2011 Mep 803 wiring for house

TheAlfredo said:

If you do that, then the generators housing is no longer grounded and a rod should be used to ground the housing.

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That is not correct. With a 4 wire setup the ground and neutral are extended from the main panel. The chassis is grounded through the ground lug and connected to the ground rod at the main panel via the ground wire.

I stand corrected. Thank you

You're welcome. We are all here to help each other.

Howdy,

Connected to a house, bonding strap disconnected.

In the middle of a field, bonding strap connected, and ground rod in the ground.

Question. Wouldn't having the skids on the ground be grounding the gen. That's 11 feet of 2" skids...throw in a rain storm...

A thin layer of paint can prevent electrical conductivity. I believe these units require a copper clad ground rod driven into the ground at least 8 feet. I recall reading something about desert operations requiring a deeper ground penetration due to dry loose sand being a poor electrical ground when compared to moist well compacted soil.

There isn't much, if any paint in the bottom of the skids (as it gets scraped away every time the gen is moved). And while silica isn't conductive, wet organic soil is (as we have in South Florida). In some places down here, you'll hit the water table with a ground rod after a couple feet. I'm guessing the logic would be less resistance for a short to go down the ground cable than through the skids? Though I guess it depends on where the "system" is shorted?

TheAlfredo said:

There isn't much, if any paint in the bottom of the skids (as it gets scraped away every time the gen is moved). And while silica isn't conductive, wet organic soil is (as we have in South Florida). In some places down here, you'll hit the water table with a ground rod after a couple feet. I'm guessing the logic would be less resistance for a short to go down the ground cable than through the skids? Though I guess it depends on where the "system" is shorted?

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The earth ground will be the path of least resistance for unwanted electrical surges/problems in your machine: think of a loose wire contacting the aluminum case while you are leaning against it. No earth ground and you get fried by the electrically energized case. If you have an earth ground the path of least resistance is NOT through your body and you just get a little tingle, if that. Here's a couple articles that popped up on a search of "why you need a proper electrical ground":

http://inspectapedia.com/electric/Electrical_Ground_Required.php
http://www.esgroundingsolutions.com/about-electrical-grounding/

....there are many others. I bet a search of the SS site will provide a lot of good grounding info as well.

I 100% understand grounding. My question has to do with this particular setup. If the generator is grounded via the house ground wire, the current has over 150-200feet to travel before it grounds out at the service entrance. That all equates to resistance. Or the stray current can travel through the 11" on the skids making contact with wet soil and ground there.

Wouldnt it it make better sense to hook up the neutral and 2 hot legs to the house and ground the generator with a rod, leaving the neutral unbounded at the generator? This would ensure that any fault in the line would be grounded by the SE and any fault at the Generator would be grounded by the rod of the generator.

I am not an electrician but I did a lot of reading and research on the subject of grounds and the bonding of ground to neutral.

My understanding is you can have any number of grounds. The more the better. You can only have a ground bonded to neutral in one location. Most home breaker panels will have the ground and neutral bonded.

I have a ground rod on my home and another on my generator.

My breaker panel in my house has the ground bonded to the neutral. I also bonded the ground and neutral in my load bank. Since it is never connected at the same time as the house I can leave the bonding strap disconnected in the generator.

csheath said:

I am not an electrician but I did a lot of reading and research on the subject of grounds and the bonding of ground to neutral.

My understanding is you can have any number of grounds. The more the better. You can only have a ground bonded to neutral in one location. Most home breaker panels will have the ground and neutral bonded.

I have a ground rod on my home and another on my generator.

My breaker panel in my house has the ground bonded to the neutral. I also bonded the ground and neutral in my load bank. Since it is never connected at the same time as the house I can leave the bonding strap disconnected in the generator.

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Here's a good talk about it https://www.youtube.com/watch?v=qNZC782SzAQ&t=812s

But it is connected at the same time. Most transfer switches are only 2 poles (only switching over the 2 hot legs). The Neutral is still connected to the utility. Even if you have a 3 pole transfer switch, your breaker panel has a bonded ground to a rod at your house.

So so even if you switch the 3 poles to your generator, you are still bonded to ground at your panel. And if your bonded to ground at the generator...you are creating 2 parallel paths for current to run if there is a short.

You our can't have two grounding points on the same line/wire/circuit.

