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Wiring a Generator to Your House

95 points by savrajsingh 14y ago

dsr_ 14y ago
This bears repeating: If you try to wire your generator to your breaker box as a DIY project, you probably will not be in compliance with local electrical codes. Also know that it's extremely dangerous. For example, if your ground wiring is not done properly, you may inadvertently put 200+ volts on 120 volt lines, immediately frying bulbs and electronics connected to those lines, and potentially starting fires. Don't do it. In addition to all that, don't use a double-male cable to just plug a generator in to your house. Don't. You can kill people that way.
- maxerickson 14y ago
  Are you talking about people not throwing the main breaker and energizing nearby lines, or is there something more subtle?
  - Turing_Machine 14y ago
    People don't expect a male plug to be live, but that's exactly what you can get with a double-male setup. Someone picks it up and ZAAAAP. I agree, don't do it.
  - JagMicker 14y ago
    Does anyone else remember the "Blotto Box"? http://cd.textfiles.com/group42/ANARCHY/COOKBOOK/BLOTBOX.HTM http://cd.textfiles.com/group42/ANARCHY/COOKBOOK/BLOTBOX.HTM
    - evan_ 14y ago
      The guy who wrote that has apparently never heard of fuses...
- dholowiski 14y ago
  Yes, that need a bigger disclaimer. A huge one in fact. As well as the extreme importance of having a 'generator interlock' - something that physically disconnects your house from the power grid, so you aren't electrifying external power lines (lines that people expect to not be electrified when the power is turned off).
  - electromagnetic 14y ago
    It's also important to remember if you're DIYing the project, that if your neighbour didn't use a generator interlock, your wiring may have enough power to make you need a trip to the hospital. Seriously, speaking as someone who has worked as an electrician. Unless you're experienced, don't play with it.
    - dholowiski 14y ago
      Yeah, this is a bad project to DIY.
      - electromagnetic 14y ago
        It's literally only DIYable by someone who has enough experience that they could do it professionally. Installing your own generator interlock is no easy feat. Installing companion wiring for a generator, again, is no easy feat. Easiest permanent DIY job would be to wire a dedicated outlet to your fridges and freezers and any important electrical equipment, and switch them to the generator outlet when you need it. No crossing circuits, no real problems. If you have no electrical experience, deal with the extension cords.
    - ars 14y ago
      > that if your neighbour didn't use a generator interlock, your wiring may have enough power to make you need a trip to the hospital. If that happened you would know because your lights were on. And what would actually happen is nothing, because the generator circuit breaker would blow from trying to power the entire neighborhood. The only way this could happen is if you were right at the end of the feeder line, and managed to down a line such that only you and your neighbor were online - in which case enjoy the free power. (And then yell at your neighbor to fix it.) Do things properly, sure, but don't over estimate the danger.
- noonespecial 14y ago
  Wish people took the dangers of cars this seriously. It seems to me that far more people are hurt by the careless use of cars than bad wiring.
ChuckMcM 14y ago
One of the things we did, before we put solar panels on our house, was a power survey. We actually measured the power draw of our house every day for a year by reading the power meter and keeping a notebook (great for power disputes as well :-). We discovered that we were using 23.2 kWh per day, or just under 1kW. But like the author our peak loads were higher (we don't have air conditioning or a pool so those power suckers aren't an issue). We also found that a 5.5kW generator would cover our needs. So when the wiring was under modification for a kitchen remodel, we had the electrician install a transfer switch on which we put our 10 most 'useful' circuits. Then when the power went out we could fire up the generator outside, plug it into the transfer switch and transfer power from the AC 'mains' to the generator. That works fine but you have to be careful because the power generated by Home Depot generator is pretty crappy power. The computer systems were protected by using a UPS system that used AC primary power for battery charging and ran the load off an inverter. At some point I'll find a datacenter throwing out an old AC line conditioner and I'll get that.
forgotAgain 14y ago
What about the peaks when motors turn on. I'm thinking blowers cycling for hot air heating or the mentioned pump for the well. If you're measuring for wattage you need to capture the peaks which will only last a few seconds. You also need to account for multiple motors turning on simultaneously which you may not catch with a simple measurement. You need to understand what the demands for power are as well.
- ars 14y ago
  Most generators can handle short peaks of around +25%. They are even rated that way 3200/4000 is a typical rating. Size for the normal load, and let the peak rating handle the startup currents.
MattRogish 14y ago
A few years ago I had to wire a generator up to a distribution warehouse so that goods could still be shipped in event of a power loss. The actual wiring process wasn't too difficult (have a properly licensed electrician do it. NO EXCEPTIONS!) but the process of wiring it up to the building natural gas we hit a snag. We had a 25kW generator spec'd but using natural gas required more pressure than the utility could supply. We switched to propane (which is less efficient) and used building gas as a last-ditch failover (if I recall correctly it only had enough pressure to supply half load or something). Note that disel and plain old gasoline generators push out really noisy power. Do not hook up electronics to gas generators without a line conditioner or UPS in the middle (and the UPS will probably complain about voltage sags and/or lack of grounding). If you're going to make it a permanent fixture to your home that you can actually rely upon, you really ought to make it run on natural gas and/or propane (as a failover). Quieter, cheaper, and less likely to be a shortage (most homes without power in NY/NJ still have natural gas and a modestly sized propane tank could run our generator for a whole week at full load, and we had contracts with multiple firms to bring propane). Also, make sure you test and condition the generator periodically, as any oil-lubricated engine left idle will eventually freeze up. Finally, you want to oversize the generator just a touch, as running them at 100% is a great way to burn it out relatively quickly. If you can keep it at about 80%, it'll increase the longevity of the unit, and also give you some fudge factor.
