Powering an entire house from a backup generator with only 120 Volts - Safely.

snorky18 · Nov 27, 2012

I have an idea in my head of how to power every 120 Volt circuit in a house from a 120 Volt generator, and I’d like to hear your feedback.

For the sake of this discussion, let’s assume you have a 3600 Watt Generator, which produces 30 amps at 120 Volts.

Let’s also assume you have a proper generator inlet box on the outside of your house, connected to your load center with a properly sized wire, and a properly installed manual interlock kit installed in your panel. (No need to start another flame war about suicide cords, killing linemen, etc).

(I think you could consider this circuit to be a continuous load and therefore would need to derate your backfed breaker by 20%, but let’s not get hung up on details like wire size or breaker derating, there’s plenty of that discussion in other threads).

Let’s also assume you live in the boonies, and there is no AHJ or inspector, so you just plan to follow the NEC.

Let’s also assume you have no MWBCs.

So you sized your wire to handle 30 Amps at 120 Volts, say a 10/2 WG.

In the panel, you take the single hot conductor from the generator with 30 amps, and pigtail it into two other #10 wires, and use those two #10 wires to backfeed TWO INDIVIDUAL SINGLE POLE 30 amp breakers, rather than the usual 240 volt backfeed double pole breaker.

When you have a power outage, turn off EVERY circuit in the panel, plug in the generator, start it up, open the main breaker (turn it off), then the interlock kit allows you to close (turn on) your two backfed breakers providing power to the panel from the generator.

Obviously it is imperative that you leave all 240 Volt appliances turned off while you are on generator power.

At this point, every single pole 120 volt breaker in the house has power available to it, regardless of which leg of the panel it is on. You can pull up to 30 amps total either onto a single leg of the panel, or split it between the two legs, and it does not matter how much power is on which leg. Your neutral going back to the generator is already sized for 30 amps, so it’s not overloaded. Your hots are protected by a 30 amp breaker at the generator, and the single pole 30 amp backfeed breakers in the panel.

I’m sure there’s someone out there who thinks this is either a violation of NEC or a generally bad idea, or both. Please tell me why, as I’m throwing this plan out there to be critiqued, and please include NEC references if you can.

snorky18 · Nov 27, 2012

I finally found the thread that inspired my question.

http://www.garagejournal.com/forum/showthread.php?t=156864&showall=1

I couldn't find it for the longest time b/c I was searching for 120 Volt

If you've only got 110 Volts, you either have a problem with your service from the POCO, or you're a farmer at the end of the electical distriubution system in the early 1900s.

pattenp · Nov 27, 2012

Technically it will work. But, will the interlock keep both of the singles from being flipped when on POCO power? You may need to put a handle tie on the breakers.

madosta · Nov 27, 2012

I tossed this idea around too since I would want to have a smaller generator for just the essentials. I even wanted to have two 2000 watt generators and have one fire up if the load was needed.

But I lost the battle in my head with phasing.

Is POCO power usually in sync between the two legs @60hz?

snorky18 · Nov 27, 2012

madosta said:
I tossed this idea around too since I would want to have a smaller generator for just the essentials. I even wanted to have two 2000 watt generators and have one fire up if the load was needed.

But I lost the battle in my head with phasing.

Is POCO power usually in sync between the two legs @60hz?

I brought the battle from my head to GJ for others to help fight :thumbup:

the two 120 volt hot legs from the POCO are out of phase, which is how you get 240 Volts. Each leg has 120 volts of potential difference from ground, and 240 volts difference from the other leg.

theoldwizard1 · Nov 27, 2012

snorky18 said:
I have an idea in my head of how to power every 120 Volt circuit in a house from a 120 Volt generator, and I’d like to hear your feedback.

For the sake of this discussion, let’s assume you have a 3600 Watt Generator, which produces 30 amps at 120 Volts.

Let’s also assume you have a proper generator inlet box on the outside of your house, connected to your load center with a properly sized wire, and a properly installed manual interlock kit installed in your panel.

So you sized your wire to handle 30 Amps at 120 Volts, say a 10/2 WG.

In the panel, you take the single hot conductor from the generator with 30 amps, and pigtail it into two other #10 wires, and use those two #10 wires to backfeed TWO INDIVIDUAL SINGLE POLE 30 amp breakers, rather than the usual 240 volt backfeed double pole breaker.

