# Westinghouse W9500 THD Concerns



## Pedal-Force (Aug 7, 2020)

Like everyone else on the East coast I'm now considering a whole house generator. Almost certainly going to plumb it into the natural gas and put in a transfer switch, make it a portable whole home setup basically, so when we move it comes with us (and is cheaper than the permanent units) minus the wiring and bit of natural gas plumbing.

Seems like the best generator for my use will likely be the Westinghouse W9500, and it gets wonderful reviews everywhere, etc. However, the THD rating is <23% or somewhere around there, which is really bad. Considering almost literally everything I run will have electronics in it (Fridge, Dishwasher, Microwave, Washer/Dryer, VFD pool pump, laptops, monitors, TVs, almost everything is electronic) I'm concerned, but nobody seems to have any complaints who has used them.

Is it a case of Westinghouse being conservative, or some edge case of use or something? I'd even maybe step down to the 8500 Pro size to get the <5% THD, but that one doesn't have a 50A socket.

Is there a better generator for my use or am I making too much of a number that doesn't matter much in practice?

Thanks.


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## tabora (Sep 6, 2018)

That unit is NOT a whole house generator, just a very big portable. I recall seeing other folks that complained about the THD on that unit as well, but the unit seems to get very good reviews. 

That unit does about 40A continuous, so would likely be a good pairing with a GenerLink MA24 meter-mounted transfer switch, which I use with my somewhat smaller PowerMate unit.









GenerLink 40 Amp Meter Mounted Transfer Switch MA24-N - The Home Depot


The GenerLink is a plug and play transfer switch that gives the homeowner the ability to use anything in their electrical panel up to the capacity of the generator. The GenerLink is UL listed and is a



www.homedepot.com


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## Pedal-Force (Aug 7, 2020)

tabora said:


> That unit is NOT a whole house generator, just a very big portable. I recall seeing other folks that complained about the THD on that unit as well, but the unit seems to get very good reviews.
> 
> That unit does about 40A continuous, so would likely be a good pairing with a GenerLink MA24 meter-mounted transfer switch, which I use with my somewhat smaller PowerMate unit.
> 
> http://[URL]https://www.homedepot.c...LBoCkmwQAvD_BwE&gclsrc=aw.ds&modalType=drawer[/URL]


Thanks. My meter is completely on the other side of the house from the panel and the gas meter (which are a couple feet from each other) so I was most likely going with a 200A Service rated transfer switch/panel combo, since I'm out of space in my main panel anyway (had to remove a double pole we don't use in order to put a surge protector in) and put it right next to my main panel and convert my main to a sub panel.

Not sure what distinction you're making between whole house exactly. I'll have to be selective with my loads and inrush but I can run almost everything I want to with that unit. So while it's not a 15kw Generac or something, I feel like something that size would suit my needs, along with a 50A transfer.


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## tabora (Sep 6, 2018)

Pedal-Force said:


> ...Not sure what distinction you're making between whole house exactly...


By definition (Electric Generators Direct): "We refer to standby generators capable of producing enough power for all of your home's circuits as "whole house" generators. If you're not able to provide power to all of your home's circuits, you don't really have a whole house generator. "

Anything less than that requires manual power management on your part. I have a 6000/7500W PowerMate that does ALMOST everything, except the kitchen oven and clothes dryer and secondary water heater.


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## Pedal-Force (Aug 7, 2020)

Fair. I'd say by that definition then it _could_ be a whole house generator, depending on your loads. There's nothing inherent about the generator, just the combination of generator to house.

And yes, I'd need something more like 20kw to be a true whole house don't need to worry about anything affair.

We'll call it a mostly house generator then. Either way, my question stands.


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## iowagold (Jan 22, 2020)

run ups units on the sensitive electronics with power correction is one way..

too bad super large battery storage is still too pricy..
i would say whole house inverter system then charge it with what every you have for power..
solar, wind, hydro, fuel powered generator....

they let you stack the inverter units to as large as you need for power on some of the good brands...
or just split the house to use separate boxes and separate gens...
have the super large gen for just the high current 240 vac stuff...
and then run a smaller gen for the basics. lights, internet, computer, tv's
i can get by with less than 1000 watts in the winter...

so what did your site survey say on power needs?
or if you have not done one yet you need to do that first.


