Installing A Generator Transfer Switch at Zach’s House. 2/12/11

Zach says… Let’s make it easy, so Elmo can do it..  

Zach wants a standby generator

My first choice for a transfer switch allows you to transfer four to six different loads over to the generator VS moving the whole breaker box off the commercial grid and onto the generator. I find people get into big trouble with the bulk transfer switches, and a lot of people learn the hard way as to what they shouldn’t do.  Some who know and like the term ‘whole house generator’ are inexperienced and they might tell you they’d do it differently next time.  My approach to getting through an outage is to get through with reasonable comfort, not live with every convenience. Load management is pretty easy, and simple relay logic can automatically strip (kill) other loads when a hard to start load runs (a well pump is a typical example).   People learn in a hurry that some loads are hard to start but once running, the generator can easily carry them and more.

In Zach’s house, we will be using a six circuit transfer switch, and one or all can be transferred back and forth from commercial to the generator power.

The house breaker panel is near ideally located on the east wall of the garage (front of the house facing south). The builder  installed the electrical service boxed in a ‘raceway’ so the circuit panel is really easy to run gen wiring to.  We’ll be able to bring in a dedicated generator cable from outside, up the raceway and directly into the panel or the transfer switch with little effort.  The goal is to be able to monitor the generator performance from any live plug in in the house with a Kill A WATT, and to be able to start it and transfer loads to the Generator from the breaker panel in the garage.

This house uses natural gas for hot water heating, for the kitchen stove top, and for a gas fireplace in the family room.  The natural gas furnace needs 120 VAC only for the blower motor, there’s only two 240 VAC loads in the whole house, one is for the electric clothes dryer, one is for a kitchen oven.  Lee and and Dana (Zach’s Mom and Dad) developed their priority list, they decided they’d cook in the microwave, or on the natural gas stove top, and the Clothes Dryer was just not all that important of load when the power is out.

 Six Circuits will provide essentials and many conveniences while on the generator, and making changes in priority will be easy if they decide to do so later.

In this case, the transfer switch was mounted up against the left side of the raceway with the bottom of the surface mounted transfer switch even with the bottom of the circuit panel cover, this gave the appearance of symmetry, and the transfer panel and the circuit panels are level with one another making it look like there was a plan when it was installed.  There are eight wires total that run from the transfer switch, two wires each for six circuits, plus a ground and a neutral wire. All eight of these wires run through a piece of metal conduit about two inches showing from the bottom of the transfer switch through the side of the raceway and then up through the bottom of the main breaker panel.

Each circuit has a red wire, and a black wire. In our case, we chose a Reliance brand transfer switch, and I found the best price to be though Amazon even after paying our high State Sales Tax. I believe I saved about $50 over the local Home Depot price, but I didn’t get the DVD, nor did I get a remote box to put a generator plug in, but I didn’t need for this install. All the info on the DVD is also on line, so no loss there.


The small picture to the left shows watt meters, and that round plug to the right doesn’t have to be mounted when you don’t need it. If you are curious, the watt meters use a current transformer, the generator’s hot wire passes through the center of the small current transformer. Notice the ganged together breaker in the center, this is for a 240 VAC circuit, and if you don’t need it, just take the metal tie off the two center transfer switches and use them as individual 120 VAC transfers.

Installing the transfer switch is a snap, you’ll run the heavy neutral wire (white)  to the neutral bus bar, and the green wire to the ground bus which in most cases will be the neutral bus when it’s the main breaker panel as it is in this install. Once these are made. look for the red and black wires with the letter “A” on them. Turn off the breaker you’ve identified, and remove the breaker, with a screw driver, loosen the screw and remove the circuit wire going to the breaker.  Strip the red wire, insert the stripped end into the breaker and tighten the screw, now take the black wire, and strip it, and use the correct size wire nut to tie the circuit wire and the black wire marked “A” together. Always tug on the wires after you get them in the wire nut, and prove a good connection. Replace the breaker, dress the wires neatly back against the sides of the box, and turn the breaker back on.  Make sure that the A switch on the Gen transfer switch is in the ‘line’ position (down).

