Carnation Construction

011 - Techniques - Electrical Design

Building code

These snippets come from the IRC 2009 rules (which come from NEC 2008 rules (National Electrical Code), but note that building codes vary in different local areas so you will need to do your own checking up on codes in your area.  Also, this is just a few of the building codes that caught my eye and appeared relevant to my case.  It is not a full set, so you should consult a full code book to make sure you meet all the codes.  Also note that building codes get updated every few years.

You are required to have good access to both main panels and sub-panels.  You need 3 clear feet in front of the front face of the panel (a bit extra if you have railings).  You need the space in front to be at least 2'6" wide (evenly distributed either side of the panel, ie at least 6" either side).  The working space in front must be at least 6'6" high with no plumbing pipes or any other wet stuff above or below.  Code says "The service disconnect must be readily accessible and when installed inside the house must be near to where the service conductors enter the building".

In my case the main panel and the service disconnect main switch is in the yard.

When wiring for 240V, ie using two Live wires, the Neutral must be the same gauge as the Live wires.  The Earth can be thinner, eg #4 for a 200A feed.

Personally I recommend making the Earth the same size as the other wires.

Electrical cable buried in the ground (eg in conduit) must be at least 18" below grade.

IRC 2009 requires you to use tamper proof power outlets everywhere.

Breakers that are either 15A or 20A (except for the exemptions given below) must all be "AFCI" (Arc Fault Circuit Interrupter).  These special breakers have a test button and a separate neutral wire.  They detect if there is any unintended arcing occurring that might cause a fire.  As of January 2008 only "combination type" AFCIs will meet the NEC requirement.  The 2008 NEC requires the installation of "combination type" AFCIs in all 15 and 20 amp residential circuits with the exception of laundries, kitchens, bathrooms, garages and unfinished basements.
Combination AFCIs provide for series arc detection down to 5 amps.  This series arc detection is beneficial to detect lower level arcing in both branch circuits and power supply cords.  Combination AFCI protection is required by the NEC as of January 1, 2008.

An AFCI can be used in conjunction with GFCI protection to provide both arcing fault protection as well as 5mA ground fault (people) protection.  A common way to provide both types of protection is to use an AFCI circuit breaker and a GFCI receptacle (as the first outlet in the chain).  AFCI's can also incorporate 5mA GFCI protection into the same package, but this is currently not commonly available.

GFCI outlets are required in lots of places around the house.

I recommend that you use a GFCI outlet as the first outlet on all chains of power outlets and connect all the other outlets in the chain to the load terminal of that GFCI socket.  This way all outlets in the house will be protected and therefore safer.  They typically have a green LED that shows if they are working.

You can use GFCI breakers in your electrical panel but they are expensive compared with GFCI outlets and you will have to run back to the panel every time they trip.  Also you will need AFCI breakers in your electrical panel.

The GFCIs should be tamper proof 20 amp.  All the downstream power outlets should be 15 amps.  The wiring must be 12-2 (ie 20 amps).  Using 20 amps rather than 15 allows more outlets in a chain and may actually work out cheaper than using 15 amp (less runs back to the electrical panel).

Outside power outlets must also be weatherproof as well as tamper proof.  It's also good to use weatherproof in wet rooms such as bathrooms.

In a residential house there is (currently) no limit on the number of power outlets or lights that can be in a chain, ie connected to one run back to the electrical panel.  This great because I like to have lots of power outlets in convenient places and in practice only 10% get used at any one time.

Try to have a separate run to each room and then just provide plenty of convenient sockets in that room off that run.  Larger rooms may need 2 runs in order to give you enough total power for the room.

In a kitchen by code you need at least 2 electrical chains of power outlets.  They all need GFCI protection (can be shared using the load terminals on the GFCI outlet that is the first outlet in the chain).  All places on the counter top must be within 2 feet of a power outlet.  Separate feeds are required to permanently installed appliances (eg dishwasher, eg fridge)

It is worth having power outlets every 2 feet above all counter tops (ideally even more).  Don't scrimp because kitchens have lots of plugin appliances and will have even more in the future.

Code requires one power outlet within 6 feet of a door and every 12 feet thereafter.  Any wall that is 2 foot or wider needs an outlet.

Power outlets that are in the same chain (ie same feed from the panel) are relatively inexpensive so it is worth exceeding the minimum code requirement significantly.  Having lots of outlets is a much appreciated convenience.

