Running a house panel on 110volt only

[Highbeam]

I have a legal generator interlock panel on my home. It allows me to backfeed the panel from a generator inlet plug that feeds the backfeed breaker. 30 amps of 220 through a 10/3 circuit. It works well with my 3500 watt genset.

I have been genset shopping and my criteria has always been a very low wattage 220 genset so that I can backfeed the home and keep fuel consumption down. The best inverter gensets are only available with 110 volt outputs.

I have been advised to create an adapter to feed the 110 power to both "phases" of the 220, 30 amp, twistlock plug going into the house. This would of course eliminate the possibility of me using 220 volt appliances but that is not a problem.

I am concerned about side effects. Especially the netural conductor. Since the full load is now in phase, it would seem that the neutral is now doing double duty.

What are your opinions?

 

[luvit]

i would not hesitate as long as the wire, breaker were within amperage specs.
another security feature is if your generator has a built-in breaker as a sanity check on your wiring job and calculations.
.

 

[aandpdan]

The problem you might run into is if you have any multi-wire branch circuits. They are commonly found in the kitchen. Two circuits, on opposite legs, share a neutral. Correctly wired, if you are drawing 20 amps on each side the neutral would be showing 0 amps.

In your case, wired up on just one leg, you'd be pulling 40 amps through the neutral. It could overheat and possibly cause a fire.

 

[Highbeam]

The problem you might run into is if you have any multi-wire branch circuits. They are commonly found in the kitchen. Two circuits, on opposite legs, share a neutral. Correctly wired, if you are drawing 20 amps on each side the neutral would be showing 0 amps.

In your case, wired up on just one leg, you'd be pulling 40 amps through the neutral. It could overheat and possibly cause a fire.

That's the same principle I'm referring too on the neutral between the genset and the panel. In 220 operation the neutral is seeing 0 amps. If both 30 amp legs are in phase, then the neutral is seeing 60 amps.

Look at the whole house as a single MWBC.

 

[aandpdan]

It's not that bad, to say it's the whole house.

220 volt appliances just won't work. You'd have the same leg on both sides so 0 volts.

Most circuits will be fine. It's only a problem if you have any mwbc's. Do you? If not, don't worry about it.

 

[luvit]

no one would expect a 3500W generator to support any 240V devices.
be mindful, though.. 120V items (fridge, lamps, fans, coffeemaker) would be expected to be just fine.. but don't run the coffee maker and your wife's 1500W hairdryer together.

 

[nehog]

...

I have been advised to create an adapter to feed the 110 power to both "phases" of the 220, 30 amp, twistlock plug going into the house. This would of course eliminate the possibility of me using 220 volt appliances but that is not a problem.

I am concerned about side effects. Especially the netural conductor. Since the full load is now in phase, it would seem that the neutral is now doing double duty.

What are your opinions?

1. If the total generator output is less than 15 amps, then it presents only minimal problems. Your observation on the neutral is accurate, while with normal 240 it would only carry the difference in current in both legs, with the two legs connected together it carries the sum of the currents.

2. A better solution would be to use a transformer to allow true 240 volts.

 

[BigGMC]

You want less than 3500 watt? Wow, that's unusual, everyone else wants more power. I'm guessing your home is very energy efficient, but remember anything with a sizeable motor (fridge, freezer, furnace blower) has a large inrush demand.
I've seen a 3500 generator struggle to start up a fridge and chest freezer (granted, they were old units).

 

[Highbeam]

no one would expect a 3500W generator to support any 240V devices.
be mindful, though.. 120V items (fridge, lamps, fans, coffeemaker) would be expected to be just fine.. but don't run the coffee maker and your wife's 1500W hairdryer together.

I do run one 220 volt appliance with the 3500 watt genset! I have cooked many pots of ramen noodles on the electric stovetop with genset 220 power. A single burner is not that many watts.

When backfeeding with 220 the neutral only carries the difference in amperage between the two legs. When running in 110 mode, the neutral must carry the sum. As such, I am limited to 30 amps of 110 going out of the genset. Can be all on one leg or split, shouldn't matter.

That's fine though since the point is to use a small inverter genset which is generally only available in wattages under 3000.

 

[luvit]

yeah, one burner, true dat.
i leave the breaker off for the range / oven.. but if i didn't have kids who forget about a power squeeze..

