Help me understand something re: generators and inverter generators

[BigJohnfromCT]

I have a Quadrafire Mount Vernon AE stove, installed around March of 2011. I also have a Generac 10kw portable that I use during power outages. I understand that, perhaps, some folks have stoves with computers that might not respond well to power that is a little dirty. What I do not understand is why. In my house, besides the pellet stove, I have televisions, computers, a refrigerator, cable boxes, a furnace, programmable stuff, phones, etc. all with computers in them. Even the mirrors in my bathroom have chips in them. They all work off my portable generator. Can there really be that big a difference? I know you're right, if it doesn't work on your generator, it doesn't work but why? Any thoughts? Thanks.

 

[peakbagger]

Power electronics used to be very sensitive to power quality, long ago electrical standards pushed manufacturers into installing more robust electronics in them to deal with poorer power quality.

Inverter generators in theory put out cleaner regulated power but their biggest gain is far greater partial throttle efficiency.

Of course flick on surge load like water pump and either type of generator is likely to sag the voltage.

 

[jackman]

It's a great question. I'll throw an answer out here that may be dismissed by some. In general, it doesn't matter if the generator is producing enough of a sine wave. Generators that output an approximated sine wave that resembles more of a square wave will be rejected by some of your electronic devices. The good electronic devices will sense this less than pure sine wave and simply shut down the input or accommodate for it with their own circuitry to make it an acceptable source. Some devices may struggle with it and cycle on/off trying to establish the proper input. The long term effects to a sensitive device from a less than pure sine wave input may also have a damaging effect. A second concern is the brown-out condition that may occur when the generator starts to run out of fuel and the voltage output surges and then sags repeatedly.

One way to clean up the source from a non-inverter generator would be to use a pure sine wave UPS connected to your input device such as the pellet stove. I recommend that.

 

[SidecarFlip]

Far as I'm concerned EVERY biomass appliances needs at least some sort of line protection between the line cord and the wall outlet. I use a Tripp-Lite myself but running without is inviting trouble at some point and it's usually the circuit board that gets toasted.

 

[BigJohnfromCT]

Far as I'm concerned EVERY biomass appliances needs at least some sort of line protection between the line cord and the wall outlet. I use a Tripp-Lite myself but running without is inviting trouble at some point and it's usually the circuit board that gets toasted.

Totally agree. Also use a Tripplite. Still don't understand why why some stoves need an inverter generator rather than a regular genny. Cheap, unstable power supplies?

 

[Highbeam]

Since that “need” was established decades ago, generators have gotten much better and electronics more tolerant. If you’re willing to risk your refrigerator and other expensive equipment then run the pellet stove on it too. It’s just more Chinese electronic boards and motors, nothing special.

 

[SidecarFlip]

Totally agree. Also use a Tripplite. Still don't understand why why some stoves need an inverter generator rather than a regular genny. Cheap, unstable power supplies?

I believe it has something to do with the overall quality of the solid state devices in the brain box and we all know those brain boxes are super expensive.

I will say that both the farmhouse and the shop are on one emergency standby generator. it's 35KW Generac, John Deere Diesel powered, 110-1 / 220-3 and during an outage, other than the Tripp Lite on the stove, I never give it a thought as far as PSW or MSW power is concerned. Everything runs just fine. I will also say that if we go for an extended period on backup, I do notice the electric clocks will loose time which tells me I'm not getting true 60cps. Not a lot but in a few day time period it's noticeable. I believe the Generac head has what is called 'skewed windings' which supposedly improves on the modified sine wave pattern but I'm not that well versed on what or how that impacts the output.

I have an inverter generator as well but it's not big enough to use as emergency backup. I do use it in the RV and I use it for line power when working in the field because it fits handily in the back of the back of the side by side and I prefer using 110 volt powered tools for some things over cordless powered tools and has been stated previously, the auto idle feature makes it extremely gasoline efficient.

Nice thing about a diesel standby versus a gasoline powered standby is, the diesel standby has a 4 pole head versus a 2 pole head on a gas powered unit so the diesel unit only turns at half the rpm to make power and that makes it much, much less obtrusive. Gas generators are inherently noisy, turning at 3600 rpm where as my diesel unit is turning at 1800 rpm. Of course a diesel unit costs more than a comparable gas unit but, they also last much longer and mine is plumbed directly into my 1000 gallon diesel bulk tank. It can run for weeks on end at full load if need be (barring scheduled maintenance and me keeping the bulk tank topped off.) When it's running (out next to the shop, you cannot even hear it. Best 10 grand I ever spent and it's all automatic via a vacuum transfer switch. 45 seconds after we loose utility power we are on standby and 15 seconds after utility power is restored it switches out. No danger to utility people from feedback because when it's providing power, it completely isolates the utility power from the standby power.

I think the longest continuous run was 3 days straight a few years ago.

Have the only place on the whole road with lights.

 

[BigJohnfromCT]

I believe it has something to do with the overall quality of the solid state devices in the brain box and we all know those brain boxes are super expensive.

