Trying to ground portable generator

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Old 11-30-11, 01:06 PM
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Trying to ground portable generator

I’m trying to ground my 3500 watt portable generator. When I plug an electrical tester directly into the generator outlet, it lights up and indicates “no ground”. I went to a electrical store and bought a grounding rod, ground wire, and the adapter needed to attach the wire to the rod, hammered the rod approx 5 feet in the ground and wrapped the other end of the wire onto a nut that is on the frame of the generator but when I plug the tester back into the generator, it still shows “no ground”. Am I doing something wrong here?

I’m trying to get this set up so I can run my gas furnace off of this if needed. The furnace is new and has a male plug on it and runs fine when plugged into a household outlet but when I tested it on the generator, it ran for about 1 minute and then shut down and gave me a diagnostic code that meant no ground as well. Any help would be appreciated. Thanks!
 
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Old 11-30-11, 02:45 PM
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Contact the generator manufacturer and tell them the problem you are having. Ask about bonding the ground to neutral on that model generator.

Then did you buy this generator new?

Did you or a previous owner of this generator modify it?
 
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Old 11-30-11, 05:28 PM
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This is why I thoroughly dislike the stand-alone term "ground" as most lay people (and quite a few electricians) interpret it as meaning a connection to the earth.

As you found out, connecting that "ground" point on your generator to the earth did absolutely nothing. Ninety percent of the time when you read the term "ground" it means "equipment ground" and has no meaning in regards to the earth. Ninety-nine percent of the time an equipment ground is for the sole purpose of providing a low impedance (low resistance) path for fault currents (short circuits) back to the SOURCE of the electricity causing a high current flow and actuating the overcurrent protective device (fuse or circuit breaker) to interrupt the current flow.

Your gas-fired furnace is one of the one percent of cases where the equipment ground is used for a different purpose. The flame sensor in many gas furnaces uses a principal called "flame rectification" where a small current is passed through the flame between the metal parts (connected to the equipment ground) of the furnace to the "flame rod" which is connected to electronic circuitry that "proves" the existence of the flame. Without the flame the circuitry will close the gas valve to prevent a dangerous build-up of unburnt gas. This flame sensing circuitry REQUIRES that the power supply have a groundED conductor (normally referred to as a neutral) AND an equipment groundING conductor. The equipment grounding conductor is solidly connected to the grounded (neutral conductor at the source.

Your particular generator has NO NEUTRAL conductor because no wire is connected to the frame of the generator and/or the earth. This is also know as "floating neutral" although the term "neutral" may be incorrect if this generator has only a single voltage output. The equipment grounding conductor IS connected to the generator frame (and to earth if you add the connection to the stake in the earth) but it is the BOND between the neutral and the equipment ground that is necessary for the proper operation of your furnace.

How to fix the problem depends on several variables, including how you want to connect the generator to the furnace and any other appliances.
 
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Old 12-02-11, 05:35 AM
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Thanks for the replies! Yes I bought the generator new and no modifications have been made. The way I want to connect the furnace to the generator is by plugging it into a heavy duty extension cord and plugging that into the generator. Are there any modifications that can be made to make this method work?
 
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Old 12-02-11, 05:49 AM
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Do you have a single use transfer switch?

Mike NJ
 
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Old 12-02-11, 06:15 AM
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I don't have a transfer switch, nor do I believe I'm familiar with it.
 
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Old 12-02-11, 06:35 AM
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Your furnace is hardwired correct?

Mike NJ
 
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Old 12-02-11, 08:13 AM
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The furnace currently has a male plug on it and is plugged into a wall outlet designated just for the furnace on its own breaker.
 
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Old 12-02-11, 05:55 PM
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What is the make and model of your generator? Is it a straight 120 volt or a 240/120 volt output?
 
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Old 12-03-11, 04:57 AM
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It is a Champion 3500 peak watts/3000 running watts Model 40026. I believe it is straight 120 volt. Here is the link with the specs to it: 40026 - Champion Power Equipment Thanks!
 
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Old 12-03-11, 05:39 AM
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Looks like the the current carrying line is not bonded according to the schematic. Thats fine for a 120v unit.

Plug the furnace into the unit as you describe and you will be fine.

Wait for furd to chime in also. He seems to have a good grasp on the gen codes.

If you wanted to power your home and bought a transfer switch you should be good to go also with no type of modification to the gen. This will then bond the gen at the panal whenever you plug into the inlet for the transfer switch.

I believe if you feed a travel trailer then you would want to bond the gen. A travel trailer I believe is considered a sub panal and there is no bonding at any connection in the trailer. A simple plug with a #10 wire from the so called " nuetral " to ground like this would be used. Just plug it in.




I am not an electrician and advise you to follow all state and local codes in your area. Above is all my opinion and what I feel is safe from my own use of my 120v only generator.



Mike NJ
 
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Old 12-03-11, 12:58 PM
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If you are using an extension cord to the furnace then plug the cord into the duplex receptacle only. This is to protect the cord (and furnace) with the generator-mounted 20 ampere circuit breaker. The extension cord should be one using #12 conductors and will be marked 12-3 or 12/3.