Just split the wire coming in from the generator inside the panel box into 2 #14s and connect them into a 15A 2 pole 240V breaker IN THE INTERLOCK POSITION. (Below you call them the backfeed breakers. I believe the technical term is "auxiliary input breaker". I don't like to ever use the term "backfeed". If you google that you come up with "suicide cords" which really should be call "power company utility worker manslaughter cords")

If you do it this way, you can only kill yourself or damage your own building !

When you have a power outage, turn off EVERY circuit in the panel, plug in the generator, start it up, open the main breaker (turn it off), then the interlock kit allows you to close (turn on) your two backfed breakers providing power to the panel from the generator.

Obviously it is imperative that you leave all 240 Volt appliances turned off while you are on generator power.

And that is why it is considered "illegal". The "operator" of the panel box needs to understand it is no longer a split phase 240V box, even though that is how it is labeled and if you have any 240v loads, that is how it is wired.

I am not a licensed electrician.
If you try anything I suggest, you are crazier than I am and I accept no responsibility for any outcome ! :eyecrazy:

darkk · Nov 27, 2012

My son in law just did this. He used the generator from his race trailer. He just shut off all the 220 volt appliances and was a little frugal in his electric used during the last storm. His big generator used too much gas so he just connected the little generator to the transfer safety switch on the panel where the big one was. You need to have a proper transfer safety so no one gets killed, It worked for the whole house.

madosta · Nov 27, 2012

I mean not to stir the pot, but if you backfed the grid wouldn't you most likely trip the breaker or over-current protection on the generator or even stall it? I can understand if your service entrance is broken in your yard and a lineman picks it up, but if you're boosting a transformer in reverse, it seems like it would kill any 50amp breaker.

madosta · Nov 27, 2012

snorky18 said:
I brought the battle from my head to GJ for others to help fight

the two 120 volt hot legs from the POCO are out of phase, which is how you get 240 Volts. Each leg has 120 volts of potential difference from ground, and 240 volts difference from the other leg.

I was thinking more of the lines of the phases being in unison with their waveform. Like top of the wave on A is top of the wave on B (high) - not sure... lol

theoldwizard1 · Nov 27, 2012

madosta said:
I tossed this idea around too since I would want to have a smaller generator for just the essentials.

As long as all 240V loads are turned off and you don't exceed the output breaker of the generator, you should be fine.

I even wanted to have two 2000 watt generators and have one fire up if the load was needed.

But I lost the battle in my head with phasing.

Is POCO power usually in sync between the two legs @60hz?

Yes, phasing is the issue. The 2 legs of the line coming in from the POCO are perfectly phased to produce 240v.

I do not know of any generators that can stay perfectly in phase and produce split phase 240V.

There are inverters ($$,$$$) that can be phased to produce split phase 240V. The can even wired to produce 3 phase !

I am not a licensed electrician.
If you try anything I suggest, you are crazier than I am and I accept no responsibility for any outcome ! :eyecrazy:

snorky18 · Nov 27, 2012

theoldwizard1 said:
And that is why it is considered "illegal". The "operator" of the panel box needs to understand it is no longer a split phase 240V box, even though that is how it is labeled and if you have any 240v loads, that is how it is wired.

I'd like to know WHY specifically it is illegal (as in, code reference) or WHY it would not technically work.

If some ***** (that could only be me) flipped on a 240 Volt appliance while on generator power, the appliance would not run properly, and might be damaged, and might even trip the breaker on the genset, but I don't understand what the safety hazard would be.

Admittedly, I don't know exactaly what would happen if you fed two in-phase 120 volt hots to an appliance designed for 240. I'm curious, but not going to find out the hard way.

snorky18 · Nov 27, 2012

madosta said:
I mean not to stir the pot, but if you backfed the grid wouldn't you most likely trip the breaker or over-current protection on the generator or even stall it? I can understand if your service entrance is broken in your yard and a lineman picks it up, but if you're boosting a transformer in reverse, it seems like it would kill any 50amp breaker.

This would not backfeed the grid. Your main breaker is open (off) - there is no connection to the grid. Google the interlock that I mentioned above.

theoldwizard1 · Nov 27, 2012

madosta said:
I mean not to stir the pot, but if you backfed the grid wouldn't you most likely trip the breaker or over-current protection on the generator or even stall it?

