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Old 08-29-2011, 03:25 AM   #1
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Generator Surging (voltage) and Oscillating Under Load


I have a Briggs & Stratton 8000w Generator:

http://www.electricgeneratorsdirect....ator/p887.html

http://www.amazon.com/Briggs-Stratto.../dp/B000E327VS

I have it wired into the house using this transfer switch:

http://www.connecticut-electric.com/...HRCutsheet.pdf

The generator is connected to the transfer switch through an L14-30R 30 amp cable:

http://gasolineportablegenerators.bl...ower-cord.html

My issue is this.

When a new load is connected to the generator, the voltage surges so much that lights get about 30% brighter for about 2 seconds before returning to normal.

Also, when the generator is loaded to about 1500w on one leg, it seems that adding any more load causes the voltage to oscillate (surge and sink) at about 3-times per second on both legs. For example, just turning a computer on starts this oscillation. Turning the computer off off stops the oscillation after a few seconds.

During this time, lights become between 20% more bright than normal and 20% dimmer than normal at a rate of about 3 times per second.

Any ideas what would cause this?

Thanks.

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Old 08-29-2011, 04:20 AM   #2
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Generator Surging (voltage) and Oscillating Under Load


Regulator ? Give it an enema of a load test.

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Old 08-29-2011, 09:18 AM   #3
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Generator Surging (voltage) and Oscillating Under Load


Do you notice the engine RPM varying at all when this happens? Sometimes the engine governor can be adjusted to be too sensitive and surging happens.

Also, most portable generators produce what is known as "dirty" power. You really shouldn't be running sensitive electronics on it.
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Old 08-29-2011, 11:33 PM   #4
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Generator Surging (voltage) and Oscillating Under Load


There is no change in engine RPM when this happens.

The surge that occurs is severe. In fact, it cooked one of our surge protectors.

This happened during hurricane Irene (yesterday) in Maine. The generator works fine when connected to appliances/computers via extension cords. but when it's plugged into the house (via the transfer switch), this occurs, but only when triggered by a new substantial load being added to the system.

After searching, some said it could be a bad neutral connection, but I checked and it's properly connected and secure at all locations from the wire to the transfer switch box.
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Old 08-30-2011, 02:12 AM   #5
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Generator Surging (voltage) and Oscillating Under Load


When you hook up the generator to the stand by system did you ever check the load to see if it is balanced between the two legs ? if not that will cause uneven voltage I have see it before few time so one side of the MWBC is only 4,000 watts while other side of MWBC is 4,000 watts also so it will sum up to 8,000 watts total per nameplate { I useally loaded up to about 80% max wattage for small portables }

Did you have any MWBC { mulitwire branch circuit } in the house ? if so did you double check the circuit which it used on the transfer switch.

What kind of substanal load it did add to the generator ? if motour load type like fridge or even Mircowave oven can do funny thing with generator.

Merci,
Marc
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Old 08-30-2011, 11:15 PM   #6
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Generator Surging (voltage) and Oscillating Under Load


Quote:
When you hook up the generator to the stand by system did you ever check the load to see if it is balanced between the two legs ?
Yes. The load was about 1500 watts on 1 leg and about 750 watts on the other leg. The transfer switch has watt meters on it.

Quote:
if not that will cause uneven voltage
Can that be responsible for huge surges that make lights increase brightness 50% and/or oscillations? We also lost at least 1 surge suppressor when this was happening.

Quote:
Did you have any MWBC...
Do you mean a circuit that has both legs running to it? If so, I'm not sure, I'll have to check it out.

Quote:
What kind of substanal load it did add to the generator ?
The load was about 1500 watts on 1 leg and about 750 watts on the other leg. The gen is rated for 8000 watts, 13,500 peak, so I was well under the limit.
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Old 08-30-2011, 11:52 PM   #7
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Generator Surging (voltage) and Oscillating Under Load


Ok then did you test with voltmeter on both legs of the generator output one at the generator receptale itself and one at the transfer swtich with your normal load what you ran before and the voltage should be the same on each leg.

The MWBC mean mulit wire branch circuit so you will have two hot conductor and netural and ground as one circuit.

Many Gaz generators will surge a bit unloaded { the LP gaz is genrally more smoother due dry fuel and even mixure } but the govenour setting some can be too senstive and some are not. but once you loaded up near max rating it will run smoother with less surge some case disappair.

For most Briggs I know they are gear driven govonver on generator verison and there is a adjustment spring or screw to change the senstive of surgeing if you have to adjust it do it with the load on it { a cheap portable heater will do a trick to put a load on the generator } and adjust it a little until it run smooth { you may want a generator repair shop or small engine shop assist you on this one to get it set up properly }

Few case with bad surgeing can cause due from old fuel or inproper adjusted carbubatour.

Hope that help you some of the situation you have.


Merci,
Marc
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Old 08-31-2011, 12:35 AM   #8
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Generator Surging (voltage) and Oscillating Under Load


Thanks for the info.

The generator engine runs very smooth and the RPMs are very steady. I have UPSs that displays Hertz and they report 60 Hz +/- about 1/2 Hz, so that's pretty steady too.

Also, this weekend during Irene (the hurricane), after severe surging and oscillating, we switched all the circuits in the transfer switch to OFF (they are 3 position: Power Station / OFF / Generator), then we ran extension cords to everything we needed and had no problems and no surging at all.

The generator has a binding wire that ties ground to neutral at the generator. In doing some research I found that this is supposed to be disconnected when the generator is connected to a house transfer switch.

I wonder if this could cause the problems???

I will do a voltage test at the gen and at the outlets and see what I get.
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Old 08-31-2011, 10:26 AM   #9
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Generator Surging (voltage) and Oscillating Under Load


I am glad you brought up that question and I know couple generators they have to get the netural et ground seperated once you start hook up to the house system due majorty of the portable generators I ran into they are not a floating netural connection set up which it mean both netural and ground is tied together and they have to do that on portable mode.

I know I have ran into this pretty often with Honda verison and once you get the netural and ground seperated and you have to put a warning label that the netural and ground is seperated { part of OSHA requirment } so you can use for the transfer switch panel.

I have to dig up that tibbits on that there were a TSB { tech service bulletien } on that I think that did cover few other brand name but pretty simauir all the way thru.

The larger units { trailerable and stationary units } are not a issue due they have netural and ground allready seperated.

For your unit I will dig it little more so give me a jour or duex to find it.

Merci.
Marc
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Old 09-04-2011, 01:00 AM   #10
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Generator Surging (voltage) and Oscillating Under Load


Thanks for the help.

I called Briggs and asked about a paragraph I found in the manual. I have a scan of the paragraph below. It's worded a little strangely, so I called them to ask if lifting the generator-bridge wire would separate neutral from ground. They said it would.

So, would having the generator's neutral tied to ground AND having neutral tied to ground at the main box cause this type of surging/oscillating problem?

Thank again!
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Old 09-04-2011, 01:02 AM   #11
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Generator Surging (voltage) and Oscillating Under Load


The attachment didn't work on the previous post. Here they are...
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Generator Surging (voltage) and Oscillating Under Load-system-ground.jpg   Generator Surging (voltage) and Oscillating Under Load-generator-features-controle.jpg  

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