# Generators & THD



## 50ShadesOfDirt (Oct 23, 2021)

Another post was pointing out the high THD value of a Westinghouse genny, and of course, I had ordered one based on other features (automatic choke, remote fob start, etc.), before I saw that post.

As we are rural and off-grid, and there is a Magnum ms4024pae inverter and lithium battery set in between the house loads and solar/genny, I believe THD shouldn't affect us at all (inverter cleans everything up). We run Duromax (reported THD <12%) and now Westinghouse (reported THD <23%) gennys, both in the 9kw to 12kw range, and both running the 457cc engine, so basically the same unit.

However, it's an interesting/disconcerting issue all by itself, and that means research into THD is needed. Not wanting to become an expert, I went to these guys first to understand Total Harmonic Distortion (THD):

https://generatorbible.com/blog/what-is-thd/

This was just a starting point, and more research is needed. As the article and comments point out, our gennys (supply) put out THD, our electronics (loads) sometimes put out THD, and so on. Perhaps this is best addressed from a "where is the THD" in a whole system, and play "whack-a-mole" wherever it exists.

Also trying to determine the difference in values between Duromax and Westinghouse, when so much is the same on these units, but maybe it's an AVR issue or other component choice? I'll add that research if I can uncover it.

We never seem to get all the research done _first_, so we implement something, and see what works with it and what doesn't. To that end, everything in the house loves the inverter (pure sine wave, 120/240 device). When batteries are topped off by solar/generator, no issues anywhere; LiFePO4 batteries have bms' that allow high draw from inverter, so there's nothing we can't run. Summary: an inverter (high-quality, pure sine wave, etc.) is a good thing.

When a genny runs to augment supplying power to the batteries, the inverter grabs all the power it needs to charge the batteries, and passes thru the rest to house loads. At this point, some things get iffy, but don't know if that is a THD problem, or simple "not enough power" problem (my guess is latter, but I'll ask Magnum what they think about all of this):

- UPS: UPS' in front of computers did not like getting such passed-through power, and they cycled a lot; APC seemed to be the best UPS for us, but even they clicked/cycled, and ran down their standby capacity. We yanked the UPS's, as the inverter/battery system is basically a great big UPS anyway.
- microwaves: if genny is weak in any fashion, it'll sag down when mwave clicked on, and mwave gets unhappy; if genny is new/strong/running-right/sized-right, mwave is also happy (in short bursts, not long defrost/cook cycles).
- water booster pump: if the grundfos kicks on, it's the same as the mwave. also need to investigate a (plug-in, not wired-in) load-smoothing doo-dad, for this big motor device.
- haven't noticed much issue with other motors or electronics. Smaller motor loads (washing machine, water pumps, etc.) all happy with any source of power. Every once in a while, we get a piece of electronics in (with highly computerized brains) that can be unhappy ... my guess is the computer brain is interfering, which is my experience with anything using a computer brain these days (newer cars, other devices).
- no devices have died an "early" death, that we can spot, due to high THD or other power issues; all seem to be lasting their normal lifetime.

As long as our Duromax's (THD <12%) are at peak operations, it's all good. If any weakness in operations (aging unit, outstanding maintenance issue, etc.), then the loads getting pass-through power might start complaining. When the Westinghouse gets unboxed and set up, we'll run the same loads on it, and report back.

What does all this mean to you? Perhaps consider an inverter/battery/generator type of system (or some portion thereof), even though that adds to the cost; grid-tied for most of you, and off-grid for the rest of us. Again, Magnum inverters seem to take whatever a genny dishes up, and does the right thing with it; batteries & solar means the genny just doesn't have to run much. When we ran a Generac 24kw standby unit, it was flawless ... just couldn't keep it running for long, and couldn't justify the higher initial costs and services; in the city, this might be different.

As we are off-grid and rural, we just can't run Generac's ($4k+), so we utilize these mid-tier gennys ($1k+).

More research coming ...please add what you know or have found ...


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## 50ShadesOfDirt (Oct 23, 2021)

Interesting:
- wgen9500 is <23% THD (457cc engine)
- wpro8500 is <5% THD (457cc engine)

These are Westinghouse generators; don't know what the "pro" means, but I'm guessing it's got different components on it that produce better THD values. Question now is, can something be replaced on the wgen model to make it a wpro model?


