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 > Disconnect load before stopping generator?

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pianotuna

Regina, SK, Canada

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Posted: 07/12/19 01:04pm Link  |  Quote  |  Print  |  Notify Moderator

Since MrWizard has the Champion 3400, he does not need to disconnect loads for spin down. The Champion does it for him.

4x4van wrote:

MrWizard wrote:

4x4van wrote:

The idea that load must be removed prior to starting/stopping a generator seems to fly in the face of AGS systems used to keep an RV cool (for pets, for example) while the owner is not there.


NO..it doesn't ... think about it

the ATS in the RV does not connect the RV to generator until after the the generator has started running, there is NO load on the RV generator until the ATS closes, then the A/C can come on
And when the generator stops?



Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

MrWizard

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Posted: 07/12/19 06:24pm Link  |  Quote  |  Print  |  Notify Moderator

Only thing I can think of
Is that there was a temperature control connection for the AGS right that says we need the a/C start the genny

Doesn't that same control keep the genny running until a low temp setting has been reached ? And maybe even for a specific time duration
Which means the a/C would either be off, or at a minimum blower load,
Not running the compressor,
Maybe somebody here can give us an answer


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Matt_Colie

Southeast Michigan

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Posted: 07/13/19 12:16pm Link  |  Quote  |  Print  |  Notify Moderator

The old Onans were famous for blowing out the bridge for the field when shut down with much load on. That thing was not easy to get at most times.

Many of the less primitive units still have trouble because the fancy output voltage regulation system doesn't know it is being shut down and the system kills itself trying to hold the output up.

Matt


Matt & Mary Colie
A sailor, his bride and their black dogs going to see some dry places that have Geocaches in a coach made the year we married.


MEXICOWANDERER

las peƱas, michoacan, mexico

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Posted: 07/13/19 12:48pm Link  |  Quote  |  Print  |  Notify Moderator

Field forcing is a generator killer. My little KATO has six 1000PIV 150 amp rated rectifiers which is overkill times 4 the maximum possible field primary exciter potential. But the Delco H9000 regulator ramps down softly as it approaches 55 Hz. No free lunches it is still bad for the loads when an uncontrolled spin-down occurs.

I still unload the generator before shutdown and it has a turbo prtection 5-minute timer borrowed from a White Freighliner chassis.

joebedford

Finally back home in the north

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Posted: 07/13/19 02:33pm Link  |  Quote  |  Print  |  Notify Moderator

"computer controlling the digital inverter"

How retro.

hotpepperkid

Kingman AZ

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Posted: 07/13/19 07:26pm Link  |  Quote  |  Print  |  Notify Moderator

We had a saying at the phone Co. graceful and ungraceful. Disconnect the power before pulling a card or just pull out a card under power. I built a box with 30A twist lock and 50A socket with a switch and V/A meter so I can disconnect the load before turning on or off the gen.


2019 Ford F-350 long bed SRW 4X4 6.4 PSD Grand Designs Reflection 295RL 5th wheel

jodeb720

Los Angeles

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Posted: 07/24/19 07:44am Link  |  Quote  |  Print  |  Notify Moderator

Many years ago, Prof95 did an analysis on this exact subject.

I'm not an engineer, but his argument went something like this:

when a generator is shut down/runs out of gas under load - as the motor spins down the generator attempts to compensate for the loss of power with a spike of current out of the generator head.

His argument was, it probably won't blow anything out but it's putting a strain on the components that's unnecessary.

If Mr. Wizard is correct for his Champion, then the inverter will recognize a loss in rotation and will disconnect to protect itself.

For me, I just disconnect completely from my Eu2000 let the engine idle for 30 seconds or so and then shut down the generator.

Again - it may not be necessary, but why take a chance and stress the components?

Chum lee

Albuquerque, NM

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Posted: 07/24/19 05:09pm Link  |  Quote  |  Print  |  Notify Moderator

"What happens exactly that they're concerned about?"

From a purely mechanical (non-electrical) temperature related issue: Heat soak

When you are running an air cooled engine (anything really) at high power loads, the engine is generating maximum heat/power. When you shut it down without a cooling period, the cooling systems stops, abruptly. However, the cylinder head, piston(s), exhaust valves continue to shed heat to the cooler parts of the engine without an operating cooling system. The oiling system is also shut off. Under some conditions, the engine oil, which also serves as coolant, especially in an air cooled engine, can overheat and coke. It doesn't happen all at one time/overnight, but over time, many an air cooled engine, especially with turbo chargers, overheat and burn the oil up creating sludge which can eventually kill the engine/turbo.

Many auto manufacturers of the late 70's and early 80's learned their lesson BIG TIME with their turbo charged cars that weren't equipped after run cooling systems. Premature turbo failure (under factory warranty) was common because owners typically shut the engines off without a cool down period. This eventually led the big push to modern synthetic oils which could handle higher temperatures without coking up.

My first boss had the habit of chopping the throttles on his Cessna 310 (twin air cooled engines) when descending from 12,000 feet @ 65% power at well below freezing. As a young pilot with more mechanical knowledge than flying time, I told him that was a bad idea. He laughed saying, "Naaahhhhhh, it's fine, I do it all the time." He stopped laughing when he got the $25,000 bill for multiple cracked cylinders/pistons/exhaust manifolds. He was lucky to make it home safely. For engines, shock cooling/heat soaking is NOT a good thing.

Chum lee

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