I created this page to answer some of the questions that are normally asked to me by my customers. Please understand that it was created only as an FYI so that you can have a better idea of what you're looking at and a basic understanding of how they work. There are many different types of installations so based on your needs and your home's wiring. Multiple electrical panels can create installation issues as far as controlling emergency loads in different panels for example.
You can also go to Utube to see some installations but a lot of those videos are dangerous do it yourselfers, so stick to the professionals and manufacturer's videos.
Please be advised that if you do not get an electrical permit on an installation you are setting yourself up for problems later on. A lot of these contractors are just throwing equipment together knowing that it is not getting inspected. The grounding and wiring must be done right or you will void your warranty on the equipment and have a serious potential for a dangerous installation. It is rare that any two installations are the same, so make sure you call licensed professionals and get it inspected.
There are two basic types of emergency generator systems. I've described them as best I can so you can decide which one you will want to go with depending on your needs and finances. Just like anything else, you can get entry level models or you can go high end.
Many times homeowners will go with the manual type transfer switch because they are much cheaper to install, control only emergency loads, and do not require you to bring in a property survey for the location of the stand alone type, nor do you need a plumbing contractor for the alternate fuel supply, i.e. natural gas or propane.
Portable Generator with a Manual Transfer Switch
Control emergency loads safely
*Amount of circuits that can be controlled contingent on size of generator, 220 volt receptacle configuration and generator wattage capacity.
How it works
You pick which circuits you want to control in the event of a power outage and we run them through the transfer switch. These circuits will run normally on "street power". When the power goes out, you plug in your generator with a power cord made especially for this application and then walk over to your transfer switch and manually turn on the circuits you want to control. The transfer switch has a neutral position on the switch and two "on" positions. One "on" position will have street power running through it in a normal condition. When you flip the switch to other "on" position, the emergency position, now power is coming through the switch from your generator cord. This is very important because when power comes back on from the street there is no chance that the two power sources will collide because the three position switch prevents that. Once power is restored you'll know because the other non-emergency loads will turn on by themselves. At that point you would just shut your generator down, unplug the cord and flip the switches back to the normal position.
Remember this, power outages in the summer are generally short and you can just plug your refrigerator, light, sump pump and other "cord connected" loads into a portable generator. Winter ice storms however can last much longer because of the downed trees, power lines and the big reason you need power...you need heat to prevent your water pipes from freezing and bursting open. When they thaw the water damage can be devastating especially if you are not home because you are staying elsewhere and not able to shut off the water main. Your furnace can not be cord connected to your generator nor can your well if you have one.
*Other creative methods of "back feeding" circuit breakers is very dangerous. There is a potential for damage to the generator from overloading because you can have too many circuits trying to run and worse....if you do not turn off the main circuit breaker coming in from the street you are "back feeding" and energizing the power lines coming in to your home and can kill someone
working on the outage!
Simple all in one kit *Available in 6 or 10 circuit.
There are ways to do this safely back feed an electrical panel through a device called an "Interlock Kit". This type of installation is ideal for an installation that has multiple electrical panels being fed from one generator or a user that has more 220 volt needs than what is provided through the manual type transfer switch. Ideally used with the larger generators of 7000 watts and above. This device is safe if used correctly but you have the potential to overload your generator and possibly damage it. The main circuit breakers on the generators are only going to trip so many times before they fail open. I've installed quite a few of these purchased through this UL tested and approved manufacturer. You will need that UL listing to pass the required electrical inspection on that installation. I also think these guys provide the best product and have a great video to show you how it works. **Again, repeated overloading of your generator can damage the generator, so unless you are completly comfortable with this type of installation, opt for the manual type transfer switch.
*Be aware that if your interlock is not made from the manufacturer of your electrical panel then it must be UL listed approved for use or you will not pass an electrical inspection.
New installation of service equipment with an integral Interlock built in to the cover from the manufacturer.
Avoid waiting too long to get started. Any hint of a coming storm has all available generators and supporting equipment sold out in a hurry. Ideally the generators with a 4-wire, 250 volt, 30 amp twist-lock receptacle can handle more loads than the smaller 20 amp 4-wire models which are installed on smaller generators so bigger is better, but it must have a 4-wire receptacle. This receptacle sends 220 volt power, a neutral and a ground wire. 3 wire configurations on generators are made for construction site applications, i.e. table saws, and can not be used to control a transfer switch.
Keep in mind that the smaller 6 circuit transfer switches are sized for generators under 6000 watts and generally have 15 amp circuit breakers for your lighter loads, i.e. lighting, furnace and maybe one 220 volt for a well. If you want to control 20 amp circuits, i.e. kitchen circuits then you will want to go with generators above 7000 watts and a 10 circuit transfer switch.
*No matter what generator you buy, it must have a 4-wire twist lock receptacle. This configuration will carry 2-120 volt "live" phases (220 volts) a neutral (white wire) and a ground wire (green).
