Generator question (household wiring to be more accurate)

[joefromga]

You would assume that linemen don't go without insulators while working on the lines because the power is out.

Like you said above, the solar panels and other systems that backfeed probably don't have shutoffs either.

 

[buckeyefarmer]

Here solar systems have to have an external disconnect, and the power company approves them, so they know who has them. I can see power restoration taking a lot longer with all the grid tie systems here.

 

[SPYDERLK]

I have not read every post, so if someone else has mentioned this disregard. The weak link in a generator supplied power source is the size of the wire between the generator and the service panel. I personally if going to wire a 20 kW generator in for whole house would place the generator as close to the house meter, as possible and use a 200 amp manual disconnect. # 1 wire will carry 150 amps for short distances. I would use this type wire from the generator to the disconnect. Wire Capacity Chart

A lot of people have acute acid reflux when they start pricing the per foot cost of # 1 copper for the run from the generator to the service disconnect or the 3/0 (200 amp) or 4/0 (230 amp) copper service wire which will be needed to go from the service disconnect to the meter or from the service disconnect to the main service panel.

for a 20kw generator one most likely could get by with a #4 copper or a #2 aluminum wire, longer distances up a size, for the line from the generator to the transfer switch, they only can produce about 80 amps per leg,
and I would guess most of the time one would only be running 30 or less amps per leg,

mount the transfer switch on the meter pole or near, and the large wire from the meter to the transfer switch would be very short,
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and the smaller the generator the smaller the wire need, on a 10 kw generator if the wire length was short a #10 would carry the 25-30 amps the generator can produce,

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the wire chart in the quote IMO is wrong when it comes to 12 volt capacity, I am not saying that auto 12 volt wiring is under sized in most instances as it carries in such short bursts of power, thus able to mataine the load for the duration, but for continuous loads the chart IMO is not accurate, for example you feed a 100 amps in a #10 wire for any length of time your insulation is going to melt, try it some time if you do not believe me, amps is amps, the voltage of the line has little to do with how many amps the wire can carry, (the amount of power it can carry is a combination of volts and amps), the higher the voltage the more power is carried for a given amp load, that is why transmission lines have high voltage, they can move a lot of power on a fairly small wire, and then a transformer drops the voltage down, and the total amount of power would now need a very large wire to carry the same power,

the KW rating is the sum of that power, where voltage and amps is the mix that makes up the KW rating, (kW Times 1000) divided by Volts =amps

Well stated. ... I think those high 12V capacity numbers are single wire open air short runs. Turbulence under the hood would favor it. -- Electrical novice beware.

 

[aczlan]

You would assume that linemen don't go without insulators while working on the lines because the power is out.
Like you said above, the solar panels and other systems that backfeed probably don't have shutoffs either.

Most (all?) of the solar panel systems do not start backfeeding until they sense power from the grid.

Aaron Z

 

[joefromga]

Most (all?) of the solar panel systems do not start backfeeding until they sense power from the grid.

Aaron Z

I was thinking that may be the case.

 

[buckeyefarmer]

Do the microinverters? Not sure how they sense that.

Edit. i looked up enphase and they do isolate and not backfeed when utility is out.

The point i was making is backfeeding in itself is not against code as some claimed.

 

[buickanddeere]

You would assume that linemen don't go without insulators while working on the lines because the power is out.

Like you said above, the solar panels and other systems that back feed probably don't have shutoffs either.

All Code Compliant Grid Tie Invertors isolate when the AC utility power is lost.


https://static.hydroottawa.com/documents/specifications/ECG0002.pdf

 

[LeedsCase]

The code addresses the integration of solar and other systems. Regarding the use of generators, there actually are several exceptions that address the use of a temporary portable generator

Saying that a section of code doesn't strictly apply is inaccurate. When there is uncertainty, the code that bet matches the situation will be applied. That is standard practice with safety guidelines. That is why a shipyard is held liable for LOTO requirements in a different part of the standard.

Working from the 2008 codebook, A temporary generator would be considered an Optional standby system which is covered in detail in article 702.
There is an exception to the transfer device requirement detailed in 702.6 for temporary connections of a portable generator, provided the normal servicing means is isolated using a lockable disconnect, or by physical disconnection of the normal supply service.
705.12 details where you can connect the generator. It also details the backfeeding of the system by verifying that breakers are intended for such a use. You still have to comply with overcurrent protection requirements and grounding requirements however.
Article 240 addresses the overcurrent protection requirements.
Article 250 addresses the grounding requirements.

If your actions result in someone getting injured, you can be held criminally and civilly liable. I would rather spend $500 doing it right, and not have to worry about the power company or someone else suing me for hundreds of thousands of dollars.

If your using a portable generator to get through a power outage, plug the devices you need into the generator.

 

[buickanddeere]

Internet experts, or inspector? Are you referring to the Op's case or Aaron's?

All the people who refuse to install an interlocked break before make transfer switch for the backup generator.

 

[buickanddeere]

I asked Leedscase about the code section prohibiting backfeeding from a subpanel, because he's the one who said it.
I asked you to define who the experts are that have told us we are "purposely doing something wrong"
So far neither have replied to what i asked.

I suggest some research "service entrance", and "back feed". You do know that grid tied solar, and other load sharing cogen systems backfeed every day, and it is perfectly legal and code compliant. Right?

I have my code book open, i see nothing that prohibits what the OP or Aaron is trying to do. Commercially it is not uncommon. Section 702 allows what the OP is trying to do, it's up to their AHJ to allow it.

For SAG, i did google "elecrical code backfeeding standby generator". Know what i found, a lot of references to "may be illegal", "could be dangerous", one from a county which wrongly referenced section 700, which is legally required emergency systems. None that gave a solid code answer, but i did not look at them all.

Bottom line is, when people replying here and use wrong terminology, or blindly say don't because I think it's dangerous, then yes, I am not going to believe you. When you start name calling, then you have already discredited yourself.

I have designed and worked on quite a few generator projects, and have held the title AHJ.

What are your credentials that I should believe you?

I hold an Inter Provincial 309A ticket plus a bunch of others.