Wiring a Home Generator Transfer Switch

[RobS]

I finally picked up a portable generator for back up power at the house. I'm now trying to scope out the work to install a transfer switch to decide if I do it myself or hire it. I find plenty of simple diagrams that show how the transfer switch switches between the generator, off and grid power but no details on the wiring itself.

Can anyone explain how each chosen circuit is actually wired into the switch. I have two 200 amp panels and will choose circuits from each. Do the circuit feeds come off the existing breakers and into the transfer box? How are neutrals and grounds handled? 120 vs. 240 circuits?

My generator is 5000W continuous and has a 30A 240V recep available. I don't intend to run the whole house, just the basics including the well pump, fridge, freezer, furnace etc. Furnace, stove and water heater are all propane. I'm looking at a 30A, 10 circuit transfer switch.

TIA, any insights appreciated.

 

[heehaw]

be careful: get it wrong and you could fry the poor lineman trying to restore power for you. a licensed electrican should be able to do this in a couple hours, why not do that and be safe!
heehaw

 

[RobS]

a licensed electrican should be able to do this in a couple hours, why not do that and be safe!
heehaw

I certainly won't rule that out heehaw, just want a better understanding of what's involved to make a better decision.

 

[schmism]

be careful: get it wrong and you could fry the poor lineman trying to restore power for you.

if you have a proper disconnect setup, you wont.

as for how the circuits are wired....

i belive you put the transfer switch after the main pannel. the wires that come out of the transfer switch go TO the proper breakers in the main pannel, the wires comming from the house go into the transfer pannel.

when you need to run the genny, you throw the switch, (disconnecting the main pannel) and know your gererator is set to supply power to the house and not backfeed the main.

 

[MrJimi]

I'm wondering if your 5,000 watt generator has enough watts to run the items you want to run. Have you considered a couple of heavy extension cords for this ? It may be easier and lots cheaper for as much as you will need it
Jim

 

[Highbeam]

5000 watts is probably plenty. If need be, you can manage your consumption by shutting off the well breaker or some other breaker just to prevent every transfered circuit from drawing at once. If you notice, your typical 200 amp panel is filled up with circuit breakers that when summed up equal more than 200 amps. You really don't want one any bigger due to the huge fuel consumption.

You can buy a 30 amp extension cord with the twisloks already installed at each end from Home Depot for less money than the parts. The extension cord will connect your genset to the transfer panel.

I just finished up my whole house transfer panel installation this last weekend by running the generator circuit to the male twistlok receptacle. 30 amps through the 10 gauge wire to backfeed my house. I certainly will need to shut off the circuits that are automatic like the electric water heater. Manage power demand by breakers.

 

[RonMar]

It sounds like he is refering to the add-on transfer panels that some manufacturers produce such as these models shown on the Gen-Tran website. Gentran Corporation: Generator Transfer switches for home & business

This type has an individual A/B switch/breaker for each circuit that is to receive backup power. If you are not color blind and can follow the instructions, I do not think it is really possible to miss wire it and still have it function in normal/commercial mode. But having an electrician review your install is certainly good advise.

I will use one circuit as an example. You now have a power panel with a circuit breaker and a wire leaving that circuit to feed a load in your house. To add the transfer panel, you first shutdown the main panel breaker and the individual breakers in question. The wire feeding the load from the breaker is disconnected and spliced to a wire comming from the new transfer panel. A new wire to the transfer panel is connected to the existing panel breaker. You are basically placing the new transfer panel(A/B switch) between your existing circuit breaker and the house circuit it normally powers. You repeat this process for each circuit you wish to configure for backup power. Neutral and ground wires from the transfer panel are connected to the main panels ground and neutral busses.

Many of these transfer panels have a large electrical receptical for plugging in a feed cable from the generator and the generator portion of the individual circuit A/B switches is already wired. In fact, you never open up the new transfer panel, just wire it's harness into the main panel as I described above. This is what makes it VERY difficult to misswire and still function in normal power mode. If I recall, the gen-tran website has the complete installation instructions available on line for their prioducts.