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## Pedal-Force (Aug 7, 2020)

iowagold said:


> run ups units on the sensitive electronics with power correction is one way..
> 
> too bad super large battery storage is still too pricy..
> i would say whole house inverter system then charge it with what every you have for power..
> ...


All good ideas, but I think buying a genset that has a lower THD is probably simpler, if I find it's actually a legit concern.

Rough survey below. Some is nameplate, some is estimated still. I need to nameplate (or measure) the AC, since that's the biggest load, obviously.


ScenarioRunningEverything Summer16145Everything Winter12345Moderate restrict Summer8195Moderate restrict winter5195Very restricted Summer5025Very restricted winter2025


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## iowagold (Jan 22, 2020)

wow!
you need to be at 2x the rating for good operation...
and so it will not pull the stuffins out of the gen set! lol! think over heat issues.
so a 30-40 kw gen set for the max power... 
wow on the system mins!
pm me your work sheet.

are you all led lights?
when was the last time you replaced the fridge freezers?
the newer units use less now.
same on the hvac compressors.
check for something else doing massive current drain in the system...

if you are on well pump run a larger bladder tank and do faucet restrictions for lower gpm on sinks and showers.
that helps on the pump.
also up date the pump!


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## speedy2019 (Jan 29, 2019)

If you do buy a UPS to work with your generator, make sure its a generator friendly UPS because the power isn't steady enough coming from a generator to stop a normal ups going between battery and mains power all the time.

A few years a go, we had a generator from our power supply because they were working on the powerlines, and the power coming from that generator into the house was really steady at 240volts acording to my UPS with hardly no fluctuation in the voltage. Since then I bought myself a cheapish gen just over a yr ago and I havent had to use it once yet,, typical hey?

Also going off topic, does anyone know the thickness of a incomming mains cable, because the cable has come all unclipped around the outside of the house? So I need to buy more cable clips to fix the cable back to the house, but I have no idea of the size of the clips I need.


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## Pedal-Force (Aug 7, 2020)

iowagold said:


> wow!
> you need to be at 2x the rating for good operation...
> and so it will not pull the stuffins out of the gen set! lol! think over heat issues.
> so a 30-40 kw gen set for the max power...
> ...


Most lights are LED by now, not all, but the ones we mostly use are. Fridge is from last year. The small freezer in the garage is ancient, but also small. HVAC is also new two years ago.

Not on a well, and haven't measured anything, just read name plates or manuals or took a first approximation guess at it to refine later. Likely over estimating and being conservative (I'm an electrical engineer, but below 4kV isn't my thing).

Link to spreadsheet here. Home Generator

Prices sheet is still very much a work in progress, probably changing a lot about how I do it, just haven't updated yet.




speedy2019 said:


> If you do buy a UPS to work with your generator, make sure its a generator friendly UPS because the power isn't steady enough coming from a generator to stop a normal ups going between battery and mains power all the time.
> 
> A few years a go, we had a generator from our power supply because they were working on the powerlines, and the power coming from that generator into the house was really steady at 240volts acording to my UPS with hardly no fluctuation in the voltage. Since then I bought myself a cheapish gen just over a yr ago and I havent had to use it once yet,, typical hey?
> 
> Also going off topic, does anyone know the thickness of a incomming mains cable, because the cable has come all unclipped around the outside of the house? So I need to buy more cable clips to fix the cable back to the house, but I have no idea of the size of the clips I need.


Good idea about making sure it's not switching constantly. A whole house UPS would be nice in general but probably pretty expensive I'd imagine. Not a bad idea, I'd thought about it but not looked into it yet.

For the cable size, it depends on your service size. For 200A it's probably 2/0 Cu or 4/0 AL. Nothing stopping them from having used something bigger though.


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## Resnick98 (Aug 9, 2020)

Hi Pedal-Force, did you ever find an answer to your original question? ie. do WGen generators with THD < 23 have issues with smart equipment? I'm also considering buying a WGen (probably the 7500DF one) and had the same concerns about the high THD. Like you said, although there are many positive reviews for these generators, no one says if they had issues with smart devices or LED lights,etc. I'm tempted to "assume" they do not but I hate to do so. On the other hand, I have also read, that many of these issues are due to the high frequency in some generators and that it was not necessarily due to the THD. Does anyone know? Thank you in advance.


