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Ron of Va
09-03-2010, 01:50 PM
I just got a 15,000 watt generator with a 22,500 surge. The main outlet plug is a 50 amp 4 wire, which will only deliver 12,000 watts. It also has a 30 amp 120/250 twist lock outlet (4 wire), and according to Generac will deliver the other 3000 watts, on extension cords, but they would not give me any advice on how to wire it to combine the two power sources into my panel.

(I am back feeding the power after shutting off the main breaker)

The question is about connecting the 30 amp 4 wire to the panel via a separate wall receptacle, like I am doing for the 50 amp.

A friend said I should drop the neutral or the ground to prevent a “loop” situation. Could someone please comment? Can I just wire the 30 amp receptacle with 4 wires like I am doing with the 50 amp, or will that cause any problems?

winchman
09-03-2010, 02:31 PM
Unless you have a completely separate sub-panel that you're going to feed from the 30-amp gen-set output AND you shut off the main breaker for that sub-panel, you're not going to be able to keep the loads separate.

I'd suspect they didn't give you "advice on how to wire it to combine the two power sources into my panel" because they don't want you to use the gen-set that way.

"(I am back feeding the power after shutting off the main breaker)"

I'd suggest you look into an automatic or manual generator transfer switch. What you're proposing probably won't pass code or be acceptable to the power company.

Ron of Va
09-03-2010, 02:47 PM
Unless you have a completely separate sub-panel that you're going to feed from the 30-amp gen-set output AND you shut off the main breaker for that sub-panel, you're not going to be able to keep the loads separate.

I'd suspect they didn't give you "advice on how to wire it to combine the two power sources into my panel" because they don't want you to use the gen-set that way.

"(I am back feeding the power after shutting off the main breaker)"

I'd suggest you look into an automatic or manual generator transfer switch. What you're proposing probably won't pass code or be acceptable to the power company.
I don’t want to keep the loads separate. I want to combine them to utilize the 15,000 capacity of the generator, not just the 12K from the 50 amp outlet.

I am very much aware of how to back feed a generator. I am very cautious and I have been doing it for years with a 5500 watt generator. I got a great deal on this 15k generator and I want to have access to its full potential.

The tech support at Generac told me it would work, that I could combine the two inputs into the panel, but would not tell me anything else, and I understand why. The thing I am most interested it is how the 30 amp should be wired. My friend said I could use just the two hot legs, because the neutral and ground will be fed through the 50 amp side.

I trust my friend, but he is not a professional, so I though I would ask for other comments.

TGTool
09-03-2010, 02:47 PM
I'd suggest you look into an automatic or manual generator transfer switch. What you're proposing probably won't pass code or be acceptable to the power company.

Ron,

Take this issue very seriously. It can be a life threatening hazard to power company employees trying to re-establish pwer after after a loss. It's simply not good enough to day "Oh, I'll make sure to shut off the main so I don't feed back to the line."

Ron of Va
09-03-2010, 03:05 PM
Ron,

Take this issue very seriously. It can be a life threatening hazard to power company employees trying to re-establish pwer after after a loss. It's simply not good enough to day "Oh, I'll make sure to shut off the main so I don't feed back to the line."
I take it very very seriously. I know what can happen if my power escapes my home through the power lines. Trust me, it is not going to happen. I also know what can happen should the power come on while my generator is connected. I know back feeding a generator gives most people the creeps, because of all the incompetent and careless people out there.

I am considering a transfer switch, but right now I just want to get connected.

I think the wiring of the 30 amp side will be OK with two hot legs, and one ground, dropping the neutral. I want to keep the ground because if the 50 amp breaker trips, I will loose ground to the 30 amp side. Do any electricians have any comments on this?

Your Old Dog
09-03-2010, 03:36 PM
Ron, are you looking to run the home as though there were no power outage? I have 7500 generac and we make a half effort to conserve and have no trouble with it. I don't run electric dryers or ranges but aside from that, unless you want to have every light in the house on and your neighbors as well this may be an overkill project?

