Introduction: Easy Generator to Home Hook Up
A generator is a core component to many people's emergency preparedness plans. (Maybe you have a cool charcoal powered or a multi-fuel generator.) However many fail to think through how exactly they will power the items they want to run when the grid is down.
In June of 2012 my family experienced a 10 day power outage. It was eye opening. It was 100 degrees during the day with periods of heavy rain. I had to run a sump pump to keep my basement dry, a refrigerator, freezer for food preservation, a portable AC unit in the living room to protect my infant, we charged phones, and ran the wifi router. I had power cords everywhere. It was a pain. I decided then and there I would find a better way.
A generator transfer switch is the legal and proper way to power your home with an emergency generator. There are three main types: automatic, manual transfer sub panel and a breaker interlock. Each has varying degrees of complexity, benefits and expense.
Automatic transfer switches will sense a power loss, start your standby generator and automatically move your load to the generator. These are awesome - but very expensive and require a full time dedicated standby generator.
Manual transfer sub panel switches are good option. They are less expensive than the automatic transfer switches (Starting around $300) and can be used with a portable generator. They typically only cover a few breakers which was problematic for me.
Breaker Interlock is the option I chose. It is National Electric Code compliant and is in my opinion the least expensive and most flexible option. My setup cost was just under $150. In this setup you use a breaker to energize your existing breaker box. Switching it on is easy and safe. My wife did an unassisted dry run in under 5 min - which included getting the generator out of the building.
The breaker interlock system has come in very handy for us. We can turn on overhead lights, wash clothes and keep our food cold, charge our phones, run the internet and much more....all while keeping our doors and windows closed and no tripping on extension cords!
I am not an electrician. After much consulting and over sight from a licensed 25 year Master Electrician I believe these instructions to be correct and accurate for my jurisdiction. Electrical codes vary from place to place. In my place of residence home owners are allowed to do their own electrical work if it is up to code. You are responsible for any code violations, permits or awesome good stuff that comes from doing a project like this.
Step 1: NEVER DO THIS
I've listened to and have even seen people using a double male plug to energize their house during a power outage. This is dangerous.
- It is an electrical code violation.
- It is illegal in most places.
- It is a fire hazard. The power created by your generator is generally greater than the rating for the receptacle, wire and breaker.
- If you don't disconnect your main breaker it can shock the power company linemen - and you will get sued.
- You can easily get shocked because the male plug prongs are exposed.
Step 2: Determine Your Generator Plug Type and Amperage
First you have to figure out what type of amperage and plug type we are working with. You only want to do this on a generator with a big round plug. This will provide 220V (in the US) and power both sides of your breaker box. You will see the amperage written near the plug. Mine is a 30 Amp L-14-30.
For your convenience these are the most common sizes:
Nema L14-20 - 20 amp
Nema L14-30 - 30 amp
Nema CS6365 - 50 amp
Step 3: Supplies
Gather your supplies.
For the sake of this build we are going to assume you have a 30 amp plug on your generator - like the one shown. If your have one different please adjust your supplies.
Breaker interlock kit. Buy a UL rated device that fits your specific breaker box. These have been tested and validated to work. Many insurance companies and jurisdictions require the UL rating.
30 Amp 2 pole (double) breaker. Again you will need to buy one that fits your breaker box. All breakers are not the same.
Wire. I bought 10 feet of 10 gauge wire in black, red, green and white.
30 Amp power Inlet box.
Schedule 40 electrical conduit and fittings
Flexible Non-Metallic Conduit and fittings (optional)
30 Amp generator extension cord. (Search Amazon for (your plug type) extension cord.)
Notice how all the amperage match. If you are using a 50 output on your generator you will need a 50 amp breaker, 50 amp power inlet box, a 50 amp extension cable and 8 gauge wire.
Step 4: Drill (or Find) Access Hole
Measure 5 times drill once.
My house had an conduit old hole in the foundation. Most people will need to drill one. A hammer drill is extremely helpful for making one. Try to get the conduit hole as close to the panel as you can.
Step 5: Mount Power Inlet Box
Remove the front cover from the power inlet box.
Remove a knock out and attach the PVC fitting. You can see here I opted for the water tight connector. Glue works just find too.
Using tapcons mount the power inlet box to the wall.
Step 6: Test Fit and Glue Conduit
Use a hack saw and cut the conduit to length.
Don't glue it until you know it fits. Once you are good glue it down.
Step 7: Wire the Generator Inlet Plug
Once the glue is dry we can start to work on the wiring.