Cable through studs must be at least 1.5 inches from the surface of the stud.  That means that on a 2x4 stud the hole for the wire must be exactly in the center of the stud.  If this is not possible due to some obstruction then metal protection plates must be installed.

In my case the 2x4s are installed flat faced, ie they are only 1.5" thick (rather than 3.5"), but they are installed over the polystyrene of the ICF, so the polystyrene can be cut away to route the wires.

Cable must be clamped (eg using an insulated staple) within 8" of an electrical box.

Even though not explicitly stated, my assumption is that the insulated staple should be at least 1.5" in from the inside face of the drywall.  After the polystyrene is cut away it should be possible to nail into either the concrete or the ICF plastic webbing.

Cable must be secured (eg using an insulated staple or by routing through a hole) at least every 4.5 feet.

I try use staples sparingly because it makes wiring electrical boxes harder, so I tend to wait until the inspector insists on it in a particular situation.

All cable joins require boxes and the boxes need to be accessible.  If a wire is not long enough then you need to pull it all out and replace it with a new wire.


Wire types and sizes

Gauge and current capability

The current capability of the larger wire gauges varies a bit with temperature, but here are the approximate specs...

14           15A
12           20A
10           30A
8             45A (if not encased, otherwise 40A))
6             60A (if not encased, otherwise 55A))
4             80A (if not encased, otherwise 70A)
3             90A
2           100A (if not encased, otherwise 95A)
1           130A
1/0        150A
2/0        200A
3/0        225A
4/0        250A

A key point here is that 2/0 copper wire is allowed by NEC 2008 and IRC 2009 to carry 200 amps.  This is significant because electrical panels are often 200A and 2/0 tends to be the best value for money of all the high current wires because it is sold in the highest quantity.

Two 2/0 wires in parallel are allowed by code to carry 300 amps, ie the current is de-rated to account for any uneven load sharing.  In practice however, having two parallel wires will reduce voltage drop much more than the official de-rating suggests.

In my case I am using single run 2/0 wires to a house sub-panel, but I am using two sub-panels mounted next to each other in the house.  As well as other benefits described below, this avoids any de-rating.

Cable Naming

NM cable (NM stands for Non Metallic) (sometimes called Romex) is for Internal house wiring.  It cannot be used outside or in wet or damp locations.

UF cable (UF stands for Underground Feeder) is for Outside use.  It can be used it wet locations and can even be directly buried in the ground, but it CANNOT be used in conduit because of heat build-up issues.

W/G means that the cable also has a ground wire (usually not separately insulated).

The number after the dash gives the number of insulated conductors (ie not counting the ground wire if present).

For example:
Cable called "NM 12-2 W/G" has two insulated 12 gauge wires (a black Live and a white Neutral) plus a bare copper Ground wire and is only for use inside your dry house.
Cable called "UF 14-3 W/G" has three insulated 14 gauge wires (a black Live-1, a red Live-2, and a white Neutral) plus a bare copper Ground wire and is suitable for use outside in your yard or in other wet areas.

The term THWN (Thermoplastic High Water-resistant Nylon-coated) refers to the insulation round individual conductor wires, as does the term THHN (Thermoplastic High Heat-resistant Nylon-coated).  For use outside in the ground inside conduit you need wire that is rated as THWN.  Confusingly, most (but not all) wire called THHN is dual rated to meet the THWN spec as well as the THHN spec.  You need to check the THHN wire you buy to make sure it also meets the THWN spec.

Recommended wire gauges

Only ever use copper wire (not Aluminum).

Additional considerations over and above the wire gauge current capability spec come into effect when deciding what gauge wire to choose.  Firstly the wire has too be able to take the current for the breaker that is used on that circuit.  If you have a 30 amp breaker then you must make sure that all the wire on that circuit can handle 30 amps (as determined by NEC 2008 and IRC 2009).  Another consideration is that even though a particular gauge of wire can safely handle the breaker current, you will still get a voltage drop along the wire and for a typical long run that may be more voltage drop than you are willing to accept.  The last factor is to choose a wire type that is sold in the highest quantity and is therefore the best value.  Here are my recommendations on what wire to use for different breaker currents in their typical applications, together with HomeDepot pricing.