I took conventional 110 outlets, split the little jumper between the two sides and wired one side to the fuse box, the other side to the generator. Then I put a regular plug on the furnace blower, water pump, kitchen circuits and one for bedroom light. I marked each side of the outlets as "gen" and "panel" and hung a yellow ribbon from each plug. When the power goes out I go down to the basement and switch the 4 plugs from "panel" to "gen" and it works great for us. I brought the 220 circuit into the basement from the garage on 12 guage 220V line. When the power does come back on the generator is isolated from it but we still have the other lights in the house come on to tell us all is clear.

winchman
09-03-2010, 03:55 PM
"I think the wiring of the 30 amp side will be OK with two hot legs, and one ground, dropping the neutral. I want to keep the ground because if the 50 amp breaker trips, I will loose ground to the 30 amp side."

Neutrals and ground don't normally go through breakers, so I don't understand how having the 50-amp breaker trip will cause you to lose the ground.

It's sounding more and more like this is going to be a non-standard make-shift hook-up, and you'll be the only person on the planet that understands how it's supposed to work. That's an invitation to disaster.

Black_Moons
09-03-2010, 03:57 PM
Short awnser: Don't, can't, bad idea.
Long awnser: Can, Requires math, nerves of steel, and really good connections.

Basicly, to 'balance' the loads, your best bet would be calculating the resistance of the two lines from the generator to the panel, Given the AWG and length. Run them into seperate fuses/breakers, apporate for each line. Current should more or less balance if wires resistance is correct. May need to make one line longer, or thicker/thinner wire to balance the current. (Basicly you need to balance the resistance of the two lines to a 50/30 ohm ratio)

As for the neutral.. Debatable, Technicaly, there should be very little neutral current, and either neutral should be capable of handleing what current there will be. I would likey leave both connected, Its not likey to cause a problem, and loss of neutral is a very bad thing that can fry your 120v appliances.

Before connecting the two however, you must get the phases right. Connect up two 120v bulbs in series (or use a 240v bulb) and run it beween the 2nd generator line and panel where you plan to connect it, If it lights, you have the phases wrong, if it does not light, the phases are correct.

PS: ground and neutral are never fused or run through breakers (Unless installed incorrectly.. Extremely incorrectly)

ADGO_Racing
09-03-2010, 04:42 PM
If it is a single phase generator, it shouldn't matter, you have two hot legs (110V each) coming off the generator, they are always in phase. The Generator probably only has one output, and the receptacles are probably wired from a common buss.

If this is the case, why not just remove the cables to the buss for the receptacles, and just wire the main cable into the box, or add an appropriate plug that will handle 80 amps.

winchman
09-03-2010, 04:54 PM
Balancing the load has nothing to do with the resistance of the wiring, and everything to do with the loads from lights, appliances, tools, etc. that are connected to the circuits.

A 220V dryer (with no 120V device inside it) represents a perfectly balanced load. There would be no current on the neutral.

Several 120V kitchen appliances (microwave, blender, toaster) turned on at the same time on the same circuit when nothing else is turned on represents a totally unbalanced load. All of the current would be going through the neutral.

Five 100W lights on one 120V circuit and five 100W lights on another 120V circuit could represent a totally balanced or a totally unbalanced load, depending on the connections in the breaker panel.

Ron of Va
09-03-2010, 04:55 PM
Short awnser: Don't, can't, bad idea.
Long awnser: Can, Requires math, nerves of steel, and really good connections.

Basicly, to 'balance' the loads, your best bet would be calculating the resistance of the two lines from the generator to the panel, Given the AWG and length. Run them into seperate fuses/breakers, apporate for each line. Current should more or less balance if wires resistance is correct. May need to make one line longer, or thicker/thinner wire to balance the current. (Basicly you need to balance the resistance of the two lines to a 50/30 ohm ratio)

As for the neutral.. Debatable, Technicaly, there should be very little neutral current, and either neutral should be capable of handleing what current there will be. I would likey leave both connected, Its not likey to cause a problem, and loss of neutral is a very bad thing that can fry your 120v appliances.