I will say that both the farmhouse and the shop are on one emergency standby generator. it's 35KW Generac, John Deere Diesel powered, 110-1 / 220-3 and during an outage, other than the Tripp Lite on the stove, I never give it a thought as far as PSW or MSW power is concerned. Everything runs just fine. I will also say that if we go for an extended period on backup, I do notice the electric clocks will loose time which tells me I'm not getting true 60cps. Not a lot but in a few day time period it's noticeable. I believe the Generac head has what is called 'skewed windings' which supposedly improves on the modified sine wave pattern but I'm not that well versed on what or how that impacts the output.

I have an inverter generator as well but it's not big enough to use as emergency backup. I do use it in the RV and I use it for line power when working in the field because it fits handily in the back of the back of the side by side and I prefer using 110 volt powered tools for some things over cordless powered tools and has been stated previously, the auto idle feature makes it extremely gasoline efficient.

Nice thing about a diesel standby versus a gasoline powered standby is, the diesel standby has a 4 pole head versus a 2 pole head on a gas powered unit so the diesel unit only turns at half the rpm to make power and that makes it much, much less obtrusive. Gas generators are inherently noisy, turning at 3600 rpm where as my diesel unit is turning at 1800 rpm. Of course a diesel unit costs more than a comparable gas unit but, they also last much longer and mine is plumbed directly into my 1000 gallon diesel bulk tank. It can run for weeks on end at full load if need be (barring scheduled maintenance and me keeping the bulk tank topped off.) When it's running (out next to the shop, you cannot even hear it. Best 10 grand I ever spent and it's all automatic via a vacuum transfer switch. 45 seconds after we loose utility power we are on standby and 15 seconds after utility power is restored it switches out. No danger to utility people from feedback because when it's providing power, it completely isolates the utility power from the standby power.

I think the longest continuous run was 3 days straight a few years ago.

Have the only place on the whole road with lights.

Thanks sidecar, good explanation and confirms what I thought.

 

[Highbeam]

You can buy 4 pole generators with gasoline and propane engines too, that’s not just a diesel thing. Oh and you can buy 2 pole diesel gensets too. The difference is that all 2 pole generators need 3600 rpm to give 60hz but 4 pole heads only need 1800 so they’re usually quieter, smoother, more fuel efficient, and last longer whether gas or diesel.

Do you guys really think the utility power is made by an inverter? Nah, a high quality noninverter genset is fine as far as power quality is concerned.

 

[SidecarFlip]

Utility power is at 60 hz because of the rpm the the utility generator is spinning at. CPS is entirely dependent on the rpm the unit is revolving at.

 

[SidecarFlip]

Inverter generators have typically multi pole heads (my Yamaha Inverter had a 7 pole head and so does my Champion) because the electronics produce the cycles per second, not the rotation of the generator head itself.

I have to say I've never seen a conventional gas generator with anything other than a 2 pole head because gas generators use the engine rpm to produce the necessary Hz (3600 running rpm = 60 hz) Converesely a diesel standby (most diesels produce maximum power output at 1800 rpm).

I guess anything is possible but I've never ween one.

 

[peakbagger]

The problem with any generator is sudden load changes (step loads). The generator does not "store" power like a battery so its always converting a certain amount of fuel to power. It does store a bit of momentum as the rotating parts work like a flywheel. If there is a big load added like a water pump, the engine will slow down slightly drooping the frequency output and the voltage will also drop to try to make up for the larger load. The governor will sense the drop in speed and add more gas and the engine will speed up until the point where it overspeeds. There is a lot of "slop" in a mechanical governor, if you look at the voltage and frequency output its not going to be utility grade. Diesels tend to be heavier and the governor acts directly on the fuel rather than a fuel air mix. The result is diesels can have faster response to load surges. In general if the load change is small compared to the generator capacity, the step load issue is far less. Large generators unfortunately tend to be inefficient at low loads so the temptation is buy a small generator.

Inverter generators changed things a bit, they usually have electronic throttle and do not have to run at synchronous speed (3600, 1800, 1200, 900 etc. ). They are a DC generator that can run at any speed to match up to the load. Its a lot more efficient and then the DC is converted to AC.

Something that few really understand with grid power is that the grids are the largest machines in the world and they have a 60 HZ heartbeat (50 HZ in Europe and other parts of the world). Every electric generator on the grid is running at the same frequency, if you try to hook up a generator that is not connected to the grid to the grid, things will break unless the generator frequency matches the grid frequency as the grid will try to force the generator to the same frequency. In the rare occasion someone tries, they usually snap the coupling between the generator and the turbine. Most generators these days have automatic grid synchronization but most still have a manual syncroscope to do it by hand.

BTW, I did some work at a large papermill complex in Maine (GNP) that had the biggest private hydroelectic system in the Northeast Its now on the grid). They generated 40 HZ power. It was fine for electric motors but incandescent bulbs would flicker. They sold power to a local town electric appliances would run but at a lower speed and electric clocks had to be custom.

 

[SidecarFlip]

You ought to know working on Peaker's units... Just so happens I have a good friend who is the head 2nd shift lead boiler operator at the DTE coal-NG fired plant in Monroe, Michigan and I've gotten the 10 cent tour before.

