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post #1 of 25 (permalink) Old 07-05-2019, 04:50 PM Thread Starter
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Generator Help Please

I purchased a Harbor Freight 3500 inverter generator. I was using it to power audio and video equipment. I was running everything through a power conditioner. The volt meter on the power conditioner kept fluctuating up and down. My projector shut down several times because of uneven power supply. I ran projector direct into honda 2200 and worked fine. On the Harbor Freight generator when i use a two prong adapter the power smooths out and is steady. I am baffled any help is appreciated.
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post #2 of 25 (permalink) Old 07-05-2019, 05:34 PM
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Welcome to the forum! If it's a recent purchase, I'd probably just exchange the generator. No need to take on a mystery research project if you can just swap it.

If it helped to just use 2 contacts, instead of 3 with a ground, maybe you're getting some sort of voltage on the ground contact, somehow? Have you checked it with a multimeter? What do you get from hot contact to neutral? And ground contact to neutral? And I guess also hot to ground. I'd check for DC voltage in addition to AC, just to be safe.
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post #3 of 25 (permalink) Old 07-05-2019, 06:49 PM Thread Starter
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sorry i probably didn't explain very well. The generator has a steady voltage when i plug in power conditioner power fluctuates. When i plug in same power conditioner with an adapter power is steady.
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post #4 of 25 (permalink) Old 07-06-2019, 02:45 PM
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Am I understanding correctly?

- HF 3500: output voltage is steady.
- HF 3500 -> power conditioner: output voltage fluctuates.
- HF 3500 -> 2-prong adapter -> power conditioner: output voltage is steady.

I would still do the voltage checks that I mentioned previously. It sounds like some sort of interaction between the generator's ground, and the power conditioner, is somehow making things unstable?
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post #5 of 25 (permalink) Old 07-06-2019, 09:04 PM
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Definitely a grounding issue. Curious, You have an inverter unit which provides very clean power (OK, probably more of a square than sine wave) and you feed your gear through another conditioner? Does the equipment specifically call for that or are you being conservative based on the bad rap gensets get for "dirty power?" If the gear is designed for the commercial market-plugged into convenient outlet-it can tolerate a pretty dirty electrical environment. Commercial power is anything but clean, has all kinds of droops, surges, spikes and other hash coming in. I've run flatscreen tv's computers, etc. for years on regular gensets with no issues.
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post #6 of 25 (permalink) Old 07-07-2019, 10:39 AM Thread Starter
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should these units be self grounded? Could it just be as simple as a bad unit? My honda generator doesn't have the same problem and i believe are self grounding. I know absolutely nothing about generators and really need it just to work without these issues and without damaging my electrical equipment.
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post #7 of 25 (permalink) Old 07-07-2019, 02:37 PM
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Could it be just a bad generator? Absolutely, it seems to me. Like I said, if you're within the return period, I'd exchange it. It seems like weird behavior to me, sounds like something is wrong. Now, if there's no chance to exchange it, then by all means, I'd try to dig in more, to try and figure out what's going on. But it should be working fine out of the box, and doesn't seem like that's what it's doing.
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post #8 of 25 (permalink) Old 07-07-2019, 04:50 PM
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Your issue is combined harmonics on the ground leg hosing up what the inverter regulators target voltage is.

Once you know how a device, system, ect operates, finding the root cause in the event chain is easy. Until then, you will always be chasing/repairing the effects. Learning is a life time event, if you want to outsmart, whatever item you want to repair.
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post #9 of 25 (permalink) Old 07-07-2019, 06:05 PM Thread Starter
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thank you everyone. I will return it and see if the next one has the same symptoms. Hopefully just a bad unit. I really am in a position where it just has to work flawlessly. If the next one does it as well i may have no other option to spend the cash on a honda.
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post #10 of 25 (permalink) Old 07-07-2019, 06:25 PM
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If the next one does the same thing, could you omit the power conditioner?

Searching the reviews here:
https://www.harborfreight.com/3500-W...tor-63584.html

Someone said they connected theirs to an oscilloscope, and it was a clean sine wave output, like utility power. If that's the case, the power conditioner may not be doing a lot for you?

It depends on what the conditioner is trying to do, I guess. If it's trying to smooth out the sine wave, then that shouldn't really be needed. If it attempts to help "fill-in" brief voltage sags, it might be able to provide some benefit. But brief voltage sags due to sudden big loads (such as a compressor starting, which sounds like it wouldn't apply here), can be indicated by listening for the engine suddenly slowing down as a big load hits. And that can be minimized by leaving the engine running full-speed, rather than setting it to reduce the engine speed as the load reduces.

But I'm not an EE, and I have always been a bit puzzled by power conditioners, and what exactly they're supposed to help with. Maybe they're really effective, I don't know. I better understand how an expensive "online" UPS is able to clean up power, as it can use the input power, and its internal batteries, to sort of re-create the sine wave that is needed.
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