- ars 14y ago
  > The actual wiring process wasn't too difficult (have a properly licensed electrician do it. NO EXCEPTIONS!) Why no exceptions? This isn't really that hard to do, as long as your have some knowledge, and you researched in advance what to do. Obviously if you are unsure of your skill and/or knowledge level don't do it. But you don't have to be licensed to know what to do.
  - MattRogish 14y ago
    Because if you do it wrong and kill someone or burn your house down or any of the other innumerable bad things a 5+kW combustion engine device can do, it's your fault, and your insurance may not even cover it (not to mention any legal issues). Having a properly licensed/bonded electrician do it, generally, will keep the liability out of your hands. Given how cheap it was for the actual labor, I'm not comfortable taking that risk. YMMV.
ph0rque 14y ago
How about deep-cycle 12 volt batteries? You can buy a single battery for ~$130. This battery produces 55Ah and contains 660 watthours of energy. you'll need about 22 of these batteries, and it will cost about $3000 So for a 3-day supply, you would need $9k in batteries? Not bad...
- dholowiski 14y ago
  I think he's over-estimated the cost of batteries. I'm pretty sure you could get 55Ah 12V lead acid batteries for about 1/2 that. This is relatively common for people running off of solar power.
  - savrajsingh 14y ago
    After some further investigation, I discovered that my calculation exactly matches the upper bound stated by the National Renewable Energy Lab's estimates on cost, "$200/kWh" http://www.nrel.gov/docs/fy02osti/31689.pdf http://www.nrel.gov/docs/fy02osti/31689.pdf But yes it looks like you can also manage about half that cost for a similar system (their stated range is $80-$200 per kWh).
- lutorm 14y ago
  I think they meant to load-average so they could get away with a 600W generator instead of 5.5kW.
- lumberjack 14y ago
  That's significantly more expensive though. A 5KW gasoline generator is $500 new, significantly less used and definitely much more reliable than car batteries. It would also probably out last them. And it requires practically not maintenance whereas most car batteries that aren't in use would die without constant maintenance.
ry0ohki 14y ago
tldr; Call an electrician - oh and I run a company that has something to do with saving you electricity
- falcolas 14y ago
  It's good, practical advice, and pointing out how his service provided some real world value (saving money purchasing a generator) wasn't at all contrived. What's the problem?
  - ry0ohki 14y ago
    The title of the article was "Wiring a Generator to Your Home". The crucial part missing from the article was "How to Wire a Generator to Your Home", which he says an electrician should do. Just feels like blog spam to me.
    - Dylan16807 14y ago
      The title was fine. The article talked about what and why rather than how.
  - aes256 14y ago
    The author goes into a fair amount of detail about the process, but that detail is ultimately useless to most people, because the overriding advice is "Don't try this at home, get an electrician to do it for you" Their main concern is clearly to plug their product, not to provide useful advice on installing a generator, and the fact that they are exploiting a natural disaster to do so is pretty low.
herge 14y ago
With regard to the environmental costs, specifically in terms of greenhouse gases, 15 kwh per day in electricity in New Jersey will set you back 6.5 kg of CO2, while your 4 gallons of gas per day will emanate 36 kg, so almost 6 times more.
phasetransition 14y ago
Personal background: 10+ years as a moonlight freelancer in live concert production in addition to the two engineering universities. Have instructed more than one "licensed electrician" about production power from panels and generators. Two clarifications on the article: 1. A L15-30 is a three phase delta twistlock connector. The author means the L14-30. 2. "For example, if your ground wiring is not done properly, you may inadvertently put 200+ volts on 120 volt lines, immediately frying bulbs and electronics connected to those lines, and potentially starting fires." - What the author means to refer to here is accident lifting of the neutral connection. See this excellent thread (complete with demonstration video) on the professional sound forum: http://soundforums.net/lighting-electrical/4812-why-open-neutral-kills-120v-devices.html http://soundforums.net/lighting-electrical/4812-why-open-neu... If you're interested in a general understanding of generators and grounding, you can read a post of mine, also on the professional audio forum: http://soundforums.net/lighting-electrical/5216-running-generator-boat.html#post36225 http://soundforums.net/lighting-electrical/5216-running-gene... If you've got any specific questions on the topic of generators, I'm happy to give them a go.
- rdl 14y ago
  It's always interesting in audio (or lab/automation) how you want to filter out noise (isolated ground, etc.), but naive ways of doing that can cause serious problems.
  - phasetransition 14y ago