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## Pedal-Force (Aug 7, 2020)

Resnick98 said:


> Hi Pedal-Force, did you ever find an answer to your original question? ie. do WGen generators with THD < 23 have issues with smart equipment? I'm also considering buying a WGen (probably the 7500DF one) and had the same concerns about the high THD. Like you said, although there are many positive reviews for these generators, no one says if they had issues with smart devices or LED lights,etc. I'm tempted to "assume" they do not but I hate to do so. On the other hand, I have also read, that many of these issues are due to the high frequency in some generators and that it was not necessarily due to the THD. Does anyone know? Thank you in advance.


I did not get a resolution to that particular question, no.

I'll probably need to do some more research, but I'm also leaning towards a slightly bigger DuroMax that has a 10-12% as well, to at least help some.

Edit to add:

My initial thought is that basically every single electronic thing with circuits that would care isn't actually using the raw AC anyway. They're all using switch mode power supplies to convert to DC, and those, by nature, have huge operating input ranges of both voltage and frequency and do a great job filtering inputs. I find it unlikely that a few extra third harmonic content would affect them at all. Especially for just a few days a year.

I borrowed a harbor freight 2 cycle little camping model for last week's outage and ran all the routers and monitors and laptop and was able to work without any issues. I even ran the TVs for the family. I can't imagine the quality of power coming off that POS.

I'm a work from home consultant so every hour I'm without power I'm not getting paid, which makes justifying whatever generator a pretty easy call.


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## Resnick98 (Aug 9, 2020)

Pedal-Force said:


> I did not get a resolution to that particular question, no.
> 
> I'll probably need to do some more research, but I'm also leaning towards a slightly bigger DuroMax that has a 10-12% as well, to at least help some.
> 
> ...


I started reading the bad reviews to see if anyone would say anything relating to this topic. So far, the only issues I've seen are 1) Out of the box issues with not starting or not providing power 2) some guy who returned a WGen because of leaky gas tank and poor quality power. Apparently his dishwasher panel would go crazy. However, this is low on my priority list.

With the above said, I also looked at some similar models from Generac and they also do not post THD rating. However, their XT 8000/8500EFI models seems to have <5 THD. Plus they are fuel injected, use pressurized oil, and the 8000 model has idle control. Just an FYI in case you might be interested. Also Costco has a good deal on one of them. I would have pulled the trigger (I may still do ..LOL) but I think 8.5KW might be too much for me. Plus, I was keen to look for a dual fuel one. In case something happens with Gas. I live in NJ and during Sandy (I think) we lost power for 7-8 days and there was a shortage of gas in the area. I even thought about getting an XT one and getting a conversion kit to natural gas. But I do not think they would work since they are fuel injected.


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## iowagold (Jan 22, 2020)

for basic backup with low fuel consumption start with a honda eu2200i generator.
good clean power.
and then upgrade that to tri fuel
click here for the honda eu2200i accy page


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## Jacob from Iowa (Sep 2, 2020)

Pedal-Force said:


> Like everyone else on the East coast I'm now considering a whole house generator. Almost certainly going to plumb it into the natural gas and put in a transfer switch, make it a portable whole home setup basically, so when we move it comes with us (and is cheaper than the permanent units) minus the wiring and bit of natural gas plumbing.
> 
> Seems like the best generator for my use will likely be the Westinghouse W9500, and it gets wonderful reviews everywhere, etc. However, the THD rating is <23% or somewhere around there, which is really bad. Considering almost literally everything I run will have electronics in it (Fridge, Dishwasher, Microwave, Washer/Dryer, VFD pool pump, laptops, monitors, TVs, almost everything is electronic) I'm concerned, but nobody seems to have any complaints who has used them.
> 
> ...


Can I ask what you decided on?

I have exactly the same situation as you: I want to power most of my house from a 50A transfer switch and am trying to decide how big of an issue THD really is. I have several expensive pieces of electronics that I don't necessarily have to use during a power outage, but some I do, like a modem, router, large flatscreen TV. I also don't want to risk frying my fridge electronics or my High Efficiency furnace electronics.

interestingly, I have noticed that A-iPower claim <5% THD for their SUA10000EC model. I am just really skeptical that it's true, given it's hundreds of dollars cheaper than more established brands, yet claims to be that much better...


