Grounding Rod For Portable Generators Necessary?

[jel1988]

Running a generator without a ground works 99.999 percent of the time. That other .001 percent can be fatal. You can ground to your house copper plumbing if your close, you can drive a piece of copper or even a piece of rebar into the ground in most areas there is enough moisture in the ground (if not add some) to give a better ground that you!!!

 

[grsthegreat]

if your running a 4 wire feed to the house, your tying into the houses existing grounding system. thats why portable units dont require them.

 

[CobyRupert]

A note to those who power their houses with a portable when the power goes out: to protect the guys and gals who come out in that storm to get your power back on for you, you must break all three legs between the house and the transformer. If you think that just flipping the main breaker protects the outgoing lines, you are wrong. You can give shocks out there in the world by current feeding into the neutral lead.
Wow, it's hard to believe that the linemen would get a shock of the neutral seeing how the neutral is bonded to ground (earth/ O volts) at your panel and the utility's transformer, and there is no neutral on the primary lines. The way I dealt with it is, I power only two light and outlet circuits when the power is down for extended periods. I don't run my shop, heat, or refrigerate with the portable. I do run all my lights and electronics (don't want to miss the big game).

What I did was connect the two circuits' romex to a split duplex outlet next to my breaker box. I put three pronged plugs on each of the romexes going on to those two circuits. They are plugged into that duplex under normal circumstances. When I'm on the generator, I pull the two light/outlet circuit plugs from the temporarily dead house power duplex, and plug them into a ganged duplex on the cable coming in from the generator. Under these conditions, I'm relying on the genset's own breakers. So, these two circuit's neutrals and ground conductors are isolated from your panel? So the ground conductor in these circuits are not grounded through a ground rod and the neutral is not bonded to ground anywhere and is floating when running on the genny? This would mean that in a fault, the electricity has no way to get back to the neutral of the genny and fault current may not become excessive enough to trip the breaker, instead it energizes metal parts that should be grounded, but are not, waiting for someone to touch them. Hopefully the neutral of the genny is bonded to the genny's ground. My understanding is that this bond sometimes exists, but may be left up to the owner depending if the have a transfer switch, and what type of switch that is (i.e. is the neutral switched (i.e. "a separately derived system")). If not, it may be a good idea to ground the genny with a ground rod and bond the neutral of the genny to its equipment ground so that the neutral doesn't float and is locked to 0 volts.

Our PUD line folks are great heroes of mine. They get out there in all conditions and at all hours. I don't want them to get any shocks from me. They have told me they appreciate this.

I hope I'm wrong, you should get this checked out before something goes wrong.

 

[CobyRupert]

The ONLY time you need to use a grounding rod is if the generator is part of a separately derived system AND perminantly mounted.

Separately derived system is the key.
Do you have a transfer switch that switches the neutral? Whether your power comes the utility or a generator you need the neutral bonded to ground. This does 2 things: 1) Pegs the neutral to 0 Volts and not floating. 2) In the event of a fault (short) there is a low resistant path (on the ground) back to the neutral of the transformer (or generator) so that the fault current (of the circuit loop) is high enough to trip the breaker (repeat: You want low resistant loop path that provides a high enough fault current to trip the breaker).

If your (4 wire) transfer switch switches the neutral, you have a separately derived system and need ground rods and bonding of the neutral to the ground at the genny (or transfer switch), otherwise neutral and ground should only be bonded in 1 place only (usually at your panel).

 

[Tractor Seabee]

A generator does not have a reference to earth ground unless you create one. That is why a genset in a truck does not create a problem as it does not have that reference. The code describes this as a seperatly derived neutral. If you take a volt meter and test from the hot side of an outlet to a ground rod it will not read any voltage. Utility power depends on the earth reference to provide a safe system. Our local code states grounds for panels are required to be copper clad 10' rods driven full length. If ground potential is not tested and recorded a second ground 10' away is required (the common situation for residential as the second rod is cheaper than the test).

My umbilical cord from the genset to the house includes the green ground wire; that then grounds the generator frame and the neutral to the house grounding system. Neutral and ground are required to have the same ground potential. As far as my code recollection goes a utility/genset transfer switch is not required to be included in the switching. It is not required by the serving utility either. Yes a poor ground connection could feed back on the utility neutral but would be shunted to ground at the firsts transformer. The first thing utility workers during an outage is ground all the conductors before starting work. This is all recollections on my part, you electricians out there correct this dialog once and for ever. I haven't cracked a code book for 5 years now.

Ron

 

[danspartan]

Seem to have stirred up a discussion.

At my furnace when I wired in the plug,

HOT from panel was disconnected
NEUTRAL from panel was disconnected
GROUND from panel was CONNECTED

In the panel GROUND AND NEUTRAL are together, the panel is grounded to my incoming water supply just as it exits my house.

My understanding is that with the ground connection above, that the whole generator system is grounded and any short/failure will dissipate through the ground--no backfeed potential.

 

[Looking4new]

Okay, here s the way mine is done.
Genny is a neutral bonded set. I've got a 6' piece of copper pipe pounded into the ground, the 4 wire 30 amp connector from the genny goes into the house and stops at a DPDT (double pole double throw) transfer switch. When the power (hydro) is off I power my well pump off the genny. The hydro goes into the top half of the transfer switch and on through to the pump (which is protected by it own double fuse [15 amp] beside the tank) (220 V) this is a sub panel off the main. The genny feeds into the other half of the transfer switch and on to the well pump as well. [Switch in the up position and only hydro is feeding the pump]{switch in the down position and the genny is feeding the pump} After all that, I have 3 separate fused switch boxes that the genny ONLY feeds and they are connected to 3 duplex outlets and everything else (fridge, sump pump, lights, fan for woodstove, and a computer or two {through APC battery backups} runs off them via extension cords.

Is there anything 'wrong' with this setup?

 

[Tractor Seabee]

My umbilical cord from the genset to the house includes the green ground wire; that then grounds the generator frame and the neutral to the house grounding system. Neutral and ground are required to have the same ground potential. As far as my code recollection goes a utility/genset transfer switch is not required to have the neutral and ground included in the switching. It is not required by the serving utility either. Yes a poor ground connection could feed back on the utility neutral but would be shunted to ground at the first transformer. The first thing utility workers during an outage is ground all the conductors before starting work. This is all recollections on my part, you electricians out there correct this dialog once and for ever. I haven't cracked a code book for 5 years now.

Ron

Sorry guys I screwed up that second paragraph. The red is what I left out.

Ron

 

[grsthegreat]

here in the USA its hard to find a whole house transfer switch that switches the neutral. theres some after market 30 amp units, but not on the 200 and 400 amp residential units that i have installed. I guess that some countries require the neutral to be switched, but the NEC doesnt require it of us.

Ive been installing these inspected and passed UL approved systems for nearly 20 years of my career. Im not a lineman and have no knowledge whats at the top of the pole, but i was under the assumption that every pole mounted transformer has a solid copper wire stapled to the pole and embedded to the depth of the pole. this is what establishes the neutral at the transformer as we use mostly grounded wye systems up here. So any power sent back up the neutral would be grounded out. thats why theres not the need to separate the neutral. Some countries have open neutral sysrems that arnt grounded to the transformer case. those i could see an issue.

 

[ENC]

Does the grounding of generators have anything to do with these straps I see dragging the ground on a lot of welding trucks? And if so why don't all of them have them?