No. 3 prong is hot, neutral, ground. Hots joined on 4 prong side of adapter. See (broken link removed). Cause genny only delivers 125v. Note that its described: the NEMA L14-30R is a 30 Amp, 125/250-Volt, 4-prong female connector.
Back Up Generator ?
- Thread starter MiMod
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil. -
Super Cedar firestarters 30% discount Use code Hearth2024 Click here
jatoxico
Minister of Fire
You have it backwards. The 3 prong goes into your inverter which is only capable of putting out 120 v in a single phase. The x and y that are normally separate are tied together in the one hot on the three prong. With the adapter the 2 hots run then through the extension cord as separate wires but they are in phase. So you are feeding your 2 pole panel with a single phase source.
It's semantics. This is all single phase. Two legs for 240, one and a neutral for 120. The two wires in the connection cable designated as 'hots' are joined together in the 4-prong side of the adapter.
jatoxico
Minister of Fire
I'm only trying to alert you to a potential problem/danger so don't take my persistence as being a PITA. It may be semantics but no question you can overload the neutral if you try running a circuit wired as an MWBC. It takes a couple minutes to check for them.
It is extremely rare and weird, though possible, to have any multi wire branch circuits in a residence.
Be careful not to confuse illegal backfeeding of a panel with legal (in the us) backfeeding of a panel equipped with the proper interlock device.
Be careful not to confuse illegal backfeeding of a panel with legal (in the us) backfeeding of a panel equipped with the proper interlock device.
I guess depending on situation and location. Almost every 120 volt 15 amp circuit in my house is a multiwire branch circuit. Our house was built in 2014. It saves a lot of money for the electrical contractor, they have to pull half as many cables, and uses 2/3 the copper.
That sheet metal back-feed device that you have to manually throw, before you start to backfeed? I don't see much of a difference.
It physically prevents the main and the backfeed from being on at the same time. So when the power goes out on a Saturday night after you've had one too many, the panel can't be accidentally energized by the backfeed breaker while the main is on.
It just forces you to remember to turn off the main first.
Our generator is easy enough to start that my wife could probably do it if I wasn't home to do it.
The interference interlock makes it a lot easier to tell her how to configure the electrical connections safely and keeps me from botching the same.
Its cheap insurance to save some lineman's life.
Yes! It is how the way to make backfeeding safe and legal. Mine was permitted and inspected.
You, @Sodbuster , are correct that it is functionally the same except the lockout eliminates the possibility that you forget about shutting off the main first.
A couple of things could happen if you forgot to throw the main because you failed to install an interlock. One, your poor generator tries to energize the whole city. Bam! the generator's breaker pops. Or two, say the powerline between your home and the transformer is broken, then you have just created a hot line laying on the ground that could actually zap someone.
Around here, when you call in a power outage they ask you if you'll have a generator running, I always say yes. I assume as computerized things are theses days that the information goes right to the lineman's computer letting the crew know their is a chance of a hot wire.
jatoxico
Minister of Fire
No evidence to prove it but I wouldn't be surprised to find it's regional. I looked and sure enough I have a couple. Installed incorrectly too. The breakers are supposed to be connected (that's what those holes are for) when wired as an MWBC so they throw together.
maple1
Minister of Fire
I have MWBCs also. Never knew what they were until reading about them in this place. Explained that issue that time when I tried to feed 120 to both sides of my panel.
Wish Interlocs were legal here. Sure would make things simple. I think their logic is, that it isn't 'fool proof', because the hardware is attached to the panel cover (or at least the ones I looked at were that way), so if the panel cover is removed, there goes your safety device. Which I guess they may have a point on, but seems silly to me. Are there that many people who take their panel cover off? There are likely many fold more people who just throw the main (as long as they remember - and also remember to unplug the genny before they unthrow it again) & do it a more 'wrong way'. Which come to think of, I don't think I have ever heard of anyone actually getting in serious trouble for somehow.