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## MattN (Sep 2, 2020)

I'm also curious on how much THD should factor into the decision.

We lost our power for 9d during the last storm, and ended up running everything of a DuroStar DS4000S, which supposedly has a THD <12%. Sensitive electronics seemed fine with it -- no issues on {Router, Modem, Monitor, Desktop Computer, Laptops}. As already mentioned earlier most of these run on small-scale switching power supplies anyway (aside from the desktop computer). You could definitely hear some kind of ringing when running any induction/motor-based appliance though (e.g. fans). Doubling the THD to ~23% sounds scary, though, so I'd love to hear if anyone tried it 

In retrospect I realized during this outage that we didn't really need that much power anyway: For our internet-driven work-from home & powering {freezers, refrigerators} we ended up using around ~700W continuous (and ~2kW when preparing food), so I'm actually thinking of just going for a smaller inverter generator for {less noise, fuel usage}

(Though it sure is tempting to get a large one & power central AC with it)


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## ToolLover (Jan 13, 2020)

Most electronics now have a smoothing RC network tied to the AC incoming power. It would take a really out of the ordinary THD to cause damage.


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## speedy2019 (Jan 29, 2019)

Surely it depends how well you look after your generator, because a un-maintained geneator will produce dirty, none constant power?


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## RedOctobyr (Aug 8, 2018)

I don't think generator maintenance would really affect output power. Unless you're talking about something like a dirty carb, so the engine speed is surging up and down, in which case your electrical frequency (at least) would be varying constantly. Which is bad. 

Pedal-Force, that sounds like a _lot_ of watts for your loads! My first generator was 5500W. I installed an analog load panel, to help me understand how close I was to overloading it. We have natural gas, forced hot air heat. Gas stove and hot water. Fluorescent & LED lights. I make no attempt to run the whole-house AC (which isn't wired to the generator anyhow). But I tried to get the fridge running, furnace, etc, and I think we were around 4500W. I believe that was also including the sewer pump in the back yard.

I'm not claiming I couldn't get it to go higher. Just the 1300W microwave would add about 1800W from the wall. But the 5500W was fine. 

I have since transitioned down to an EU2000i (which I'd bought for a hobby). That (1600W continuous) runs our essentials, including furnace, fridge, lights, TV, internet, etc. I turn the inverter microwave down to 30% power to reduce its wattage draw. 

I added a second EU2000i in parallel, for more capacity, and a bit of breathing room for capacity (now 3200W continuous). 

The inverter units are quiet, fuel-efficient, and have very-clean output power (low THD). The downside is that the inverters are 110V-output, until you get to around 5000W inverters.


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## iowagold (Jan 22, 2020)

like i have said before.
if you want to have good clean power stick with the honda eu series!!
our testing has put them way a head of the others out there.
the eu2200i is a good choice for all around power. i can stack 4 of them with my system.
click here for the generator connection page
and if you need the 240 vac then go with the eu7000is... both units can be converted to tri fuel as well.

for me i have a lot of cash invested in electronics gear...
so why risk it with a low cost generator!
bad power erodes electronics over time..

at the end of the day...
do what works best for you!

stay safe out there!


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## jasonjax (Mar 15, 2020)

After agonizing over my decision for months I couldn't be happier with my Winco. <6% THD ... I have tested it a couple of times with my natural gas hookup and manual lockout xfer to my breaker panel using the 45AMP connection on the genset. 

It isn't cheap, but designed for tri-fuel, a Honda engine, and made in the USA were enough to make me comfortable with the investment.

I can run my whole house on it including the A/C startup (installed a hard start which I think helped)


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## Captain Q (Mar 9, 2021)

jasonjax said:


> After agonizing over my decision for months I couldn't be happier with my Winco. <6% THD ... I have tested it a couple of times with my natural gas hookup and manual lockout xfer to my breaker panel using the 45AMP connection on the genset.
> 
> It isn't cheap, but designed for tri-fuel, a Honda engine, and made in the USA were enough to make me comfortable with the investment.
> 
> I can run my whole house on it including the A/C startup (installed a hard start which I think helped)


Jason, 

What model of WINCO did you get and what did you end up paying? 

