Generator woes

[nmantas]

Any ideas of what/how to test my generator to make sure it is clean power? I have my 5500 watt (10hp) generator back filling my panel with a square D manual interlock and has worked fine in the past and on Monday and Tuesday. Last night I had a gfci plug go off and will not reset even with a zero load, everything else was fine in the house so I figured the gfci was probably on the way out and variances in generator power pushed it over the edge. We are not overloading it. After I left for work this morning my wife said that 4 of the 5 LED bulbs in the light fixture in the kitchen went out all at once. LED's are typically pretty tolerant of power variances so this is a bit distressing. The generator is powered off now but I am looking for any guidance to check when I get home. Should've bought a Honda!

 

[Chuckster in NJ]

The only way to check for "clean power" is to use an oscilloscope and sophisticated test equipment.
My advice is to save the money on testing this genny and buy a Honda……. You will thank me later.

 

[nmantas]

Do you think it could be a frequency issue or just surges in voltage? I agree on the Honda.

 

[rlitman]

Power quality issues could be caused by your generator but are more likely caused by something in its load. The issue is that any generator's subtransient reactance is way smaller than that of the transformer from your service, so while noisy equipment may work just fine on utility, the noise reflects back from the generator and causes all sorts of havoc.

At work, I chase such problems using a clamp meter that can tell me THD current. I can clamp onto each circuit and see what the harmonic current is individually to isolate the source of the noise. I can also measure THD V from the generator without load, to ensure it is within spec. But I don't think you can find such a tool for under $400. I'd suggest turning on load circuits one at a time to see how they run on gen.

Nothing against Honda (I own two), but while all inverters are inherently active harmonic filters, that's not the right answer.

 

[BillK]

If the generator has been working fine in the past than I would tend to think that it is not the problem. I would start by checking all of the connections, especially grounds and neutrals.

 

[nmantas]

Well apparently my wife left it running and I have another circuit that is down (I don't know if a gfci went or what)......at least it is off now. My next door neighbor is an electrician but he is more of a wiring up new construction kind of guy and I doubt he has and oscilloscope or a meter that can measure THD. He once joked that my Fluke 787 was better than any meter he had.

 

[theoldwizard1]

First, you can NOT reset a GFCI outlet unless it has power going to it.

Second, while inverter generators are better, most generators provide "clean" power, that is, relatively low THD. The exception is brushless generators ! Stay away from them ! Clean does not mean perfect 120VAC, 60Hz.

The power coming out of a typical generator may not be exactly 120VAC, unless it has a built in voltage regulator. You may have to tweak the voltage regulator. Even with a voltage regulator, the frequency might NOT be spot on 60Hz. Frequency is strictly controlled by engine RPM. 58-62 Hz is acceptable. Voltage should be +/- 10% of 120V, from no load to full load.

 

[nmantas]

Thanks everyone for all the info. Well I finally got home from work and fired it back up and noticed that many things in the house weren't working......took the panel cover off and noticed that one side had a massively low voltage (like 48V) wile the other was fine (118V). I went out to check out the generator output values and the twist lock cord wasn't locked and was not seated giving it a dangle look. I think the neighbor may have hit the wire last night when he disconnected his extension cord as I share the juice. So everything seems great, one side puts out a steady 113V and the other 118V. Hopefully nothing was damaged with the extended brown out on the left side of the panel but there is nothing I can do about that.....so far everything is fine. I think I have to bend the terminals slightly to get a tighter lock on the twist-lock.

 

[wyliesdiesels]

Thanks everyone for all the info. Well I finally got home from work and fired it back up and noticed that many things in the house weren't working......took the panel cover off and noticed that one side had a massively low voltage (like 48V) wile the other was fine (118V). I went out to check out the generator output values and the twist lock cord wasn't locked and was not seated giving it a dangle look. I think the neighbor may have hit the wire last night when he disconnected his extension cord as I share the juice. So everything seems great, one side puts out a steady 113V and the other 118V. Hopefully nothing was damaged with the extended brown out on the left side of the panel but there is nothing I can do about that.....so far everything is fine. I think I have to bend the terminals slightly to get a tighter lock on the twist-lock.

well that explains why the GFCIs wouldnt reset. newer GFCIs wont reset unless power is present.

 

[Worsedog]

First, you can NOT reset a GFCI outlet unless it has power going to it.

Second, while inverter generators are better, most generators provide "clean" power, that is, relatively low THD. The exception is brushless generators ! Stay away from them ! Clean does not mean perfect 120VAC, 60Hz.

The power coming out of a typical generator may not be exactly 120VAC, unless it has a built in voltage regulator. You may have to tweak the voltage regulator. Even with a voltage regulator, the frequency might NOT be spot on 60Hz. Frequency is strictly controlled by engine RPM. 58-62 Hz is acceptable. Voltage should be +/- 10% of 120V, from no load to full load.

Your comment about brushless generators is hogwash. They provide clean, well regulated power provided proper design and quality construction. The also tend to run lower gen head temps and are very efficient. We have a mobile command post loaded with comm gear, satellite, LTE, VHF, UHF, 800 MHz, WiFi etc. and networking for a hundred plus clients both wired and wireless and it was spec'd with a brushless genset for clean, transient and noise free power.

 

[theoldwizard1]

Your comment about brushless generators is hogwash. They provide clean, well regulated power ...

Go watch James Condon's YouTube channel. Look at the waveforms that come out of a brushless generator.

Put a 'scope on the output of your generator. I don't know why they are so bad, but I will never buy one !

 

[Worsedog]

Have you turned off the electricity off to your house? Most utility and critical infrastructure uses are brushless. Hospital, data center, EM all use it.

 

[ez-duzit]

...I think I have to bend the terminals slightly to get a tighter lock on the twist-lock.

I think you have to replace a bad twist-lock.

 

[nadogail]

There are only two kinds of plugs, good and bad ones. Any plug that has to be bent or wiggled to make it work is not a good plug.

 

[rlitman]

There are only two kinds of plugs, good and bad ones. Any plug that has to be bent or wiggled to make it work is not a good plug.

True, but in this case the plug blades are not the problem (unless severely oxidized, and they can still be cleaned). The problem is the lack of tension in the worn out springs in the connector/receptacle.

 

[nadogail]

True, but in this case the plug blades are not the problem (unless severely oxidized, and they can still be cleaned). The problem is the lack of tension in the worn out springs in the connector/receptacle.

In that case, install a replacement connector body or recepticale.

 

[rlitman]

In that case, install a replacement connector body or recepticale.

Exactly. Once a brass connector has fatigued, there's no fixing it.

 

[nmantas]

You guys are great. The plug is new but I have sourced a new outlet and will instal it.