    Yes, naive ways cause big problems. While I've seen people do many ill-advised things in home and studio audio, professional concert audio is decidedly more buttoned down: Grounding is not isolated, but NEC-compliant star grounded (See NEC 400.8, 520, 525, 530 (movies), and 640 (carnivals) ) Loop area is actively minimized Signal transmission is via instrumentation amplifier topology (i.e. differential) Shielding is designed to minimize shield current induced noise (SCIN) These Rane tech notes gives a good overview on some of the topics above: http://www.rane.com/note165.html http://www.rane.com/note165.html http://www.rane.com/note166.html http://www.rane.com/note166.html The AES standard for audio interconnects is here: http://www.aes.org/publications/standards/search.cfm?docID=44 http://www.aes.org/publications/standards/search.cfm?docID=4...
leoedin 14y ago
This is a nice article, but I think it really managed to miss the point that should be made. I always find it amazing how little power you actually need to live a near-normal life. With 0 power, you definitely notice it. Once you have enough power to cover some low level lighting and entertainment (perhaps a few hundred watts), the value of any additional power is greatly reduced. The author is right in saying that they don't need a 23kW generator. They probably also don't need a 5kW generator. If they actually investigated the cause of the various power peaks, I bet they could disable or replace that usage with something else. A graph is nice, but a few labels ("this is where we turn the kettle on", "this is when we get home from work") would provide so much more information. Just a little power management could probably cut peak power down to a couple of kW, and slightly more effort could get it lower still. Beyond heating (which is woefully inefficient if electrical), there's very little that a person (or family) need at any one time that draws above a kW.
- aes256 14y ago
  I see your point, but you seem to be forgetting things like refrigerators, freezers, air conditioning units, etc. Granted you can survive without these devices, but it may be thoroughly unpleasant, result in an awful lot of spoilt food, and if a power outage is longer term, having to significantly adjust your eating habits.
  - schiffern 14y ago
    >refrigerators, freezers That's easy. My (old) fridge/freezer used about 80 watts when averaged over time (peak is 300W when self-defrosting). There are Energy Star refrigerators that use only 34 watts averaged.[1] >air conditioning units This is certainly true for now. Over the long term, low power passive cooling can be surprisingly effective. Taking advantage of evaporation, diurnal temperature changes, "wind chill", thermal mass, phase changes, passive geothermal, and solar gain reduction have the potential to provide comparable comfort for a lot less energy. A small personal anecdote: in college I had no AC, so I would circulate night air through my apartment ($15 fan + $5 timer). It reliably kept it 5-10 degrees cooler than it was outside, but doing nothing it was 5 degrees hotter. It cost $6/month, drawing 60 watts on average, even with a very inefficient motor. [1] http://www.energystar.gov/index.cfm?startNum=1&resultsperpage=20&fuseaction=refrig.search_products_submit&pd_code=RRF&configuration=Top%20Freezer&total_volume_pair=16%2E0%3A19%2E0&sortColumn=PB&sortColumn_order=DESC&layout=default&phase=search http://www.energystar.gov/index.cfm?startNum=1&resultspe...
tomfakes 14y ago
One thing that needs to be mentioned is ventilation for the exhaust gasses of these things. The Pacific Northwest had a similar (but smaller) storm to this in 2006. We had much less sea damage, but more wind damage from trees falling over. Power out for 10+days for some people. 14 people dead in WA state, but 8 of these came from CO poisoning - 5 in 1 family because they ran the generator in their garage! http://en.wikipedia.org/wiki/Hanukkah_Eve_wind_storm_of_2006 http://en.wikipedia.org/wiki/Hanukkah_Eve_wind_storm_of_2006 My in-laws used a generator for this time. They were out for 10 days, and needed to walk 2 miles each way (due to downed trees) to get gas for the darn thing. No-one thinks about the gasoline infrastructure needed to keep vehicles and generators going if the power is out for multiple days. New Jersey is finding this out right now!
brasmasus 14y ago
I'm seeing a lot of generator hookup DIY naysayers in here - and caution is warranted - but c'mon this is HN; and it really isn't complicated stuff if you have a good reference. Get 'Wiring a House' by Rex Cauldwell and start with Chapter 14: Standby Generators. It's all in there. I put 4 circuits (well pump, fridge, server, entertainment) on a three way switch panel and we've been using the generator as needed for the last 3 years. I'd recommend using the quietest, smallest inverter generator you can get away with.
wglb 14y ago
To really do this right, check out ham radio publications such as http://www.arrl.org/shop/Emergency-Power-for-Radio-Communications http://www.arrl.org/shop/Emergency-Power-for-Radio-Communica.... There is much more to it than the article might imply to you.
anovikov 14y ago
You only forget the difference between active and reactive load. If you have active loads on your system only (i.e. light bulbs) than your calculations are valid, reactive loads (like electric motors found in a/c units, fridges etc) then they are not: you have to budget for several times their power in order to make them able to start up. So the guy selling you 20KVA (they are labeled in KVA, not kilowatts, which isn't same thing!) unit is probably not all that wrong, this is 14KW and is just right for you when you say, have a peak load of 4.8KW of which 3.6KW is active and 1.2 is a conditioner that you are starting up at this moment - it will make an equivalent on 10KW or so load. So 20KVA is just right or only slightly more than you need.
- phasetransition 14y ago