You will also need to make the "bonding adapter" that Mike has pictured and insert it into the other side of the duplex receptacle. This bonding adapter is a regular plug with a wire connecting the "neutral" (wider and silver-colored blade) to the equipment grounding (round and green-colored blade) connections in the plug. I suggest using a longer loop of wire than Mike shows and then tying the adapter to the generator so it won't get lost.

As for using it with a transfer switch to power other things in the house at a later date...please come back for more advice at that time.
 
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Old 12-03-11, 06:47 PM
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You will also need to make the "bonding adapter" that Mike has pictured and insert it into the other side of the duplex receptacle
Furd so you would bond a 120v only gen? Is that optional in the code, and or is it required?



Just trying to get clarification for my own notes.

Mike NJ
 
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Old 12-03-11, 09:47 PM
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Let's call ground "low" and electricity "high"...

If a hot electrical wire accidentally touches the metal frame of an appliance like a washing machine, that metal frame goes "high" in voltage. If you touch that metal frame, the electricity then flows through your body to the "low" ground floor.

Grounding that metal frame has double protection...

1. The metal frame is connected to earth ground. And copper is a better conductor than your body. So the electricity instead flows through the ground wire to ground instead of through your body. You are safe!

2. The ground wire is bonded (connected) to the neutral wire at the main panel. So when that hot electrical wire accidentally touches the metal frame of the appliance, the electricity travels through the ground wire, then to neutral, then this causes a "short" between hot and neutral. Thus the circuit breaker trips and turns off the electricity. You are safe again!

Double safe.
 
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Old 12-04-11, 07:08 PM
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First off, thanks to everyone for the replies. I just made the “bonding adapter” and plugged it into one of the outlets on the generator. Then I tested the furnace out and it worked perfectly! Now just 2 more questions. Do I still need to use a grounding rod for safety? And second, someone told me that using a generator and furnace can be risky because the way a generator can have fluctuations/surges in power can damage the circuit boards within the furnace. Anyone heard of this? (brand new furnace so I don’t want to take any chances)
 
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Old 12-04-11, 07:40 PM
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Yes the power from a generator can be "dirty" electricity. Like this...
Power quality from various backup devices

You can use an "online" "pure sine" UPS to clean that up.

Search google.com for: online pure sine ups
 
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Old 12-04-11, 08:13 PM
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Get a kill a watt meter. $20 bucks. Every gen owner should have one.

Its the Hz. Most gens are set higher so when under load it comes down. But my gen did not and stayed up around 63hz.

the kill a watt meter ley me fine tune the governor to about 61.5 hz. At 1/2 load it brings it to the 60 hz I like to see.

I constantly monitor this meter when under emergency power. I keep it pluged at the gen or in a outlet in the home thats running off the gen.



Amazon.com: P3 International P4400 Kill A Watt Electricity Usage Monitor: Home Improvement


Here the Hz mine used to run at before I adjusting the governor and an example of the kill a watt.

[IMG][/IMG]




Also Get a outlet tester like this. My gen has a floating nuetral. With this device plugged into my gen it shows a open ground. As it should its not bonded.

But when I plug it into my home wiring with the L14 20 you see in the pics below it now shows my gen outlets as normal. Two yellow lights on this tester all is good.

[IMG][/IMG]

Just some info for you.

Mike NJ
 
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Old 12-05-11, 09:27 AM
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Originally Posted by Bill190 View Post
Yes the power from a generator can be "dirty" electricity. Like this...
Power quality from various backup devices

You can use an "online" "pure sine" UPS to clean that up.

Search google.com for: online pure sine ups
Would the UPS be able to handle the inrush current of the blower motor?
 
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Old 12-05-11, 10:28 PM
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Originally Posted by lawrosa View Post
Furd so you would bond a 120v only gen? Is that optional in the code, and or is it required?



Just trying to get clarification for my own notes.

Mike NJ
In the case of a single-voltage generator being used in a stand-alone situation, i.e. when it supplies a cord-and-plug appliance then yes, one side of the generator output should be bonded to the frame of the generator AND a three-wire (hot, neutral and equipment ground) extension cord run between the generator and the appliance.

If you are running a single-voltage generator to a transfer switch/panel AND the panel has a bonded neutral then the generator should NOT have the bond to the frame. This also means that the generator-mounted circuit breaker will NOT respond in the case of a "line-to-ground" fault but only overloads and direct short circuits.
 
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Old 12-05-11, 10:36 PM
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Originally Posted by bobbsledd View Post
Would the UPS be able to handle the inrush current of the blower motor?
That would depend upon both the inrush current and the particular UPS. An on-line pure sine wave UPS would be rather expensive. I would suggest an automatic voltage regulator such as this one or whatever the load requires.

LC2400 Automatic Voltage Regulator/Line Conditioner - 120Vac 2400W
 
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