Before connecting the two however, you must get the phases right. Connect up two 120v bulbs in series (or use a 240v bulb) and run it beween the 2nd generator line and panel where you plan to connect it, If it lights, you have the phases wrong, if it does not light, the phases are correct.

PS: ground and neutral are never fused or run through breakers (Unless installed incorrectly.. Extremely incorrectly)

AAh! Now we are getting somewhere. I knew about the phases, and my friend reminded me about them too. That will not be a problem. He also talked about the resistance being balanced. This somewhat confused me. But I am beginning to get it.

So if the phases are right and the resistance is balanced, four wire connections from each outlet on the generator, back to the panel would be fine?

Black_Moons
09-03-2010, 06:15 PM
Ron: Yes, If each wire is independantly fused/breakered at its current/plug limit. (idealy at the generator, but at the panel will do too.)

You might not achive 100% power (70A) before one breaker trips, causing the other to trip right after, but you should be able to get it close if you get the wiring runs resistance with the right ratio.

ADGO_Racing makes a good point at rewriting it, Unfortualy I don't know of any commonly avilable plug over 50A. Hardwiring it is an option, though you'd still need to add a 80A (or 100A?) breaker at the generator, something to match the wiring capacity anyway.

winchman: He has two 240v circuits from the generator, the problem is balanceing the load beween the two cable runs (And the generators breakers/connections) safely, Not beween the 120v circuits and neutral.

Glenn Wegman
09-03-2010, 06:42 PM
Unfortualy I don't know of any commonly avilable plug over 50A.

Pin and Sleeve connectors.

Ron of Va
09-03-2010, 06:55 PM
This unit is a beast. http://www.poweredgenerators.com/guardian/ultrasource-15000.html

Both 50 amps and the 30 amp are individually fused at the generator. I will use 6/4 SO for the 50A and 10/4 SO for the 30 amp. My friend is calculating the resistance to determine how to match the lengths of the extension cords. Approximately 20 feet of cords.

They will be plugged into an appropriate sized outlet with a 50 amp breaker and a 30 amp breaker in the panel of my detached garage which is connected to the main panel of the house with 2/0 copper wire.

The main panel of the house will be turned off, (before I do anything) and the cover is locked with a hasp and padlock with a warning sign. (Even though it is only me and my wife living here)

darryl
09-03-2010, 09:32 PM
I won't speak to the issue of safety and transfer switching, etc, since you are aware of that and I don't need to further comment one way or the other.

On the issue of how the power from the generator is divided, it probably is as ADGO and Black Moons have said, two common hots feeding multiple breakers. If you did have a large load on the 12000 watt circuit, exceeding the rating, it would probably result in the breaker blowing if it was sustained loading over some time. I wouldn't doubt however that you could load that output down to the full capability of the generator for brief periods of time without causing problems or blowing the breaker all the time. If you tried to draw a consistent load near the maximum of the generator, it should blow that breaker, but you will get some peak current time before that happens. Unless you know that your loads will be that high, and sustained, you can probably just wire up that one output and it'll give you the full power peak on an intermittent and short term basis. No need to combine all the outputs to try and achieve the same thing.

Of course you don't go about drawing 3000 watts from those other outputs, then expect 20k from the main at the same time. Just consider that those other outputs aren't to be used at all when the generator is wired to your panel.

It's for you to find out and know what the loading condition is actually going to be. You will likely be popping the big breaker from time to time, depending on whether the dryer is running, electric heat is on, and two motors decide to start at the same instant- but a sustained load at the full 20000 watt level is unlikely in a domestic situation. I don't think you have a problem that needs solving- use the main output and ignore the others, and be done with it. If you're close to rated current from the one main output already, then you should be running a bigger generator.

