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Old 01-15-2011, 09:38 AM   #1
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Generator to panel wiring


My panel is off the grid and has one 220V breaker on a convenience outlet.

I believe the 110V breakers are split between X-N and Y-N.

My generator has a floating neutral and 240V socket with X-Y-N-G.

I want to power the panel from the 220V convenience outlet.

Advice on the web was emphatically to use the X-Y-G from the generator into the X-Y-N of the convenience outlet but I am seeing no voltage on my 110V circuits.

Any advice before I rewire my adapter to have generator X-Y-N into convenience outlet X-Y-N?

The web info is at:
http://members.rennlist.com/warren/generator.html

and it provides:

"Neutral floating at generator, neutral not switched at transfer panel. This is a correct configuration. Neutral for the entire system is bonded at the main service panel. There will be no ground conductor current. Only live lines are switched with a two pole transfer switch."


Ken C

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Old 01-15-2011, 10:41 AM   #2
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Generator to panel wiring


Connect X-Y-N of the generator to the respective terminals (X-Y-N) in the panel. If you use a cord and plug from the panel to connect to the generator receptacle, you must have a transfer switch that makes the plug prongs dead when alternate power is applied to the panel. If you have a utility connection you must have a transfer switch or other mechanical arrangement that prevents both the generator and utility power from entering the panel at the same time and prevents generator power from going out to the utility pole.

Do not make a cord with male plugs at both ends or any exposed metal that is live depending on what order you connected the ends to the generator or panel and or what order you flipped switches. You may not infuse power into a panel or other electrical system using one of the system's receptacles to receive it.

Also connect G to G if the cord and plug has that, otherwise string a ground wire (at least within one size of the power wires) between the panel and the generator frame. Use #6 wire for this and also connect it to a ground rod you drove at the generator if the generator is not portable.

Leave the neutral and ground floating (unbonded) at the generator.

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Old 01-15-2011, 11:32 AM   #3
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Generator to panel wiring


Thank you.

A few additional questions:

(1) The generator LR-14-30R N (more correctly W) will be connected to the panel W, which is grounded at the panel. If I connect the generator chassis ground to the panel ground, it will also be shorting the generator LR14-30R W to the chassis ground. Is this any different from changing the generator neutral from floating to bonded?

(2) My adapter converts the generator LR14-30R into a 6-20R in a "grounded" steel box. However, the "ground" is actually the W from the generator. Will the box be a shock hazard? Can I use it to power 220V appliances? If I change my adapter so that the generator LR14-30 X and Y go to my 6-20R X and Y, with the generator W and G both going to the G of the 6-20R, don't I accomplish what you recommend?

Ken C
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Old 01-15-2011, 12:37 PM   #4
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Generator to panel wiring


Yes the generator's frame and neutral become bonded when you connect it X-Y-N-G to the panel X-Y-N-G respectivley. This part is proper.

But you should not also make a connection N to G at the generator itself when such a bonding is present at the panel.

The idea is that for current flow, the current returning on the N must not be able to use G as an alternate route which could happen if the N between panel and generator happened to have a loose connection and G was connected to N both at the generator and at the panel.

In a subpanel, N and G must be separated. If a generator is connected to a subpanel (with a transfer switch that deisconnectes the subpanel from the main panel) then the generator itself should have N and G bonded within. The generator N and G are also to be bonded within when the generator is out in the field and tools are plugged in and there is no connection to a building power system.

However I would not go through a main panel and laboriously unbond N and G in order to permit use of a generator whos N and G could not be unbonded (floated) within or because N was connected to a steel box between the generator and the panel. Here I would rather use extension cords to connect up lights and appliances instead of connecting to the panel.

Normally a steel junction box should not have a white wire (N) connect to it.

If the steel box is part of the generator than the white wire (N) connected there is the same thing as having the generator neutral not floating. So long as G is tightly connected (bonded) between the generator and the box and between the box and the panel (if you are powering the panel) I do not think there would be a shock hazard.
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Old 01-15-2011, 01:26 PM   #5
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Generator to panel wiring


I wired it up so I go generator XYW to panel XYW.

The 120V circuits all properly energized.

W shows 0 VAC to house earth (actually jumps around between -1.5V to -1.5V).

I am seeing 40VAC between W and generator chassis ground. I guess this will go to zero if I run an earth wire to panel common, as you suggest. Darned if I see why I can't do that with a shunt right inside the LR14-30 plug at the generator.