  You are combining two concepts here, though the overall point is a good one: 1. The starting current of a motor, which is higher due to multiple factors (e.g. no back emf, "starter winding" current, charging motor starter capacitors, etc.). 2. The concept of power factor, which represents the fraction of in-phase current traveling in the circuit (i.e. the current actually performing mechanical work) Generators give output ratings in KVA to reflect the total amount of power that they can source from their prime mover without no consideration of power factor. Most larger generators also give a "real" power rating in watts that de-rate for the power factor. See this small commercial genset as an example: http://www.multiquip.com/multiquip/DCA45SSKU.htm http://www.multiquip.com/multiquip/DCA45SSKU.htm Only the current and voltage that are in phase perform work on the device under power. If the power factor is 1 (i.e. completely in phase) then the KVA and KW ratings would be the same. This, as you say, is the case for purely resistive loads. For loads with a reactive component, there is a current fraction that remains in quadrature is bounced back and forth between the source and the load. Since real world conductors and generator windings also have ohmic resistance, the quadrature current fraction is partially dissipated as heat, and lost outright. Many municipalities mandate a certain power factor for the industrial customers. Typically 0.9 or greater. This is to minimize the ohmic losses in transmission lines from the reflected quadrature current. Industrial facilities are typically inductive in nature, because of the large number motors. So, at the outlet of the facility they will install some shunt capacitance to offset the phase angle of the motors inductive character and bring the current back in phase. The worst-case power factor I've ever personally seen was on cruise ships. Since those things are essentially one giant mechanical plant (motors galore), and have multi-megawatt electric propulsion they have a power factor of 0.7, or even slightly less!
jpdoctor 14y ago
Would love to hear recommendations for easily purchasable generators that are reasonably quiet. I got one from HomeDepot that wakes the neighbors and causes babies to start screaming, all for want of a decent muffler. (Yes I could get one welded on. I have a need for additional generators, and for some reason noise level seems to be a state secret with those things.)
- phasetransition 14y ago
  For small, consumer-facing generators, the quietest model I am aware of is the Honda EU6500. These, and the rest of the Honda EU line, have the added advantage of being inverter generators that output a very clean sine wave. In both the live concert and movie production worlds the Eu6500 is a frequent fixture on site as the small generator of choice. I also have good experience with the smaller EU3000. The line can be found here: http://powerequipment.honda.com/generators/inverter-generators http://powerequipment.honda.com/generators/inverter-generato... Yamaha also makes a line of low noise inverter gensets. They also have a 4500 watt class model. A friend of mine choose one of the Yamahas over the Honda: http://www.yamaha-motor.com/outdoor/products/modeloverview/cat/2007/55/model_overview.aspx http://www.yamaha-motor.com/outdoor/products/modeloverview/c... Please note that both the Honda and Yamaha lines are much more expensive, and put out much cleaner power, than the typical construction generators prominently featured for cheap at the big box retailer. Buy once, cry once. Since you indicate you are considering multiple generators, you could move up the food chain to one larger enclosure-mounted installed generator. There are many choices, but my personal recommendation are the ones from Onan, who dominate the recreational vehicle (RV) generator market: http://cumminsonan.com/residential/ http://cumminsonan.com/residential/ For perspective, a common "small" portable generator for technical show power is the Multiquip (MQ) DCA45. It is a 45KVA-class generator with equivalently sized diesel prime mover: http://www.multiquip.com/multiquip/DCA45SSKU.htm http://www.multiquip.com/multiquip/DCA45SSKU.htm
  - jpdoctor 14y ago
    Many thanks. My plural-of-generator comment meant only that I am investigating for parents and friends too. The smaller Honda 3000 (wheels are good) seems about right. 57 dB (A) is 1. advertised (hooray!) and 2. very acceptable. Ordering such beasts from the web gives me a case of the willies, hopefully I can find distribution nearby. Thanks again for your answer.
tocomment 14y ago
So I just bought a 4000w portable generator and there's a little bolt you're supposed to attach some kind of ground wire to. The instructions completely didn't say what to do with it. When I looked it up online people are saying you need to have an 8 ft metal rod going into the ground?? Who's going to do that for a portable generator. What do you guys do for grounding? And if you install a transfer switch does that change the grounding needs?
- jpdoctor 14y ago
  > Who's going to do that for a portable generator. People that worry about becoming the path of least resistance to ground when they touch the equipment.
- mindslight 14y ago
  (Disclaimer: I'm an EE who has done non-for-hire house wiring, not an electrician. It is up to you to decide for yourself if my opinion concurs with anything else you've read, common sense, the laws of physics, etc. I presume you've obtained a generator at this time because you are indeed out of power and looking to get up and running quick, not for an ideal or best-prepared situation) I personally wouldn't worry about a grounding rod if I was just running a few extension cords from the generator to power a handful of necessary things. The important thing is for all of the devices to be grounded back to the generator. This means 3 conductor cords for 3 prong devices, 4 conductor cords for 4 prong stove/dryer. 2 conductor non-polarized cords should be fine for modern 2-prong "double insulated" devices. In NO circumstance do you want to be using a 3-prong to 2-prong "cheater" adapters or anything similar. Once you start talking about transfer switches and wiring it into your house, the picture completely changes. Unless you have experience doing house wiring, are up for dealing with live non-current-protected wires, and are open to learning something new while meticulously checking yourself, you really do want to talk to an electrician
  - tocomment 14y ago
    I think I would hire an electrician but I'd still like to know the right way to do it. If you install a transfer switch could the generators ground be connected to the houses ground?

