Backup Generator Wiring


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Old 09-19-08, 10:24 AM
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Backup Generator Wiring

So I had an electrician come to finish up my generator install and basically said I had wasted my time. The automatic transfer switch that came with it has only a 2 foot lead to go to the main panel, so I bought individual wires of the same gauge and ran them all in a plastic conduit. 30 feet in all, because my panel is 30 feet away not 2. So I now understand it is against code to do this, but he couldn't or wouldn't tell me what the risk was. I am happy to follow code, or laws, but I have to know why it exists. Does anyone know the risk of running individual wires in their own pvc coating together in a plastic tube ? If I have to buy 30 feet times 16 strands of romex then I have priced myself out.

Thanks
 

Last edited by luftzeug; 09-19-08 at 10:26 AM. Reason: fat finger
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Old 09-19-08, 12:39 PM
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There could be a few codes that you're bumping up against, but my guess is that it's either derating or conduit fill.

Derating limits the number of conductors you can put in a conduit to prevent heat build-up. Too much heat reduces the lifespan of the wire insulation and may cause it to fail. With standard residential circuits, the limit is usually about 9 wires before this rule takes effect. Specialty circuits may be affected with as few as 3 or 4 wires.

Conduit fill deals with the "fullness" of the conduit, which can only be 40% under most situations. The hazard in overfilling a conduit is that you have to pull the wires with too much force which can skin or tear the wire insulation or cause the wires to twist and jam in the pipe.

There could be other factors too depending on the type of wire and conduit you used.

The compliant solution in your case is probably to run multiple conduits, but there may be other solutions too.
 
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Old 09-19-08, 01:10 PM
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so would I be more compliant since the wire conduit runs only in crawlspace to remove the conduit and loosely keep the wires together with tiewraps ? That way they'd breath more ?
Ok forget compliant, just less heat risk.
Thanks
 

Last edited by luftzeug; 09-19-08 at 01:20 PM. Reason: add
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Old 09-19-08, 01:45 PM
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No, individual conductors must be in conduit. Sure, there would be less heat risk, but a lot more damage risk and inductive heating risk and still not compliant to electrical code or listing of the materials.

In my opinion, the correct solution is to install the correct number of conduits to accommodate the number of circuits.
 
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Old 09-19-08, 01:54 PM
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thanks for the info, I figured there was no way to get around buying $800 of romex....and restring it through the narrow crawlspace and ruin the plaster wall where the main panel is to gain egress...I wish I could go back to the moment right before I clicked buy on the generator.
 
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Old 09-19-08, 02:38 PM
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There are always multiple correct ways of solving the problem, one of which may be to extend these circuits out to the generator panel. If you give us some more details about the panel, transfer panel, generator and locations of each, we may be able to suggest a different solution.

Also, exactly what materials do you already have installed? You may be able to salvage or re-use what you have in a different way that makes the installation compliant.
 
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Old 09-19-08, 02:57 PM
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sounds like you might have this backwards. the transfer switch goes next to the electrical panel. from there you feed the generator. the sizing of those conductors would be based on the size of your generator and transfer switch.
 
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Old 09-19-08, 04:01 PM
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There is no room next the to main panel in the kitchen, nor will my wife accept it to be in the dining room (behind). The auto Xfer switch is bulky. So it goes in a closet about 10ft away as the crow flies but requires about 34 feet of wire going in the crawlspace. The Xfer switch came with a 2 foot whip with stranded wires ranging from 8 gauge to 14. It backs up 8 circuits. So I have 3 8 gauge wires (black-red-green) that routes mains power to the switch, then a 30/30amp 10 gauge (3 wires, red-black-white), a 12 gauge white-black and then 5 14 gauge pairs. The 2 foot whip that came with it had individual stranded wires going in a conduit, so I just duplicated this in the from of a 32 foot whip. So 2 feet is ok, but not 32 obviously now. It was about $125 of wire and $40 of conduit. So I guess I need to use romex (and there is not enough egress into fuse box for all this romex without major wall/stud rework). Right ?
Thanks
 

Last edited by luftzeug; 09-19-08 at 04:06 PM. Reason: add
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Old 09-19-08, 04:34 PM
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this will work but code says more than two current carring conductors in a raceway and you must derate. but its a real world out there and this would not be the first time someone did not derate. as for heat what size pipe did you run? im out the door now but will ck in later.
 
