How do large portable generators (inverter) handle low loads?

[aunsafe2015]

I'm thinking about buy something like a Champion 100520 7000 W inverter generator: https://www.championpowerequipment.com/product/100520-8750-watt-open-frame-inverter/.

I'd install an interlock on my electric panel and use it to power my house during outages.

The specs for that generator predict a 10+ hour run time at 1/4 load. My question concerns operator of the generator at low load. So it has a max continuous output of 7000 W. Say I've got it on and running, and my house is only using 1000 W. Or 2000 W. Whatever it happens to be, much less than 7000 W.

How does the generator handle that ? Is it able to modulate its output basically infinitely from 0 to 7000 W? If it cannot modulate all the way to match a very low load, what then?

If my average load is 1000 W and only occasionally spikes to 4-5000 W (e.g., both a/c, electric oven, and dryer all running), is there a good reason to get a smaller version such as the 5000 W continuous load version of the same generator? Or is it simply a matter of efficiency/fuel usage?

Thanks for any input.

 

[u3b3rg33k]

it modulates just like your car. no load at idle, just waste heat. the generator doesn't "make power flow" it creates the potential to allow it to.

you could charge only your iphone off of it if you wanted to, or run a 1/4W neon night light. it'll run just fine.

 

[MongoTA]

I saw it does have an "eco mode" setting. Turn that on and at low loads the engine rpm will decrease, saving fuel and increasing run time. When load incease, the engine's rpms automatically increase to meet the load.

 

[mike93lx]

That's not going to be that much quieter than a traditional generator under load. The enclosure on many Inverter generators makes a huge difference.

The only options that I know of for 240v inverters with enclosures are the Briggs q6500 (I own one and like it) and the Honda 7000 (very, very nice and very, very expensive)

Under minimal load, any will run just fine. I bet it never uses less fuel that that 1/4 load rating though

 

[ngray]

Whereas normal generators need to run 3600rpm to generate 60hz, they burn a relatively high amount of fuel even under low load compared to inverter generators, which run from low idle (say 1k rpm) up to 3600rpm. This is because a traditional generator runs an AC generator directly to the panel, but an inverter generator rectifies the generated AC into DC, and then runs a sine wave inverter to create AC again from it. Under low load, that inverter system can easily run 1k rpm and generate 60hz, which a traditional genset never could.

 

[mike93lx]

Whereas normal generators need to run 3600rpm to generate 60hz, they burn a relatively high amount of fuel even under low load compared to inverter generators, which run from low idle (say 1k rpm) up to 3600rpm. This is because a traditional generator runs an AC generator directly to the panel, but an inverter generator rectifies the generated AC into DC, and then runs a sine wave inverter to create AC again from it. Under low load, that inverter system can easily run 1k rpm and generate 60hz, which a traditional genset never could.

they could run 1000 rpm, but i doubt they actually throttle down that far. I can't find a spec on my briggs, but it definitely quiets down when using their eco mode. a former neighbor had the honda 7000 and damn, that was quiet.

 

[510ebl]

I have that same generator. Don’t expect it to be Honda quiet. Or any kind of quiet.

It does run at lower rpm and less loudly at lesser loads.

 

[Chilliwack Murray]

At high loads many of the inverter generators are louder than a direct drive unit as they typically run up to about 5000RPM at full load. Anything more than about 50% load the noise and fuel consumption should be about the same.

Since you shouldn’t really be running at full load for long periods in practical use the inverter units should be quieter than the identical non inverter. At low loads it will be much quieter and use much less fuel.

I have a Yamaha i1000 I use overnight to keep the house furnace and a few lights on It runs for about 12 hours on the tiny built in tank. When the furnace blower slows to minimum speed the gen runs about 1000rpm and near silent.

Biggest difference between brands is serviceability. Buy a brand name and it’s repairable and will run for several thousand hours. Buy the Chinese brands (or rebranded Chinese made units) and they are disposable. Not sure what makes more sense economically but I hate to buy things twice.

 

[aunsafe2015]

Awesome, thanks to everybody for the replies.

 

[TractorJeff]

5000rpm on a 4 stroke air cooled engine?
I question that Data?