Maybe, maybe not fast enough.

<sarcasm=on>
How about you try it for use. Climb a 30' pole and grab the input lines to a transformer. Remember these are now output lines from you generator and they are a lot higher that 240V !
<sarcasm=off>

Yeah, amps will kill you, but volts can interrupt your heart beat !

snorky18 · Nov 27, 2012

madosta said:
I was thinking more of the lines of the phases being in unison with their waveform. Like top of the wave on A is top of the wave on B (high) - not sure... lol

If I remember correctly, and it's been a while since my (limited) electrical schoolin, as you move along a horizontal axis, the TOP of wave A is perfectly in sync with the BOTTOM of wave B. I think of it as the top of wave a being 120 Volts above zero, the bottom of wave b being 120 volts below zero, and the horizontal line in the center is zero. Hence each wave is 120 volts away from ground and 240 volts away from the other wave.

I may be wrong there, and feel free to correct me if I am, though that will cause a thunderstorm in my head and make me rethink my understanding of 240.

madosta · Nov 27, 2012

snorky18 said:
This would not backfeed the grid. Your main breaker is open (off) - there is no connection to the grid. Google the interlock that I mentioned above.

I know what an interlock is. I was talking theory. Probably better for a different thread. Didn't mean to :hijack:

theoldwizard1 · Nov 27, 2012

snorky18 said:
I'd like to know WHY specifically it is illegal (as in, code reference) ...

I am not an electrician.
I am not a lawyer.
I am not an National Electrical Code "lawyer".

Common sense man ! The panel is design and LABELED for 240v split phase use. An unknowing user of this equipment can change it into a totally different device in a few steps.

Why not change the way a transmission works so the the D position makes the car go backward and the R position.

Most of the NEC is there to prevent operators (homeowners) from being able to hurt themselves of other.

pattenp · Nov 27, 2012

theoldwizard1 said:
As long as all 240V loads are turned off and you don't exceed the output breaker of the generator, you should be fine.

Yes, phasing is the issue. The 2 legs of the line coming in from the POCO are perfectly phased to produce 240v.

I do not know of any generators that can stay perfectly in phase and produce split phase 240V.

There are inverters ($$,$$$) that can be phased to produce split phase 240V. The can even wired to produce 3 phase !

I am not a licensed electrician.
If you try anything I suggest, you are crazier than I am and I accept no responsibility for any outcome !

You've confused me by this statement. So how does a generator produce 120V/240V if it's not split phase? Split phase is how you get 120V out of 240V single phase.

snorky18 · Nov 27, 2012

theoldwizard1 said:
Why not change the way a transmission works so the the D position makes the car go backward and the R position.

That's an awesome idea! Let's do that to a really nice ride, then park it in the middle of a big empty parking lot in a bad neighborhood with the keys in the ignition and the windows down, and let the police use it as a bait car. The video from that would be hysterical.

theoldwizard1 said:
I am not an electrician.
I am not a lawyer.
I am not an National Electrical Code "lawyer".

Common sense man ! The panel is design and LABELED for 240v split phase use. An unknowing user of this equipment can change it into a totally different device in a few steps.

Why not change the way a transmission works so the the D position makes the car go backward and the R position.

Most of the NEC is there to prevent operators (homeowners) from being able to hurt themselves of other.

I'm not trying to pick on you wizard, I'm just genuinely curious :thumbup:

If it makes you feel better, if I were to do such a thing, I would be the homeowner, I would be the only one using/operating the panel, and you better believe if I ever sold the house I would swap the "auxiliary input breaker" for the generator feed back to a 2 pole 240 volt.

(Whoops, guess that means my assumption should have included in a 10-3 wire instead of a 10-2).

offroadsteve · Nov 27, 2012

Every single time someone who appears competent suggests something even slightly non-standard having to do with a generator, the whole world comes down on their head...

Back to the original question, what I would do in this situation is wire up a standard 30 amp generator input to a standard, 30A 2-pole breaker with an interlock kit, therefore all of the permenatly installed wiring is to code and there is no funny business hiding in the walls or electrical panel.

To make your idea work, I would then fab up a custom cord to connect your generator to the standard L14-30P generator input. Inside the receptacle on the house end of the cord, jumper the "X" and "Y" contacts together and connect those to the "hot" pin on the generator end of the cord. Therefore you have 120V on both legs headed into the house.