Thanks


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## edwardbarnett (Apr 19, 2021)

From the very beginning, I can say that this generator Westinghouse W9500, although it is expensive but very effective. I think the 45 AMP would be perfect for you. I had a similar question, but I was not helped in my time as you are. Just be careful with the tension, man. By the way, I recently bought myself a 40 AMP, and not the newest one. I buy from old factories or factories, old parts, but which are still working. That's just when I found a website where I buy all these things. Good luck with your business, my friend. I hope you heard me, if you have any questions, write in PM.

*_*






Home | Automation USA


Home | Automation USA




www.automation-usa.com


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## Chip (Sep 4, 2021)

ToolLover said:


> Most electronics now have a smoothing RC network tied to the AC incoming power. It would take a really out of the ordinary THD to cause damage.


Never heard of this. So, If most electronics are newer they would have this smoothing factor?


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## iowagold (Jan 22, 2020)

depends on the design in the dc converter power supply.
some will stand for more hash than others.
the issues we see are in motors... some will not stand much hash....
and causes all kinds of issues...
so we use honda eu7000is inverter gens on all of the construction sites now in the fleets.
it stopped the issues on chop saws and table saws for sure...
and have yet to loose a battery charger from the new switch over in 2021.


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## ajnuzzi (12 mo ago)

I own a wgen9500df and run it off natural gas. I have all the usual smart devices (alexa, router, fios ont, etc) and everything runs fine off the gen except my LED lights flicker. I had a durostar ds12000eh and they both performed about the same. I ended upgrading to the Wgen12000df which has a supposed <5% thd. I don't have a way of measuring the thd but I can say this: on the 12000df the frequency is much more stable and none of my lights flicker. If it wasn't for the price being double I would say it's a no brainer but with that in mind the 9500df works fine too - like others have said put UPS's on electronics you're concerned about. I like the amazon line interactive UPS. I have them on my router, ONT, tankless water heater, and my entertainment setup (tv, ps5, receiver). Hope this helps


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## Columbotrek (11 mo ago)

I use the 9500DF for my home backup through a manual 50Amp transfer switch. Everything works that I am powering with it. Home theater, routers, wireless, ups, 3 ton AC, furnace, microwave, wired nest door bell camera, smart switches/outlets, and LED lights all work correctly. The ups may switch to battery when the AC compressor starts. At first, the Smart dimmer LED lights strobbed horribly and the UPS complained but I solved that by adjusting the frequency down to at or below 60hz. The non Smart dimmer attached LED bulbs and the C by GE smart bulbs worked correctly above 60hz. It appears to me that the devices which malfunctioned on the Generator did so because the frequency was to high. Out of the box the wgen9500 was doing 63HZ no load. By adjusting the governor stop screw to 60.4hz after warmup and no load, the gen runs my typical house load at 59.8 hz and bigger loads at 59.4 hz. Smart dimmers and UPS are happy.


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## OrlyP (Oct 19, 2021)

What I see people on Youtube knowledgeable on these things do is to set the frequency at around 61.5Hz, no load.


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## Columbotrek (11 mo ago)

OrlyP said:


> What I see people on Youtube knowledgeable on these things do is to set the frequency at around 61.5Hz, no load.


61.5hz keeps the ups happy. But my smart light dimmers (wemo) strobe at 60.1hz and above. They work fine at 60hz and as low as I tested (57.5). The ups and everything else seems fine in the 59-60hz range. The clock in the microwave and coffee pot gets slow. Have to reset them if they have been on the generator for a length of time. We're it not for the wemo dimmers, I would set the speed up a hz so as it loads up it moves closer to 60 than away from 60.


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## OrlyP (Oct 19, 2021)

It's 2022 and it's a wonder why digital clocks on appliances still derive their 'beats' from the 60Hz line. Is it really that more expensive and complicated if they used an independent timekeeping component like Quartz crystals?

But I digress.

I suppose, most appliances should be fine with up to 5% deviation from 60Hz. More so if it has a 50/60Hz power supply. It's really the inductors (AC motors, transformers, etc.) that are powered directly by line power that's going to have _some_ issues with going above or below 60Hz. I am surprised about your Wemo dimmers. I would think it would've preferred nothing but right smack in the middle of 60Hz.


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