**Also - Because generators can have fluctuations in voltage and often do, they can damage electronic equipment. If your generator does not have a power conditioner feature that comes with the more expensive models, then you should buy one for your more expensive TV's and computers. They can run $100. each and upwards depending on how many items you want to protect at each location. Different locations would need one at each location. A power conditioner is not to be confused with a surge protector type "power strip" that protects against voltage spikes from say, a lightning strike. Unlike an incandescent light bulb that can be dimmed by decreasing the voltage, electronic equipment needs a constant clean power source, and that's what a power conditioner does.
Automatic or Manual Standby
How It Works
The Automatic Standby Generator System starts automatically in the event of a power outage – even if you are not at home. And, it is designed to shut down when utility power is restored.
A manual type is very similar but the transition is done by a single manual switch similar to the main circuit breaker in your home and designed to prevent a "back feeding" condition to the utility power. Not recommended for those who like to travel.
*There are many options that come with this type of system and is based on your type of alternative fuel, propane or natural gas for example. Also the amount of loads to be served would be the main factor in sizing a generator. You could either control your whole house, or just a preset amount of emergency loads. There are also other options that can be considered like an automatic scheduled start up for some of the higher end models to ensure your system will be ready when you need it. I strongly advise you to have a generator service contractor to maintain the system. You can save a lot of money buying it yourself and hiring the contractors to install it but after the installation, neither an electrician nor a plumber will have service parts in the event an electronic or engine part fails. It's just not what we stock or do as contractors. We are installers whereas generator service contractors install, repair and do maintenance to the engine and the electronics. They do not have to be licensed as an electrical or plumbing contractor and normally will sub contract out the installation portion that needs licensed contractors for the installation and permits. Hardwired electrical installations rarely fail so there's nothing much we can do to repair it so a service contractor would be the cost effective and timely way to get it done. They will know the equipment and know the parts that fail the most, generally a circuit board that they can easily get from their suppliers. They also do oil changes and other scheduled maintenance to the engine.
Personally I advise my customers to have larger companies that have licensed electricians and plumbers do the whole job. They will sell you the generator, install it, maintain it and be there if it fails. They will know what the error codes that read out on the display mean and generally will have the parts available. The last thing you want is to have an impending storm approaching and a contractor tell you they can't get there to test the unit or worse, have it not start and then tell you they don't know what's wrong with it. Quite honestly you're not really saving any money being the contractor and buying it yourself.
Here's a few links if you want to order them yourself. Keep in mind there are many different options based on what your needs are. You can get a whole house type or just control some basic emergency loads or somewhere in between:
Here's a link to one of the higher end manufacturers and with some manufactures, are only sold to certified installers Cummins Onan
Not all generators will come with the automatic transfer switch included so you may have to order that as an accessory item and a 12 volt battery needed for start up that can be purchased at a local auto supply store. Some other options can include a remote operable digital display for inside your home.
There are so many things to consider when purchasing a generator. Mainly you have to decide, do you want to control your whole house or just emergency loads? This will have the biggest effect on the size of the generator and the controllers.
FYI - The permit process for this type of system if you are acting as the general contractor:
Before you purchase a generator, bring a copy of your property survey to the local building dept along with a sketch of where you want to install the generator. This will normally be as close to your electrical panel and gas piping as possible. They will then let you know if you can install it there based on the property set backs from your neighbor's property lines. Just like a central air conditioning unit, there are set back requirements for noise and in this case emissions too so you can't be too close to your own windows.
If you are approved, pick up the permit folder and have your electrician and plumber fill it out and you will fill out your portion as the general contractor and submit the permits for approval. Once they are approved, you can go ahead and order your generator and create a "pad" like the one shown made of crushed stone, concrete, or a premade composite pad like the one shown over crushed stone. Then give your contractors a call and we'll do the rest!
*Keep in mind these units can easily get over 400 lbs.
Here's a great tool for sizing your generator, they don't have to be that big to get the job done. Just pick what you want to control and the tool will calculate the size and recommend an generator and transfer switch.
(1) Kitchen circuit is a 20 amp - 120 volt circuit each.
(1) Lighting & receptacle circuits 15 amp -120 volt circuit each.
(1) Gas or oil fired furnace - 15 amp - 120 volt circuit each.
(1) Sump Pump - 15 amp - 120 volt circuit
(1) Well Pump - 20 amp 240 volt circuit (2 breaker spaces)
And so on....
Keep in mind that it may be best to just go to your electrical panel and pick the circuits that you want to control based on the circuit breaker ampacity and just add up the circuit breakers. *A 240 volt circuit breaker would take up two circuit breaker spaces in the new emergency panel.
These are just rough estimates as many business and homeowners like to have an idea of what the equipment is going to look like and price ranges. Obviously you would want to go over it with your electrician before you order the equipment.
Or you can use this quick table.
These are general sizes and vary by manufacturer.