15A        House lighting (dry areas)      120V

Interior Copper NM 14-2 with Ground                                       $44 for 250'

Wire NMB 14-2 (Internal) 

20A        House power sockets (dry areas)          120V

Interior Copper NM 12-2 with Ground                                       $65 for 250'

Wire NMB 12-2 (Internal) 

20A        Yard power/lights                     120V

Sch 40 Conduit, with Solid Copper THWN 12 AWG, 3 insul wires       3 x $65 for 500'

Wire THHN/THWN 12 gauge blackWire THHN/THWN 12 gauge white Wire THHN/THWN 12 gauge green

(Note for comparison that 14 gauge is $42 for 500' and 10 gauge is $110 for 500')


20A        Shed                                         240V

Sch 40 Conduit, with Solid Copper THWN 12 AWG, 4 insul wires       4 x $65 for 500'

Wire THHN/THWN 12 gauge redWire THHN/THWN 12 gauge blackWire THHN/THWN 12 gauge white Wire THHN/THWN 12 gauge green

30A        Big Electric boiler                          120V

Interior Copper 10-2 and earth                                       $142 for 250'

55A        Big Electric range                          240V

Interior Copper 6-3 and earth                                         $??

40A        Well house                               240V

Currently I have Exterior Copper 2/0 with 3 insul wires & earth             4 x $2.17 per foot
But a WellHouse only really needs L1+L2 at 40A, ie 8 AWG.

200A      House sub-panel                     240V

Exterior Copper 2/0 with 3 insul wires & earth   $2.17 per foot x 3 + earth
Separate runs to each sub-panel (I have two sub-panels).
If money is tight, fit one run of 2/0 (200A) and provide conduit for a second sub-panel later.
Lowes is a good supplier of 2/0 wire.  If you buy 500 feet then it is $1.94 per foot.

Panel earth stake

Exterior copper #4 (one daisy chained wire with no joins)

It is ok by code to use eg #4 bare copper for the earth for a 200A service.  It wants to be uninsulated so it is in contact with the ground all the way.

I have two 200A panels in the house, so need to use two #4 bare copper wires.

A 200' roll of #4 copper wire is $197 from HomeDepot.

Speaker wire

Wire speaker 16 gauge  Details are here .


Copper price

Copper is a rather volatile commodity on the world market.  Lots of the world's copper supply is being used up in China's building boom.  When placing a large order for all the wiring in your house it is worth trying to time your purchase when copper prices dip.  Below are live charts that gives the price over the last 3 years and 3 months.  There will probably be a small delay before any change in the world commodity price changes the price of a bundle of wire in Home Depot, but it absolutely will cause a change.  A high price for copper is $4 per pound, but the hope is that it's below $3 per pound.  In the 2008 crash it was $1.50 per pound, and if it ever hits that again then I will do a copper roof!


Getting power to your house

Choose an underground utility connection

Power to your site needs to be installed by the electrical utility company.  You can request either an above ground wire from a pole or an underground feed.  You should definitely choose the underground feed.  Depending on circumstances it may even come out to be about the same price, and it's certainly more robust, less ugly, and less general hassle.  With an underground feed the utility company will provide the wiring all the way to the electricity meter (which is not the case with an overhead feed).

Street transformer

The utility company will install a transformer near the edge of the street in a big green box on a concrete pad.  These transformers make an annoying humming noise so it is best to try to get the utility company to position it out of ear shot relative to where you typically like to sit in your yard.  The job of the transformer of course is to take the high voltage that the utility company uses for distribution and change it down to the 120/240 volts that your house needs.

Street transformer 

Typically what is delivered to a house is "one phase with two live wires" rather than three phases.  This is also known as "single phase, three wire".  The two live wires are referred to as L1 and L2.  From L1 to neutral is 110-120V, from L2 to neutral is also 110-120V, and from L1 to L2 is 220-240V  This diagram explains it...

Electrical wires and phases 

Electricity meter

From the transformer, wires run underground in conduit (assuming an underground service) to an electricity meter that is typically positioned on the outer wall of your house at a height of about 5 feet (to allow easy reading).

Electricity meter 

Free standing outside panel assembly

Another option (particularly if your house has not yet been built) is to have a free standing panel arrangement in your yard.  This is what I have...