You meet your goal without having anything non-standard in the house, and you maintain control of the custom cord, preventing future "persons unknown" from running into trouble.

As you said, you need to make sure all the 240V circuits are turned off, though its probably not a huge deal since those appliances would see 0V between the two legs instead of the 240V you typically get, but each leg is still 120V from ground / neutral. Probably some funny operation, but I wouldn't expect the magic smoke to leak out.

I did something similar for our race car trailer in college, which had a 240V, 50A marine twist-lock power inlet on the side. I got a standard 5-15 extension cord and wired the hot leg up to both "X" and "Y" hot legs going into the trailer. similar adapters exist for folks with RV's with 240V/50A inlets when they need to use a 120V/30A pedestal. Note that typically in a RV, all loads are 120V, just divided between the two legs. This was also the case in our race trailer.

In my opinion, everything is safe because your weak link is the generator. Applying too much load will open the circuit breaker on the generator, but everything downstream has a higher current rating, so no problems.

And, as a bonus you are all set up to upgrade to a generator with 240V / 30A output in the future if you are so inclined.

theoldwizard1 · Nov 27, 2012

pattenp said:
theoldwizard1 said:

I do not know of any generators that can stay perfectly in phase and produce split phase 240V.

Click to expand...

You've confused me by this statement. So how does a generator produce 120V/240V if it's not split phase? Split phase is how you get 120V out of 240V single phase.

Sorry about that. (One of my own made up sayings is "English is an imprecise means of communication !")

The thought I was trying to convey (and hopefully accomplish this time) is that I do not know of 2 individual 120v only generators that can be combined to create (accurate, stable) split phase 240v.

I assume (and we all know what "assume" means) that 240V split phase is generated in a single generator by using the center tap of a single stator winding as neutral.

theoldwizard1 · Nov 27, 2012

snorky18 said:
(Whoops, guess that means my assumption should have included in a 10-3 wire instead of a 10-2).

Just to confuse you more ...

Non-Metallic cable (what we commonly call Romex, is typically solid wire up to about 10 gauge) does not count the ground conductor. So NM 10-3 actually has 4 conductors.

However, "portable cordage" (an extension cord without a plug or a receptacle, is typically stranded wire regardless of the gauge) does count all conductors. 10-3 cordage has 3 conductors (acceptable for 110V or "true" 240V, no neutral).

snorky18 · Nov 27, 2012

theoldwizard1 said:
The thought i was trying to convey (and hopefully accomplish this time) is that I do not know of 2 individual 120v only generators that can be combined to create (accurate, stable) split phase 240v.

I recently went searching for just such a thing, and the closest thing I found was a youtube video of some guy who had two Honda EU2000 generators hooked up to some sort of box that was attached to a display of some kind (oscilloscope?) and he says something like “See, there you have it, perfect 240 volt from two seperate 120 V sources”.

But I couldn’t find the product he was referring to, just the youtube video.

Personally, I'm attracted to the redundancy, portability, and versatility of 2 smaller generators rather than one big boy.

theoldwizard1 · Nov 27, 2012

snorky18 said:
If it makes you feel better, if I were to do such a thing, I would be the homeowner, I would be the only one using/operating the panel, and you better believe if I ever sold the house I would swap the "auxiliary input breaker" for the generator feed back to a 2 pole 240 volt.

Assuming you were still around when the house was sold. (Not wishing any ill will upon you.)

Actually you don't need to swap the auxiliary input breaker, just the way the wires coming from the generator are connected to it.

Electrician know that you are allowed to use a 3 prong GFCI receptacle on a circuit that does not have a ground wire. To be "legal" you must apply a sticker to the receptacle that says that the ground is not connected, thereby "announcing" to the world that this common looking device does not operate like all of the other similar devices.

If you relabel you panel with all of the exceptions needed to safely operate it and someone else gets hurt using it, maybe you won't be sued (Nah, this is America. You will be sued !)

(Seeing as this thread is going all over the place ...

A GFCI receptacle on a 2 wire, non grounded circuit is theoretically safer than a 3 wire, grounded receptacle. A GFCI trips if any of the current supplied to the load "leaks". To say it another way, a GFCI will trip if the current going to the load and the current coming from the load are not equal.

snorky18 · Nov 27, 2012

theoldwizard1 said:
Just to confuse you more ...