Reliance Transfer Switch Typical-Installation

NOTE: There are folks that strip wires with diagonal pliers, side cutters, knives, and other things. When you are installing a $250-$300 transfer switch, you will buy or borrow a quality stripper and you will use the correct gauge hole!  Nicking solid wire is not smart, as for stranded, you want every strand to be whole and none nicked or cut. If you are guessing at gauge, start with the bigger hole and work down till you are able to remove all the insulation.

With the “A” circuit done, Identify the next breaker on your priority list, and find the RED and Black leads marked “B” from the gen transfer, repeat the steps till you’ve got all six circuits wired. If you are carless, if you want to work with higher safety.. open the main breaker and do your work on a dead box.  A lot of experienced hands will check out each circuit as they go, and catch errors as they go.

Once you get all six circuits wired in, and all six circuits switched down to ‘Line’,  you can use the breaker panel and circuits as normal. The next step will be to wire in the generator, and that might be on another day, so this is a good place to stop.

Do take note that we are doing this particular install with 120VAC circuits only, and that allows us to wire our generator for 120 VAC only operation.  There is a big advantage as we need not worry about balancing the load on our generator, the stator windings will be wired in parallel, and we will need run only three wires between the generator and the transfer switch. these will be a white for Neutral, a green for Ground, and a Black or RED for the hot wire (120VAC).

One mistake people make a lot of the time is setting up a generator wrong as per grounds WHEN it is wired into a main panel as this one is.  At the generator you will drive a ground rod, and tie it to the generator frame. YOU WILL NOT tie the neutral and ground together at the generator head as this will violate our grounding plan.  A neutral is designed to carry normal current, a ground is designed to carry fault current only. If you were to strap neutral and ground together at the generator end, AND the panel end, you are effectively running without a ground.

As we think about this run between the generator and home breaker panel, we also think about remote start, low oil pressure alarms, and other items. In our case, we are installing an electric start generator, we will run a number of control leads, and a small battery lead back to the generator start battery so we can trickle charge the battery. With this in place, we can place a small light near the panel powered by the generator battery so we might use it to see our switches, monitor alarm lights, and starter switch. Whatever leads we run will be placed inside conduit between the bottom of the raceway, through to the outside wall, and to the generator set.  Pictures will be added to this page as we progress with the install.

Here’s some drawings done quickly in ‘paint’ to show you exactly how the transfer works.

Ckt Breaker

Ckt Breaker

Above: Here’s one circuit in that big panel, but they’re all the same in this case,  The circuit breaker is what feeds the individual circuits in the house, the black wire leaves the breaker and powers a specific circuit or circuits in your house.  Now look at the next drawing to see how we add the transfer switch to the circuit above.

Transfer Switch in normal position for ‘LINE’ side operation

In this drawing, you can see that we just put our transfer switch in series with the breaker and the wire that feeds our individual circuit we wanted to power from the generator. Note that the transfer switch acts like a ‘pass through’ when it’s in the normal commercial or ‘grid’ power position.

Zach’s installation is a work in progress, expect more to be added to this post.  In my opinion, this is a fairly easy job. Popping the breakers one at a time can allow you to do all the work on a hot box if you are careful.  Any worries on your part about becoming dead from electrocution can be set aside by killing the main breaker, just work on the project dead.  Outside of killing yourself, beginners make mistakes by improperly stripping wires, (cuting into the copper) leaving connections loose, like not tightening the breaker screw tight enough, or not using the proper sized wire nut for the gauge size and number of wires joined.  Always look to assure both bare ends are equal in length, and fully inserted into the wire nut before twisting them together.  Double check your work, and remember loose connections can ruin appliances and even start a fire.  This is an easy job,  Zach and Elmo could likely do it after they read this post, and the instructions that are found on line for the Reliance Transfer Switch.

For those who read this far, it’s very important that you use a quality screw driver bit to loosen the screws on circuit breakers, newer ones have more positive fasteners that can take a little more torque when you try to loosen something that was over tightened when installed.  If the screw is a standard slot, use a brand new quality screw driver bit, and make sure you are square and at the bottom of the slot before you attempt to remove it! When you strip that screw head off, you’ll be going to the hardware store to find another breaker, and you’ll hope they have your brand.