MrDan
09-03-2010, 09:47 PM
My brother in law is an electrician and has wired up multiple houses for me to back feed. I asked him about getting one of the highly touted generator switches. His opinion was, as long as you can flip breakers correctly, it's just added expense for no gain as all it did was isolate the house, which is the same thing as flipping off the main. I guess if you want to be extra safe you can pull the meter or put isolators on the terminals so it doesn't have connection.

In one house, we simply back fed through a 50 amp circuit that I normally ran my welders off of. The 50 amp circuit was wired across both poles/legs so that each side got 110 and the 220 circuits were fed from both, or so he tells me, I don't open load centers. As for nuetrals, grounds, etc. That was all normal spec, no special hook ups to my knowledge. 99% of the time that circuit was providing power to my welders so it must have been normal code wiring.

The house I'm in now has a separate sub panel that again is wired back into the main load center across both poles. The only difference I see to the user (me) is that the sub panel has an extra protection of having it's own shut off. The sub panels are cheap and do make for a nice clean setup.

As for only needing certain amounts of wattage, it depends on your house size and what you need to run. My current house if about 5k square feet, just the lights suck up a bit of juice.

Living in in hurricane alley let me offer one other lesson from experience. After having lived with generators for weeks while we waited for power to be restored, you get to a point you need to fire up the fridge/freezers to keep the food. If you go that long, have your generator on line having shed what load you possibly can before you connect your fridge/freezer. I was amazed to see a 15k watt generator brought to it's knees every time a residential fridge was fired up. Once the compressor was running, very little draw, but that initial start up is a killer. We have one fridge and two freezers. You have to bring them online one at a time. When you back feed the house, make sure they are offline before feeding any power to the house for an easier transition over to generator power.

Feel free to tell me I'm wrong and crazy, I'm just glad I finally had some experience to share on this board. All I've done is suck knowledge from you guys.

J Tiers
09-03-2010, 10:06 PM
Personally, I think there is no point to this, the last 3000 watts is no big issue...........

The very first issue is to discover if the two have a common source.

if they come from one winding, then

1) they "could" theoretically be combined into one load.

2) this is not a good idea.

3) it involves some code violations, depending on how it is done.


problems:

a) you are paralleling wires of sizes that are too small to allow paralleling per code. You DO have separate overcurrent protection for them.

b) you do NOT have sufficient overcurrent protection for what I assume is smaller wire in the 30A circuit. The 50A source would be connected to it at teh end where they are combined, and so it would not be adequately protected. You might argue on the 'tap rule" but I don't know how far you would get.

c) you depend on plug polarity to avoid a line--to-line short, which is dubious.

If the two are separate source windings, 'a" does not apply, but "b" and "c" DO.

As for neutrals and grounds.

One equipment grounding conductor of the proper size for the combined currents should be sufficient.

If there is ONE source winding, only one neutral is needed if you paralleled wires. Another does no harm, but offers a chance to fry it if it is not the same as the largest wire in the system.

Naturally, you do NOT "bond" the neutral to the equipment grounding conductor..... that will be done by the "bond" in the service box. I assume that any "bond" existing in the generator is removable.

Personally, I would not do the paralleling. Do it right, or don't do it at all. And, regarding the transfer switch.....any problems on the line, any injury etc, and your lack of transfer switch plus your obvious generator connection will make you the goat, regardless of real fault, unless YOU can PROVE that someone else did it.

If you want the whole power, your best bet is the "cam type" connectors. This is the type you see on the generator when a small carnival sets up. There are very high current ones, and lesser current ones. They are single pole, and you can rig them on the generator to take the entire output.

http://www.leviton.com/OA_HTML/ibeCCtpItmDspRte.jsp?item=564323&section=10112&minisite=10026

http://www.leviton.com/OA_HTML/ibeCCtpSctDspRte.jsp?section=29578&minisite=10021

The so-called "pin and sleeve" connectors are fine...... One of them can cost you up to several hundred dollars. You need two. The "cam" type can be had for 20 bucks or less per each, color coded, good for lots of current.

Or, hard-wire in, using rated connection blocks.