Non-Metallic cable (what we commonly call Romex, is typically solid wire up to about 10 gauge) does not count the ground conductor. So NM 10-3 actually has 4 conductors.

However, "portable cordage" (an extension cord without a plug or a receptacle, is typically stranded wire regardless of the gauge) does count all conductors. 10-3 cordage has 3 conductors (acceptable for 110V or "true" 240V, no neutral).

Believe me, I know, and the nomenclature difference drive me absolutely crazy, and I believe it is the source of a lot of miscommuncation.

People may or may not call the ground a conductor. Some people only call the normally hot wires conductors. Neutral wires, anything goes.

Some people think 10-3 means #10 wire with 2 insulated conductors + a ground (3 wires total)
Some people think 10-3 means #10 wire with 3 insulated conductors + a ground (4 wires total).

On a side note, you can get romex all the way up to #2, but most people aren't aware of that b/c it's so expensive that few people use larger than #6 or so.

SEU and SER cables are equally bad. Southwire goes so far as to put the “old names” of SER on their current spec sheet, in addition to the current nomenclature.

theoldwizard1 · Nov 27, 2012

snorky18 said:
I recently went searching for just such a thing, and the closest thing I found was a youtube video of some guy who had two Honda EU2000 generators hooked up to some sort of box that was attached to a display of some kind (oscilloscope?) and he says something like “See, there you have it, perfect 240 volt from two seperate 120 V sources”.

But I couldn’t find the product he was referring to, just the youtube video.

Yeah, while I am calling ******** !

The only way this could possible work is with an inverter generator (Honda EUx000i) and extra wiring and internal modification that would send the "clock" signal from the "master" generator to the "slave" generator which has its "clock" signal disabled. (Wow, that sounds pretty simple ... in theory !)

Such a design does not help Honda's customer base for this product (RV owners), who need more current (amps) not more voltage, to start their A/C units.

Another way of achieving 240v out of 120v generator is a transformer ! A transformer that has a 2:1 winding ratio can be used as a step down or a step up as long as the KVA rating is not exceed (ignoring losses in the windings). Of course the 240v side needs a center tap for neutral if you want to connect it to a split phase load center.

theoldwizard1 · Nov 27, 2012

snorky18 said:
I recently went searching for just such a thing, and the closest thing I found was a youtube video of some guy who had two Honda EU2000 generators hooked up to some sort of box that was attached to a display of some kind (oscilloscope?) and he says something like “See, there you have it, perfect 240 volt from two seperate 120 V sources”.

But I couldn’t find the product he was referring to, just the youtube video.

Personally, I'm attracted to the redundancy, portability, and versatility of 2 smaller generators rather than one big boy.

Found the video. Lots of "extra" wires coming out of those generators !

snorky18 · Nov 27, 2012

theoldwizard1 said:
(Wow, that sounds pretty simple ... in theory !)
Such a design does not help Honda's customer base for this product (RV owners), who need more current (amps) not more voltage, to start their A/C units.

I think if it were mass produced, it could be done safely, reliably, relatively simply, and inexpensively.

To do it in your garage and post it on youtube is probably none of the 4. And like you said, if they sell to mostly RV owners, and all their loads are 120, then who needs 240?

Highbeam · Nov 27, 2012

offroadsteve said:
Every single time someone who appears competent suggests something even slightly non-standard having to do with a generator, the whole world comes down on their head...

Back to the original question, what I would do in this situation is wire up a standard 30 amp generator input to a standard, 30A 2-pole breaker with an interlock kit, therefore all of the permenatly installed wiring is to code and there is no funny business hiding in the walls or electrical panel.

To make your idea work, I would then fab up a custom cord to connect your generator to the standard L14-30P generator input. Inside the receptacle on the house end of the cord, jumper the "X" and "Y" contacts together and connect those to the "hot" pin on the generator end of the cord. Therefore you have 120V on both legs headed into the house.

You meet your goal without having anything non-standard in the house, and you maintain control of the custom cord, preventing future "persons unknown" from running into trouble.

As you said, you need to make sure all the 240V circuits are turned off, though its probably not a huge deal since those appliances would see 0V between the two legs instead of the 240V you typically get, but each leg is still 120V from ground / neutral. Probably some funny operation, but I wouldn't expect the magic smoke to leak out.