 

[rlitman]

In 220 operation the neutral is seeing 0 amps. If both 30 amp legs are in phase, then the neutral is seeing 60 amps.

But back to reality for a second: the generator isn't capable of putting out 60A, now is it?
So, a 2000W generator isn't going to overload a neutral, will it?

Even if he gets a Honda EU3000, the most any wire could see would be 30A, not 60A.

Of course, this will never meet code . . .
Maybe it would be wise to just turn off all 2-pole breakers before trying something like this. You do have circuits with a shared neutral on a shared breaker, right?

. . . I've seen a 3500 generator struggle to start up a fridge and chest freezer (granted, they were old units).

Probably very old. I've run each refrigerator and stand up freezer (pretty big one) in my house off of my 1000W inverter generator. Never had an issue, but I never tried to run anything more than one of those at a time.
Just plugged each one into an extension cord, and rotated which cord was plugged into the generator every few hours.

A 1000W generator is really cheap to run. It weighs 27lbs, so it is totally portable, and uses only about 1 gallon of gas a day. It isn't enough to run more than one fridge at a time (each one is about 700-800W), but I don't need them running continuously to keep the frozen food frozen. Just a couple of hours a day is sufficient if you're relatively diligent about not opening the door too much.
I can certainly understand the benefits of doing this, but when my power was off for a week after hurricane Irene, you can bet I fired up the big generator to keep the TV's working, and the wife's sanity intact.

 

[Highbeam]

But back to reality for a second: the generator isn't capable of putting out 60A, now is it?
So, a 2000W generator isn't going to overload a neutral, will it?

Even if he gets a Honda EU3000, the most any wire could see would be 30A, not 60A.

Of course, this will never meet code . . .
Maybe it would be wise to just turn off all 2-pole breakers before trying something like this. You do have circuits with a shared neutral on a shared breaker, right?

You're right. The 30 amp capacity of that neutral is sufficient for a genset large enough to run normal household stuff.

I have no MWBCs in my home. Good ol' regular stuff but two fridges and a microwave that I'd like to keep working.

You say it is not code. Well is it specifically against code? Is there a reason for that? such as a safety risk?

 

[nehog]

. . .
Maybe it would be wise to just turn off all 2-pole breakers before trying something like this. You do have circuits with a shared neutral on a shared breaker, right?

A shared neutral doesn't mean that there is a shared breaker.

 

[eljefino]

If your stove is what's stopping you just get a hot plate, $16 at walmart. Millions of college students cook ramen noodles with this or with hot water from "Mr coffee".

I might be a wierdo, but I think they should make a microwave with a high/lo magnetron (not a pulse width on/off one) for RVs and power outages. It would also give more control when nuking fragile small servings of food-- like precision nacho cheese melting.

I had a McCulloch Mite-e-lite generator from 1977 with 3300 watts and a 220V output, "squinty eyes" shaped 15 amp outlet. Never used that feature, didn't need the 15 amps. Everything that runs on 220 needs 30-40. Maybe that's why they stopped making them.

 

[malibu101]

I might be a wierdo, but I think they should make a microwave with a high/lo magnetron (not a pulse width on/off one) for RVs and power outages. It would also give more control when nuking fragile small servings of food-- like precision nacho cheese melting..

Not weird at all.
I thought I was the only one who wished for "variable heat" from a microwave instead of just turning the magnetron on and off.

 

[theoldwizard1]

2. A better solution would be to use a transformer to allow true 240 volts.

A transformer is 80-90% (?) efficient at best. A Honda EU2000i puts out 1600 watts continuous (2000 peak). After the transformer you only have 6 amps @ 240 volts.

OP is being very smart, NOT oversizing his generator

Personally I thing the EU2000i is too small. The EU3000iS is more appropriate size, but the price is CRAZY.

Inverter generators in the 2500-3000 watt range include

• Yamaha EF2800i (2500 watts, 2800 max)
• Boliy Pro3600SI (3000 watts, 3600 max)

 

[kert]

If I needed a generator as backup power at my house enough to be concerned about fuel consumption, I think I'd be looking for something big enough to run some lights, furnace fan, and well pump all at once. I'd hate to get up in he morning after the power has been off all night in the dead of winter and have to turn off the furnace just so I could take a shower and flush the toilet.

