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Connecting a Generator to House with its own Dedicated Receptacles

Connecting a Generator to House with its own Dedicated Receptacles

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  #1  
Old 03-05-11, 07:14 PM
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Connecting a Generator to House with its own Dedicated Receptacles

Hello everyone -

Long (LONG!) time lurker - first time poster. I've been searching for my answer for a long time but couldn't find it so I figured I'd post.

I have a small portable generator - a Centurion by Generac - 3250 running watts, 20 Amps but all of the outlets are protected by a 14 Amp breaker (manual is here).

I know it's a small generator but it should still be big enough to power just my gas furnace (3/4 HP blower) and a refrigerator/freezer.

I don't want to install a transfer switch for this small generator mostly because my breaker panel is in my finished basement recessed in the wall behind some artwork so the transfer switch would stick out and be ugly. I can get by if I just had some dedicated receptacles that were powered by the generator. Once the receptacles were powered by the generator, I could run an extension cord to the fridge or to the furnace (I would install a single circuit transfer switch for the furnace - like a Reliance Controls TF201W). The generator power would NEVER be connected to the house/street power, it wouldn't be connected to any existing circuit, there would be NO backfeeding, and there would be NO "suicide cords" involved.

I'm a handy homeowner but I've never messed around with 220V. I think I know what I'm doing but I'd sure like someone to check my work. What I need to do is go from the 220V output of the generator to 2 receptacles inside the house that are 110V. I drew a diagram which is posted below (or click here for a bigger size).

Can you please tell me if I have this right or if something needs to change?



Thanks!!
 
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  #2  
Old 03-05-11, 07:21 PM
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It's late but the one thing I see is the neutrals will need to be pigtailed. and run to both receptacles.
 
  #3  
Old 03-05-11, 07:36 PM
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I don't know whether this setup would actually fall under code proper since it's completely isolated from the panel.. So I'll defer to those that know better..


As long as you use a 20A inlet, I don't see anything terrible. The genny has a main breaker, so there is circuit protection, and I would definitely use GFCI for the inside receptacles (you would have to pigtail the neutral to split it, you can't use the Load side as in your diagram). I would also put some kind of permanent label on both the inlet and receptacles to indicate they are a closed system, in case you sell your house, so the new owners (and their inspector) would know why there is a set of non-working outlets inside and a weird male outlet on the outside.

Another thing to consider is that there are transfer panels that have an optional flush mount. I don't know how your basement is laid out, but you can by all means extend the whip that comes out of the transfer panel, it doesn't HAVE to be next to the panel.
 
  #4  
Old 03-05-11, 07:55 PM
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If your generator has a built-in GFCI then you may (probably will) have trouble with the additional GFCI receptacles. You need the equipment grounding conductor bonded to the house grounding electrode conductor and the generator neutral needs to be bonded to the equipment grounding conductor, which it may already be internally.

As described you have a "separately derived system" in the words of the NEC. Bonding the neutral and equipment grounding conductors to the house grounding electrode makes it a bit safer in my opinion.

The other part that bothers me is the use of type NM cable running through the wall to the outside mounted inlet connector. NM is not to be used outside although just entering an outside box is (marginally in my opinion) acceptable. I'd rather see non-metallic conduit with type THWN individual conductors. Also, that type of inlet connector is NOT weatherproof when in use and would have to be mounted where driving rain would never hit it. This is a picture of my inlet connection.



The generator interconnect cable comes out of the bottom of the enclosure.
 
  #5  
Old 03-05-11, 07:58 PM
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Normally the 240v receptacle(s) on a generator are not GFCI protected. The 120v receptacles are usually actual GFCIs, not a GFCI breaker.

And I thought SDS was when you have more than one transformer in a building... ? This is, for all intents and purposes, a glorified extension cord...
 

Last edited by JerseyMatt; 03-05-11 at 09:18 PM.
  #6  
Old 03-06-11, 05:41 AM
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Thanks for pointing out my errors! I revised my diagram so now it looks like this (larger size here)


Can I run my grounds like in the diagram or do they need to be pigtailed too?
 

Last edited by jfinn; 03-06-11 at 05:58 AM.
  #7  
Old 03-06-11, 05:47 AM
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Originally Posted by Furd View Post
If your generator has a built-in GFCI then you may (probably will) have trouble with the additional GFCI receptacles. You need the equipment grounding conductor bonded to the house grounding electrode conductor and the generator neutral needs to be bonded to the equipment grounding conductor, which it may already be internally.

As described you have a "separately derived system" in the words of the NEC. Bonding the neutral and equipment grounding conductors to the house grounding electrode makes it a bit safer in my opinion.

The other part that bothers me is the use of type NM cable running through the wall to the outside mounted inlet connector. NM is not to be used outside although just entering an outside box is (marginally in my opinion) acceptable. I'd rather see non-metallic conduit with type THWN individual conductors. Also, that type of inlet connector is NOT weatherproof when in use and would have to be mounted where driving rain would never hit it. This is a picture of my inlet connection.



The generator interconnect cable comes out of the bottom of the enclosure.
Thank you, Furd.