Remove the cover on the conduit body. Pull the wires through one at a time attaching them to the plug as you go along. Remove about 3/4 of an inch of the insulation. Use a large flat screwdriver or a nut driver to tighten the terminals.
Green - Ground to the power inlet box.
White - Common, W terminal
Black and Red - Load - either X or Y terminal.
Step 8: Push Wiring Inside
Push the wires through the conduit into the house one at a time.
Replace the conduit body cover, checking proper fit of the gasket.
Fill any gaps between your conduit and the house with silicone or expanding foam.
Step 9: Prep Breaker Box for Wires
Turn off all the branch breakers and the main power breaker.
Remove the front panel of the breaker box by taking out the four screws.
Remove one knockout and screw in conduit adapter or in my case a blue non metallic conduit adapter.
Pull wires through conduit and into the box.
Step 10: Create Open Breaker Space
The breaker interlock method requires the to most upper and right breaker space to be free.
Generally you will need to move a breaker or two down. Most boxes will have enough spare wire to move things around a bit. If you do not have enough room and your breaker is 30 amps or less you can use a short piece of insulated wire and a wire nut.
DO NOT wire nut copper and aluminum wire together. They will corrode over time. You will need to pick up a wire splice at your local home store.
Step 11: Install Generator Breaker and Wires
Install your new breaker in the freed up space in the upper right of your breaker box.
The red wire goes to one terminal on the breaker and the black goes to the other.
The white wire goes to the common bond rail in the box.
The green wire goes to the ground rail.
Note: In a 2 wire home like mine - meaning no 3rd ground wire in the outlet box or the outlets in the home. It is acceptable in my jurisdiction to put the green ground wire to an open common terminal. It is not appropriate to use the ground wire for the common at the outlet.
Step 12: Install Breaker Retainer
Now it is time to lock down that breaker from moving. Install the retaining bracket. My retaining bolt was located between the main breakers and the 30 amp breaker.
Step 13: Install Inter Lock on Panel Cover
Flip the cover over and use the provided template.
Pre-drill the holes and then finish them out withe the bit size noted in your instructions.
Turn the panel back over and install the sliding interlock bolts.
Reinstall the panel with all the breakers in the off position. With the main in the off position turn the generator breaker to the on position. Ensure the interlock allows for the on position. You may have to shift the position of the panel cover.
Turn the generator breaker to the off position and drop the slide so it can not be turned on. Ensure the Main can be turned to the on position. Adjust panel cover if it will not.
If it does turn the breakers on one a at a time - with a 5 second delay between breakers. This will distribute the start up load.
Attach decals included in your kit to your breaker box and the outside service box.
Step 14: Operation
Time to load test! Write down these instructions and put them in your breaker box.
- Confirm power outage
- Place generator 15 feet from your home - with the exhaust pointing away from open windows and doors
- Start generator and ensure normal operating speed
- Attach generator extension cord to the generator with an inward push and gentle clockwise turn
- Attach extension cord to the home power inlet box with an inward push and a gentle clockwise turn
- At the breaker box turn off all the breakers
- Turn the main breaker off
- slide interlock up exposing the on position of the generator breaker - turn generator breaker on
- Turn on selected breakers with a 5 second delay in between each - ensuring the generator takes the load.
Avoid turning on HVAC, standard hot water heater and the stove unless your generator can handle it. As long as you can get past the initial start up load you can run a lot off of 30 amps.
Power off sequence:
- Turn off all branch breakers
- Turn off generator breaker
- Slide down generator interlock exposing the on position of the main breaker - turn main breaker on
- Turn on branch breakers one at a time with a 5 second delay between each one until they are all back on
- Power off generator and allow to cool
- Remove generator extension cord.
Enjoy your set up. It has come in very handy for us. We can turn on overhead lights, wash clothes and keep our foo
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A couple of things,that I can see that would help your project would be to install a ground rod on the generator (or the box leading to the generator) grounding the circuit. It could preclude instances of getting shocked if touching something energized (a hotplate) and a device already installed in the home (the stove, range hood etc..) it's possible, not likely. Adding a ground rod would help. Also don't run any high end appliances while on generator (unless you keep a close eye on the fuel level). When the generator runs out of fuel, it dosen't just stop, it runs down. While it is doing this it will decrease the amount of voltage to the house. that run-down can damage power supplies in flat screens, desk top 'puters (not lap tops) etc... Find an old picture tube type TV if ya have to have a TV.