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## 50ShadesOfDirt (Oct 23, 2021)

Apparently, THD values may not be that important, except from the dreaded marketing viewpoint, which may be why vendors hype them or don't hype them on a particular model. Read post #113 from:

Total Harmonic Distortion of Portable Generators

I'm not qualified enough to interpret ...


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## OrlyP (Oct 19, 2021)

From what I gather in the product info for those Westinghouse generators... at least that's how they define their use cases:

Pro - For professional use on job sites
Non-pro - For residential use

I get conflicting information about the effects of high THD on electrical loads.

First argument: Some say that a high-THD power source affects inductive loads like transformers and AC motors. It results to core losses and noise from inductive motors. However, electronic devices that has a switch mode power supply (SMPS) would be fine because in principle, they do AC-DC-AC-DC conversion so any THD present in the source has been filtered out many times over in the conversion before it actually reaches the device it's powering up.

Second argument: It's exactly the opposite of the first one, in that, high THD is bad for electronics but no such notice exist when running other loads, particularly inductive loads.

Though, we can all agree that resistive loads are largely unaffected by line distortion.

Anyway, my generator is a cheap AVR kind and all my UPS (APC SmartUPS and couple of no-name basic ones) don't have a problem with it. Neither does any of my smart home devices (Echo Dots, Google Home Mini, WiFi switches, smart power plugs, etc.) It's also the same story with my PC, laptops, servers, and inverter ductless A/Cs. They all work as they should on generator. Though, I do hear subtle humming noises when I turn on the bathroom ceiling fan, but that's it.

So going back to those Westinghouse gennys, if they imply that the "Pro" version with the low THD is best deployed on work sites because that's where you typically use power tools (mostly inductive), that would line up with the first argument. However, that means that the "Non-pro" version with the high-THD would be powering up a home, which is mostly swimming in electronics.

See why it gets confusing?


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## iowagold (Jan 22, 2020)

yup!
and the difference is in the details...
the pro versions are more money right??

stator and rotor have better machined slots and some are epoxy in place windings for better angle accuracy.

in general you get what you pay for in generation...

for me i make up for it with a good inverter design.
the honda eu series of gen sets depends on the inverter to keep the power spot on as close to perfect as you could ask for.
and you pay for that as well.
buy the best and never look back is the best advice.

same if you get in to the BIG power out there.
hard to beat the power from a cat generator in the BIG class of power.
that is why more city's have switched over to cat for the utilities backup power in water, sewer, and police stations and jails. as well as court house locations.
i am starting to see a few in my area for high traffic intersections now as well for the traffic lights and the lighting of the inter section.

back up systems if planned right can last for many many years...
so choose wisely and have a system with great resale value.


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## OrlyP (Oct 19, 2021)

Upon closer review, here are the other subtle things I found that sets the Pro apart from the other.

The Pro is 1,000W shy of the no-Pro version but it has auto-idle. Particularly useful on the job site when you don't have power tools running all the time. On the other hand, the non-Pro does not have auto-idle, which also makes sense as once you have it connected to your home, there's always one device turned on to prevent it from idling down, making the feature pointless.

But despite these differences, both models can be used on the job site AND as backup power at home. It's down to whether that THD and/or wattage differences bother you enough to choose one over the other.


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## 50ShadesOfDirt (Oct 23, 2021)

Our inverter vendor (magnum) says "we don't care about THD ... it won't bother the inverter", so the inverter is capable of handling any level of THD in the incoming power from any generator.

When the inverter is in charging mode, it is consuming a percentage of the power from the genny to charge the batteries, and passing the rest through; in this bypass mode, what is passed through isn't cleaned up. In theory, It might possibly impact something in the house ... in practice, an occasional high-draw device will whine about not getting enough leftover power from the genny when the genny is driving the inverter/charger, which is more of a load issue. We also see this if generator isn't running right, for some reason.

When _not_ in charging mode, then the inverter is pulling power from the (dc) batteries and giving us pure sine wave AC power in the house, for any size load. No genny involved, so no issue with THD, that we've seen.

Don't have a pocket oscilloscope (yet), so can't get waveforms from gennys or inverter ...

I'll just test the Westinghouse genny, and see if anything feels different from the Duromax genny. If nothing jumps out at us, then the THD level isn't impacting us or our devices. I can also throw a smaller inverter at both gennys, and see what happens. The automatic choke from the Westinghouse is a key feature we need ...