Free standing electrical panel arrangement 

An important consideration is that the electricity meter needs to be physically close to where your main panel is (that has the main breaker).  If the meter is on the outside of your garage wall then typically the electrical panel will be on the inside face of that same wall in the same location so that the link between the two is only the wall thickness.  If you are mounting your electricity meter free standing outside then that means your electrical panel will also be outside as part of that same arrangement.  This is perfectly ok, but in practice it means that you will probably install sub-panels inside your house that are fed from the outside main panel.  In my case the main panel feeds two 200 amp sub-panels (that our mounted in the basement) from the 600 amp main panel that is outside.

Electrical Main Panel 

Main breaker

The "Service Entry" wires from the adjacent meter box come into the main panel and the two live wires go directly to the main breaker.  In my case it is a 600 amp breaker because I have a 600 amp electrical service from the utility company.  Note that each live wire in the picture below is actually 2 wires in order to be able to handle the high current.

Service entry wires into main panel 

Neutral plate/bus

The neutral wire (again actually two wires in parallel to handle the current) is routed to the Neutral plate that (in my case) is in the bottom half of the main electrical panel.

Electrical neutral plate in main panel 

Neutral connects to ground in Main Panel

In the case of a "Main panel", the neutral plate/bus also needs to be connected to earth.  This means it needs to connect to big copper stakes that are driven into the ground and it also needs to be connected to the metal enclosure that houses the main electrical panel.  In the picture above you can see the wire with green tape round it that goes to the metal case and the bare copper wire that goes to the stakes in the ground.  The rest of the connection block is for attaching all the neutral wires for all the feeds that you want from the electrical panel.  In the picture above there are only two neutral wires as the main panel is currently only feeding two destinations (two sub-panels).


The live connections for feeding off to whatever you want to power are connected via breakers.  Out of the bottom of the main breaker come two thick metal bus strips.  These are Live1(L1) and Live2(L2).  The breakers attach to these live busses.  In the case of wanting 110V power then the a single breaker that just attaches to one of the live busses is used.  If you want 240V then two breakers ganged together are used (one breaker on L1 and one breaker on L2).  Breakers come in different current ratings and different physical sizes.  In the picture there are three 240V breakers each capable of 200 amps (that are used for powering sub-panels) and there are a number of smaller breakers that range in current from 20 amps to 100 amps.

Electrical breakers 

My main panel happens to be a GE "A Series Panel".  It takes breaker type "THQB" available from .
A 40A dual breaker is at         $55        (For SawMill)
A 60A dual breaker is at     $55    (For Transfer panel)
A 200A dual breaker is at    $158    (For house sub-panel)

Little breakers for the yard

Even though your house power will come from sub-panels, having the smaller breakers (eg 20 amps) in the main panel can be useful for powering various things in your yard.

Thick wire reduces light dimming

The wires from the main panel to the sub-panels in your house need to be good thick wire.  The minimum for handling 200 amps is called "2/0" but if you can afford it it's better to use even thicker gauge wire.  The reason for using as thick as possible is that you want to minimize the voltage drop that you will get in the wire when everything in your house is turned on.  It is really annoying to have your lights dim when someone turns on a hair dryer or an electrical heating appliance.  Obviously the thing pulling in the other direction is the fact that thick gauge copper wire is very expensive.

Two sub-panels also reduce light dimming

One of the nice things about the luxury of having two 200 amp sub-panels in the house is that you can use one for your heating appliances and use the other one for your lights and other low current appliances such as assorted electronics.  This will avoid the lights varying in brightness.

There is however a slight building code worry about having two separately fed sub-panels in your house.  Building code says you can only have one service entry feed to a residential house, but if your main panel is outside in the yard this does not by the letter of the law contravene this rule because your main power cutoff is the switch in your yard.  It is though a little worrying because two sub-panels means that the user needs to turn off two switches to cut all power from the building.  If you do use two separately fed sub-panels then it would be wise to mount them next to each other and put permanent labels on the switches to make sure it is clear that there are two switches that need to be turned off. <TODO:17>

Panel brand and types

The sub-panels both need to be rated at 200 amps, but only one of them (the one for the lights and electronics) needs to to have a large number of output connections.  A good brand of electrical panel (and one that is capable of being used in sub-panel mode) is Siemens.

Siemens 40/40 panel   Details are here .

Whatever brand you pick, get one that uses copper bus bars.