 

[Yankeefarmer]

5000rpm on a 4 stroke air cooled engine?
I question that Data?

My 1982 Yamaha Seca 400 was a 4 stroke air cooled engine, and, IIRC, redline was around 10k rpm.

 

[mike93lx]

My 1986 Yamaha Seca 400 was a 4 stroke air cooled engine, and, IIRC, redline was around 10k rpm.

That was designed to be moving when it revved that high. Sit still and see how it goes

 

[Yankeefarmer]

That was designed to be moving when it revved that high. Sit still and see how it goes

Completely different subject. Only means bottom end was capable of those rpms. Stationary air cooled engines incorporate cooling fans.

 

[American Locomotive]

5000rpm on a 4 stroke air cooled engine?
I question that Data?

That was designed to be moving when it revved that high. Sit still and see how it goes

Why is that unbelievable? An air-cooled engine can run at any arbitrary RPM the manufacturer designs it to. 100 RPM, 5000 RPM, even 15,000 RPM. Doesn't matter as long as it has adequate cooling.

An EU1000i generator will run up to 5,000 RPM, the EU2200i about 4,500 RPM, and Honda's 4-stroke string-trimmer engines will wind up to 10,000 RPM.

 

[u3b3rg33k]

It makes sense from a power density and weight perspective, too. people want a light generator to run their fridges/TVs when the power goes out. rev it up when they load it up, keeps the HP/lb numbers favorable.

 

[Chilliwack Murray]

5000rpm on a 4 stroke air cooled engine?
I question that Data?

I had the factory training about 12 years ago and that is right out of the Yamaha Generator Technical Guide... Of course, its the Canadian edition so that's metric RPM.

 

[MongoTA]

they could run 1000 rpm, but i doubt they actually throttle down that far. I can't find a spec on my briggs, but it definitely quiets down when using their eco mode. a former neighbor had the honda 7000 and damn, that was quiet.

I have the Honda eu6500, I think it has been replaced by the 7000. Not positive. But I've had it for close to 10 years.
It is indeed freakishly quiet. A conversation can be had at normal voice levels while standing next to it.
Two of my neighbors have non-inverter generators, in my yard I can hear theirs but not mine. Eco mode is pretty good. I'll fire it up sometime and see hat the RPMs are at eco idle. I'd guess 1750 but I don't recall.

 

[jlv03]

I wish more companies would come out with battery packs that can start a generator as needed. No need to run a gen all night just to run a few things, let the battery cover base load and kick on a generator as needed to either charge the batteries or handle the big loads.

I know there is one company out there that has something, but it is both new and expensive: https://ecoflow.com/products/ecoflow-delta-max-power-station

 

[dcg9381]

The only reason to get a smaller generator is if you want lower fuel consumption at moderate loads.
I have 2 of the champion dual fuel 3200 watt inverter gensets (open frame). Being honest, they are just as loud as the non-inverter gensets at load. The "eco" mode of the inverter generator allows them to throttle down a bit and they are less noisy. When there is a larger demand of power, they throttle back up to 3,600 rpm.

I think the 7k deal is a good choice if you're trying to power a house (at least partially).

 

[TractorJeff]

Thanks! I didn't realize that Honda was running the engines that high. Worked on too many OLDER 3600 rpm Briggs, Kohler, Tecumseh and Wisconsin engines. Way back in the day, there were South Bend and Clinton engines too!

 

[Chilliwack Murray]

I wish more companies would come out with battery packs that can start a generator as needed. No need to run a gen all night just to run a few things, let the battery cover base load and kick on a generator as needed to either charge the batteries or handle the big loads.

I know there is one company out there that has something, but it is both new and expensive: https://ecoflow.com/products/ecoflow-delta-max-power-station

Onan had a hybrid system 15 years ago but it never caught on. Every one I ever saw had insufficient battery capacity installed and people thinking it didn’t work properly. They were horribly complicated with all kinds of safety interlocks to keep it from starting the generator if the vehicle was indoors etc.

People just want to hit a button and have power.

Paid out way more in warranty than they ever made on that product and 90% of it was operator or installer error.