But out though it is probably against code, I don't see why you couldn't have 2 independent ground lines with ground rods.

Any electricians want want to chime in?

Hi there, FNG here.

When running 1-phase off the 803a, is that an "unbalanced" load?

Are you wasting fuel by not using the machine for its designed purpose?

Can you cause damage to the generator?

thank you

https://www.thespruce.com/balancing-electrical-loads-1152238 explains balancing electrical loads.

An 803A run in single phase 240/120 does not become unbalanced until you pull more power from one of the hot legs than the other. 2 ea 120volt legs can provide 240 volt to your dryer. This is a balanced load because dryer needs both of the hot legs. Major unbalanced loads can damage the generator, so best to balance loads. Your electrical contractor should have done this when they built your house.

Search out the TMs on this site to better understand how to operate your generator. And drop a ground rod 8 or 9 feet in the ground before you start playing with it.

Your 803A gives you 3 choices for power output - see pic.
My house will need 240/120 single phase.....and the loads need to be balanced.
My camper (30A) will need 120 single phase. The generator is delivering power on only 1 leg at 120 volts so no balancing needed on my part.
I don't own any 3 phase equipment.

Anyone trying to figure out how to "drop a ground rod", it's easy. Good videos on making a ground rod water drill on youtube.

You buy a 5/8" female hose adapter and a 10 foot length of conduit. Tap the adapter into the conduit. Wrap tape around conduit at 2' 6" from hose end. You can also cut about 1/2" off the other end, cut and flatten it out and silver solder it into the end lengthwise to help divert water to the sides.

Here's the cool part. Connect a garden hose, climb up on a ladder maybe 5-6' while water's running, press end to ground and keep pressing.

I drilled 3 ground rod holes in rocky ground in less than 5 minutes a few years back to ground my ham radio antenna tower (hexbeam), used it again later at a friend's, used it to set ground rod for electric fence. Net cost about $12, I recall.



Question I've got is, while the amperage rating on this unit is 52A at 120/240 1 phase, SURGE is what I'm most concerned about if I'm installing a breaker inside the genset (closest to the source), while my power distribution box has 20 and 30A breakers for 120 and 240 1 Ph outlets, the extra insurance seems reasonable.

I'm reading so much here about 80% vs 100, 110%, 120% rating, calculated 12,500 watts continuous, but how high a surge to expect from, say, a two-ton HVAC system (I don't own yet, and mfrs are a little sketchy on some of these details).

Is a 60A double-pole breaker too small? Just right?

Thanks in advance.

Norm

The surge rating of the generator is insignificant compared to the surge rating of your utility power. When you look at a breaker rating you will see something like "KAIR" or "AIR". that is the current interrupting ability. Your breakers should be good for 10,000 AIR (10KAIR). A 803 I doubt is even 10% of that.

The trip rating of the breaker is all about protecting the components in the distribution system (wire & connectors). If you put in wire and connectors that are good for 50a then you MUST use a 50a breaker. You can use a breaker rating under the distribution system's rating but no over. Surge doesn't come into play here. That stuff is built into the trip curve of the breaker.

How it relates to the generator is if you want to dip into the excess capacity of the generator you need to install distribution components rated for that amperage. A 60a breaker is the most you should have to put in for a 803 setup.

If you look at the label on your compressor you'll see a number labeled "LRA". That is Locked Rotor Amps. That should be the peak amperage your compressor will demand. That number will fall very rapidly as the compressor motor starts to rotate. For a 3T compressor I would expect it to be around 100a. My 803 starts my 3T heatpump easily.

DieselAddict said:

The surge rating of the generator is insignificant compared to the surge rating of your utility power. When you look at a breaker rating you will see something like "KAIR" or "AIR". that is the current interrupting ability. Your breakers should be good for 10,000 AIR (10KAIR). A 803 I doubt is even 10% of that.
The trip rating of the breaker is all about protecting the components in the distribution system (wire & connectors). If you put in wire and connectors that are good for 50a then you MUST use a 50a breaker. You can use a breaker rating under the distribution system's rating but no over. Surge doesn't come into play here. That stuff is built into the trip curve of the breaker.
How it relates to the generator is if you want to dip into the excess capacity of the generator you need to install distribution components rated for that amperage. A 60a breaker is the most you should have to put in for a 803 setup.
If you look at the label on your compressor you'll see a number labeled "LRA". That is Locked Rotor Amps. That should be the peak amperage your compressor will demand. That number will fall very rapidly as the compressor motor starts to rotate. For a 3T compressor I would expect it to be around 100a. My 803 starts my 3T heatpump easily.