The thing that is an even higher factor in picking the brand of panel may well be price of AFCI breakers in go into it given that AFCI is needed on almost all 15 and 20 amp circuits.  As it happens, the Siemens AFCI breakers are as low cost as they come (which at $35 each is still expensive).

In my main house the sub-panels are mounted in the basement garage area on the eastern end of the garage north wall. 

Sub-panels must have separate earth and neutral

In a sub-panel it is necessary to keep the Neutral and the Earth connections separate.  Good panels (such as the Siemens) allow you to separate the neutral bus to make it into two separate busses (one for neutral and one for earth).  Only in the Main Panel are the two connected.  This means that the wire from the Main Panel to a Sub-panel needs to have 4 conductors:  Live1, Live2, Neutral, and Earth.  It is ok for the earth wire to not be separately insulated, but the other three need to be individually insulated.  When connecting wire to the sub-panel for a 110V circuit (eg a string of power sockets) then you will connect the live to a suitable breaker, the neutral to the neutral bus, and the earth to the earth bus.

Main-Lug sub-panels

If you decide that it is not a required convenience to have a master on/off breaker on your sub-panel, then you can use a "Main-Lug" instead of a full panel.  This may be a reasonable choice if you just want to distribute power to a shed.  If there is no main breaker then you will rely on the breaker in the main panel to provide the current limiting and to provide a master on/off switch.  A good Siemens main-lug that provides 8 spaces for full sized breakers, has copper bus bars, has an included earth bus bar, and can be installed outside is here .

Siemens 8/16 Main Lug Outdoor 


Having good grounding for all your electrical panels will protect the electronics in your house and might even safe your life.  When surge protectors trigger they need to be able to dump excess energy into the ground and you need to get rid of that energy or else the surge protector will not help you.

Rather than just using the two building code specified 6 foot separated metal stakes in the ground it is worth going above a beyond.  Using 10 copper clad 8 foot long 5/8" diameter stakes driven into earth (not stones) that rain water will flow to will provide a much better ground.  Put the first two stakes close to the panel with about an 8 foot spacing because this will ensure you meet building code.  In my case I have two subpanels so I need two stakes for each panel to meet building code.  Put the other 8 stakes in an earth swale (shallow ditch to channel ground water flow).  Use 6" of gravel in the swale to help water collect.  Put the stakes about 10 feet apart and bang them in so that the tops are 6" below the surface (the 6" will be covered by gravel).  Connect all the stakes using thick stranded copper wire of at least #4 diameter.  Use good quality ground clamps (UL approved for burial) to daisy-chain attach the wire to the stakes.

Ground clampDetails are here .

Keep the wire a continuous piece rather than having any joins.  It is best to wrap the wire round the stake and put the clamp over the wrapped wire.  Burry the wire between stakes 6" below the surface.  If you have a Well then layout the stakes in the direction of the Well and continue the wire on past the stakes to the Well metal casing.  This will need something like a total of 150 feet of earth wire because there is a building exclusion area of 100 feet radius around any Well.  The metal casing of a Well is a very good earth so it is highly beneficial to connect it into your grounding system.  I route the earth wire along the south edge of the driveway in a small swale.  In the ditch there are 6 stakes (in addition to the two on the west of the house and the four north of the north house wall just behind the electric panels).

Even though a sub-panel must separately connect the earth back to the earth of the main panel (and the ground in the sub-panel must not be connected to the neutral in the sub-panel), it is still highly desirable to provide a grounding system associated with the sub-panel.  Having a good earth close to your actual house (rather than the main panel in your yard) is actually the most important because all your sensitive electronics will mainly be in your house.  In my case, the main panel in the yard just has a grounding system that just meets code by having two earth stakes.  Associated with the house (ie the house sub-panels) there is a really good "12 stake + Well" grounding system.  If the main panel in the yard gets hit by lightning then it may even be that the lowest resistance path to earth will be via the ground wire to the sub-panel and from there to the house grounding system, but that's perfectly ok.

Inside your house you should run a ground wire back to the panel ground for anything large that is metal, eg duct work, garage door runners, etc.  To avoid having to run too many ground wires it is best to avoid metal conduit, metal pipes, and metal electrical boxes.  Using plastic is a much better choice.

Whole house power surge arrestor

It is highly recommended that you install a whole house power surge arrestor in your main panel and in any sub-panel that feeds electronic equipment.  A good brand I have found is from Tytewadd and it's detailed here .