When you are pricing a transfer switch, think about the cost of the quality SPDT switches and  circuit breakers and the other pieces that are often included, it may be false economy to attempt to build one.  There are other solutions out there, one is an interlock system that you can get for your house breaker panel, it creates an interlock system where your main breaker must be off, before you activate another breaker to feed your main panel.  A potential problem with an interlock system is the difference between a circuit breaker and a switch.  In some jurisdictions, the circuit breaker MUST be rated for use as a switch, (they may be more expensive) and opening the main circuit breaker and using another breaker to feed the panel may be illegal unless it meets this rating.  It’s best that we assure that every part of the job meets every electrical code in your area.  Part of the code is to have every breaker labeled.  Another sign of unprofessional work is when wires are found entering a ragged hole in the metal box,  you need an approved grommet. You want your job to be 100 percent legal.

Study your needs prior to the install

Before  installing the typical interlock system,  turn off every breaker and verify all the plugs lights, and appliances it feeds. It’s very handy to make yourself a note book for the generator with this informaiton in it. The first position transfer switch might include the lights in the garage if that’s where your transfer switch is.  The second might be lights in the kitchen, and dining area.  The third is often the family room, where entertainment and news is available, this is often the gathering place during outages.  The following transfer switch position might be the bathroom on the main floor.  

Do a good job of marking panels, and what the switches feed.  Turn them on in order, and watch to assure you do not exceed the rated load of the generator.  

Some people forget the sequence of events, and the person that knows the operation is not always there when the back up generator is needed,  this is the reason you need a simple set of instructions above the transfer switch.

Step one.  Assure that none of the transfer switches are in the generator position.

Step two.  start the generator after verifying fuel, lube oil, and more.

Step three, verify frequency and  voltage from generator.

Step four, Stat Generator, let it wwarm up, Start transfering loads from commercial power to the generator one by one and watch the load.  

The generator transfer switchs are more fool proof, and it’s more difficult to make a mistake compared to the bulk transfer switch.  Of course that’s my opinion, and I could easily write a book as to why. Part of the reason is it allows us to make use of a smaller generator with more certainty that we won’t overwhelm the generator. Larger generators burn a lot of fuel, one of the more popular strategies of getting through an outage is to conserve the fuel you have on hand.  To blaze through all your fuel half way through the outage and sit in the dark for a day or two is no fun, but you won’t be able to claim you were the first to do it..      

It’s always smart to start out with a consulting session, Zach says “Make it easy for Elmo to do it.”

If you live down South where Air conditioning is ‘a must’ part of the year, your approach may be very different than what we typically do up North.  No matter what your requirements are, it all starts with a priority list of items you want to power during an outage.  Most of us think about where we huddle during a storm or hurricane, we may want lights there, and of course we’ll want the TV, radio, our WIFI router, and our telephone to work.  Cell phone chargers are normally a high priority. It passes time to have the news about how bad things are out there, if the local gas station is without power, you won’t venture out to get fuel there.  Being able to make hot/cold drinks, soup, and of course to keep the stuff in the fridge from spoiling are normally high on the priority list.

We might have a natural gas or propane furnace, hot water heater, or fireplace, will they work without electricity? Are there electric igniters or blowers that must work in order to use them? These loads may be higher priority as well.

Another important load is the well pump if you have one, and what about some plug ins in the kitchen, overhead kitchen lights, maybe even the light in the master bedroom and the bathroom light? Here’s where the transfer switch can come in real handy with a small generator, some generators just barely start a well pump, and you need to know your generator will do that BEFORE you buy it! Monitoring the voltage with an inexpensive  KILL A WATT is a good way to see how that pump starts. Stripping off all the loads, starting the pump by itself, allowing a pressure tank to fill, and then turning off the pump Is a viable solution, once the pump is off, you turn the other load back on.

The bravest of married men will make a priority list on their own, if you have a women in the house, it’s wise to get her input of priorities, .. especially if she is going to cook your meals, but if she wants her electric clothes dryer, and electric hot water heater to run at the same time during a power outage, it may be cheaper to just divorce Her than buy that big generator, and the fuel you’ll burn might be a shock..

Following are other articles about the generator install at Zach’s House.


more to follow, so come back and visit.

George B.