Is the metal adapter box (shorted to generator W) a shock hazard if I am not hooked up to the panel? Would it be less of a hazard if I also shorted it to chassis ground?

I can wrap it in tape and put a plastic front plate on it that solves the problem.

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Old 01-15-2011, 10:25 PM   #6
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Generator to panel wiring


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Originally Posted by cprstn54 View Post
darned if i see why i can't do that with a shunt right inside the lr14-30 plug at the generator.
never do that
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Old 01-15-2011, 11:04 PM   #7
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Generator to panel wiring


The W (white; N; Neutral) is not supposed to be bare or touched.

So long as the generator frame is not connected to any of the house system grounds, (the frame is floating) any voltage measured between it and W is unpredictable.

Still you should investigate to see that the 40 volts is not due to some short between energized parts and the frame.

Alternatively, that 40 volts could well be "phantom voltage" induced by the juxtapostion of part of the metal frame to wiring or energized parts with no metal to metal contact. Digital voltmeters are more apt to show readings from phantom voltage compared with analog (needle) voltmeters.

If you try to use that 40 volts to light a very small 120 volt incandescent lamp (bulb)such as in a night light, if the voltage drops to zero then you can assume it was phantom and harmless. If the lamp glows then you have a short somewhere.

The 40 volts will go away (or almost go away) when the generator frame is bonded to the house system ground using a separate wire (G) accompanying the X, Y, and N to the panel.

About the N shorted to the metal box, did it come that way from the factory?
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Old 01-15-2011, 11:35 PM   #8
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Generator to panel wiring


> About the N shorted to the metal box, did it come that
> way from the factory?

No. I made the adapter -- to go from the L14-30R on the generator to the 6-20 at my panel. I put a 6-20R in a metal box and face plate from Home Depot. I now have the X, Y and W of the L14-30 going to the X,Y and G of the 6-20R. The 6-20R receptacle shorts the box to the G, so the box is actually at the generator's W voltage.

Apparently dryers and some other 220V appliances have the W connected to their chassis, although this is now disapproved.

I will look for a plastic box and plastic face plate. Failing that, I will insulate the metal box with gaffers tape.

The adapter seems to work just fine wired this way. It energized one breaker with an incandescent lamp on it and a second one with some 4 ft fluorescents. Inasmuch as the W is shorted to earth in the panel, the box ought not be energized when hooked up to the panel. When the box is not yet hooked up to the panel, I am concerned that it could be hot.


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Old 01-16-2011, 12:12 AM   #9
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Generator to panel wiring


What are you using that disconnects the utility at the same time you move your double pole breaker to the generator 'on' position? You cannot meet code if you do not have some kind of interlock or one throw DP switch between the generator breaker and the utility main. The act of turning the generator breaker on must also disconnect the main in a single throw. In other words you cannot turn on the gen breaker then reach up and turn off the utility main ...it must be single throw movement of the hand or in the case of an interlock the main has to be turned off in order to turn on the generator breaker and vice versa.

Also you seem to be running a generator cord that is only 3 wires to this so called steel box. So if I am understanding correctly you are saying you have bonded the neutral in the power cord to the metal of that box that holds the receptacle ?
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Old 01-16-2011, 07:10 AM   #10
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Generator to panel wiring


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What are you using that disconnects the utility at the same time you move your double pole breaker to the generator 'on' position?

Also you seem to be running a generator cord that is only 3 wires to this so called steel box. So if I am understanding correctly you are saying you have bonded the neutral in the power cord to the metal of that box that holds the receptacle ?
I am the transfer switch that disconnects from the grid. This is a stand-by generator in my garage at the panel that is manually engaged and starts off connected to nothing but a fan for cooling and ventilation and a floodlight, using the 5-20R's on the generator. First, the power goes out. Then I open my garage doors manually to avoid asphyxiation. Then I start the generator and get some light and ventilation Then, I open the panel main breaker to disconnect from the grid and ensure the breaker for the 6-20R 220V outlet at the panel is open. Then I connect the 6-20R at the panel to the L14-30R of the generator. Then I close the 6-20R breaker, which energizes the panels' 120V breakers.

This worked OK for 25 years with a Coleman 4000 watt generator that had a 6-20R outlet and 2-hour gas tank. I just upgraded to a Honeywell generator with a 6-hour gas tank and an L14-30R and 5-20R's but no 6-20R. The adapter was needed to go from the L14-30R of the generator to the 6-20R at the panel.

