Advice on pre-wiring new house for future generator

katmuOctober 30, 2013

I'm still in the planning stages of a new home build. My new house will be in Minnesota, 1 level of 1450 sq ft on the main level with a walkout basement. It will be myself, and for the interim my young adult son with special needs.

I'm interested in pre-wiring my new house with a transfer switch so I will have the option of a generator in the future. I'm leaning towards eventually going with a generac type generator but I think at this point, I don't know what I don't know. I'm also debating if I should install an extra natural gas line to where I would likely put the generator.

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Ron Natalie

Running a gas line suitable to feed the generator you intend to use is probably not a bad idea.

You have to ask yourself:

Do you want to get a generator big enough to power the whole house or just several key circuits?

Do you want an automatic transfer switch?

    Bookmark   October 30, 2013 at 5:31PM
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It really depends on how accessible the gas pipes and electrical is and where the genset might be in relation to the gas meter. If you have an unfinished basement, there might not be much point in doing much special right now. A stub in the gas line with the line of sufficient capacity should be good enough.

One thing I am not sure of is whether you should have a bigger gas service to support the genset.

    Bookmark   October 30, 2013 at 6:01PM
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I mostly want to be able to run the essentials- fridge, heat, stove ignition, a few lights, and my laptop in the event I get a call from work. (I'm basically on call 24/7 365.)

I would be ok with a manual transfer switch I think.

I will check on the size of the gas line.

    Bookmark   October 30, 2013 at 6:21PM
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Ron Natalie

Then the best thing to do is make sure the essential items are on circuits distinct from non essential circuits. I am assuming that with a house this small there is only the single panel. Leave room for a transfer panel adjacent. Then run either wiring or conduit between that vicinity and the proposed generator location (you can leave it unterminated in an accessible box).

    Bookmark   October 31, 2013 at 7:16AM
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Lots of new panels now can have an approved generator interlock installed. If the occupants of the house can be relied upon to manage use of high wattage devices and turn off lights when they are leaving the rooms, you can use anything in the house with a relatively small genset.

If the occupants do not have a good head for that sort of thing and can not follow directions, splitting off essential loads and making use of flashlights is a better plan.

The built-in interlock solution is a device that will not allow the main breaker to be used at the same time one of the breakers at the "top" of the bus bar is engaged. The backfeed breaker can not be turned on unless the main breaker is off. It is the least expensive to buy and install and is a compact solution. Note that aftermarket interlocks are available. I think they were available before the panel manufacturers started making them, but now everyone seems to be in the act.

I searched on "ge generator interlock kit" and got some good hits with pictures immediately, but Gardenweb does not like the link for some reason.

You'll easily find the aftermarket devices as well.

    Bookmark   October 31, 2013 at 10:41AM
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I could have been more clear about the gas line. No matter what the location, you need a large enough meter and pipe. You will also want a pipe stub to extend to the genset.

If the genset is going to be remote from the meter on a line with the cook stove or space heating equipment it is a bigger deal to revise later. Your plumber should size that run so you can add the genset. If the first gas pipe is too small, you will have to replace it later or install a second pipe. A larger pipe to start with will certainly be less expensive than revision.

Even if the genset is going to be at the meter, you want to make sure that there is a large enough meter and pipe there and a stub for later extension.

Get an install manual and specifications for a generator of the size that you will be buying and talk to the contractor or plumber about it. They'll need to know how much fuel the engine will be using at full capacity and that will be in the install manual.

    Bookmark   October 31, 2013 at 10:52AM
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Since your needs and home are small, putting your 'essential' circuits into a subpanel is a good approach. Leave room in the panel (ie, get a larger panel) for any thing extra you might want to add later.

The generator size you're talking about now is not that big, like 5k-10k. Many of these are gasoline. If your outages are infrequent, then you might do fine with storing the gas. If your outages are more frequent and of a long duration, you might not want the hassle of storing and trying to go find gas. There has been advice here about NG generators, but I'm not sure what the smallest size is, or if something smaller than 12k is available. Search would be your friend.

If your outages are going to occur during inclement weather (blizzard), you might want to think about how you house it, ie in a shed or something.

If you don't want to go any farther with the generator purchase/install, then the electrician can still install the main panel, subpanel and transfer switch. He can run the generator side to a box on the outside. He could leave you a plug so you could connect a portable unit any time, or you could install a more permanent (NG) unit later and still wire to the box (or through it).

    Bookmark   October 31, 2013 at 12:04PM
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The information so far has been very helpful. In my current house, I have had a couple of outages that have lasted more than 48 hours in the last few years, both after really significant summer storms (one was a tornado that hit about 5 miles from my current home). Luckily, I haven't had those types of outages during the winter in the 18 years I've lived here .

About locating the future generator- does it need to be outside? The subdivision covenants require that I put in a 3 car garage. Since my son doesn't drive (and won't ever), could I locate the generator in the 3rd stall of the garage? Or am I better to put it outside, maybe near the A/C unit off the back of the walkout basement?