BTW, my power was off for 24-hours last winter. Spent the day at work asking around to find somebody with a generator I could borrow so I could get a little heat and take a shower. Worst part was the power went out while the thermostat was in daytime "save energy while I'm gone" mode, so it was already chilly when I got home.

 

[rlitman]

A shared neutral doesn't mean that there is a shared breaker.

It doesn't mean there is, but there -should- be. That's all I was saying.

A transformer is 80-90% (?) efficient at best. . . OP is being very smart, NOT oversizing his generator

Huh? My first thought was that typical transformers are 98% efficient from a power perspective, but in rethinking the issue, when you're on your own generator, the power factor is more important, so 80-90% efficient may actually be reasonable (depending on the sizing, and the load).

Yes, there's no reason to oversize the generator and waste fuel.

 

[nehog]

A transformer is 80-90% (?) efficient at best. ...

Transformers (good ones, not imported junk) are typically 95-97% efficient, and the best are about 99.5% efficient.

Any transformer that is 80 to 90% efficient is trash.

 

[Highbeam]

There's no reason at all that I need 220 volt power for 220 devices. The only reason I thought I needed 220 volts was to backfeed both sides of the panel with power that is most like utility power. I did not know, and am trying to find out, if there is any reason that I couldn't use straight 110 power and stop using a 220 genset output.

Couple reasons really. Most gensets that make 220 with an AVR only regulate voltage on one leg of the 220 so if your loads are not balanced, you can get some pretty large voltage swings. Also, with 220, each 110 volt leg is limited to half of the gensets output. My genset can provide 100% of its output through the single 110 connection so I actually have a much better supply of 110 power than I do with a split 220. Finally, my next genset will also be small and the best options do not provide 110 output. My critical power demands are 2 fridges and a microwave, all 110.

Is there any reason that I can't just feed both sides of my house panel with a single 110 current source? I understand that 220 stuff won't work.

Thanks for the replies so far, I'm just not yet confident that something won't catch on fire.

 

[Norcal]

There's no reason at all that I need 220 volt power for 220 devices. The only reason I thought I needed 220 volts was to backfeed both sides of the panel with power that is most like utility power. I did not know, and am trying to find out, if there is any reason that I couldn't use straight 110 power and stop using a 220 genset output.

Couple reasons really. Most gensets that make 220 with an AVR only regulate voltage on one leg of the 220 so if your loads are not balanced, you can get some pretty large voltage swings. Also, with 220, each 110 volt leg is limited to half of the gensets output. My genset can provide 100% of its output through the single 110 connection so I actually have a much better supply of 110 power than I do with a split 220. Finally, my next genset will also be small and the best options do not provide 110 output. My critical power demands are 2 fridges and a microwave, all 110.

Is there any reason that I can't just feed both sides of my house panel with a single 110 current source? I understand that 220 stuff won't work.

Thanks for the replies so far, I'm just not yet confident that something won't catch on fire.

Read the data plate on your genny, they do not produce 110 or 220V.....

 

[theoldwizard1]

Most gensets that make 220 with an AVR only regulate voltage on one leg of the 220 so if your loads are not balanced, you can get some pretty large voltage swings.

Any generator more than 5 - 10 years old and even some new one do NOT have any kind automatic voltage regulation.

Is there any reason that I can't just feed both sides of my house panel with a single 110 current source? I understand that 220 stuff won't work.

Now this scare me. I'm not sure why, but the system was not designed to work this way.

Thanks for the replies so far, I'm just not yet confident that something won't catch on fire.

Running on only one leg of 240V is not an uncommon failure. I have seen a couple of house like this when one of the underground feeds was cut. No problems, just half of the lights worked and no hot water.

 

[rlitman]

Transformers (good ones, not imported junk) are typically 95-97% efficient, and the best are about 99.5% efficient.

Any transformer that is 80 to 90% efficient is trash.

If you look at my post, I agree that 98% is a reasonable guess for the efficiency of any random transformer, but that's real power efficiency. In terms of power efficiency, only the heat lost from the transformer is counted, because that's the only component that adds to your power bill.

When running on your own generator, you need to take into consideration the reactive power too, as too much reactive power can overload your generator just as easily as too much real power, and in the right circumstances, you can have 0W of load, but still overload your generator with too much kVA.