Amazing stuff especially the way the boilers are fired with pulverized and injected coal (never seen them on NG). Looking in the viewport is like looking into hell if that is what hell actually looks like.

Very interesting stuff.

 

[SidecarFlip]

Why my diesel standby genset totally isolates the utility before it assumes the load and vice versa and why I'd never ever consider doing the 'Rube Goldberg' method of using a portable genny to power my home in a power outage. The utility must be totally isolated for the welfare of utility workers that maybe subject to backfeeding. Just because you have 220 (or 110) on you home don't mean that backfeeding that transformer on the pole isn't stepping that backfeed voltage up to whatever the transformer was reducing the power to. I sure as hell have no desire to electrocute a utility worker who may be working to restore my power because of my stupidity.

 

[velvetfoot]

I had a main panel interlock for a portable generator before I recently got my air cooled lp Generac with transfer switch. My plan for a long outage is to shut down the big unit and use a small inverter generator to conserve fuel and machine wear and tear. Of course, your diesel is built for the long runs, and sips fuel, so you don't have to worry about that!

 

[SidecarFlip]

Don't know if it sips fuel or not but it has at least 600 gallons to sip from. The Generac air cooled units are good units from what I read. The bank up town has one for standby. With diesel fuel costing what it does today, not sure it's a bargain.

Living in a very rural area, when the power goes out, it usually stays out for a long time.

 

[Tonyray]

all great technical info from you people..
I cannot add any 'inside baseball" of how it works other than we have a portable 7500 watt gas generac which is connected to a 10 circuit transfer switch.
we lose power probably 6-7 times per year...
I have run power via the system mentioned over 8 yr period of outtages..
fridge, oi furnace for hot water, tv's, computers, microwave, 220 v AC, hard wired rooms, pretty much everything but electric stove, dryer etc.. never had a problem with any appliance or devices being harmed... I think key for me is to never let it run out of fuel while on the transfer switch.. yes i fill it while it's running when it gets low which if carefull and slow is safe...

 

[SidecarFlip]

In my view, the one most important aspect of powering your abode with ANY standby generator is not backfeeding the utility and causing potential harm or electrocution to utility personnel working on the electric lines and that entails a transfer switch that isolates the utility power from your generated power.

I sure as hell would never want to be responsible for any injury or death to any utility worker ever. They are there to maintain the grid, not get cooked by someone backfeeding the lines by using a a genny to power their abode without a transfer switch and isolation.

 

[Tonyray]

In my view, the one most important aspect of powering your abode with ANY standby generator is not backfeeding the utility and causing potential harm or electrocution to utility personnel working on the electric lines and that entails a transfer switch that isolates the utility power from your generated power.

I sure as hell would never want to be responsible for any injury or death to any utility worker ever. They are there to maintain the grid, not get cooked by someone backfeeding the lines by using a a genny to power their abode without a transfer switch and isolation.

you are 100% correct would never backfeed under any circumstances..

 

[BigJohnfromCT]

In my view, the one most important aspect of powering your abode with ANY standby generator is not backfeeding the utility and causing potential harm or electrocution to utility personnel working on the electric lines and that entails a transfer switch that isolates the utility power from your generated power.

I sure as hell would never want to be responsible for any injury or death to any utility worker ever. They are there to maintain the grid, not get cooked by someone backfeeding the lines by using a a genny to power their abode without a transfer switch and isolation.

Sorry, did I miss something in this thread. Who was talking about back feeding? Not me. I was just trying to understand why inverter genny vs regular genny.

 

[SidecarFlip]

Sorry, did I miss something in this thread. Who was talking about back feeding? Not me. I was just trying to understand why inverter genny vs regular genny.

You didn't miss anything. I injected that as a 'waring' if you will about making sure your utility power is isolated from your backup power as a safety precaution. I've seen people not do that plenty of times in the past.

 

[peakbagger]

Folks rarely try to electrocute linesmen they just dont understand the risk and when its cold and dark in the house its tempting to hook up a generator in the garage and backfeed the house through a cheater cord. It works great as long as the line is broken going to the street but during restoration that is when a lineman in rush can get bit. Most utilities just gave up and require a safety procedure in place assuming someone is backfeeding a dead circuit. its takes longer meaning slower restoration but beat a funeral.

 

[BigJohnfromCT]

You didn't miss anything. I injected that as a 'waring' if you will about making sure your utility power is isolated from your backup power as a safety precaution. I've seen people not do that plenty of times in the past.

Got it sidecar. Totally agree.Unfortunately many people knowingly back feed gen power through, perhaps, the dryer plug without any isolation and console themselves by saying, "Oh, I'll remember to blah, blah, blah....." until someone gets killed.

 

[SidecarFlip]

If the can on the pole out front is dropping the utility line voltage to say 220 from 1400, then backfeeding the can by not isolating the house is sending 220 into the can and the can is increasing the voltage to 1400 or whatever it is. Cans don't know which way the juice is coming from. Just windings in cooling oil. Out here at least, the poles all have disconnects. problem is they are all manual and have to be manually pulled and reset.