Tytewadd whole house power surge arrestor 

This will clamp your 120V to stop it exceeding 130V, and clamp your 240V to stop it exceeding 260V.  In the case of a large event such as a lightening strike it may sacrifice itself in the process and become a short circuit to trip your breaker.  You should install it on an in-use high current dual pole breaker in your panel so that it's obvious to you if the surge arrestor has had to sacrifice itself.

In my case I have one in the 600A main panel but connected the other side of the 200A breaker that feeds the primary sub-panel in the house.  It protects all of the 600A circuit but only the 200A breaker will trip if it has to sacrifice itself.  I also have another one in the house sub-panel that feeds sensitive electronics.  This is connected just after the main sub-panel switch, ie relies on the breaker in the main panel that feeds the sub-panel.  If the one in the house sacrifices itself then I will know because none of the lights in the house will work.


When digging a trench it is worth adding lots of spare conduit.  This picture shows the first set of conduit.

Spare electrical conduit

The following picture shows the second layer of conduit (almost all 2" diameter).

Second set of conduit at main panel 

In terms of diameter for your money, 2" schedule 40 conduit is a good choice because it is sold in high volume and that keeps the price down.  A 10 foot length of 2" conduit is about $4.  You can just about pull 4 wires of 2/0 diameter each through a 2" diameter conduit.  In my case I have four runs of 2" diameter conduit from the main panel to the house.

Make sure you label all your conduit because it's easy to forget where they all go.

Label all the conduit 


Backup Power

General principle

You cannot just feed power from a generator back into your house wiring.  This would be very dangerous and may electrocute power workers who are working to restore utility power to your house.  It is necessary to have proper certified changeover switches that switch from utility power to generator power via a completely off state.  You could use a huge switch into your main panel for this, but a much better idea is to use lots of smaller switches on the circuits that you will actually need during a power outage.

Example things that need power during an outage include:

Well water pressure pump
Well submersible pump
PC and home network for internet
Fans etc for heating system
One or two small electrical heaters

Septic systems don't need to be powered during a power outage, assuming the outage only lasts a maximum of a day or two because the first tank has enough extra capacity without being pumped into the second tank.

In practice you will want to keep the total power usage to under about 4000 watts so that you can buy a mainstream economical generator.  Here are some guideline power usage figures...

Power usage guidelines


It is very important to get a generator that has a 230V (ie dual pole) output.  Here's one that I think is a good choice.

Champion generator 46514 Details are here .

I recommend buying two economically priced generators rather than one more expensive one so that you have redundancy rather than a single point of failure.

Generator Transfer Panel

Once you have decided which circuits will need power,  you wire from the generator transfer panel.  The generator transfer panel looks like and behaves like a subpanel.  The unit chosen needs to be able to accommodate arc-fault breakers.

TransGen Wiring Diagram

The best units are made by GenTran.  They do internal and external versions with various power handling capabilities.  Here's one I think is a good choice for outside use...

GenTran R200660 20-Amp 6-Circuit Outdoor Generator Transfer Switch for Generators up to 5000 Watts

Details are here (including installation instructions).

The instructions actually make it sound harder than it really is.  You feed the transfer panel from a 60A dual breaker in the Main Panel.  This goes via four 6-guage wires to the Transfer Panel.  Because the Transfer Panel is a Sub-Panel, the earth and neutral is kept separate.  All things that you want to be available for backup power you wire to the breakers in the transfer panel.

GenTrans generator panel 

For use inside your house use an internal version.  Only the internal versions have power balancing meters, so are the best choice for household circuits.  Here's what I think is the most suitable model...

GenTran 200660 PowerStay 20 Amp Manual Generator Transfer Switch       $273 + tax

Generator Transfer Internal Panel 

Here's the GenTrans wiring details (both internal and external) (click image for higher resolution)...

GenTrans wiring details

An interesting point is that all the circuits that you decide need power during an outage will always be powered by the generator transfer panel even when not using a generator.  To cater for the fact that you will not be as power conscious when not in a power outage, the generator panel can provide more power when not in generator mode.  The GenTran units shown above are fed with a dual pole 60 amp breaker from the main panel.  You need to make sure the maximum current you ever use when not in a power outage is below that dual pole 60 amps.

Exterior connection box and cable

If mounting inside then you will need a connection box on the outside of your house (the generator MUST be used outside because of exhaust fumes).