EDIT: And another thing - why aren't there more 240v inverter gennies on the market? One of those would be sweet. I stumbled on a nice looking Champion 6000w open frame one last night on the net. Not available in Canada. Huh, OK. So it's a $5000 Honda, or a $3000+ B&S that has mixed reviews and not sure is available here or not either.
Wish Interlocs were legal here. Sure would make things simple. I think their logic is, that it isn't 'fool proof', because the hardware is attached to the panel cover (or at least the ones I looked at were that way), so if the panel cover is removed, there goes your safety device. Which I guess they may have a point on, but seems silly to me. Are there that many people who take their panel cover off? There are likely many fold more people who just throw the main (as long as they remember - and also remember to unplug the genny before they unthrow it again) & do it a more 'wrong way'. Which come to think of, I don't think I have ever heard of anyone actually getting in serious trouble for somehow.
EDIT: And another thing - why aren't there more 240v inverter gennies on the market? One of those would be sweet. I stumbled on a nice looking Champion 6000w open frame one last night on the net. Not available in Canada. Huh, OK. So it's a $5000 Honda, or a $3000+ B&S that has mixed reviews and not sure is available here or not either.
Last edited:
I have known several folks who pull the panel cover and just plug in a 240 dual breaker to backfeed a panel. The rational from one friend (an electrician) was during an extended power outage they were driving around the neighborhood with a generator to allows several homes to have power for a few hours to run their heat and keep the freezers running. The houses did not necessarily have standard dryer plugs or secondary panels with the right breakers so to them it was easier to open a basement window , drag a cord in, pop the panel cover and plug in an appropriate sized breaker. It usually took the people he was helping having the breaker trip out once or twice until they figured that the power from the generator was not unlimited.
That's how I had to power the house during an extended outage when we first moved in. We had a Coleman contractor generator that had 240v out. I knew what i was doing but still wouldn't trust myself and triple checked to make sure there was no backfeeding.
You can blow the boards on any electronic devices unless you unplug them during a power outage. It is why the power company advises you to unplug any sensitive power equipment while the power is out, because when the power is restored it can cause a surge.
Great advice, but the homeowner often has absolutely no clue when an outage or a power surge is going to occur. They may be away from home at work or the outage then surge may occur within seconds. We have a UPS now in front of all most valuable electronics, but not all. Some are harder to protect now that they are in our ovens, washers, dryers, dishwashers and refrigerators.
That is true, if you are not home or unaware of the outage, then you are out of luck. The only thing I can offer, is at least with out Power Company is they advise that you do this. If you aren't home theirs not much you can do. I can say that I've never had a product fail over a power surge.
A friend down the road had his heat pump electronics fried during a power surge. Now he has a surge protection circuit installed. When it will happen is unknown. Some areas and devices will be more prone to failure than others.
If the surge to the heat pump came in from the grid, a good Surge Protection Device (SPD) on the incoming power line from the utility in the main panel will protect the equipment. If the surge came in via a lighting strike or reflected strike then all bets are off. I am careful to note a good SPD as some like the old Delta "can style" are safety devices designed to shunt power to ground to protect the wiring of the house rather than the equipment. Ideally the SPD should be sized to shunt at voltage close to the line voltage. Midnight Solar is a recognized US manufacturer that makes these lower shunt voltage devices http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=23&productCatName=SPD They have various videos on You Tube showing how SPDs work and comparisons between brands.
Note that SPDs do not protect from under voltage from a utility (or a generator). a motor draws power which is measured by wattage (volts times current (expressed in amps)). If the voltage is low, wattage is high and that is what an equipment fuse or circuit breaker is for. Some folks get confused that the fuse or circuit breaker in the panel is sized to protect the equipment, that is incorrect, the fuse or breaker in the panel is sized to keep the wiring, switches and outlets from overheating and possibly melting. Sure it protects from a high current flow like a short in the equipment but a sustained low voltage event can cook a piece of equipment if its not equipped with its own breaker or fuses.
