Buying Advice Aurora Silent Diesel Generator

[ayelvington]

Wet stacking: I had heard of this before, but I never dealt with it until my generator stopped working because of a carbon-clogged injector. If you're running a diesel generator for prime or back-up power, it's something you need to be aware of and mitigate by ensuring you have enough of a load on the engine.

Here is a great primer to help you along: http://www.kraftpower.com/pdfs/KPC_I...t_Stacking.pdf

Space heaters make very affordable load banks for small generators, and the one that I referenced before ensures a balanced and purely resistive load. I remember watching a portable generator grunt at a cabin when someone plugged in a toaster!

Another trap folks get into is testing a battery-powered transfer switch while the batter charger is connected. (I've seen this go very badly under emergency conditions.) Make sure that the transfer equipment works properly with only the battery running it. Boiled batteries can appear charged to a charger, and do nothing for you when the lights go out.

Anyway, no matter whose generator you buy, be sure to exercise it periodically under load to make sure it works, and to blow the carbon out.

[Skyco]

I called Aurora and talked with Ron. He pointed out that a malfunctioning fuel pump solenoid will lean the mix, make the generator run hot, and eventually cause the generator to shut-down.

I hope that isn't what he told you. A diesel always runs "lean" unless it is overfueled (notice I did not say -rich-) it cannot be run too lean and there is no "mix"..

[BobRip]

I agree! Our generator really only logs about 12 hours a year. If you're going for continuous service, be sure to match to your load or you'll have troubles with carbon build up. I just ordered a 240V space heater to act as a test load bank and supplemental load since our generator doesn't really get loaded until everything is on (including the water pump). TPI Corp. electric space heater model H474TMC 4000 watt heavy duty 240 volt | eBay is an affordable load bank with 2kw/4kw settings.

Do you have to keep it loaded most of the time or just occasionally?

[ayelvington]

I hope that isn't what he told you. A diesel always runs "lean" unless it is overfueled (notice I did not say -rich-) it cannot be run too lean and there is no "mix"..

Actually, it can when it's malfunctioning! (I agree with you for normal operation, but this was not normal.) The generator was running with virtually no load, so it was in the process of wet-stacking since much of the fuel was not burning (too rich). As the jets clogged (there are 4), the mix leaned, but the engine did not slow since there was virtually no load. As the air/fuel mix went to lean (abnormal operation), the combustion temperature went up which explains why the head got so hot. Eventually the last jet clogged and the engine stopped running.

None of this could/would have happened if the engine had been properly loaded so that the temperature would have been where it belonged, and changes in the quantity and time of the fuel injection would have changed the available power/torque/rpm.

[ayelvington]

Do you have to keep it loaded most of the time or just occasionally?

It's really not a good idea to run it unloaded because of the gradual wet stacking. Mind you, my machine had over 60 hours on it before it grunted, but it was not good for it. I strongly recommend you read the document that I referenced earlier, and I'm going to exercise mine at 80% load (4 kW) from now on. I have current meters on the way so that I can monitor the load when the house is being backed up, and make sure there's at least a 50% load on it to prevent wet stacking.

The reference document that I cited earlier gives the NFPA code requirements for exercising an emergency generator. Good reading!

This is the first time that I've dealt with a generator that was too big for the load! I guess it's one way to learn

[Skyco]

I hope that isn't what he told you. A diesel always runs "lean" unless it is overfueled (notice I did not say -rich-) it cannot be run too lean and there is no "mix"..

Actually, it can when it's malfunctioning! (I agree with you for normal operation, but this was not normal.) The generator was running with virtually no load, so it was in the process of wet-stacking since much of the fuel was not burning (too rich). As the jets clogged (there are 4), the mix leaned, but the engine did not slow since there was virtually no load. As the air/fuel mix went to lean (abnormal operation), the combustion temperature went up which explains why the head got so hot. Eventually the last jet clogged and the engine stopped running.

None of this could/would have happened if the engine had been properly loaded so that the temperature would have been where it belonged, and changes in the quantity and time of the fuel injection would have changed the available power/torque/rpm.

You hit on the likely real problem in your last sentence. Again a diesel, especially a single cylinder one, cannot run too lean.

What likely happened is as the injector clogged the timing was off since injector pop off pressure changed or the injector was dribbling (in effect uncontrolled timing) and THAT is what made your diesel overheat.
If timing stayed the same as the injector clogged power would go down, but it will not and cannot run "too lean".

[DarkBlack]

It's really not a good idea to run it unloaded because of the gradual wet stacking. Mind you, my machine had over 60 hours on it before it grunted, but it was not good for it. I strongly recommend you read the document that I referenced earlier, and I'm going to exercise mine at 80% load (4 kW) from now on. I have current meters on the way so that I can monitor the load when the house is being backed up, and make sure there's at least a 50% load on it to prevent wet stacking.

The reference document that I cited earlier gives the NFPA code requirements for exercising an emergency generator. Good reading!

This is the first time that I've dealt with a generator that was too big for the load! I guess it's one way to learn

That sounds like a double PITA. You have to worry about a minimum 50% load, so there goes any fuel savings, and then if you have it loaded with dummy loads, then you risk not having enough headroom for some real loads that may kick on. Also 50 hours seems like an awfully short time to fail.
I think I'll stick with my petrol backup.

[daybreak1998]

Howdy,
Any generator (gas, diesel, propane, natural gas) should have a load put on it. This is not just for the engine, but for the magnetic needs of the generator (alternator) head. The same thing can be said about someone not using a generator for a long time and then runs it, only to find it then does not produce power. You would then need to do a field flash, which is like jump starting the windings and making a magnetic field to then produce energy.

Engine have rings, the pistons might go up and down, but the rings need to seat. Like anything, non-use is hard on a engine. Even a old old car, the engines still needs to run and brought up to proper operating temperture. That is why the standby generators out there have the exercise cycles which obvoisly run longer than 5 minutes.
60 hours on a generator is longer then you think.

[DarkBlack]

Howdy,
Any generator (gas, diesel, propane, natural gas) should have a load put on it. This is not just for the engine, but for the magnetic needs of the generator (alternator) head. The same thing can be said about someone not using a generator for a long time and then runs it, only to find it then does not produce power. You would then need to do a field flash, which is like jump starting the windings and making a magnetic field to then produce energy.

Engine have rings, the pistons might go up and down, but the rings need to seat. Like anything, non-use is hard on a engine. Even a old old car, the engines still needs to run and brought up to proper operating temperture. That is why the standby generators out there have the exercise cycles which obvoisly run longer than 5 minutes.
60 hours on a generator is longer then you think.

I disagree. Gas generators do not "stack". It's totally not the same issue.

[BobRip]

I disagree. Gas generators do not "stack". It's totally not the same issue.

Stacking is not a problem, but non use is. That was the point he is making.