Highpower
09-03-2010, 10:22 PM
My brother in law is an electrician and has wired up multiple houses for me to back feed. I asked him about getting one of the highly touted generator switches. His opinion was, as long as you can flip breakers correctly, it's just added expense for no gain as all it did was isolate the house, which is the same thing as flipping off the main. I guess if you want to be extra safe you can pull the meter or put isolators on the terminals so it doesn't have connection.
All of this makes me glad I went with the K.I.S.S. method.

http://img.photobucket.com/albums/v82/Highpwr/Temp1/10a60bf.jpg

Single connection from the generator to the outside receptacle.
Individual transfer switches for each circuit to isolate them from the main line without the need to remember to shut off the main.
Dual watt meters to allow you to balance the loads as needed.
Piece of mind. (No manslaughter charges....) :D

Easy peeezy.....
JMHO.

winchman
09-04-2010, 02:20 AM
If I understand it correctly, the yellow and red things next to the breakers are wire nuts which connect the original circuit leads to the wires running to the transfer switches, and only the wires coming back from the transfer switches are now connected to the breakers.

The transfer switches can select either the power company or the generator for individual circuits. The house circuits are still protected by the original circuit breakers.

Like you say, that's simple and safe.

Don Young
09-04-2010, 11:11 PM
Paralleling the outputs of both receptacles can certainly "work". There is absolutely no reasonable way to ensure that the load is proportionally shared by the two circuits. Even if you do some mathematical calculation of wire resistances, the unknown and varying resistances of the breakers, receptacles, plugs, and various connections will make those calculations meaningless. At full load one of the circuits will almost assuredly be overloaded, and it could be either one. If one breaker trips, the other will follow in short order.

The situation is somewhat akin to paralleling two seperate generators. It is not impossible, but requires some fairly sophisticated controls to ensure proper load sharing.

If you insist on having a connection rated for the full generator output, you will have to use a single connection which does not involve the existing breakers or receptacles. There is no other practical way.

Edit: I am assuming you will only consider a single load feed and will not consider splitting the loads. That could be a workable approach.

Highpower
09-05-2010, 12:10 AM
If I understand it correctly, the yellow and red things next to the breakers are wire nuts which connect the original circuit leads to the wires running to the transfer switches, and only the wires coming back from the transfer switches are now connected to the breakers.

The transfer switches can select either the power company or the generator for individual circuits. The house circuits are still protected by the original circuit breakers.

Like you say, that's simple and safe.
The transfer switches (upper row) are indeed double throw, allowing you select power from the service line or the generator for each circuit. Power from the main panel breakers feed into the transfer switches and then back out to the house circuits through the "line" side of the switch.

On the "gen" side of the switch however, power is coming in from the outside receptacle to the switches and then fed through the transfer circuit breakers (lower row) to protect the house circuits instead. That is what prevents back feeding. Power from the generator never gets to the main panel circuit breakers and the service line.

I only have 9 of the house circuits wired for generator use. Not that you would, but it is possible to run those from the generator and the rest of the house from the service line at the same time -- as long as you have line voltage of course. :p

Not as nice as an automatic system of course, but a whole lot cheaper and only takes a minute to connect the generator to the house and flip a few transfer switches - then Bob's your uncle. :)

Ron of Va
09-05-2010, 04:53 AM
I am getting cold feet on this project.

I believe that the 12k main 50 amp feed will power my house with plenty to spare, except when my 4 ton AC starts up, and my 50 gallon quick recovery hot water heater calls for power. I can manage these two manually, which is something I didn’t want to do.

I have considered contacting Generac and taking the unit to their service center to combine the two outputs of the generator into one feed, and use the cam lock connectors. (I already have two sets of them on a buzz box welder I installed 20 years ago)
I don’t know if they would do it though.

I appreciate all the advice you guys have given.

I am glad we will no longer have to heat hot water in a turkey fryer for a bath. Since my wife can’t help, and carrying a pot full of boiling water to the bathtub is getting too hard on me.