
Wiring a Generator to Your House - savrajsingh
http://blog.wattvision.com/wiring-a-generator-to-your-house
======
dsr_
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.

~~~
dholowiski
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
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
Yeah, this is a bad project to DIY.

~~~
electromagnetic
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.

------
phasetransition
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-
neu...](http://soundforums.net/lighting-electrical/4812-why-open-neutral-
kills-120v-devices.html)

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-
gene...](http://soundforums.net/lighting-electrical/5216-running-generator-
boat.html#post36225)

If you've got any specific questions on the topic of generators, I'm happy to
give them a go.

~~~
rdl
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
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/note166.html>

The AES standard for audio interconnects is here:
[http://www.aes.org/publications/standards/search.cfm?docID=4...](http://www.aes.org/publications/standards/search.cfm?docID=44)

------
MattRogish
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
> 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
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.

~~~
ars
Do you know how many things you can do wrong and kill someone?

This is way down on the list. Hire someone if you want, but don't tell people
"no exceptions" there are plenty of quite handy people who would have no
trouble doing this properly.

Like you said: It's not really that hard.

~~~
oconnore
Those people also know enough (or know too little) to ignore advice on the
internet. For everyone else, disclaimers are good.

------
leoedin
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.

~~~
Dove
The big ones -- at least around here -- are the clothes dryer, the range, and
the dishwasher. They're all a kW or more, and it would be a significant
inconvenience to do without them.

Oh, and the microwave.

~~~
marquis
>clothes dryer, the range, and the dishwasher

I've worked and lived under emergency conditions with no power, running off a
generator, and the clothes dryer, range and dishwasher were the last things we
cared about. Light, telecommunications (we had long-distance antennas) and
phone charging were the most critical needs.

I've also spent time in 100%-self-powered villages, and with good solar and
wind power you can indeed have your dish-washers etc, just not in an emergency
when you need to conserve and share energy (people running around sharing
newly-charged battery packs was a common sight).

Generating electricity isn't really an issue if you have a good solar/wind
pack: it's battery. I've often found running a converter from a car has been
more efficient than relying on someone's home-built battery pack.

~~~
Dove
Sure. I've gone camping, too.

I'm just saying trying to live _normally_ on a peak power of a couple kW might
be optimistic. The dryer alone draws two or three.

~~~
leoedin
I have never owned a dryer. In the UK owning a clothes dryer is quite unusual
- clothes drying racks work quite effectively.

I suppose if you decide that you must live a "normal" life, then you can't
really change anything about it. If you decide that you want to live a
comfortable but low impact life, then there's plenty of things you can do to
reduce your peak power.

~~~
krzyk
Same here in Poland, I would have never seen clothes dryer if I weren't in the
US few years ago. Doesn't the use of such dryer make ironing harder?

~~~
Dove
I suppose it might! All the clothing I have that should be ironed is also dry-
clean only, so it never sees the dryer.

I do have some clothes that I dry on a rack, and they always come out very
stiff compared to the stuff that goes through the dryer. I feel like I should
hit those sweaters with a rugbeater or something before I wear them.

------
tomfakes
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>

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!

------
ChuckMcM
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.

------
brasmasus
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.

------
jpdoctor
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
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-
generato...](http://powerequipment.honda.com/generators/inverter-generators)

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/c...](http://www.yamaha-
motor.com/outdoor/products/modeloverview/cat/2007/55/model_overview.aspx)

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/>

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>

~~~
jpdoctor
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.

~~~
phasetransition
Welcome,

The Honda generators are as nice as the price would indicate :) In general be
wary of generators that give sound levels with out a distance and weighting
curve specification.

------
anovikov
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
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>

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!

------
ry0ohki
tldr; Call an electrician - oh and I run a company that has something to do
with saving you electricity

~~~
falcolas
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
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
The title was fine. The article talked about what and why rather than how.

------
forgotAgain
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
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.

------
tocomment
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?

~~~
mindslight
(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
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?

~~~
mindslight
Generator's ground would definitely be connected to the house ground. I have
not read the NEC in relation to generators. I would guess that neutral and
ground should not be bonded together at the generator (this is a modification
from how most generators come) and that if the generator is an appreciable
distance from the service panel, another ground rod should be driven at the
generator/interconnect.

------
wglb
To really do this right, check out ham radio publications such as
[http://www.arrl.org/shop/Emergency-Power-for-Radio-
Communica...](http://www.arrl.org/shop/Emergency-Power-for-Radio-
Communications).

There is much more to it than the article might imply to you.

------
ph0rque
_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
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
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>

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).

------
herge
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.