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Old 09-19-08, 05:11 PM
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Originally Posted by jjkjr View Post
this will work but code says more than two current carring conductors in a raceway and you must derate. but its a real world out there and this would not be the first time someone did not derate. as for heat what size pipe did you run? im out the door now but will ck in later.
Thanks. Every couple of feet I used black tape to bind the wires together so it would stay together to get through the conduit. At the black tape points the circumference is 2.25" and then at inner circumference of the plastic conduit is 4.25"
 
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Old 09-19-08, 06:52 PM
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i dont know if you can but it would be a good idea to remove that tape as this is the point were the heat will have the greatest impact on the conductors. this is called bundling and is also against code. pipe size is more then enough for the wires you are running.
 
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Old 09-19-08, 07:38 PM
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I don't know what size romex you are talking about but $800 of NM cable ought to wire about three quarters of your house.
As far as being 30 feet away, there is nothing wrong with this as far as I know.
I assume that we are talking about a Guardian "Generator Ready Panel" here.
 
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Old 09-19-08, 08:27 PM
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It is this exact thing right here


you can see the 2 footer there, I have made that into a 30 footer. I guess I should price my romex not using the per foot price on amazon.com. I am also about 60 feet from my gas meter, so I guess I need to rent a manometer. All this being said, I tested it today running my central air and blower. Everything worked perfectly, but only for short while because I am still not sure about the risk of heating.

Thanks
 
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Old 09-20-08, 02:16 AM
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Something is not adding up right with this type of transfer switch.,,

Let start this part first .,, Do you have main breaker located outside or not ?

Next thing is the #8 AWG cables that marked red and black and Green ??

also with the #10's black, red and white.

and the #12's black and white.

If that is the case you may run some issue with it allready because I normally treat the transfer switch in two diffrent fashon depending on set up but that transfer switch that you show to us that can raise the issue espcally if used as subpanel and it will not meet the code due missing #8 white conductor because you mention #10 and #12 white conductor.

{ especall this is true if you have outside main breaker and load centre in the wall it will automatically become 4 wire feeder set up }

Now the other issue it may arise here is the Natrual gas metering set up most of resdential gas meter are useally set up for 150,000 to 175,000 BTU rating { some do go up much as 250,000 BTU rating } and when you are running the generator they can really can cause some issue if you did not change the pipe or meter.
Espcally true if you used 7" WC system { natrual gas } the LP typically run 14" WC but I am aware some home do have 2 PSIG system in there then it can handle it pretty good depending on the pipe size and #'s of bends.

This part you may want to get a hold of your gas company or POCO if they have Natural gas divison in there and they can come out and take a look at your gas meter to see if that meter can handle both generator and furnace load at the same time { espcally true in cold weather }

Merci,Marc
 
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Old 09-20-08, 04:20 AM
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It sounds like the issue is that you need larger wire sizes, not lots of Romex. It is certainly easier to run one or two conduits and pull individual conductors than to run a boatload of Romex cable. The trouble is that you have 12 wires in one conduit, so each wire has to have double the capacity it would have if run on its own. That means instead of 14-12-10-8 ga, you need 10-8-4-3 ga. That still shouldn't be overly large for the pipe though, you ran 4".

Code makes allowances for excessive numbers of wires in a conduit without derating. But only when the run is short... like 2'...

One last note: Size of conduit has nothing to do with the need to derate for heat. In a run of any length (other than short nipples) there is no airflow inside the conduit, so the heat being put off can only escape through the walls of the conduit. So a bigger conduit doesn't make any real difference to how hot the wires get. The charts showing how many wires can go in a conduit are only to make sure the wire gets pulled in without injury.

Taping wires together is also a bad idea because it makes the wires harder to pull in, they need to be able to move independently in order to pull smoothly.
 
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Old 09-20-08, 08:52 AM
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Originally Posted by mukansamonkey View Post
It sounds like the issue is that you need larger wire sizes, not lots of Romex.
Thanks, I just taped the wires because I couldn't get them to behave (uncoil) to even go in the conduit. I think I better check the water column on the gas and then decide if I put the generator on craigslist. I nearly killed myself taking the generator off the palate and putting it in place and killed my knees running the wire in the crawlspace, and then 60ft of gas flex pipe in the same crawlspace. Lots of time and spilled blood invested in this endeavor. I have the know how, but not the know right. Thanks for the tips. I'm off to make my own manometer.
 
 

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