Another option is the installation of an interlocked plate which allows you to safely backfeed your existing main panel. I used to have a link to a company that sells 50 state UL approved interlock plate kits. It is posted somewhere on this forum, I am sure you will find it if you search back thru the generation and backup power threads as it was not all that long ago. What this does is mechanically connects the main circuit breaker in the panel to another breaker so that it is not physically possible to have them both on at the same time. To this other breaker you connect your generator. To shift to generator, you shut off loads that you do not wish to power, or do not have the generator capacity to power, then you shut off your main breaker. You slide/rotate the interlock plate which holds the main breaker in the off position and allows you to energize the backfeed breaker. With the backfeed breaker in the on position, it holds the plate so the main cannot be turned on. This is probably the least expensive backup power option and is the easiest to install as you have to do very little panel wiring and no additional wire beyond that needed to wire the generator to the backfeed breaker. Since you mentioned powering circuits in two main panels, this may not be an option for you.

Edit: Larry D posted the link I was thiking of last month in this thread on backup power wiring.
http://www.tractorbynet.com/forums/projects/112976-generator-setup-house.html

But as mentioned, if you are not familliar or comfortable with this type work, best to have an electrician do it.

Good Luck

 

[RonMar]

I'm wondering if your 5,000 watt generator has enough watts to run the items you want to run. Have you considered a couple of heavy extension cords for this ? It may be easier and lots cheaper for as much as you will need it
Jim

He should be fine, I run everything he plans on runing and a bit more on 3KW. It does require that you think about what you are doing when in backup mode. It is also kind of hard to use an extension for a hardwired 240 load like a well pump.

 

[ragkar]

You want to get as small a generator as possible to minimize gas consumption. My 6500 watt generator will run 13 hours on its 7 gallon tank. I keep 12 gallons in reserve so after a day and a half I'll be looking for a gas station that has its own generator. Power outages of a week sometimes happen.
It seems that power outages most often occur on the winter which is a heck of a time to go looking for extension cables and plugging them in. I'd suggest lots of labels on circuit boxes and generators as it might be a couple years before you need the generator and you forget.
You have a choice of auto switchover at twice the cost or manual. I went for manual. You will need a sounder for an un-generator-powered socket to tell you that the power just came back. Luckily for me my driveway alarm fills that function.
Regarding switching the well pump off, it's really hard living without water to wash and flush toilets. So I regard it and the entertainment centers as must haves. Microwave and sewage pumps are needed too.
I had the electrician wire my setup and also put an outside outlet at the generator site to recharge the battery.

 

[MossRoad]

I finally picked up a portable generator for back up power at the house. I'm now trying to scope out the work to install a transfer switch to decide if I do it myself or hire it. I find plenty of simple diagrams that show how the transfer switch switches between the generator, off and grid power but no details on the wiring itself.

Can anyone explain how each chosen circuit is actually wired into the switch. I have two 200 amp panels and will choose circuits from each. Do the circuit feeds come off the existing breakers and into the transfer box? How are neutrals and grounds handled? 120 vs. 240 circuits?

My generator is 5000W continuous and has a 30A 240V recep available. I don't intend to run the whole house, just the basics including the well pump, fridge, freezer, furnace etc. Furnace, stove and water heater are all propane. I'm looking at a 30A, 10 circuit transfer switch.

TIA, any insights appreciated.

Rob,
I have a 4500W and use it a couple times a year. It will run the well pump, freezer, 'fridge, furnace blower, etc... just not all at the same time. It runs really rough if all of the load is on one leg, too. With 220V appliances, it is not a problem. But with the fridge, freezer and lights, it is easy to get more of a load on one 110V leg than another.

So, plan your loads accordingly. I found that if I have one large 110V appliance running on one leg, I can put a few lightbulbs on the other leg to balance it out if it is a problem.

A panel with built in meters on each leg is a good idea, if you plan on using it much. But really, how many power outages have you had? You probably just want something to keep the food from spoiling, water to flush and wash with, and heat if it is winter, and maybe some lights.

You could just put an on-off-on switch between your meter and main panel with the first ON being your electric company power, the OFF to isolate the two services, and the second ON being your generator. Then you manage the load with your breakers. This method takes the least amount of wiring, is most likely code legal as the two power sources cannot be mixed, and probably the cheapest in the long run, although you will be shocked at the price of an on-off-on switch at first. But the ease of installation and no need to pull circuits from existing panels may make it more attractive.