 

[theoldwizard1]

Technically any electric power generating device that make alternating current is called an alternator. Yes, the one in your car makes DC but that is because their are diodes inside the alternator that convert AC to DC.

Inverter generators use permanent magnets in the field (the rotor). The stationary windings output alternating current at a voltage and frequency that varies with the engine RPM. (Just to confuse you more, it's probably 3 phase). Diodes are used to convert that to high voltage DC (something over 200V). This then charges a capacitor (temporary power storage).

Now remember voltage times current equals power. While the incoming voltage and current may be changing, the energy in the capacitor is always sufficient for some "smart" electronics convert it into nice, clean 120VAC @ 60Hz. If the energy in that capacitor starts to drop, some other "smart" electronics kicks up the engine speed.

If you want 240VAC, the simple method is just run 2 120VAC inverter locks 180 degrees out of phase.

 

[dcg9381]

If you want 240VAC, the simple method is just run 2 120VAC inverter locks 180 degrees out of phase.

I recently bought 2 Champion 3200 dual-fuel inverter generators. I *assumed* because there was an interlink kit with a 50A 4-prong connector on it that they would be out of phase and provide 240V power.

I was incorrect in that assumption. But I do have 50A of 120V power. So now I need a 3rd generator if I want to have a portable welder.. :-(

 

[theoldwizard1]

I recently bought 2 Champion 3200 dual-fuel inverter generators. I *assumed* because there was an interlink kit with a 50A 4-prong connector on it that they would be out of phase and provide 240V power.

I was incorrect in that assumption. But I do have 50A of 120V power. So now I need a 3rd generator if I want to have a portable welder.. :-(

So you think you can make 3 phase ?

Same problem. The phase must be EXACTLY 120 degrees apart !

 

[u3b3rg33k]

he can make three phase with one! just pull the rectifier out

 

[u3b3rg33k]

I recently bought 2 Champion 3200 dual-fuel inverter generators. I *assumed* because there was an interlink kit with a 50A 4-prong connector on it that they would be out of phase and provide 240V power.

I was incorrect in that assumption. But I do have 50A of 120V power. So now I need a 3rd generator if I want to have a portable welder.. :-(

I took a look at it - they advertise 50A 120V. shows a single pole breaker. RVs are typically full of 120V motors and the extra amperage just gets you more capacity. that looks like what they did here.

 

[Ole Slewfoot]

I took a look at it - they advertise 50A 120V. shows a single pole breaker. RVs are typically full of 120V motors and the extra amperage just welds the plugs together

Fixed that for you

 

[dcg9381]

@Ole Slewfoot, yep - thanks for making that clear... Exactly.

 

[Davegvg]

I'm thinking about buy something like a Champion 100520 7000 W inverter generator: https://www.championpowerequipment.com/product/100520-8750-watt-open-frame-inverter/.

I'd install an interlock on my electric panel and use it to power my house during outages.

The specs for that generator predict a 10+ hour run time at 1/4 load. My question concerns operator of the generator at low load. So it has a max continuous output of 7000 W. Say I've got it on and running, and my house is only using 1000 W. Or 2000 W. Whatever it happens to be, much less than 7000 W.

How does the generator handle that ? Is it able to modulate its output basically infinitely from 0 to 7000 W? If it cannot modulate all the way to match a very low load, what then?

If my average load is 1000 W and only occasionally spikes to 4-5000 W (e.g., both a/c, electric oven, and dryer all running), is there a good reason to get a smaller version such as the 5000 W continuous load version of the same generator? Or is it simply a matter of efficiency/fuel usage?

Thanks for any input.

If it works like all of my other inverters then 1/4 load is basically what it puts out idling.
So 1750 watts is your baseline output, it wont ramp up RPM until you draw more power.

The smaller genset would use marginally less fuel at idle.

 

[dcg9381]

I saw it does have an "eco mode" setting. Turn that on and at low loads the engine rpm will decrease, saving fuel and increasing run time. When load incease, the engine's rpms automatically increase to meet the load.

This. I have two of their 3200 watt open frame inverter models. In "eco" mode it drops RPM, but not by a lot. I'd guess maybe a drop of 1000 - 1500 RPM, it doesn't turn down to anywhere near idle. Throttles up on demand.