    Bookmark   October 31, 2013 at 12:33PM
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They are usually located outdoors. There are engineering and design solutions that will allow indoor installation, but it might be prohibitively expensive. It might not be, however, with a new construction. I could see walling off part of the garage and dedicating part of it to a generator. That part would probably have to be extensively passively ventilated. The trouble with that is that it probably would not count as garage space anymore.

The biggest problem might be finding a residential architect or builder that knows how to do it.

A 3-car garage for that size house? Geez, the garage will half as big as the house!

These things are noisy so you would not want it "in" the house anyway, even with extensive sound insulation. Depending on the layout of the house and garage, you might want to build a shelter on the side of the garage that will have open or openable sides on three sides. Make sure your covenant does not have prohibitions on generators! Due to the noise, some do.

    Bookmark   October 31, 2013 at 12:57PM
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Thanks ionized. I think I will stick with having it off the back near the A/C unit.

The covenants are goofy IMO. A one level has to be at least 1100 square feet but it still has to have a 3 car garage. The 3rd stall will be set back a bit but still.

    Bookmark   October 31, 2013 at 1:46PM
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I guess they want to be absolutely sure that there will be no cars parked outdoors.

    Bookmark   October 31, 2013 at 7:24PM
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You could build a 3 car garage as a two car garage with a one bay extension for the generator and a workshop. The third bay could be designed to provide additional ventilation (maybe with garage doors on both ends) and have the safety features required for the generator, but still allow normal use of the remaining two car garage.


    Bookmark   November 1, 2013 at 5:37PM
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I don't think you can use the garage if it is not detached from the home.

    Bookmark   November 1, 2013 at 8:24PM
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I am looking into having a stationary natural gas generator installed. I read something about having the right gas meter. I was not aware that there is such a thing as a separate gas line evaluation. I wonder if your gas company might have some helpful info about this?

>> Standby generators typically run on natural gas or liquid propane. After the load evaluation, natural gas customers will get a gas evaluation. Depending on the generator, some homes may not have adequate delivery pressure. The gas company would then have to install a higher-volume gas meter, at the homeowner's expense. Bob Brennan, a Connecticut Natural Gas spokesman, says that could cost about $2,000.

"First, though, make sure that the residence is supplied by a high pressure gas distribution system," he says. "Advise your heating contractor to contact the local gas company's marketing department to coordinate that information."

A link that might be useful:

    Bookmark   November 11, 2013 at 12:33AM
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First, Square D makes an interlock kit for several models of their panels. When the architect is planning the dwelling, he needs to be aware of your desire for a generator backup in case of loss of utility power. By segregating lights from plugs, the refer, furnace, AC if necessary, Microwave and a plug circuit or 2 that will be available in the required locations,(Alarms,TV, computer, modems, phones/chargers) but at least one receptacle per room. With the interlock kit, it has a pair of two pole breakers for the feeds, of which it will either be fed from one or the other. IE, normal conditions it is fed from the house panel or grid, power interruption flip the interlocked breakers and you are now set for gen power to all the loads in the second panel. It is the expense of an extra panel and not automatic this way, but it allows you to use the same brand, type, style of load centers and breakers. AND IT IS NEVER OK TO LOCATE A GENERATOR INDOORS IN A RESIDENTIAL INSTALLATION THAT I HAVE EVER ENCOUNTERED. NEVER! IN A GARAGE. CO IS A KILLER. And keep in mind a generator is one of those things that is better off a tiny bit too big than a tiny bit too small.

    Bookmark   November 12, 2013 at 12:43AM
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The interlock requires no additional panels. That is the whole purpose of it-- one panel does it all. The interlock provides for two possible inputs to the panel-- but never both at the same time.
The last interlock I did had two panels, the main and a subpanel fed from a 100 amp breaker in the main panel. The interlock on the main panel was all that was required other than the feed into the generator breaker that the interlock operates. But the interlock setup is somewhat inconvenient as the person has to do manually do several things when it is used, especially when a smaller generator is used.

The transfer switch does require an additional panel. It gets it's supply only from the generator and transfers the selected circuits from the POCO supply to the generator.
Now is the time to select which you want. Neither system is particularly low cost but the transfer switch is the higher priced setup.

This post was edited by bus_driver on Tue, Nov 12, 13 at 19:36

    Bookmark   November 12, 2013 at 5:25PM
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On the size of your genny, you might find that you'll need a bigger one than you think. I have an 1120 sq. ft. house with a 15 KW generator run on propane that basically supplies everything in the house except the heat pump - but that does NOT include the water heater or the stove, which also run on propane. If the power goes off in the winter, I have a gas fireplace for heat. BTW, the larger generators actually have better noise reduction devices on them than the smaller ones; that was one of the factors when I got mine. I added it in 2009 on my 1927 house, and the electrician placed the transfer box below the old panel box, as well as upgrading the electrical service to 200 amps. Best $$$ I ever spent for the house.

    Bookmark   November 12, 2013 at 7:23PM
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