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## exmar (Jun 29, 2015)

JMHO THD even if published by a vendor is suspect, what type of loads were connected? What load is represented, 50%, 100%, etc. THD increases as load does. THD is an actual electrical value, however, it's becoming a marketing tool. For discussion purposes I assume that any open frame generator is around 20% THD, however have used those for a lot of years with no issues with "sensitive electronics, etc." 

If you're concerned, buy a Honda, low THD, long life, good resale value, but top $$. For the occasional outage, an open frame generator with AVR will suffice. Also believe that most "emergency" generators that folks have are the open frame type. Generac has owned the whole house generator market for quite a while using open frame generators, try to get THD values from them! 

OP has a good handle on what he wants from his generators, the issues with well pump, microwave can be remedied by "stiffening the bus" (as we called it in the utility industry) to handle the additional loads they provide. More batteries, bigger inverter, etc. Not sure a bigger generator would help if the inverter is feeding everything. Hang a voltmeter across one of those circuits and observe what happens, then do the same at the inverter input.


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## TomC (Apr 16, 2021)

50ShadesOfDirt said:


> Interesting:
> - wgen9500 is <23% THD (457cc engine)
> - wpro8500 is <5% THD (457cc engine)
> 
> These are Westinghouse generators; don't know what the "pro" means, but I'm guessing it's got different components on it that produce better THD values. Question now is, can something be replaced on the wgen model to make it a wpro model?


The WPro8500 has GFCI protection and a lift bracket.


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## Columbotrek (11 mo ago)

OrlyP said:


> Anyway, my generator is a cheap AVR kind and all my UPS (APC SmartUPS and couple of no-name basic ones) don't have a problem with it. Neither does any of my smart home devices (Echo Dots, Google Home Mini, WiFi switches, smart power plugs, etc.) It's also the same story with my PC, laptops, servers, and inverter ductless A/Cs. They all work as they should on generator. Though, I do hear subtle humming noises when I turn on the bathroom ceiling fan, but that's it.


All my electronics including the 3 ton central A/C and its associated NG furnace run fine on the WGEN9500DF. I connected it to the house through a 50 Amp ProTran 10 circuit manual transfer switch. I also floated the neutral in the Generator as neutral and ground is carried through the transfer switch to the main panel. When connected up, there is N-G continuity on the Gen outlets. The computers are all behind APC Smart UPS. At first the Smart UPS did not like the generator. They would bypass the line back and forth. I figured out they did not like the 62.5 Hz line frequency they were seeing. Neither did my lights on the WEMO smart dimmers as they strobed, seemingly at 10 Hz. Solved both issues by adjusting the generator governor so as the frequency would not exceed 60Hz. That means things run between 58 and 60 HZ. Usually more like 59.4 Hz. I am not sure most electronics are all that sensitive to THD anymore after power supplies changed to the switcher type. Now everything has its own mini inverters down the path to their DC supply voltages built in anyway.


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## 50ShadesOfDirt (Oct 23, 2021)

Excellent advice wrt UPS units!

I will check my Duromax 12kw df and Westinghouse 9500 df for AVR frequency at or below 60hz, and then see if I can bring my UPS units back online. They were unhappy before (on any generator except Generac), so it must be a fine adjustment of the AVR (which I'm unsure how to accomplish, but will figure it out next).

Any evidence of THD being thrown back out onto your house wiring system, from devices within the house?

Thanks!


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## GenKnot (Dec 20, 2021)

50ShadesOfDirt said:


> must be a fine adjustment of the AVR


The AVR does not adjust the frequency, it only regulates the voltage (AVR = Automatic Voltage Regulator). The frequency is regulated by the engine speed governor, and it is fairly typical for such generators to run 60 ± 1.5-2Hz from no load to full load on the gen. Inverter generators will regulate output frequency to near perfect 60Hz regardless of load.


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## McCorby (Apr 26, 2021)

[QUOTE="GenKnot, 
Inverter generators will regulate output frequency to near perfect 60Hz regardless of load.
[/QUOTE]
……and engine rpm.


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## iowagold (Jan 22, 2020)

hz is set by the engine speed on an avr gen set..
the voltage is set by the excitation from the gens avr unit.

i guess this is why i am set on the honda eu series gens...
the cadence (HZ) is set by the inverter as well as the voltage window.
all computer controlled...
no chance on engine runaway on the HZ...

and has internal safety cut out for under and over volt....