Transformers are pretty inductive, and have a lot of reactive power (even with no load). So taking that into consideration, it is entirely possible that a transformer would be even less than 50% efficient, if you consider the reactive load that wouldn't ordinarily add to your electric bill (so in other circumstances, you wouldn't take it into account).

 

[Highbeam]

Read the data plate on your genny, they do not produce 110 or 220V.....

Sorry, but you are wrong. With a selectable tap on the windings, this and other gensets can absolutely provide 100% of their rated current through either 110 or 220 volt current. Pretty slick really.

http://www.championpowerequipment.com/generators/46514/

 

[Highbeam]

Any generator more than 5 - 10 years old and even some new one do NOT have any kind automatic voltage regulation.

My genset and most all chinese clones has an AVR. It is adjustable and I have personally had mine out, and adjusted it for proper output voltage. Older gensets used capacitors. I don't understand how a generator would work without a regulator, even the automotive alternators have regulators.


Running on only one leg of 240V is not an uncommon failure. I have seen a couple of house like this when one of the underground feeds was cut. No problems, just half of the lights worked and no hot water.


I lost one of the feeds like this too and it didn't burn anything down. That is different than pushing one feed onto both legs of the panel. Scares me too but it would be so dang handy.

Responses in blue.

 

[Norcal]

Sorry, but you are wrong. With a selectable tap on the windings, this and other gensets can absolutely provide 100% of their rated current through either 110 or 220 volt current. Pretty slick really.

http://www.championpowerequipment.com/generators/46514/

You did not read the label, modern units produce 120, 120/240, & 240 volt, power depending on the model unless it's a back alley Chinese trash, then any weird possibility...

 

[luvit]

yeah, highbeam.
i couldn't operate off of a 1000W generator
just my seated amps for my necessities exceed 1200W in the wintertime.
i'd be lucky to fit within a 1500W generator.

Wintertime
........................Amps.......Watts
Boiler Pump 1........0.71........81.65
Boiler Pump 2........0.71........81.65
Boiler Solenoid.......0.43........51.60
Furnace Fan..........2.64......316.80
Refrigerator.......... 6.50..... 825.50
........Totals:......17.29A..1357.20W

 

[rlitman]

You could operate off a 1000W generator in a pinch. I've done it for three days.
You would just need to switch between the refrigerator, and the furnace. Neither requires continuous operation, except the furnace, and only on "design days". But that's got to be pretty cold to worry about that, and even so, you could run it enough to keep the house from freezing.

Now a 2000W generator should keep you comfortable. You could run all that, and a flat screen TV.

 

[Highbeam]

You did not read the label, modern units produce 120, 120/240, & 240 volt, power depending on the model unless it's a back alley Chinese trash, then any weird possibility...

Yes, I did read the label and as I said it is either 110 or 220. So for you that would be 120/240. Not sure what that has to do with the price of beans. Where are you going with this?

 

[luvit]

You could operate off a 1000W generator in a pinch. I've done it for three days.
You would just need to switch between the refrigerator, and the furnace. Neither requires continuous operation, except the furnace, and only on "design days". But that's got to be pretty cold to worry about that, and even so, you could run it enough to keep the house from freezing.

Now a 2000W generator should keep you comfortable. You could run all that, and a flat screen TV.

Yeah, i just lived through an 8 day outage and in the winter i would want to leave the fridge and furnace run for my wife's piece of mind.
i wouldn't mind disconnecting the fridge on occasion to run a tiny 550W coffee maker, but the necessities of the fridge and boiler would have to be error-proof.. i have to keep it low maintenance and out of mind or the woman of the house frets too much.. so yeah, 1500-2000 would pull-it-off.
.

 

[dinosaur]

Can you rearrange your breakers so that you only need to make one "side" of the panel hot wiith 110v? Put the circuits that you want to run off the generator together on that side.

 

[BillK]

Highbeam,
I am not able to answer you actual question but can I ask a silly one ? How often do you lose power and how long do you have to run your present generator setup in an average year ??? Is the amount of money and trouble you are going to go through buying a new genset going to really be worth it ?

I guess if you run the generator 600 -700 hours each year it might be, but if you only use it a day or two here and there, I just dont understand the economics.