I did something similar for our race car trailer in college, which had a 240V, 50A marine twist-lock power inlet on the side. I got a standard 5-15 extension cord and wired the hot leg up to both "X" and "Y" hot legs going into the trailer. similar adapters exist for folks with RV's with 240V/50A inlets when they need to use a 120V/30A pedestal. Note that typically in a RV, all loads are 120V, just divided between the two legs. This was also the case in our race trailer.

In my opinion, everything is safe because your weak link is the generator. Applying too much load will open the circuit breaker on the generator, but everything downstream has a higher current rating, so no problems.

And, as a bonus you are all set up to upgrade to a generator with 240V / 30A output in the future if you are so inclined.

This is the correct answer. Do not fiddle with or botch the home's wiring to accomplish this goal, that is unwise for several reasons. Instead, modify the cord between the genset and the inlet to spread the 120 volt power to both legs of the panel.

Your 220 volt stuff won't know anything happened.

Funny how you were confused with 110 vs. 120. You're right of course but it is a common mistake that I made.

theoldwizard1 · Nov 27, 2012

Re-reading some other posts ...

offroadsteve said:
Back to the original question, what I would do in this situation is wire up a standard 30 amp generator input to a standard, 30A 2-pole breaker with an interlock kit, therefore all of the permanently installed wiring is to code and there is no funny business hiding in the walls or electrical panel.

I like this !!

To make your idea work, I would then fab up a custom cord to connect your generator to the standard L14-30P generator input. Inside the receptacle on the house end of the cord, jumper the "X" and "Y" contacts together and connect those to the "hot" pin on the generator end of the cord. Therefore you have 120V on both legs headed into the house.

To more specific, the cord would be a 10-3 (for a generator capable of putting out 30A at 120V) with either a 5-30 or L5-30 plug (as appropriate or a 5-20 or 5-15 for smaller generators).

If you have a Honda EU2000i or EU3000i or equivalent, buy a standard 12 gauge extension cord (make it 10 gauge if you are running it longer than 25') and cut the female end off. The receptacle end of this cord would be L14-30R with the jumper as described.

You meet your goal without having anything non-standard in the house, and you maintain control of the custom cord, preventing future "persons unknown" from running into trouble.

And this is why I like it !

Somehow label the cord as "non-standard" although anyone looking at the 2 radically different ends should know that it is "odd".

In my opinion, everything is safe because your weak link is the generator. Applying too much load will open the circuit breaker on the generator, but everything downstream has a higher current rating, so no problems.

And, as a bonus you are all set up to upgrade to a generator with 240V / 30A output in the future if you are so inclined.

Highbeam said:
This is the correct answer. Do not fiddle with or botch the home's wiring to accomplish this goal, that is unwise for several reasons. Instead, modify the cord between the genset and the inlet to spread the 120 volt power to both legs of the panel.

Yes indeed !

Somehow I missed Steve's excellent suggestion !

(My previous answer solve the problem the same way, but Steve's solution is much more elegant !)

snorky18 · Nov 29, 2012

Offroadsteve, I've been thinking about your idea, and I think it's a great one, and it has now become my future game plan.

That being said, does the NEC consider the breaker backfeeding the panel from the generator inlet to be under a continuous load, and therefore subject to be derated by 20%?

RPH · Nov 30, 2012

Some Honda generators are designed to be sychronized together. But it would be cheaper to buy the one bigger generator than a bunch on small Honda's.

theoldwizard1 · Nov 30, 2012

RPH said:
Some Honda generators are designed to be sychronized together. But it would be cheaper to buy the one bigger generator than a bunch on small Honda's.

The way they work, they double the current. They do NOT double the voltage.

offroadsteve · Nov 30, 2012

OldWizard and Highbeam - thank you for your kind words. Its not often, but every once in a while I come up with something decent. :beer:

snorky18 said:
Offroadsteve, I've been thinking about your idea, and I think it's a great one, and it has now become my future game plan.

That being said, does the NEC consider the breaker backfeeding the panel from the generator inlet to be under a continuous load, and therefore subject to be derated by 20%?