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## OrlyP (Oct 19, 2021)

It's true, some UPSs can be finicky with less than ideal power quality. But a lot of people immediately blame it on THD. Not saying it's not true but, voltage and frequency are other parameters these devices look at and measure. It's their job to do so. Sometimes, the generator only needs a minor frequency and/or voltage adjustment and the UPS will let it through.

Honda EUs are the gold standard when it comes to portable inverter gens. I wish they were more affordable, but sadly, that's not how it works. "Bang-for-buck" is oftentimes subjective and sometimes you've no choice but to settle on the cheaper, albeit, less nicer options.

Can't drive a Lexus with a Hyundai econobox money.


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## speedy2019 (Jan 29, 2019)

I think a UPS just keeps the voltage and frequency on target, but with the voltage on portable generators being up and down like a yoyo, its the UPS job to kick in until the voltage is stable..

I have a generator friendly UPS and it keeps the voltage rock stable without having to go on to battery mode at all when connected to the generator. It only switches to battery mode if there's a big drop/spike in voltage for a bref second,ie when high loads turn on/off on the generator;


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## OrlyP (Oct 19, 2021)

speedy2019 said:


> I think a UPS just keeps the voltage and Hertz on target, but with the voltage on portable generators being up and down like a yoyo, its the UPS job to kick in until the voltage is stable..
> 
> I have a generator friendly UPS and keeps the voltage rock stable without having to go on to battery mode at all when connected to the generator. It only switches to battery mode if there's a big drop/spike in voltage for a bref second,ie when high loads turn on/off on the generator;


Sorry to nit-pick on a few things....



> I think a UPS just keeps the voltage and Hertz on target


Not quite. When we're talking about traditional UPSs (not double-conversion ones), it will let through voltages and frequency that it is programmed to allow as within-spec. If the voltage is lower or higher than nominal, the line-interactive circuits (or voltage regulator) kicks in to step-up or step-down the output voltage, respectively. These types of UPSs does NOT vary the frequency from the grid.... ex. If it's 60.32Hz in, it's going to be 60.32 Hz out... no ifs, no buts. If the line voltage goes beyond the capabilities of the AVR, OR the frequency goes out of range beyond what the UPS thinks is normal (normal is 60Hz +/- 3Hz, typically), it immediately goes into battery backup mode.



> I have a generator friendly UPS and keeps the voltage rock stable


The output voltage from a conventional UPS never stays "rock stable". It varies within the boundary of what it thinks is acceptable voltage for the load. The nominal output might be 120V, but in reality, that can vary between 110 to 130V. The AVR in these things are of the relay type, so each voltage step-up or step-down adjusts the output voltage +/- 6 to 8V, typically.


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## Columbotrek (11 mo ago)

50ShadesOfDirt said:


> Excellent advice wrt UPS units!
> 
> I will check my Duromax 12kw df and Westinghouse 9500 df for AVR frequency at or below 60hz, and then see if I can bring my UPS units back online. They were unhappy before (on any generator except Generac), so it must be a fine adjustment of the AVR (which I'm unsure how to accomplish, but will figure it out next).
> 
> ...


If your APC UPS is a smart-ups and maybe a Back-ups also, it will have a USB port, With APC software you can adjust the UPS sensitivity to the line. This makes them more tolerant to the generator's power signature. The UPS was complaining about the original gen frequency of 63-62.5Hz. 62Hz was acceptable for the APC but not the smart dimmers. Those things freak out if the Hz goes to 60.1 Hz. What I settled for was an unloaded 60.4Hz. Then with some lights added, it drops to 60 then with every light in the house and the TV the frequency drop to 59.4. The dimmers and the UPS are happy until something big drags the gen down. For that one second its grunting to get back up to speed, the UPS kicks over to line bypass then kicks back. Does not seem to care about the load being removed. I added a Square-D HEPD80 (type 2) surge suppressor to the transfer switch which is supposed to shunt surges for just in case. 
As others have mentioned the AVR is about voltage and RPM governor about frequency. There is a stop screw above the alternator. On the wgen9500DF it can be identified by looking for the mechanism which connects to the throttle of the carburetor with a wire and spring. Adjust that stop screw in 1/2 or 1/4 turn increments and look at a frequency read out. I have never been able to hear the engine speed change at all. Its all the freq counter. My gen has one but do does my Smart UPS.