GenTran 20 Amp 125/250-Volt Non-Metallic Generator Power Inlet Box NEMA L14-20 with Spring-Loaded Flip Lid         $48

Generator connection box 

When wiring an L14-20 (or an L14-30) plug or socket, G is (green) ground, W is (white) neutral, Red and Black are the interchangeable Live1 and Live2 and go on the X and Y terminals.

Reliance Controls PC2020 20-Feet 20-Amp L14-20 Generator Power Cord for up to 5000-Watt Generators         $48 + tax

GeneratorCable L14-20 

For the generator you may need to put an L14-30 plug on the end of the wire (instead of an L14-20 plug).  The wiring for an L14-30 plug is as per this diagram (from:

L14-30 wiring diagram 

Other details and my plot specific details

In my case because of the configuration of the wiring around my property, I need two transfer panels and two generators, ie two separate setups.  My main panel and my electricity meter are mounted outside on the driveway.  There are feeds from there to the well house and various out buildings, as well as a feed to the subpanel in the main house.  I use an external generator transfer panel and generator to power the well house and out buildings during a power outage.

External generator transfer panel in yard

Inside the house, next to the internal subpanel that does lighting and electronics, I use an internal generator transfer panel fed via an external connector box and another generator.  Note that the other house subpanel that powers the heavy current appliances does not have any power backup so none of these will be able to operate during a power outage.

The two generators are both 4000W and are interchangeable and movable.  If one fails then one generator will be used most of the time for the house, but moved to the outside transfer panel for 10 minutes whenever the water pressure has dropped (and the faucets stop working).  Note that even when both generators are functional, it is only necessary to run the generator on the external panel that feeds the well house occasionally and this will save gas.

Take heed of the fact that you can never exceed dual pole 60 amps even when not in a power outage.  Here are the calculations for the external generator transfer panel...

Well submersible pump             6A 230V (Dual pole)
Water pressure pump               10A 230V (Dual pole)
Power tools in the well house    14A 110V (Single pole)
Well house heater                     14A 110V (Single pole)

The Well house needs a 30A dual pole breaker (possibly could be 40A).  That leaves only a 30A (possibly 20A) dual pole for everything else fed from the external generator transfer panel.

During a power outage it is necessary to keep the well house power usage to under 20A dual pole or the generator circuit breaker (in the transfer panel or on the actual generator) will keep tripping.  If this happens then you will need to in the well house sub-panel turn off the breaker to the submersible pump and just rely on the stored water in the tank.  If the tank runs dry then turn off the breaker to the pressure pump and let the submersible pump have power for a while.

The septic system does not need to be fed from a generator transfer panel on the assumption that a power outage will be less than a day or two.  To allow for a more serious longer outage it is worth putting an inline L14-20 plug and socket arrangement so you can manually plug in a generator for an hour every couple of days to pump sewage from the first tank to the second tank and out to the drain field.

It is not practical to have your garage (with lots of power tools etc) powered from the generator transfer panel.  Instead you should pick a suitable 20A single pole (ie 115V) power outlet in the yard that is powered by the generator transfer panel and then run an extension cord if you need a particular power tool during a power outage.  If it is an out-building without power tools then it is practical to feed it from the Transfer Panel.

A typical household electric hot water heating boiler is too much current to be powered from an economical mainstream generator.  In order to provide at least some hot water during a power outage (and assuming you do not have natural gas or propane available) one option is to have a small electric boiler, eg a 6-20 gallon unit.  It is good to use a 115V 15A unit (ie single pole) so that this can be used on one pole while the other pole is used for eg an electric oil filled radiator (also 115V 15A).



Wire strippers

It is worth getting great wire strippers, particularly as they are not expensive.  I recommend getting a Gardner Bender SE-92 Heavy Duty Automatic Wire Stripper.

Wire strippers Details are here .

Long nose pliers


Diagonal cutters


Flat nose


End cutters


Locknut tool

Electrical locknut tool   Purchasing details are here .


Radio flyer wagon

Contrary to popular belief, these little carts are not just for kids.  A cart is a really useful way to keep your tools organized as you move from location to location throughout the house.

Radio Flyer cart Details are here .


Electrical Outlets

All power outlets need to be tamper resistant to meet building code.


All GFCI power outlets to meet building code must be tamper resistant.  Typically you use a 20 amp GFCI as the first socket in a chain and then connect lots of regular power outlets to the load terminals of the GFCI.