 

[Highbeam]

We lose power about 3 times per year. Two days is the average time without power. I do not run the genset overnight but only the daytime hours. My investment in 2006 was 249$ for a 3500 watt genset which has served me very well.

I also camp in an RV which is hard for some to understand but it is like a cabin on wheels. We use the genset for camping as well where there are no close neighbors.

If my genset was not there then I would risk losing a freezer full of meat and veggies, the regular fridge full of milk and regular things. Also, I would not have lights, television, internet, and the microwave for food during the outage. In considering the economics you absolutely must assign a value to things like convenience, independence, comfort, etc. Not just cash.

249$. Totally worth it. Would pay 10x that much.

 

[theoldwizard1]

My genset and most all chinese clones has an AVR. It is adjustable and I have personally had mine out, and adjusted it for proper output voltage. Older gensets used capacitors. I don't understand how a generator would work without a regulator, even the automotive alternators have regulators.

Most small generators, that I have seen, rely on the mechanical governor on the throttle to maintain voltage/frequency.

Automotive alternator regulators work be increasing/decreasing the current supplied to the field (which increases/decreases the magnetic field).

 

[Highbeam]

Most small generators, that I have seen, rely on the mechanical governor on the throttle to maintain voltage/frequency.

Automotive alternator regulators work be increasing/decreasing the current supplied to the field (which increases/decreases the magnetic field).

The governor only changes frequency, hertz, of the power which must remain constant. The regulator adjusts voltage based on load by adjusting the field current based on load. I believe that all generators have some sort of voltage regulation or else you would not be able to use them.

I did make sure that each of my refrigerator units were on seperate legs of the panel to balance the load properly. I have no plans to rearrange my panel. Just want to backfeed the panel from a single 110 source.

Looks like I'll have to be the pioneer. Nobody seems to have any reason that it won't work. I can't think of any reason other than being sure not to overload the neutral which will be impossible with my genset. I still plan to flip off the breakers to all 220 volt circuits. Any other advice?

 

[eljefino]

A "regular", non-inverter 3600 RPM generator has no other purpose for its engine than turning the generator head. So if the AVR cuts in due to overvoltage, the magnetic "drain"/ resistance of the head will lessen. The mechanical engine governor will see this, IMO, faster than it would otherwise and will more quickly correct. So the AVR is a helpful part of the feedback loop. Some are also programmed to kill the engine if something goes very flaky (like over 170ish volts), a modest protection device.

It would be interesting to put an AVR generator head to head with a non-AVR one of similar construction and HP, and log-scope its output in voltage and frequency with substantial loads being applied and released.

I've checked my new AVR generators in both volts and cycles with my kill-a-watt meter. They have way less copper than my old mccollough Mite-e-lite from 1977 but the fridge "sounds" better on them. (Less harmonic distportion?). The only plus of the monster mite-e-lite was how it just blasted through the well pump turning on with its inertia.

 

[Steevo]

Note to self: Puget Sound is off the list of possible retirement locations. Unreliable power . . .

 

[Highbeam]

Note to self: Puget Sound is off the list of possible retirement locations. Unreliable power . . .

It's not bad. I actually live up in the Cascade foothills towards Mt. Rainier from the sound. About 700 feet above sea level. Those folks in the deep city right on the water might have a more dependable power grid.

 

[P0234]

Looks like I'll have to be the pioneer. Nobody seems to have any reason that it won't work. I can't think of any reason other than being sure not to overload the neutral which will be impossible with my genset. I still plan to flip off the breakers to all 220 volt circuits. Any other advice?

Any updates? I'm in the same boat, I have a bigger and much louder genset but I'd rather run the EU2000 in most cases.

 

[luvit]

Hey, man.
if you're uneasy with splitting the neutral on a low wattage genset, it's really not that hard to supply power to a single leg in the breaker box.

see the black and blue lines?
lets say you supply power to the blue leg with your 110v generator.

if the 110v appliances you wish to power happen to be on the black leg, you just move your breaker up/down a spot...
you don't have to move the breaker from a right slot to a left slot..

not all breaker boxes are laid-out like this, but majority are easy enough to raise/lower the breaker's slot position.

with that said, a 220v breaker would be two breakers above each other, each breaker on a different leg/bus.

.