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## OrlyP (Oct 19, 2021)

s.amanatalibhatti said:


> Dear researchers, I'm working on DC-MG Microgrid and i want to integrate a Diesel Generator to support the global system. The DG is connected to a 3 phases rectifier, that to a DC-DC buck converter to regulate the DC voltage and to supply a DC load.
> In the other hand, i have attached MATLAB simulation results, and the problem is the high TDH value of the DC generated current ( ==40% to 60%), which consequently reduces the active generated power of the DG. Please, can anyone propose a solution to solve this problem ???


I don't think it's the DG that's causing the high THD. You mentioned that the AC output from the DG has been converted from three-phase AC to DC then DC-DC buck and finally dumped to the DC buss or Load.

So the problem and likely source of the distortion is your DC-DC buck, which is a switching circuit. This is already beyond my expertise but I think it's a common issue with these systems. Needless to say, this is not a problem with the Diesel Generator.


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## speedy2019 (Jan 29, 2019)

OrlyP said:


> Sorry to nit-pick on a few things....
> 
> 
> Not quite. When we're talking about traditional UPSs (not double-conversion ones), it will let through voltages and frequency that it is programmed to allow as within-spec. If the voltage is lower or higher than nominal, the line-interactive circuits (or voltage regulator) kicks in to step-up or step-down the output voltage, respectively. These types of UPSs does NOT vary the frequency from the grid.... ex. If it's 60.32Hz in, it's going to be 60.32 Hz out... no ifs, no buts. If the line voltage goes beyond the capabilities of the AVR, OR the frequency goes out of range beyond what the UPS thinks is normal (normal is 60Hz +/- 3Hz, typically), it immediately goes into battery backup mode.
> ...


I have a online ups, so I can either use it like a line-interactive ups so it jumps in to action when the vots drop or spikes over 5% of the voltage its set to. Or I can have it working 24/7 keeping a steady voltage (of 240 in my case), but that mode uses more power. So I have it to jump into action when volt spikes/drops at or over 5% from 240 and thats about 10-15 volts eitherway..

This is a image of my ups when connected to the generator,, as you can see the ups is outputting a steady 239v from 230v without out using battery mode, the generator is even charging up the ups's batteries.


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## GenKnot (Dec 20, 2021)

Columbotrek said:


> The UPS was complaining about the original gen frequency of 63-62.5Hz. 62Hz was acceptable for the APC but not the smart dimmers. Those things freak out if the Hz goes to 60.1 Hz.


Hmmm... I wonder if the APC was not liking the power factor of the dimmers. They are a terrible non-linear load.


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## OrlyP (Oct 19, 2021)

speedy2019 said:


> I have a online ups, so I can either use it like a line-interactive ups so it jumps in to action when the vots drop or spikes over 5% of the voltage its set to. Or I can have it working 24/7 keeping a steady voltage (of 240 in my case), but that mode uses more power. So I have it to jump into action when volt spikes/drops at or over 5% from 240 and thats about 10-15 volts eitherway..
> 
> This is a image of my ups when connected to the generator,, as you can see the ups is outputting a steady 239v from 230v without out using battery mode, the generator is even charging up the ups's batteries.
> View attachment 11132


I take it back. That's the double-conversion UPS I was talking about. If that's what you have, then that will reproduce the 240V 50Hz, regardless of the status of the input.

But I maintain that the great majority of UPSs used in offices and homes are the conventional type. Yours is more of an exemption as most double-conversion setups, due to their cost, are relegated in the datacenters or in protecting medical equipment.


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## speedy2019 (Jan 29, 2019)

OrlyP said:


> I take it back. That's the double-conversion UPS I was talking about. If that's what you have, then that will reproduce the 240V 50Hz, regardless of the status of the input.
> 
> But I maintain that the great majority of UPSs used in offices and homes are the conventional type. Yours is more of an exemption as most double-conversion setups, due to their cost, are relegated in the datacenters or in protecting medical equipment.


Ive always had the cheaper line interactive ups's in the past, but I'd thought id treat my self after having my last one for about 10yrs. Yes 10yrs, and its still working, its had about 3-4 sets of batteries though. This is the UPS Ive got now, much cheaper than a well known ones at £400. If I had bought APC at the spec, it would of been about £1000 and the sickening thing about it, your mainly paying for the name.