Produzni kabal na jednom kraju MORA ,MORA,biti muski ana drugom zenski utikac,i nikako drugacije.!!!
Great write up. I feel steps 6 & 7 of your startup procedure should be before step 4 - the breakers should be off before connecting your extension. You do not know what is happening 'upstream' from you and could introduce power to lines currently being worked on.
I have an almost exact setup to yours (with a pair of load meters added) and, except for the above mentioned step-order change, virtually identical startup procedures. One thing I discovered during my research on this method was the vague definitions and codes regarding portable generator grounding. Several authoritative sources have said (to paraphrase):
"The only way you can use an interlock kit legally is if the generator has a floating neutral. Otherwise, you need a manual 3 pole transfer switch (or a disconnected ground/neutral bond somewhere between the service box and the generator). Being a non-SDS (Separately Derived System), the NEC requires that no neutral to ground bonds exist load side of the service equipment. Technically, in order to be code compliant, it needs to be determined if the neutral and ground are separated at the generator."
I installed a switch on my generator and connected its outlet's neutral(s) and a jumper to the original ground tie point (see image for original neutral-ground bond). I can now select between a 'floating' neutral, where the grounded-at-the-box neutral is provided by my breaker box wiring, or a 'tied' neutral, which uses the generator frame as ground (which, again, supposedly requires a ground rod to be attached).
The SDS requirements for portable generators appear to have been generally overlooked since so many are sold to customers like ourselves who want to use them as emergency home supplies, which wasn't their original intent.
Once again, great, informative submission.
Still, with this method, I turn on all breakers but my A/C units, then make sure I turn off consumers in a room I'm leaving so I can turn them on in the next room.
Caution: You showed the handcrafted illegal male to male 120 cord. Good point. But you failed to show the 220 cord and pictures of the wall outlet configuration. Everything is very clear here but you start out showing a very common failure point using 120 but then show no step focusing on the 220 cord connections. What is hidden is how the 220 plugs to the outside wall outlet. Yes, it shows it plugged in but there should be more detail at this juncture because that is the correction of the firstly mentioned failure.
There's a paste that you apply to the wires if you do have to connect aluminum and copper wiring together.
Great instruction. I also believe this is the most economical and adequate way all around. I also believe that the receptacle back-feed is only risky for the know-nothing and can be employed it in an emergency (all that needs to be done is open the main breaker).
The breaker interlock is a very efficient way to power your dwelling with a generator but does not let you know when the power comes back on as you completely disconnect from the utility provided power. A manual transfer switch, which recently have become more affordable, allow you to choose which circuits to power with the generator and which to keep on the utility supplied/line power. With this set up a light or radio not on the generator can alert you as to when the power from the utility provider comes back on. Installation of a manual transfer switch however is not for novices and should be installed by a qualified electrician.
I would not recommend to use two male ended AC plugs. However that's exactly what I've been doing for the past 30 years. Never had the finances to go more fancy.
One 220VAC male plug is plugged into the generator. The other end is plugged into the workshop's outdoor 200VAC plug. Before doing the above step, the main power switch/fuse box, to the telephone pole gets disconnected. Then the generator is started. The 8KW Generac generator runs the whole house with a heavy underground cable to the house, from the workshop.
Under normal conditions, it's the house's commercial power that runs the workshop. But with the generator being a decent distance away from the house, noise is not a problem when the Generac is running, and providing the power.
The generator is manually started, so all of these steps need to be paid attention to.
Hi wondering about the cord setup
Looks like cord plug has to be male at generator , is receptacle at wall box male style and female end of cord attatches to that .
Any chance of getting picture of interior of finished wall box.
You are absolutely correct. I don't have one of my photos on hand but here is the manufacturer's photo.
The article is great and I'm going to follow your instructions. I have a question, my board is different than yours and my electrical is not good enough to identify my type of board, pic attached. Then I can identify what type interlock I need or if one is available
Good news! You've got a SquareD breaker box. There should be a number on the bottom of the box. That is the serial number. You can use the serial number to determine the model of the breaker box. I'm guessing SquareD QO 200 amp, but don't hold me to it. More good news - once you figure out your model number the correct breaker interlock will be on HomeDepot.com - (assuming you are in the US)
My breaker box has the main shutoff at the bottom and the first breaker is not close to it. Is there a different kit for that type box? And it seems the kit simply does not allow the generator input breaker to be thrown unless the main if off first. Am I seeing this correctly.
If the double male plug is wrong, why do you show one in the photo of the generator?