95 points by savrajsingh 14y ago

dsr_ 14y ago

This bears repeating: If you try to wire your generator to your breaker box as a DIY project, you probably will not be in compliance with local electrical codes. Also know that it's extremely dangerous. For example, if your ground wiring is not done properly, you may inadvertently put 200+ volts on 120 volt lines, immediately frying bulbs and electronics connected to those lines, and potentially starting fires. Don't do it. In addition to all that, don't use a double-male cable to just plug a generator in to your house. Don't. You can kill people that way.

maxerickson 14y ago
Are you talking about people not throwing the main breaker and energizing nearby lines, or is there something more subtle?
- Turing_Machine 14y ago
  People don't expect a male plug to be live, but that's exactly what you can get with a double-male setup. Someone picks it up and ZAAAAP. I agree, don't do it.
- JagMicker 14y ago
  Does anyone else remember the "Blotto Box"? http://cd.textfiles.com/group42/ANARCHY/COOKBOOK/BLOTBOX.HTM http://cd.textfiles.com/group42/ANARCHY/COOKBOOK/BLOTBOX.HTM
  - evan_ 14y ago
    The guy who wrote that has apparently never heard of fuses...
dholowiski 14y ago
Yes, that need a bigger disclaimer. A huge one in fact. As well as the extreme importance of having a 'generator interlock' - something that physically disconnects your house from the power grid, so you aren't electrifying external power lines (lines that people expect to not be electrified when the power is turned off).
- electromagnetic 14y ago
  It's also important to remember if you're DIYing the project, that if your neighbour didn't use a generator interlock, your wiring may have enough power to make you need a trip to the hospital. Seriously, speaking as someone who has worked as an electrician. Unless you're experienced, don't play with it.
  - dholowiski 14y ago
    Yeah, this is a bad project to DIY.
    - electromagnetic 14y ago
      It's literally only DIYable by someone who has enough experience that they could do it professionally. Installing your own generator interlock is no easy feat. Installing companion wiring for a generator, again, is no easy feat. Easiest permanent DIY job would be to wire a dedicated outlet to your fridges and freezers and any important electrical equipment, and switch them to the generator outlet when you need it. No crossing circuits, no real problems. If you have no electrical experience, deal with the extension cords.
  - ars 14y ago
    > that if your neighbour didn't use a generator interlock, your wiring may have enough power to make you need a trip to the hospital. If that happened you would know because your lights were on. And what would actually happen is nothing, because the generator circuit breaker would blow from trying to power the entire neighborhood. The only way this could happen is if you were right at the end of the feeder line, and managed to down a line such that only you and your neighbor were online - in which case enjoy the free power. (And then yell at your neighbor to fix it.) Do things properly, sure, but don't over estimate the danger.
noonespecial 14y ago
Wish people took the dangers of cars this seriously. It seems to me that far more people are hurt by the careless use of cars than bad wiring.

ChuckMcM 14y ago

One of the things we did, before we put solar panels on our house, was a power survey. We actually measured the power draw of our house every day for a year by reading the power meter and keeping a notebook (great for power disputes as well :-). We discovered that we were using 23.2 kWh per day, or just under 1kW. But like the author our peak loads were higher (we don't have air conditioning or a pool so those power suckers aren't an issue). We also found that a 5.5kW generator would cover our needs. So when the wiring was under modification for a kitchen remodel, we had the electrician install a transfer switch on which we put our 10 most 'useful' circuits. Then when the power went out we could fire up the generator outside, plug it into the transfer switch and transfer power from the AC 'mains' to the generator. That works fine but you have to be careful because the power generated by Home Depot generator is pretty crappy power. The computer systems were protected by using a UPS system that used AC primary power for battery charging and ran the load off an inverter. At some point I'll find a datacenter throwing out an old AC line conditioner and I'll get that.

forgotAgain 14y ago

What about the peaks when motors turn on. I'm thinking blowers cycling for hot air heating or the mentioned pump for the well. If you're measuring for wattage you need to capture the peaks which will only last a few seconds. You also need to account for multiple motors turning on simultaneously which you may not catch with a simple measurement. You need to understand what the demands for power are as well.

ars 14y ago
Most generators can handle short peaks of around +25%. They are even rated that way 3200/4000 is a typical rating. Size for the normal load, and let the peak rating handle the startup currents.

MattRogish 14y ago

A few years ago I had to wire a generator up to a distribution warehouse so that goods could still be shipped in event of a power loss. The actual wiring process wasn't too difficult (have a properly licensed electrician do it. NO EXCEPTIONS!) but the process of wiring it up to the building natural gas we hit a snag. We had a 25kW generator spec'd but using natural gas required more pressure than the utility could supply. We switched to propane (which is less efficient) and used building gas as a last-ditch failover (if I recall correctly it only had enough pressure to supply half load or something). Note that disel and plain old gasoline generators push out really noisy power. Do not hook up electronics to gas generators without a line conditioner or UPS in the middle (and the UPS will probably complain about voltage sags and/or lack of grounding). If you're going to make it a permanent fixture to your home that you can actually rely upon, you really ought to make it run on natural gas and/or propane (as a failover). Quieter, cheaper, and less likely to be a shortage (most homes without power in NY/NJ still have natural gas and a modestly sized propane tank could run our generator for a whole week at full load, and we had contracts with multiple firms to bring propane). Also, make sure you test and condition the generator periodically, as any oil-lubricated engine left idle will eventually freeze up. Finally, you want to oversize the generator just a touch, as running them at 100% is a great way to burn it out relatively quickly. If you can keep it at about 80%, it'll increase the longevity of the unit, and also give you some fudge factor.

