AboutMaster Bob Expertise Master Electrician / Owner RKO Electric (USA Only) - can answer most of the typical residential, commercial and industrial electrical questions regarding new installations, wiring additions, lighting, switches and receptacle outlets and electrical upgrades of any nature.I will make every effort to respond to your questions as soon as possible at the end of the work day...very busy electrical company - your patience is appreciated. Stop by and see us at: www.rkoelectric.com
Experience Licensed Master Electrician with over 32 years licensed experience - updated with the latest NEC Codes every 3 years. Over see the daily electrical operations of two electrical companies. Also serve as a judge (for Electrical Contracting Products Magazine) to help select which new products are fit and safe for electricians and the electrical market.
Question First off, you must understand that so far I have run into many snags with hooking up a few circuits of our home to a back up generator. Any help you can provide would be phenomenal! I am trying to hook up our new generator to about 8 different circuits in our house. I have already done a load calculations to make sure the generator will have ample amount of power to provide. The generator is rated at 13,500 surge and 8000 watts constant. The problem I am running into with this is that the generator contains 8 15 amp 120v outlets (One of the outlets is a 30amp 220v twist lock that you plug the provided adaptor in to get four of the 8 15a outlets) So how do I isolate 8 seperate circuits from our main power. I do understand that you cannot back feed any power to the street. So far the only thing I can come up with is using 3-way switches to interrupt the hot and neutrals. I would put the side of the circuit that runs to the lights in the house on the common side of the switch and then the main power and the generator would hook up to the travelers. That way they would never be crossed. In order to do it that way though, I would need to hook up 16 switches!! I know their most be an easier way. I have seen the generator transfer boxes that they sell, and they seem like they require just one main power source to come in from the generator. My power sources would all be seperate. If you have any ideas, your help would be greatly appreciated!! Thanks!
Answer Hi Jarred,
Just getting back in from electrical jobs down-state... saw your e-mail.
I note you refer to the transfer switches....and had you installed an 8 circuit one next to your main panel...you could have been done by now....and have a Code approved installation. I certainly do NOT recommend your suggested approach of 16 3-ways...far too many connections and possibilites for errors. There are several easier ways to accomplish your goal....
Usually a generator of that size has a twist lock 120/240 V 50 amp and a twist lock 120/240 V 30 amp...but where you only have the one 30 amp and do not wish to install a transfer...here's what you may want to consider:
Mount a small 10 circuit main lug only sub-panel next to your main panel....and nipple them together with a 2 inch offset nipple. Equip the sub with 8 - 15 amp single pole breakers for your 8 essentials circuit that you wish to have back up power for....leaving 2 spaces on top of each other on one side for the a 30 amp double pole breaker. Mount a double pole 30 amp breaker in your main panel (clearly mark this breaker "Sub-panel Normal Power " )....run 2 #10's from the breaker to the main lugs of the sub...1 # 10 from the main panels neutral buss to the neutral buss of the sub....and a #10 green from the main panel's neutral buss to a ground buss (you'll need to buy the ground bar seperately sized to fit your sub-panel) NOTE: at the sub-panel...your grounds and neutrals must go to seperate busses...they can not go to the same buss like they do at your main.
Then...isolate the 8 circuits you wish to have backed up in your main panel...remove the wires from their breaker at the main and mark them so you'll know what each feeds. Run a length of #12 from each of the 8 - 15 amp breakers in the sub thru your nipple and connect one to each of these 8 wires with a wirenut...labeling each wire at both ends (numbered wire markers are great for this...) You are now half-way thru building your own combo custom sub-panel/ manual transfer system.
Run a length of 10/3 with ground heavy duty SO cord from your generator to this sub....equipping the generator end with a 30 amp twist lock to match your generators 30 amp receptacle outlet. At the sub-panel...mount a 30 amp double pole breaker in the remaining two spaces(from above). Coonect the red of the SO cord to one terminal of this 30 amp breaker...and the black of the SO cord to the other. Connect the white of the SO cord to the sub-panels neutral buss,....and the green of the SO cord to the sub-panels equipment ground bar.
Clearly mark this 30 amp breaker as "Emergency Generator Power" in the sub....and leave it OFF. This new sub will normally get it's power for the 8 circuits from the 30 amp breaker you installed to feed it in your main panel.
During an outage...the 30 amp breaker in your main panel that you marked "Sub-panel Normal Power " will need to get switched OFF....and the "Emergency Generator Power" breaker in the sub will need to then get switched ON...after the generator has been switched on. Once you know that power has been restored...reverse the above ONLY after the generator is confirmed shut off...
Sounds a little complex...if you consider this route...you may want to print this all out for guidance. But - this is a homemade transfer system....and there's a LOT to it. Of course...you'd be further ahead just buying a pre-made manual transfer system readily available at most hardware stores (Home Depot's, etc) - such as the 10 circuit one made by Pro/Tran
...see an example of this system at: http://www.mastersalesonline.com/protran/switch/f30310.html
With that transfer...most of the above work (and breakers and other materials) is already done for you...you still would have to get the 30 amp double pole breaker for your main panel (to feed normal power to the transfer) and connect the 8 circuits (as above)....as well as have the length of 10/3 w/gr. SO cord from the tranfer switch to the generator location...but the bulk of the work is done for you. You wouldn't need to build the sub-panel...you wouldn't need the nipple ,etc...
The choice is up to you....personally - I recommend going with the pre-made transfer switch route...unless you have a solid elelctrical background and just wish to custom build your own. By the time your done building your own...you'd have just about as much money (and a LOT more time spent) then if you'd bought a pre-made 30 amp 10 circuit manual transfer system.
In any event...either the transfer switch or the custom built one above must be all installed per Code....and both methods are much better then hooking up 16-3 ways and the potential problems going that route may cause.
Yes...there is an easier (and safer) way Jarred - buy the transfer and install it - and have it all working safely and per Code. Hopefully - you'll make the right choice...and avoid all the "snags"..
Hope this helps...if you need more details or run into any problems...please follow-up.
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