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THAT is why I enjoy being a member of this board.

Sharing.

I'll stick w/ 50A for now, but know I can put a 60A breaker in down the road is enormously helpful. Not sure what size AC I'll be installing, but figured I'd need the output of the 803a for it (802a helps, just not enough "oomph" to run the bigger stuff).

Thanks a bizillion.

Norm

DieselAddict said:

Per code if you are wired up with a 4-wire setup and the neutral is bonded in the main panel at the service entrance, you need to remove the bonding jumper at the generator.

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I do not think that this is correct. Although in your area, it may be. The entire purpose of "grounding" something is so YOU are not used as a circuit for electricity to flow through.

You should always use a 4 wire connection to your house, hot, hot, neutral, and ground. Your panel is already bonded (neutral and ground connected). In this case, leave the bonding strap connected at the generator as THIS is what grounds the generator chassis to the house bonded ground and neutral. No ground rod used at the generator as now both the generator ground and chassis ground are connected through the bonding strap at the generator power outlet.

IF you disconnect the bonding strap at the power outlet of the generator, the generator (power generating source) is still grounded to the house through the ground wire BUT the chassis is no longer grounded. If the generator malfunctions and power arcs to the chassis and you are touching the chassis, you are the link between the now powered chassis and earth ground and you may be electrocuted. This is why you need a second ground rod at the generator IF the bonding strap is disconnected at the generator, to ground the generator chassis.

Clear as mud right?

Now codes vary from county to county across this great land of ours called the USA. ALWAYS check with a licensed electrician licensed to work in YOUR area.

Do not confuse chassis ground with generator ground. They are 2 different grounding circuits, one for chassis ground and one for generator ground. The bonding strap at the generator output is what grounds the chassis to the generator ground which then is passed through the ground wire to the house electric panel which is already earth grounded.

Just my .02 cents worth.....

My comment is correct. If you look at the NEC (which is national and not local) it does state that with a 4 wire system the neutral and ground is bonded in only one location for the entire system. When you connect a generator it becomes part of the system unless you are off-grid. In this case you have a "separately derived system" and you CAN bond the neutral to the ground at the generator SO LONG AS you don't ALSO do it at the panel. By code you can have only ONE bonding location for the ground and neutral.

You need to review a couple different sections depending on whether you are portable versus permanent but the basics of grounding and bonding are the same. If you connect your generator to a 4 wire system you are REQUIRED to continue that 4 wire system to the generator AND remove the bonding jumper at the generator.

You'll need to review sections 225 and 250 of the NEC.

Just to make sure we aren't confusing bonding and grounding.. You can have a ground rod at the generator. No problem there. If you run a 4-wire setup the chassis of the generator will be taken to earth via the ground wire in the cable.

The bonding I'm talking about is where you connect the neutral conductor to the ground conductor. That doesn't change whether the chassis is connected to the ground rod. It only changes the fault current path between the generator and the transfer switch.

The NEC is like tax laws. A great portion of both are insane and contradictory from paragraph to paragraph.

I understand the difference between what is described as a "separetly derived system".

This is what I was taught, learned, read, and discussed with other engineers. I am not an electrical engineer. My specialty is structural engineering.

Every wire that goes to chassis ground goes absolutely nowhere if the bonding strap is not connected and there is no ground rod connected to chassis ground at the generator. You have a 'hot' chassis. So if the bonding strap at the generator is not connected, you must use a ground rod to ground the chassis as near to the unit as possible. This is for a generator hooked up to a circuit panel that is bonded.

When the chassis ground is connected to the generator ground via the bonding strap at the generator, the entire unit, generator and chassis ground, are now connected via the ground wire that goes to the electric panel which has it's own ground rod.

I had these issues come up with my pool pump and salt water chlorine generator. Even though both are connected to the panel ground on the house, I still had to sink a ground rod to ground the chassis of both units.

It is very confusing and this is what the general consensus is for the area that I live in.

I do not doubt your words of wisdom or knowledge of the subject Chris.