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12 Responses to Installing A Generator Transfer Switch at Zach’s House. 2/12/11

  1. Bill knighton says:

    I really like 3 phase motors and frequency drives because you can set them for about 1 second acceleration and the nothing dims when starting. I can start multiple 2 and 3 horsepower three phase motors from my outback inverter or listeroid with no concearns at all or dimming lights, but when the single phase table saw or well pump comes on all the ballasted fluorescent lights dim badly, though not the compact flourescents.

  2. George B. says:

    Bill, motors behave very differently depending on what’s tied to them (load), table saw should be an earier start compared to some.. The well pump builders are missing a great op I think. There’s a market for a one hp three phase down the well pump with a 3 phase VFD controller that will automatically manage a start based on the voltage drop at the single phase input. A friendly pump for inverters to run.

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  5. curlie says:

    This was a very good comprehensive article. I researched this topic extensively before installing an interlock-type transfer switch for a 5500 watt genset and did not come across the fact re: breakers must be switch-rated, so I learned something. Since I will only use the pair of breakers once every couple of years, I’ll risk that they can be turned on and off a few times per decade since there’s no strict inspection in my rural area.
    – I did come across the info about a bonded or broken neutral and many thanks to the author for mentioning that. I easily located the wiring under a cover on my genset and installed a 50A toggle to make or break the bonding. I then labeled the portable generator near the switch with my two options, Portable or Home. You want the two bonded when you use the genset as a portable, for example, running a skill saw away from house current to build a shed on the back forty and not bonded when hooked to the house. Only one ground to a system is the key.
    – I installed my xfer switch a couple of years ago and used it during Isaac-related outage recently. It worked like a charm and was very nice not to have cords (and mosquitoes) running (flying) in the windows. Although the generator is rated to handle everything in my new sub-panel, I still used caution and turned my one-room a/c (12, 000 btu) off when I started the well. I only ran the water well for a few hours each twice a day period to get everything and everyone clean.
    – Again , this is one of the most comprehensive and informative articles I’ve seen, and I’ve read many.

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  9. David Pittsley says:

    I have a problem with my newly purchased home with a generator transfer switch previously installed and the generator left by the owners, knowing that winter was on its way I started the generator to make sure I had 240 volts and I did, so chase to winter, the power is out so I start the generator and put my transfer switch to generator from the off position on the transfer switch and it pops the 30 amp circuit breaker on the generator so I could only power up the 120 v circuits on the other generator leg that was live. I disconnect the red, black, and the neutral from the generator to the house neutral and the transfer switch leads and I read 120 volts from the black feed to the generator neutral and 120 volts from the red feed to the generator neutral and 240 volts between the red and black generator leads as would be expected but when I measure the black generator lead to the house neutral I get 0 volts and from the red generator lead to the house neutral I get 240 volts and the red generator lead is the same one popping the 30 amp generator circuit, I do not see anything that could be back feeding the house neutral, even with the main off it is popping the 30 amp generator circuit, when it does this the generator almost bogs down so much that it almost stops but the circuit trips before that happens, like there is a huge load on it just on the red lead side of the generator can anyone help, I am pretty comfortable with electricity having previously wiring a transfer switch at my previous home with no problems, the only thing different is the generator ground is wired back to the house ground could this be the problem?

    • George B. says:

      First rule: Never assume! There are a lot of different types of transfer switches, and one of the most fool proof are the types that transfer circuits one at a time from the grid onto the generator. I’m not sure what you have, or whether you’re just over loading your generator, I have not ideal if it’s manual or auto trans, or a bulk transfer..

      Here’s where I would start. prove that neutral and ground are not bonded at the generator head.

      Verify all wiring between generator and the circuit breaker that feeds into your transfer switch. Make sure this breaker is open,

      Find the leads laid down between generator and main panel, (ground and neutral), lift the neutral and then read the resistance between ground and neutral looking back towards generator, you should have an open, this will prove that these leads are not bonded together rendering the ground between gen frame and ground bus in main box useless. Lay neutral back down.

      start generator and verify all is straight, that you read 120V between the black and neutral, that you have 120V between red and neutral. Now check and make sure you have 240VAC across red-black.

      Open all breakers in service box, including main, make sure you are isolated from the grid. Close gen breaker, and see if generator changes exhaust not at all, if you have amp meter on gen look for any kind of load at all. Experiment with loads onto the generator one at a time.

      This is no guide, bu rather a place to start….


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