ars 14y ago
> The actual wiring process wasn't too difficult (have a properly licensed electrician do it. NO EXCEPTIONS!) Why no exceptions? This isn't really that hard to do, as long as your have some knowledge, and you researched in advance what to do. Obviously if you are unsure of your skill and/or knowledge level don't do it. But you don't have to be licensed to know what to do.
- MattRogish 14y ago
  Because if you do it wrong and kill someone or burn your house down or any of the other innumerable bad things a 5+kW combustion engine device can do, it's your fault, and your insurance may not even cover it (not to mention any legal issues). Having a properly licensed/bonded electrician do it, generally, will keep the liability out of your hands. Given how cheap it was for the actual labor, I'm not comfortable taking that risk. YMMV.

ph0rque 14y ago

How about deep-cycle 12 volt batteries? You can buy a single battery for ~$130. This battery produces 55Ah and contains 660 watthours of energy. you'll need about 22 of these batteries, and it will cost about $3000 So for a 3-day supply, you would need $9k in batteries? Not bad...

dholowiski 14y ago
I think he's over-estimated the cost of batteries. I'm pretty sure you could get 55Ah 12V lead acid batteries for about 1/2 that. This is relatively common for people running off of solar power.
- savrajsingh 14y ago
  After some further investigation, I discovered that my calculation exactly matches the upper bound stated by the National Renewable Energy Lab's estimates on cost, "$200/kWh" http://www.nrel.gov/docs/fy02osti/31689.pdf http://www.nrel.gov/docs/fy02osti/31689.pdf But yes it looks like you can also manage about half that cost for a similar system (their stated range is $80-$200 per kWh).
lutorm 14y ago
I think they meant to load-average so they could get away with a 600W generator instead of 5.5kW.
lumberjack 14y ago
That's significantly more expensive though. A 5KW gasoline generator is $500 new, significantly less used and definitely much more reliable than car batteries. It would also probably out last them. And it requires practically not maintenance whereas most car batteries that aren't in use would die without constant maintenance.

ry0ohki 14y ago

tldr; Call an electrician - oh and I run a company that has something to do with saving you electricity

falcolas 14y ago
It's good, practical advice, and pointing out how his service provided some real world value (saving money purchasing a generator) wasn't at all contrived. What's the problem?
- ry0ohki 14y ago
  The title of the article was "Wiring a Generator to Your Home". The crucial part missing from the article was "How to Wire a Generator to Your Home", which he says an electrician should do. Just feels like blog spam to me.
  - Dylan16807 14y ago
    The title was fine. The article talked about what and why rather than how.
- aes256 14y ago
  The author goes into a fair amount of detail about the process, but that detail is ultimately useless to most people, because the overriding advice is "Don't try this at home, get an electrician to do it for you" Their main concern is clearly to plug their product, not to provide useful advice on installing a generator, and the fact that they are exploiting a natural disaster to do so is pretty low.

herge 14y ago

With regard to the environmental costs, specifically in terms of greenhouse gases, 15 kwh per day in electricity in New Jersey will set you back 6.5 kg of CO2, while your 4 gallons of gas per day will emanate 36 kg, so almost 6 times more.

phasetransition 14y ago

Personal background: 10+ years as a moonlight freelancer in live concert production in addition to the two engineering universities. Have instructed more than one "licensed electrician" about production power from panels and generators. Two clarifications on the article: 1. A L15-30 is a three phase delta twistlock connector. The author means the L14-30. 2. "For example, if your ground wiring is not done properly, you may inadvertently put 200+ volts on 120 volt lines, immediately frying bulbs and electronics connected to those lines, and potentially starting fires." - What the author means to refer to here is accident lifting of the neutral connection. See this excellent thread (complete with demonstration video) on the professional sound forum: http://soundforums.net/lighting-electrical/4812-why-open-neutral-kills-120v-devices.html http://soundforums.net/lighting-electrical/4812-why-open-neu... If you're interested in a general understanding of generators and grounding, you can read a post of mine, also on the professional audio forum: http://soundforums.net/lighting-electrical/5216-running-generator-boat.html#post36225 http://soundforums.net/lighting-electrical/5216-running-gene... If you've got any specific questions on the topic of generators, I'm happy to give them a go.

rdl 14y ago
It's always interesting in audio (or lab/automation) how you want to filter out noise (isolated ground, etc.), but naive ways of doing that can cause serious problems.
- phasetransition 14y ago
  Yes, naive ways cause big problems. While I've seen people do many ill-advised things in home and studio audio, professional concert audio is decidedly more buttoned down: Grounding is not isolated, but NEC-compliant star grounded (See NEC 400.8, 520, 525, 530 (movies), and 640 (carnivals) ) Loop area is actively minimized Signal transmission is via instrumentation amplifier topology (i.e. differential) Shielding is designed to minimize shield current induced noise (SCIN) These Rane tech notes gives a good overview on some of the topics above: http://www.rane.com/note165.html http://www.rane.com/note165.html http://www.rane.com/note166.html http://www.rane.com/note166.html The AES standard for audio interconnects is here: http://www.aes.org/publications/standards/search.cfm?docID=44 http://www.aes.org/publications/standards/search.cfm?docID=4...