As others have mentioned, that generator is 120V only. It's only going to do one side of your panel and your 240V appliances will not be functional.

I haven't seen a 240V inverter generator by Champion yet.

 

[mike93lx]

I haven't seen a 240V inverter generator by Champion yet.

Here you go

6250W Open Frame Inverter – Champion Power Equipment

Champion's innovative 6250-Watt Open Frame Inverter is 50% quieter and 20% lighter than a traditional 5000-watt generator. With Quiet Technology, Extended Run Time, Economy Mode and Clean Power, this inverter is the cost-effective, advanced power solution you need.

www.championpowerequipment.com

 

[Davegvg]

This. I have two of their 3200 watt open frame inverter models. In "eco" mode it drops RPM, but not by a lot. I'd guess maybe a drop of 1000 - 1500 RPM, it doesn't turn down to anywhere near idle. Throttles up on demand.

Eco mode on is as close as it gets to "idle" - there is no slower speed.

 

[dcg9381]

Here you go

6250W Open Frame Inverter – Champion Power Equipment

Champion's innovative 6250-Watt Open Frame Inverter is 50% quieter and 20% lighter than a traditional 5000-watt generator. With Quiet Technology, Extended Run Time, Economy Mode and Clean Power, this inverter is the cost-effective, advanced power solution you need.

www.championpowerequipment.com

Thanks! I missed that one!
Now I just need it to do propane too.. I decided to buy a Firman (on sale for about $800 from Costco currently) - largely as it's tri-fuel and has the 50A connector that I've standardized on...

Tri Fuel 7500W Portable Generator Electric Start 120/240V

The FIRMAN T07571 Tri-Fuel Portable Generator delivers powerful performance with 9400 starting watts and 7500 running watts, and the flexibility to run on gasoline, propane (LPG), or natural gas (NG). Whether you're preparing for a power outage, running tools on a job site, or powering your next...

firmanpowerequipment.com

 

[AP514]

Thanks! I missed that one!
Now I just need it to do propane too.. I decided to buy a Firman (on sale for about $800 from Costco currently) - largely as it's tri-fuel and has the 50A connector that I've standardized on...

Tri Fuel 7500W Portable Generator Electric Start 120/240V

The FIRMAN T07571 Tri-Fuel Portable Generator delivers powerful performance with 9400 starting watts and 7500 running watts, and the flexibility to run on gasoline, propane (LPG), or natural gas (NG). Whether you're preparing for a power outage, running tools on a job site, or powering your next...

firmanpowerequipment.com

That Firman only puts out 30AMPs..well, 31AMPs on that 50 AMP plug....that 50AMP plug is for connecting to your RV..but still max output is 31 AMPS

 

[dcg9381]

That Firman only puts out 30AMPs..well, 31AMPs on that 50 AMP plug....that 50AMP plug is for connecting to your RV..but still max output is 31 AMPS

Yea, that's not atypical. My first "generator screw up" was buying a 5500 watt Briggs and Statton in a situation where our Class-A on board generator failed. I strapped it to a hitch carrier, and assumed it would pull 2 AC units. Turned out, it had an a 20A breaker on the 240V side. So 18A continuous (max). Same thing on the 120V side... It wouldn't power the RV reliably. It was a miserable trip.

The successive Champion generators that were wound single phase for 120V@30A were a huge improvement. They worked better (for an RV) than a 5500 watt Briggs-Stratton, because that breaker was actually 30A and I could reliably run 1 AC unit. They also consumed a lot less fuel.

I have a "bunch" of RV connections at my shop. We are setup to host several RVs. The reality is that a 40' RV, really only needs about 6000-7000 watts, which is accomplished by 30A@240V. Well, until you get to "Willy Nelson" style RVs with more than 2 AC units (these are $500k+ not typical). About 1/2 of my 50A plugs are wired 50A, the rest are wired (and labelled) 30A@240V. I've standardized everything to a 50A NEMA plug. But upstream of those plugs, I have the correct breakers.

I get barked at on this forum a bit, but it's all NEC compliant.. And I'll cite code, if you'll wager..