I don't think my generator has GFCI built into it - at least it doesn't say it does on it or anywhere in the manual. Is there another way to know?

Also, the inlet would go under my deck so there would be no chance of driving rain - but certainly dripping rain. I looked at the style of box you have which I'd be fine with. I just figure that since this will get so little use, any open holes are good places for insects to nest.
 
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Old 03-06-11, 05:50 AM
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Originally Posted by JerseyMatt View Post
This is, for all intents and purposes, a glorified extension cord...
That's a really good description for this project! Thanks!
 
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Old 03-06-11, 05:56 AM
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Originally Posted by JerseyMatt View Post
I don't know whether this setup would actually fall under code proper since it's completely isolated from the panel.. So I'll defer to those that know better..
I don't know either - but I'd really like to keep this thing "within code". Thanks for bringing up this point.


Originally Posted by JerseyMatt View Post
I would also put some kind of permanent label on both the inlet and receptacles to indicate they are a closed system, in case you sell your house, so the new owners (and their inspector) would know why there is a set of non-working outlets inside and a weird male outlet on the outside.
Good idea! I'll add this!

Originally Posted by JerseyMatt View Post
Another thing to consider is that there are transfer panels that have an optional flush mount. I don't know how your basement is laid out, but you can by all means extend the whip that comes out of the transfer panel, it doesn't HAVE to be next to the panel.
Ok, here's the rest of the story.. I *hate* doing drywall work and adding a transfer panel would require cutting and patching. Other than that, I really think a transfer panel is overkill for this little generator.
 
  #10  
Old 03-06-11, 11:40 AM
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I also detest drywall work but it isn't really that hard, just time consuming and messy for us non-professionals.

What I did was installed an auxiliary circuit breaker panel wired through a transfer switch I bought off of the Internet. It was a 60 ampere industrial switch with three poles and double throw center off. I got a fantastic deal although the shipping was almost the same cost as the switch itself. This way I moved all my necessary loads (kitchen counter receptacles, refrigerator, furnace, TV/DVD and some lighting to the new circuit breaker panel and fed that via a 60 ampere circuit breaker in the Service panel through the transfer switch. This allowed me to install the outside power inlet for up to a 7,200 watt 240/120 generator even though my gennie is only a 2800 watt 120 volt only model. It gives me (or the next owner) the option of going to a larger generator with no rewiring.
 
  #11  
Old 03-06-11, 12:47 PM
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Originally Posted by jfinn View Post
Thanks for pointing out my errors! I revised my diagram so now it looks like this (larger size here)


Can I run my grounds like in the diagram or do they need to be pigtailed too?
The neutrals will need to terminate on the LINE terminals.

Due to the arrangement of the ground screws it may be easier to pigtail the grounds also.
 
  #12  
Old 03-06-11, 12:59 PM
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A bit OT but in addition to marking the receptacles you might want to use blue or red receptacles and or cover plates instead of white. Being mostly intended for commercial use they may be more expensive. I like the idea but that may be a male thing and the female half of the house might have objections.
 
  #13  
Old 03-06-11, 01:13 PM
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Yeah - I have no idea what I was thinking... I drew that diagram before my first cup of coffee this morning. Thanks for catching it for me.

The new, corrected diagram is here.

 
  #14  
Old 03-06-11, 01:17 PM
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Originally Posted by ray2047 View Post
A bit OT but in addition to marking the receptacles you might want to use blue or red receptacles and or cover plates instead of white. Being mostly intended for commercial use they may be more expensive. I like the idea but that may be a male thing and the female half of the house might have objections.
I was planning on using a red plate around beige 20 amp GFCIs.
 
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Old 03-06-11, 01:33 PM
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Yeah even if you use a transfer switch it's good to use distinguishable receptacles. I changed all the 'backup' receptacles to blue, so they are immediately identifiable, and put a label on the transfer switch that blue receptacles have backup - again, so if I sell the house, the new owner immediately knows what's what.

And about the genny and GFCI protection, most of them will just have a small label near the 240v outlet that says "Not GFCI Protected".. The 120v receptacle will be an actual GFCI. Unless the Main breaker has Test/Reset buttons on it, it does not provide GFCI protection to the 240v receptacle, so you will be fine installing GFCI's inside the house.

Just out of curiosity, is your breaker panel on an interior wall? Or maybe does it have a closet or stairwell behind it? You could always go through the back knockouts..
 
  #16  
Old 03-06-11, 04:29 PM
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My panel is on the inside of an exterior wall. I'm not sure but I heard once that it's required code in this area (Loudoun County, Virginia) to have the panel within X feet (maybe 5?) of the meter.
 
  #17  
Old 03-07-11, 12:08 PM
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I have the same generator, and have dedicated outlets in various parts of the house to be powered by the generator during an outage. Under normal operation, though, those outlets are powered by a charger/battery/inverter setup to serve as an uninterpretable power supply for my FIOS phone/TV/internet box, as well as router. A lot of other stuff could be plugged in as well if the power goes out, long before the generator is needed.

Those outlets are all painted green and are separate from the house power. My question.. should the green outlets share a ground with the rest of the house? Or should they have a separate ground? Right now the grounds are separate.
 
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