VFI 2000 TG | BlueWalker


Model: VFI 2000 TG SKU: 10122042An All-Rounder SeriesHuman Interface Device (HID) compatible USB connection (no additional drivers needed)Wide Input Voltage Range for All EnvironmentsIt supports AC GeneratorsIt include an Intelligent SlotThe PowerWalker VFI TG/TGB/TGS is a professional and...




powerwalker.com


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## iowagold (Jan 22, 2020)

yea the better units that are 600 to 3000 usd are a better value..
and the cool thing is if you watch you can find used units that need batteries on the cheap.
take outs from data centers.
50-400 usd as used!
i think the last pallet of apc units worked out to 200.00 usd each.
and battery kits were 130.00 usd...
for the advanced engineers....
if you run more than one ups in the same area you can rig up a master battery array charger
and then draw from real batteries to run all of the ups units from a 24 volt dc battery bank.
and those batteries last 10 years plus.


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## Columbotrek (11 mo ago)

iowagold said:


> yea the better units that are 600 to 3000 usd are a better value..
> and the cool thing is if you watch you can find used units that need batteries on the cheap.
> take outs from data centers.
> 50-400 usd as used!
> ...


Retired IT professional. Our data center UPS were Eaton 3000 VA rack mount pairs powered with 220 Volt 30 amp circuits. A bit of over kill for my home. There is a 3 year battery replacement procedure on them all. Even the data closets used rack mount UPS to support powered over ethernet phones and wireless access points. Our standby generator was a Diesel powered 3 phase beast on 13 yards of concrete slab for which we have a maintenance and fueling contract. We were on generator power 20 seconds or less after a power failure as designed. Computers, Air handlers, lights, everything ran perfectly on the Generator. They did not sell old gear. There was a recycling company which came around once every couple years and hauled away decommissioned gear. What happened to it after, I have no idea. Could be someone bought a well used rack mount 220 UPS or got a multi CPU rack mount server for cheep.


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## iowagold (Jan 22, 2020)

eaton is good stuff.
also 
best brand....
that was in dod data centers.
and yes on the over kill...

watch the ham fests for deals!
dayton had a few back in the day.
that was right around y2k change out...
lots of good quality gear swapped out back then.


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## 50ShadesOfDirt (Oct 23, 2021)

So, my UPS (APC Smart-UPS smt-750) was doing lots of clicking when the duromax 12kw open-frame generator runs; I had removed them, as the house inverter/battery-bank is basically a big UPS. I put a smart-ups back in place, and installed powerchute "business edition", which had more features/settings to fiddle with.

Finding a value called "power sensitivity" which defaulted to normal, I set it to "reduced". Clicking (of relays) stopped, and the unit's status page shows hz of 63.2. The UPS is now much happier w/ the reduced setting in place, while the duromax is running.

I'm assuming the duromax is putting out 63.2 hz, when it should be closer to 60, so it's governor needs adjusting. Do I do this after it has warmed up? I had installed an hour meter, and it shows the RPM (under load, powering inverter/charger) to be 3810 rpm's. Once I read how to adjust it, do I lower the RPM's until the smart-ups status page gets closer to 60?

This ups is not a double-conversion unit ... both input/output voltage AND frequency are the same, per the powerchute software status page.


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## speedy2019 (Jan 29, 2019)

The larger the ups, the more batteries you will need to replace when the time comes.That was my error when buying my 1800watt ups, it costs £100 to replace the batteries, but the great thing about using a light load on a powerful ups, is that you get more battery runtime.. My ups is loaded 10-15% normally and the battery runtime is about 1-2hrs.

Eaton ups's are really expensive and the thing they are basically all made the same and it wouldnt surprise me if names like Eaton and APC use cheap parts also.

here is my ups on mains power, the voltage where I live is suppose tobe 230v but it never goes below 240v, so thats the reason I have set the ups at 240v. And as you can see its not using the inverter and letting the mains power through to my devices, but if the volts went over 250 the inverter would kick in and the volts would be dropped down to 240v


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## OrlyP (Oct 19, 2021)

I've long ago set all three of my APC SmartUPS for medium sensitivity and I've had no issue with them running from the grid or generator.

