event of a loss of load (i.e. trip main breaker, fault, etc). In this case a system can be designed such that the generator shuts down if, for instance, the no-load condition remains for a predetermined amount of time.

Minimum RECOMMENDED load is manufacturer specific to maintain rated efficiencies in fuel consumption, reliability (i.e. wet-stacking), etc. This is typically 20% to 30% of rating.

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#6

Re: Generator Load

06/19/2012 1:00 AM

Having run my house with generators for 16 years I found that if I get a motor(gas) with twice the horsepower needed then adjust pully size(Larger) I can run the motor at low RPM and have it last more than twice as long as the recomended motor that has to run on 3500 rpm, with less maintnance. At the low RPM there is no minimum load but I shut it off anyway to save gas and wear and tear. There have been times I have run with just one or two lightbulbs, enough to see whatever Im working on. (Gen is 5000 watt) and have not experienced any overheating.

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#7
In reply to #6

Re: Generator Load

06/19/2012 9:53 AM

Can you tell me what your fuel consumption is? ie, how much do you spend on fuel a week/month/or whatever you go by, and what's your maximum load, say winter with space heaters, TV, etc.

I really would like to know just what it takes to run one of these as a main source of electricity.

Thanks.

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#13
In reply to #7

Re: Generator Load

06/20/2012 1:46 AM

I dont use space heaters or microwaves, I find they are hardest on the generators. I have an Onan Emerald Genset circa 1986, 4500 watt. I put it in the generator shed and hooked a gas tank from a chevy van(1977, 22gal) I could fill that tank and run the generator for a week. That generator lasted 5 years going 24 hrs a day. I wish I could find another that would last as long. The closest was an Onan motor on an old miller welder that was 25 years old when I got it. The welder was rated for continuous duty, I ran it for a year 24 hrs a day. These older models would automatically adjust the throttle to load. So I just turned them way down and if I started using a lot of juice they would power up without going over the rated voltage. The newer generators that are married to the motor, I have a room full of them, all wore out. They average 3 months. Out of all of them, one lasted 3 years. I am now useing a belt driven generator and it has worn out 4 motors, even at low revs. Has to be the best one of them all. I load them all up with lights, TV, security monitors, stereo, computer, and of course power tools, amplifier for my guitar, etc I use propane for the refrigerator, hot water, but thats another story. I dont want to take any more space, I could go on and on.

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#10
In reply to #6

Re: Generator Load

06/19/2012 3:29 PM

Does the lower RPM cause a change in output frequency (58Hz)? Are there any effects on appliances such as those having input switching power supplies that rely on 60 Hz where running at 58 Hz causes them to wear out faster or get hot?

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#15
In reply to #10

Re: Generator Load

06/20/2012 1:54 AM

When I put the bigger motors on I can use a larger pully at low RPMs to get the same speed as a smaller motor that has to go 3500 RPM. The larger pully turns the generator faster so with more horsepower I can get the same generator speed with lower RPM on the motor. The rated moter would not be able to run that slow and still have the power to turn the generator. Almost forgot, in the summer when temp. is over 100 every day I run the swamp cooler day and night.

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#9

Re: Generator Load

06/19/2012 2:13 PM

Bashir;

As far as the "maximum" safe load is concerned:

A critical fact to be aware of is the manufacturer "duty-cycle" rating of your generator.

If the generator is not rated "continous-duty" you will not be able to run at 100% of the advertised generator nameplate output rating.

The "duty-cycle" will tell you the limitations of your generator as far as maximum output is concerned.

For example: A generator with a 60% "duty-cycle" can be operated at 60% of the advertised output for extended periods (100%) of time. However the same size generator depending on manufacturer may only be rated/designed to operate at 100% loading for 60% of the manufacturer's designated time period which could be 1 hour, 2 hours, 3 hours or whatever the machine mechanical and electrical design dynamics dictate.

It is imperative that you know and operate the generator within the manufacturer's design criteria limitations in order to avoid damaging the generator and/or the engine.

You must obtain and review all pertinent operational DATA from the O.E.M. to find the answers to your questions as no two machines from different manufacturers are exactly the same.

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#12

Re: Generator Load

06/19/2012 10:45 PM

Thanks to all of you. All of the answers help me lot ......

Again thanks.

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#14

Re: Generator Load

06/20/2012 1:46 AM

Minimum Load 30 to 40% Maximum 80 to 85% Depend on load power factor. Running generator on low load Cause high oil Consumption oil Leakage From Exhaust.

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#16

Re: Generator Load

06/20/2012 6:56 AM

Wet stacking on low load does not effect all diesel engines.

eg Perkins does wet stack and Yanmar doesn't.

Apparently wet stacking (aka oil in the exhaust) is due to low combustion chamber temperatures.

Cure for it is to run the genset at high load into a dummy load to just cook it out from time to time or have a dummy load that switches on automatically under low load conditions if a smaller generator won't do..

Wet stacking can get to the point where the exhaust system chokes up and then it needs to be manually cleaned.

I will never buy Perkins again. Not because of the problem but because they couldn't explain it (I had to research it myself), denied it was occurring (that was a deal maker!) and could not provide any technical advice.

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#17

Re: Generator Load

06/20/2012 5:08 PM

At low low loads unburned fuel will collect in the exhaust box(es) and become a fire/explosion hazzard. Also at low loads because the pistons and rings are not at their full operating temperature some unbuned fuel will "blow by" and create a condition known as "fuel oil dilution" of the lube oil. This "fuel oil dilution" can result in a flammable atmosphere in the lube oil sump and is also an explosion hazzard when shut down, not to mention the loss of lubrication because of the dilution. It takes time for both of these conditions to develop. Follow the manufacturers instructions regarding proper loading. If you are forced to deviate, wipe out your exhaust boxes when shut down and test your lube oil. Your manufacturer should be able to provide guidance on the allowable dilution limits.

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#18
In reply to #17

Re: Generator Load

06/22/2012 10:36 PM

I have never had any of those problems and it has been my experience the manufacturers these days design everything by computer to break after the warranty expires. Big corporations have bought out most reputable firms and what you get these days is mostly junk, manufactured in another country. I have a room full of these types of generators. In most cases you cannot return a defective generator even 3 days after purchase, they will refer you to a repair place and even then the repair places wont honor the warranty. I consider myself to be very fortunate to be able to get one generator out of four that lasts any length of time, and even then I have to watch them closely for defects. Contacting manufacturers can be a very frustrating experience with little chance of satisfaction. Good luck!

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bashir01219 (3); Envelope Guy (1); lyn (1); nitin revankar (1); PWSlack (2); Sapper (1); SHOCKISCAN (1); spaceracer (4); szwasta (2); Wal (1); XNuke (1)

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