30A @ 240v, that will power most of what is critical at my shop... Which includes the infrastructure to run our house (water pump and UV light). The house has it's own 20KW generator, but that's not helpful if you can't push water.

I have the ability to self-fill 100 lb propane tanks (I own two) from our main propane tank. This is "OK" until it gets to 20F or so - propane tanks lose pressure.

I'm an engineer, but I've learned a lot of stuff by failure... I think I've got "one more" shop build left in me in the next 5-10 years... But that #$!$ is going to be zombie proof...

 

[MongoTA]

I'd install an interlock on my electric panel and use it to power my house during outages.

Thanks for any input.

I'll offer this as well...
My transfer panel this one from: Schneider Electric.

Took me a few hours to wire and program. If your generator has the capability, the panel can be wired/programmed to auto-start the generator in case of a grid failure. I didn't activate that feature as my panel is fed by a Honda eu6500 generator. I prefer the gas generator to not auto-start if we are not home.

The thing I love about this panel is that it is load shedding. If an over-demand occurs, the generator will never trip off. Instead the panel senses the overall demand and controls how the load is distributed to the circuits. When setting up the panel, you program what is on each circuit, the priorities for shedding, and if a circuit is to be shed, the minimum time it should remain UNPOWERED, and when repowered, the minimum time it should remain POWERED. That helps so there is no short-cycling of circuits - ie, the freezer is not repeatedly being cycled on and off in rapid fashion.

When the grid goes down, the generator (rated at 5500w continuous) can power the basic lighting and outlet requirements on the entire first floor of our house. The one thing in the kitchen that is not powered is the electric 220v wall oven. We have a propane cook top. We have full lighting and outlets, the bathroom, home offices (computers and internet), as well as the fridge and freezer powered.

On the second floor, our master bedroom suite is powered. We are empty-nesters so while my kids' bathroom has power, their bedrooms are not.

In the attic, which is a game room and home theater, everything up there is powered.

The household 220v loads in my house are my well pump, the electric clothes dryer, the central AC, the electric wall oven, and outside, the pool pump. When the power goes out we can 'survive' without all except for the well pump. Powering the well pump gives us domestic hot and cold water, hot showers, and flushable toilets, etc.

In cold weather, the 5500W generator powers most everything needed. In hot weather, it does not power the central air or the pool. When our power goes out for an extended period in the summer, it's typicaly after a hurricane or the remnants of a hurricane, have passed through. AC is generally not required at that time.

The setup is simple enough that if I'm not home, my wife (who is marginal DIY) can go outside, turn a key to fire up the generator, plug the cable in to the outlet on the side of the house, and DONE, she has power. She doesn't have to flip circuit breakers.

During extended winter outages, we'll fire up the generator in the morning. Shower, have breakfast. Let the house warm up. We might let it run until after lunch, or we might not to conserve fuel. We'll play cards or board games by natural daylight. At dusk we'll fire it up again. Cook, watch a movie or TV in the attic. When we go to bed we turn off the generator for the night. Wake up in the morning and repeat.

 

[theoldwizard1]

My transfer panel this one from: Schneider Electric.

The thing I love about this panel is that it is load shedding.

Nice feature, but expensive ! And you still can only protect 10 circuits. Would rather have a generator interlock. With that size generator you could power everything, just not at the same time.

 

[mike93lx]

Nice feature, but expensive ! And you still can only protect 10 circuits. Would rather have a generator interlock. With that size generator you could power everything, just not at the same time.

Hence the load shedding.

Not everyone wants to worry about managing loads during an outage.

 

[theoldwizard1]

Not everyone wants to worry about managing loads during an outage.

The flip side is when you realize that you did not cover the circuits "necessary" for a comfortable existence. I'll accept the responsibility of managing the load. (Quite simple if you don't have any 240V appliances.)

 

[mike93lx]

The flip side is when you realize that you did not cover the circuits "necessary" for a comfortable existence. I'll accept the responsibility of managing the load. (Quite simple if you don't have any 240V appliances.)

Sounds like you have a great solution for you.

We've been through this discussion before. I have successfully used both interlocks and limited-circuit panels. They both have appropriate applications