leoedin 14y ago

This is a nice article, but I think it really managed to miss the point that should be made. I always find it amazing how little power you actually need to live a near-normal life. With 0 power, you definitely notice it. Once you have enough power to cover some low level lighting and entertainment (perhaps a few hundred watts), the value of any additional power is greatly reduced. The author is right in saying that they don't need a 23kW generator. They probably also don't need a 5kW generator. If they actually investigated the cause of the various power peaks, I bet they could disable or replace that usage with something else. A graph is nice, but a few labels ("this is where we turn the kettle on", "this is when we get home from work") would provide so much more information. Just a little power management could probably cut peak power down to a couple of kW, and slightly more effort could get it lower still. Beyond heating (which is woefully inefficient if electrical), there's very little that a person (or family) need at any one time that draws above a kW.

aes256 14y ago
I see your point, but you seem to be forgetting things like refrigerators, freezers, air conditioning units, etc. Granted you can survive without these devices, but it may be thoroughly unpleasant, result in an awful lot of spoilt food, and if a power outage is longer term, having to significantly adjust your eating habits.
- schiffern 14y ago
  >refrigerators, freezers That's easy. My (old) fridge/freezer used about 80 watts when averaged over time (peak is 300W when self-defrosting). There are Energy Star refrigerators that use only 34 watts averaged.[1] >air conditioning units This is certainly true for now. Over the long term, low power passive cooling can be surprisingly effective. Taking advantage of evaporation, diurnal temperature changes, "wind chill", thermal mass, phase changes, passive geothermal, and solar gain reduction have the potential to provide comparable comfort for a lot less energy. A small personal anecdote: in college I had no AC, so I would circulate night air through my apartment ($15 fan + $5 timer). It reliably kept it 5-10 degrees cooler than it was outside, but doing nothing it was 5 degrees hotter. It cost $6/month, drawing 60 watts on average, even with a very inefficient motor. [1] http://www.energystar.gov/index.cfm?startNum=1&resultsperpage=20&fuseaction=refrig.search_products_submit&pd_code=RRF&configuration=Top%20Freezer&total_volume_pair=16%2E0%3A19%2E0&sortColumn=PB&sortColumn_order=DESC&layout=default&phase=search http://www.energystar.gov/index.cfm?startNum=1&resultspe...

tomfakes 14y ago

One thing that needs to be mentioned is ventilation for the exhaust gasses of these things. The Pacific Northwest had a similar (but smaller) storm to this in 2006. We had much less sea damage, but more wind damage from trees falling over. Power out for 10+days for some people. 14 people dead in WA state, but 8 of these came from CO poisoning - 5 in 1 family because they ran the generator in their garage! http://en.wikipedia.org/wiki/Hanukkah_Eve_wind_storm_of_2006 http://en.wikipedia.org/wiki/Hanukkah_Eve_wind_storm_of_2006 My in-laws used a generator for this time. They were out for 10 days, and needed to walk 2 miles each way (due to downed trees) to get gas for the darn thing. No-one thinks about the gasoline infrastructure needed to keep vehicles and generators going if the power is out for multiple days. New Jersey is finding this out right now!

brasmasus 14y ago

I'm seeing a lot of generator hookup DIY naysayers in here - and caution is warranted - but c'mon this is HN; and it really isn't complicated stuff if you have a good reference. Get 'Wiring a House' by Rex Cauldwell and start with Chapter 14: Standby Generators. It's all in there. I put 4 circuits (well pump, fridge, server, entertainment) on a three way switch panel and we've been using the generator as needed for the last 3 years. I'd recommend using the quietest, smallest inverter generator you can get away with.

wglb 14y ago

To really do this right, check out ham radio publications such as http://www.arrl.org/shop/Emergency-Power-for-Radio-Communications http://www.arrl.org/shop/Emergency-Power-for-Radio-Communica.... There is much more to it than the article might imply to you.

anovikov 14y ago

You only forget the difference between active and reactive load. If you have active loads on your system only (i.e. light bulbs) than your calculations are valid, reactive loads (like electric motors found in a/c units, fridges etc) then they are not: you have to budget for several times their power in order to make them able to start up. So the guy selling you 20KVA (they are labeled in KVA, not kilowatts, which isn't same thing!) unit is probably not all that wrong, this is 14KW and is just right for you when you say, have a peak load of 4.8KW of which 3.6KW is active and 1.2 is a conditioner that you are starting up at this moment - it will make an equivalent on 10KW or so load. So 20KVA is just right or only slightly more than you need.