So a SPD may protect for over voltage and an equipment fuse or breaker may protect from undervoltage but it may or may not protect from a third power quality issue which is frequency. Grid frequency is pretty well locked in, the entire east coast of the US is humming along at the same 60HZ frequency. Generators on the other hand need to have a governor that controls the engine speed to generate clean frequency. Generally cheap generators will have a cruder governor and the frequency can move around a bit. For most power tools it really doesn't hurt things but sensitive electronics with poor quality power supplies can be impacted. Some Harbor Freight generators used to be labeled that they were not intended for sensitive electronics. The bigger problem with frequency is a choppy waveform. AC power from the grid or standard generator should have a nice smooth sinusoidal waveform, unfortunately AC powered derived from DC sources like batteries and solar panels have to be converted to AC. Older UPS's and DC to AC inverters sometimes were sold as "modified sine wave". Instead of a nice smooth sine wave, a modified sine wave can be very choppy. This can be hard on rotary equipment as they can heat up due to the dirty waveform. Some of the solar pioneers found out over the years that various home applicances like washers, dryers and refrigerators would die prematurely and many manufactures would void the warranty for other than grid power. Computers usually have switched mode power supplies that can take dirty waveforms so an older computer UPS did not necessarily have a great waveform. Power electronics have gotten a lot better over the years and most inverters put out a good quality sine wave but if you have an older UPS it may be a source of dirty power. Its probably not a short term issue for a backup situation.
Once someone gets into three phase systems that are used in businesses and farms, harmonics start to factor in but it should be non issue for homes. The other rarer issue that pops up at farms and poorly designed commercial systems is ground currents but not typically an issue in home systems.
Note that SPDs do not protect from under voltage from a utility (or a generator). a motor draws power which is measured by wattage (volts times current (expressed in amps)). If the voltage is low, wattage is high and that is what an equipment fuse or circuit breaker is for. Some folks get confused that the fuse or circuit breaker in the panel is sized to protect the equipment, that is incorrect, the fuse or breaker in the panel is sized to keep the wiring, switches and outlets from overheating and possibly melting. Sure it protects from a high current flow like a short in the equipment but a sustained low voltage event can cook a piece of equipment if its not equipped with its own breaker or fuses.
So a SPD may protect for over voltage and an equipment fuse or breaker may protect from undervoltage but it may or may not protect from a third power quality issue which is frequency. Grid frequency is pretty well locked in, the entire east coast of the US is humming along at the same 60HZ frequency. Generators on the other hand need to have a governor that controls the engine speed to generate clean frequency. Generally cheap generators will have a cruder governor and the frequency can move around a bit. For most power tools it really doesn't hurt things but sensitive electronics with poor quality power supplies can be impacted. Some Harbor Freight generators used to be labeled that they were not intended for sensitive electronics. The bigger problem with frequency is a choppy waveform. AC power from the grid or standard generator should have a nice smooth sinusoidal waveform, unfortunately AC powered derived from DC sources like batteries and solar panels have to be converted to AC. Older UPS's and DC to AC inverters sometimes were sold as "modified sine wave". Instead of a nice smooth sine wave, a modified sine wave can be very choppy. This can be hard on rotary equipment as they can heat up due to the dirty waveform. Some of the solar pioneers found out over the years that various home applicances like washers, dryers and refrigerators would die prematurely and many manufactures would void the warranty for other than grid power. Computers usually have switched mode power supplies that can take dirty waveforms so an older computer UPS did not necessarily have a great waveform. Power electronics have gotten a lot better over the years and most inverters put out a good quality sine wave but if you have an older UPS it may be a source of dirty power. Its probably not a short term issue for a backup situation.
Once someone gets into three phase systems that are used in businesses and farms, harmonics start to factor in but it should be non issue for homes. The other rarer issue that pops up at farms and poorly designed commercial systems is ground currents but not typically an issue in home systems.
Similar threads