Snorky, I'm not an expert on the NEC by any means, so I can't give you a straight answer. However, my opinion, based on a review of the VA Residential Code, is that the generator input would classified as a "feeder" not a branch circuit. I don't see a requirement to derate feeders, probably because the actual load is highly variable (motors turning on and off, lights on and off, etc).

Having said all that, I don't see a need to derate the generator input.

Oh -on another topic that has come up in this thread - the Honda Eu2000i generators can be paralleled together to double the current output (single generator ~13 amps, two generators paralleled gets you ~26 amps, continuous), but its still 120V, not 240V. I personally own an EU2000i.

The advantage is scaleabilty and cost. You can only run one unit when you only need 13 amps, our both units if you need more power. The EU2000 retails for ~$1000, while the EU3000i retails for ~$2000. So, for about the same money, you can get about 1000 more watts out of a pair of EU2000i's paralleled together.

The parallel kit is pretty simple really, there are extra connectors on the front panel of the generators that accept bannana-plug type wires to parallel the two units.

snorky18 · Nov 30, 2012

Funny you should mention the EU2000 steve, as two of those vs one EU3000 is exactly what I was looking at, with the same price comparison as you just mentioned. Plus if I get a regular EU2000 and a companion eu2000, I just have to get the parallel cord ($40) instead of the parallel kit ($200).

In addition to the benefits you mentioned, those use so little fuel it seems like you could run two together all the time in ecoboost mode (which I have some more reading to do) and have a lot more generating capacity on demmand with little or no additional fuel consumption compared to just running one generator.
On a $ paid per watt produced (based on the purchase price), the eu2000 is the champion amongst the smaller hondas.

As a bonus, if she needed to, my wife can put one or two hondas in place easily. The 180+ pound bigger generators, probably not so much.

snorky18 · Nov 30, 2012

I forgot to add, one reason I was thinking it would be un-necessary to derate the generator input breaker is the fact that the generator already has its own breaker built in.

Highbeam · Nov 30, 2012

RPH said:
Some Honda generators are designed to be sychronized together. But it would be cheaper to buy the one bigger generator than a bunch on small Honda's.

Not so. The bigger Hondas are electric start and, well, bigger which has several drawbacks including a much higher cost per watt. I've run the small 1000 and 2000 watt hondas and they are very handy, you can grab one and walk with it like a lunch box. Cheaper to pair the 2000 watt hondas than to buy a 3000 or even the larger 4500? watt honda inverter.

Heck, they may even be wise to rig up a triple parralel kit with the capability to make 240 volt power. It would be like running a multi-stage furnace.

theoldwizard1 · Nov 30, 2012

Highbeam said:
Heck, they may even be wise to rig up a triple parralel kit with the capability to make 240 volt power. It would be like running a multi-stage furnace.

I do not know of any way to get split phase 240V out of multiple Honda EU1000, 2000 or 3000 inverter generators. Period.

Honda does make generators for 250V (overseas operation), but these are NOT split phase like what is standard in US households.

2manytoyz · Nov 30, 2012

Not a licensed electrician.

I pulled the wires from the panel on a fridge at my last house. I was going to wire it into another power source. With the wires hanging free of the panel, I touched the neutral wire, and got a slight zap. How could this be, the wires aren't connected to anything!

As it turns out, the circuit shared a neutral on the other leg of the power panel. This is a legal thing to do. They time share the current through the wire, so the 15A rating is maintained, even though two separate 15A circuits are connected to one wire.

If both of those circuits are tied together with a single 15A source, the wiring would exceed the rating since they'd be in phase.

Am I wrong?

theoldwizard1 · Nov 30, 2012

2manytoyz said:
As it turns out, the circuit shared a neutral on the other leg of the power panel. This is a legal thing to do. They time share the current through the wire, so the 15A rating is maintained, even though two separate 15A circuits are connected to one wire.

If both of those circuits are tied together with a single 15A source, the wiring would exceed the rating since they'd be in phase.

Am I wrong?

Yes, you are incorrect.

They are exactly, a perfect 1/2 phase (180°) apart.

rlitman · Nov 30, 2012

theoldwizard1 said:
Yes, you are incorrect.

They are exactly, a perfect 1/2 phase (180°) apart.

For the purposes of a normal two pole 240V panel with a center tapped neutral, you are correct. BUT based on the title of this thread, this would not be correct.

Powering an entire house from a backup generator with only 120 Volts - Safely.

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member

Well-known member