phasetransition 14y ago
You are combining two concepts here, though the overall point is a good one: 1. The starting current of a motor, which is higher due to multiple factors (e.g. no back emf, "starter winding" current, charging motor starter capacitors, etc.). 2. The concept of power factor, which represents the fraction of in-phase current traveling in the circuit (i.e. the current actually performing mechanical work) Generators give output ratings in KVA to reflect the total amount of power that they can source from their prime mover without no consideration of power factor. Most larger generators also give a "real" power rating in watts that de-rate for the power factor. See this small commercial genset as an example: http://www.multiquip.com/multiquip/DCA45SSKU.htm http://www.multiquip.com/multiquip/DCA45SSKU.htm Only the current and voltage that are in phase perform work on the device under power. If the power factor is 1 (i.e. completely in phase) then the KVA and KW ratings would be the same. This, as you say, is the case for purely resistive loads. For loads with a reactive component, there is a current fraction that remains in quadrature is bounced back and forth between the source and the load. Since real world conductors and generator windings also have ohmic resistance, the quadrature current fraction is partially dissipated as heat, and lost outright. Many municipalities mandate a certain power factor for the industrial customers. Typically 0.9 or greater. This is to minimize the ohmic losses in transmission lines from the reflected quadrature current. Industrial facilities are typically inductive in nature, because of the large number motors. So, at the outlet of the facility they will install some shunt capacitance to offset the phase angle of the motors inductive character and bring the current back in phase. The worst-case power factor I've ever personally seen was on cruise ships. Since those things are essentially one giant mechanical plant (motors galore), and have multi-megawatt electric propulsion they have a power factor of 0.7, or even slightly less!

jpdoctor 14y ago

Would love to hear recommendations for easily purchasable generators that are reasonably quiet. I got one from HomeDepot that wakes the neighbors and causes babies to start screaming, all for want of a decent muffler. (Yes I could get one welded on. I have a need for additional generators, and for some reason noise level seems to be a state secret with those things.)

phasetransition 14y ago
For small, consumer-facing generators, the quietest model I am aware of is the Honda EU6500. These, and the rest of the Honda EU line, have the added advantage of being inverter generators that output a very clean sine wave. In both the live concert and movie production worlds the Eu6500 is a frequent fixture on site as the small generator of choice. I also have good experience with the smaller EU3000. The line can be found here: http://powerequipment.honda.com/generators/inverter-generators http://powerequipment.honda.com/generators/inverter-generato... Yamaha also makes a line of low noise inverter gensets. They also have a 4500 watt class model. A friend of mine choose one of the Yamahas over the Honda: http://www.yamaha-motor.com/outdoor/products/modeloverview/cat/2007/55/model_overview.aspx http://www.yamaha-motor.com/outdoor/products/modeloverview/c... Please note that both the Honda and Yamaha lines are much more expensive, and put out much cleaner power, than the typical construction generators prominently featured for cheap at the big box retailer. Buy once, cry once. Since you indicate you are considering multiple generators, you could move up the food chain to one larger enclosure-mounted installed generator. There are many choices, but my personal recommendation are the ones from Onan, who dominate the recreational vehicle (RV) generator market: http://cumminsonan.com/residential/ http://cumminsonan.com/residential/ For perspective, a common "small" portable generator for technical show power is the Multiquip (MQ) DCA45. It is a 45KVA-class generator with equivalently sized diesel prime mover: http://www.multiquip.com/multiquip/DCA45SSKU.htm http://www.multiquip.com/multiquip/DCA45SSKU.htm
- jpdoctor 14y ago
  Many thanks. My plural-of-generator comment meant only that I am investigating for parents and friends too. The smaller Honda 3000 (wheels are good) seems about right. 57 dB (A) is 1. advertised (hooray!) and 2. very acceptable. Ordering such beasts from the web gives me a case of the willies, hopefully I can find distribution nearby. Thanks again for your answer.

tocomment 14y ago

So I just bought a 4000w portable generator and there's a little bolt you're supposed to attach some kind of ground wire to. The instructions completely didn't say what to do with it. When I looked it up online people are saying you need to have an 8 ft metal rod going into the ground?? Who's going to do that for a portable generator. What do you guys do for grounding? And if you install a transfer switch does that change the grounding needs?

jpdoctor 14y ago
> Who's going to do that for a portable generator. People that worry about becoming the path of least resistance to ground when they touch the equipment.
mindslight 14y ago
(Disclaimer: I'm an EE who has done non-for-hire house wiring, not an electrician. It is up to you to decide for yourself if my opinion concurs with anything else you've read, common sense, the laws of physics, etc. I presume you've obtained a generator at this time because you are indeed out of power and looking to get up and running quick, not for an ideal or best-prepared situation) I personally wouldn't worry about a grounding rod if I was just running a few extension cords from the generator to power a handful of necessary things. The important thing is for all of the devices to be grounded back to the generator. This means 3 conductor cords for 3 prong devices, 4 conductor cords for 4 prong stove/dryer. 2 conductor non-polarized cords should be fine for modern 2-prong "double insulated" devices. In NO circumstance do you want to be using a 3-prong to 2-prong "cheater" adapters or anything similar. Once you start talking about transfer switches and wiring it into your house, the picture completely changes. Unless you have experience doing house wiring, are up for dealing with live non-current-protected wires, and are open to learning something new while meticulously checking yourself, you really do want to talk to an electrician
- tocomment 14y ago
  I think I would hire an electrician but I'd still like to know the right way to do it. If you install a transfer switch could the generators ground be connected to the houses ground?