GFCI tamper resist 20A Cooper   Purchasing details are here .

In bathrooms and other wet rooms (as well as outside) it is good to use a waterproof version.  It does not have to be 20A (15A would do) but I use 20A).

GFCI weather and tamper resist   Purchasing details are here .

Typically regular power outlets are 15A.  I prefer the more modern "decora" rectangular style.  To meet building code, they must be tamper resistant.

Power outlet   Purchasing details are here .

You can get USB outlets for charging phones etc.

USB charging socket Cooper   Purchasing details are here .

Fill in blank positions...

Decora blank white   Purchasing details are here .

Decora with Cat-6 hole...

Decora Cat6 hole   Purchasing details are here .


It is best to use home automation switches (eg Insteon), but if you need a less expensive alternative then use regular decora rocker switches.  You can always replace these with home automation ones later.

Decora rocker switch Cooper Purchasing details are here .


Electrical boxes

Use plastic electrical boxes in the walls because it avoids having to ground them.

Use the deepest possible electrical boxes so you have plenty of room.

Label all wiring with labels designed for the purpose that will not fall off with age.  Take photos of wiring before putting up the drywall.  I also write in the Romex jacket using a ballpoint pen.

Electrical Box 2Gang 32 cu in Carlon Details are here .

Available from Lowes or HomeDepot for under $1 each.  Before using, need to perform the following operations on the box...

Pull out nails.
Cut off nail lugs with a chop saw.
Get rid of the little positioning lugs using a chissel.
Measure half way down the sides and draw a line with a square all the way up the side to the top.  Half way is about 1-13/15" from the edges, but measure from both faces to get high accuracy.

(There is no need to drill holes or bend away the wire hole lugs.)

Screw the electrical box in place using 1-1/4" screws with the box center line lining up with center lines drawn on 2-by drywall supports.  Needs to be 3/8" proud of the 2-by surface.  Use a 3/8 thick piece of wood as a template.

Electrical box protrusion spacer

Use a clamp too get the box positioned on the height line and with the right protrusion.  Use a long entension on the screwdriver so the angle is not enough to cause the box to get pulled back by the screw tightening.  The screw makes its own hole in the plastic and then into the wood.  Two screws are used on each side so the box is ridgedly supported.

Screwing clamped electrical boxes 

Electrical box double supported 

Electrical boxes and sockets fitted 

Bathrrom GFCI...

Bathroom GFCI electricsl box 

Bathroom light rough-in...

Bathroom light rough-in 


Smoke Detectors

Smoke and CO detectors

Need to use 14/03 wiring in a continuous dedecated circuit.  Note that it needs a red wire which is used as the interconnect.  Could use thinner than 14 guage but it is probably cheaper and easier to use regular 14 household wire.

Smoke alarm wiring

Buying info here .


Hidden lighting

Rather than buy expensive light fittings I like to hide the lights so you cannot see the cheap ugly bulb holder and you don't get glare directly from the bulb.


Electrical Ring Nut Spanner 

Lights Bedroom Holders



Random notes (not yet sorted)

Washington State requires 6” between high and low voltage wiring (in the house walls), which is according to NEC.

If you’re going to run low-voltage conduit (which I personally do not bother with), consider using PEX.  It’s a smooth, continuous pipe, flexible enough to bend around corners, stiff enough to prevent right angle bends that would snag cable, and it’s intended for home-run (starred) type systems.


Basic rules

Keep high voltage and low voltage very separate

Don’t share holes. Don’t share wire bundles. Don’t share boxes.

Don’t run wire in air ducts.


The rules-of-thumb for running low voltage cabling

Try to maintain 12 inch separation from HV on parallel runs; the longer the run, the more important this is.

Cross HV at right angles.

Keep your runs neat and well-corralled.

Leave a longer loose end at the box and at the wiring closet than you think you need.

Run more than you think you’ll need.

Run better quality than you think you need.

Cat6 or better for network; RG6 or RG6Quad for Cable/Satellite/OTA.

Run 4-pair for telephones (use up that leftover Cat5).

Use good quality “F”-type compression ends on coax.

Use a real tool to install those fittings on the wire.

Don’t run wire through an air duct.

Consider running plastic conduit.

Take photos before the drywall goes up or the floor sheathing goes down.