The adapter consists of an L14-30P, 4 ft of #8 3-conductor cable and a 6-20R in a steel receptacle box and faceplate. The generator X, Y and W run to the 6-20R X, Y and G (there being no W, as far as I know).

Suffice it to say that the person who figured it out for me 25 years ago when the house was built knew what was what. It might not be the best arrangement, but it is the least expensive.

No energized plugs ever have their blades exposed but I am worried about getting a shock from the adapter 6-20R receptacle box, which is at generator W potential and is not grounded, before it is connected to the panel. I also do not know if I can use the same adapter to power a 220V appliance when the adapter is not connected to the panel.

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Old 01-16-2011, 08:40 AM   #11
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Generator to panel wiring


Please use English words and phrases to describe things rather than catalog numbers or codes like L14-30R. Otherwise I and others just guess about what the item is and the reply misleads you and others.

You (any person) are not considered a good enough interlocking transfer switch. The system is still considered illegal and unsafe when any wrong move or wrong sequence of switch flipping can result in generator power going out over the utility lines.

If the box or adapter has terminals for both X and Y inside, then a receptacle or cable to serve a 240 volt only appliance can be installed or connected there. If the box has terminals for X, Y, and N there, then a receptacle to serve a 240 volt appliance with 120 volt components can be installed there. You may not connect 120 volt or 120/240 volt items to a location with just X, Y, and G.

There is a maximum amperage for any branch circuit serving lights, appliances, etc. For example if an appliance has a maximum circuit rating (not the maximum usage or draw) for 30 amps, there must be a 30 amp breaker somewhere between it and a panel or generator that can supply more. Lights and typical cord and plug appliances can go on circuits rated no more than 20 amps. Thus subpanels (with fuses or breakers) are used on heavier feed lines from generators.
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Old 01-16-2011, 08:56 AM   #12
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Generator to panel wiring


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Originally Posted by cprstn54 View Post
No. I made the adapter -- to go from the L14-30R on the generator to the 6-20 at my panel. I put a 6-20R in a metal box and face plate from Home Depot. I now have the X, Y and W of the L14-30 going to the X,Y and G of the 6-20R. The 6-20R receptacle shorts the box to the G, so the box is actually at the generator's W voltage.

Apparently dryers and some other 220V appliances have the W connected to their chassis, although this is now disapproved.
The thing is, a dryer circuit HAS a neutral. They are 120/240v appliances, NOT "220v".
The 120v current is being carried by a safe and valid neutral, not the bare ground wire of a circuit.




They way you have been doing this is VERY wrong, and potentially VERY dangerous. And DO NOT give the old line "It's worked fine for 25 years so it is safe." That is complete false security. That is like saying you can drive drunk and be completely fine. Maybe, but your chances are MUCH greater that something bad is going to happen. And it only needs to happen once.
In fact, the more time that goes by the less conscious and attentive you will tend to be. On mistake is all it takes.



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Originally Posted by cprstn54 View Post
Suffice it to say that the person who figured it out for me 25 years ago when the house was built knew what was what.
NO, the person was a hack with just enough clue to make it work electrically, yet still be unsafe enough to kill someone. Let's just hope it is not a line man working on the lines during an outage or one of your kids.



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Originally Posted by cprstn54 View Post
It might not be the best arrangement, but it is the least expensive.
WOW. This statement is simply amazing.

I can already tel that you have absolutely no intention of correcting this dangerous mess so I will refrain from any more replies on the matter.
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Old 01-16-2011, 09:03 AM   #13
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Please use English words and phrases to describe things rather than catalog numbers or codes like L14-30R.
They are NEMA codes and the best way of describing the situation. For pics, see:
http://www.elecordset.com/twistlockp...rcordsets.aspx

L prefix means "locking." R suffix means receptacle and P means plug.

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Old 01-16-2011, 09:20 AM   #14
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NO, the person was a hack with just enough clue to make it work electrically, yet still be unsafe enough to kill someone. Let's just hope it is not a line man working on the lines during an outage or one of your kids.
As a licensed electrician, you should recognize that the panel is wired fully to code and that the designer (now riding the licensed electrician's highway in the sky) was rather clever.

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Old 01-16-2011, 10:26 AM   #15
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Generator to panel wiring


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As a licensed electrician, you should recognize that the panel is wired fully to code and that the designer (now riding the licensed electrician's highway in the sky) was rather clever.
That panel may be wired correctly, but the generator backfeed was NOT clever but rather quite stupid. Same as using a 6-20 receptacle to feed a 120/240v load.

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