I have a cheaper APC and a few off-brand UPSs that does not have that adjustment. But they too, seems to be happy campers running off the generator.


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## speedy2019 (Jan 29, 2019)

OrlyP said:


> I've long ago set all three of my APC SmartUPS for medium sensitivity and I've had no issue with them running from the grid or generator.
> 
> I have a cheaper APC and a few off-brand UPSs that does not have that adjustment. But they too, seems to be happy campers running off the generator.
> 
> View attachment 11136


I guess with my ups set to 240v and the gen outputting 230, the UPS never going to allow the 230v go straight through, because its quite far from 240v and its not a stable 230v.. But thats the good thing about a online ups, the battery mode doesn't need to kick in on small voltage changes... Also I guess it can protect itself if the voltage is very high by transfering to battery mode and block the grid/mains power totally from the ups?


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## OrlyP (Oct 19, 2021)

speedy2019 said:


> I guess with my ups set to 240v and the gen outputting 230, the UPS never going to allow the 230v go straight through, because its quite far from 240v and its not a stable 230v.. But thats the good thing about a online ups, the battery mode doesn't need to kick in on small voltage changes... Also I guess it can protect itself if the voltage is very high by transfering to battery mode and block the grid/mains power totally from the ups?


That's the sort of premium you get from online UPSs. To a certain extent, an interactive UPS (fancy name for a UPS with an AVR) can do that, but the output is not a static 230V or whatever nominal voltage you set it to. But regardless, it's still going to be within a range that is acceptable for most loads.


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## speedy2019 (Jan 29, 2019)

OrlyP said:


> That's the sort of premium you get from online UPSs. To a certain extent, an interactive UPS (fancy name for a UPS with an AVR) can do that, but the output is not a static 230V or whatever nominal voltage you set it to. But regardless, it's still going to be within a range that is acceptable for most loads.


Thats another good thing with online ups's you can set the ups so its always uses the inverter for a rock stable voltage (ideal for critical equipment where you dont want any surges/spikes getting through, as it takes a few milliseconds for the inverter to jump into action)., but I use mine as a interactive UPS as it doesn't use as much power in that mode.. People mainly focus on the battery backup feature when buying a UPS, but they are much more than just a battery backup solution.


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## Columbotrek (11 mo ago)

50ShadesOfDirt said:


> So, my UPS (APC Smart-UPS smt-750) was doing lots of clicking when the duromax 12kw open-frame generator runs; I had removed them, as the house inverter/battery-bank is basically a big UPS. I put a smart-ups back in place, and installed powerchute "business edition", which had more features/settings to fiddle with.
> 
> Finding a value called "power sensitivity" which defaulted to normal, I set it to "reduced". Clicking (of relays) stopped, and the unit's status page shows hz of 63.2. The UPS is now much happier w/ the reduced setting in place, while the duromax is running.
> 
> ...


On my Westinghouse, the Hz increases a little the first few minutes after starting. Say about half a Hz then stabilizes. Then as the load increases the HZ decreases a little. If all I cared about was the UPS, I would set mine warmed up and no load at 62Hz. That will keep the UPS happy. Nothing really cares about 62Hz except for the smart dimmers. Smart bulbs (C by GE) do not care. The LED lights on a switch (even a smart switch) do not care. Some clocks calibrated for 60 would drift and become noticeable if run from the backup gen long enough. For the smart dimmers which flip out at 60.1Hz, I adjusted my set up for 60.4. My normal load brings the Hz down to 59.4-9 but nothing seems to care including the UPS. What the UPS does care about is a big load change as the generator sags for a short time before recovering. Thinking Refrigerator, Microwave, HVAC. During that sag the UPS bypasses the line but then kicks back over in a second. Really that is what it is supposed to do. 
When I was working, there was a 1500VA APC Back-ups backing up a small data closet where there was two 48 port Ethernet switches in one managed unit. One day I started getting alerts from network monitoring software that the Ethernet switch was going missing for a few minutes then coming back every 10 to 20 minutes. Went to check. Seems for the last few years, the UPS was keeping the switches alive every time a through the wall A/C unit was running its compressor. It kept them alive until the batteries wore out. Point is I have seen a home style APC bypass a line issue which must have been 10s of 1000s of times and only failed when its batteries failed. I am sure our UPS can do the same if needed.


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