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Discussion Starter #1
Hi folks. Wondering if someone here can help me understand something. I'll be honest - I haven't searched the forum yet, mainly because I'm not even sure what question to ask.

I recently bought a 3400W inverter generator to power my gas furnace and gas hot water heater during power outages. My intent was NOT to install a transfer switch due to the few times we lose power. I just wanted to be able to run extension cords to the two units. However, it turns out my furnace is hardwired and I'll have to at least install some kind of a switch for it. I intend to hire an electrician to do this - but the web has me completely confused on what I really need to have installed and how it has to be wired.

First off, let me say that I'm an electrical engineer. I've spent my whole 30+ years in low voltage DC applications. So while I understand most of the terminology, I don't feel qualified to mess with AC myself. I know my limits.

The generator I bought is an inverter, with a floating ground....no neutral/ground bond. The manual says that the generator should be treated as a 'separately derived system', and "The generator shall be connected to a transfer switch that switches all conductors excluding the equipment grounding conductor. The frame of the generator shall be connected to an approved grounding electrode." I assume this means that the neutral must be switched as well. I interpret that to mean it completely disconnects the neutral from my house neutral. However if I do this, and the generator doesn't have a bonded neutral, I will no longer have a neutral/ground bond. I realize I could create one by plugging in a jumper into a spare outlet on the generator...but I'm not clear on whether I will need one. What I took from most of my reading (right or wrong) is:

1. Separately derived system - need to switch all conductors, although I can connect generator frame to house ground. Neutral is no longer connected to house neutral. I don't know where the neutral/ground bond should be created.

2. Non separately derived system - shared neutral with house, never gets disconnected, neutral/ground bond comes from the panel.

All that said, depending on what page I read or video I watch, I seem to get completely conflicting info. Here's an example right here with the 'EZ Generator' switch.
He clearly converts the switch to a shared neutral, then says it's ready for a floating neutral generator - and I would have said the exact opposite. Now my head hurts.

Can anyone translate this simply for me? I'm assuming I'm going to need a neutral/ground bond SOMEWHERE in order for my furnace to fire (it's a fairly new high efficiency furnace). I realize that two neutral/ground bonds cause problems with GFCI circuits, but I don't think that's my question or issue. I think I just need to understand:

1. Do I need to switch the neutral or share it?
2. Where does the neutral/ground bond occur and will I need to do it at the generator?
3. How does the generator frame need to be grounded? Can I connect it to my house grounding rods, or a ground pin in a nearby outlet? Or does it need its own rod? Or will creating the neutral/ground bond at the generator with a jumper connect it to my house ground by default?

Can anyone shed some light on this for this old idiot?
Thanks
LP
 

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Welcome to the forum.

What generator is being connected? What does the installation manual specify for proper wiring?

What main load center panel is being powered?

When I installed my new Siemens P4080B1200ACU 200A 40 Spaces / 80 Circuits PL Load Center it has a provision to safely install an approved generator mechanical transfer switch interlock, consuming the top four breaker positions, as-shown in
.

It is reasonable to me that the lines would be disconnected / transferred, but not the neutral.
 

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Discussion Starter #3
It's a WEN 3800 - and the quoted section in my post came directly from the generator manual. That's part of the reason I'm confused. It does specify hooking it up as a separately derived system, and to me the language in the quote says that the neutral should be switched as well. I've even found multiple online instructional sites that say that the neutral should be switched for separately derived systems. At the same time though, other sites contradict that, including the video I posted.

I'm not trying to power a panel remember. I just want to insert a switch between my panel and my furnace so I can disconnect the furnace from the mains and connect it to my generator, that's it. I don't want a whole house solution at this point -the power doesn't go out frequently enough to warrant it.

Let's say for a moment that I followed the manual and switched both hot and neutral. I'm assuming the ground can stay common. If I did this, where would the neutral/ground bond occur? Can they be connected at the switch, or does it have to be done at the generator? It's those kinds of questions I'm struggling with.

I don't think this would be quite a problem if I didn't find so many seemingly contradictory answers at different instructional sites.

LP
 

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Thanks for the info. It looks like the generator is either this Wen 56380i 3800W Generator or this Wen DF475T 3800W Generator.

The "easy" solution I would implement would be to add a sub panel near the main panel, such as this Siemens 125 Amp 12-Space 24-Circuit Main Lug Load Center.Siemens 125 Amp 12-Space 24-Circuit Main Lug Load Center

My understanding is that this sub panel needs / should be fed from the main panel using an appropriate breaker, in this case I would use a 125A double pole breaker. Feed the sub panel w/ 2 AWG copper wire, good for 130A, per this chart. Use four wires in a conduit, line, line, neutral and ground. Tape the ends of the ground and neutral w/ white and w/ green tape.

Put a Siemens 125A Double Pole Type QP Breaker in panel positions 1 and 3, fed from the main panel. Put a Siemens 30A Double Pole Type QP Breaker in positions 2 + 4.
Siemens 125A Double Pole Type QP Breaker
Siemens 30A Double Pole Type QP Breaker

Use a ECSBPK01 mechanical interlock to act as the transfer switch.
ECSBPK01 Mechanical Interlock

Wire the 30A breaker to an external power inlet box using 10/3 wire (four conductor). Use conduit at appropriate locations.
power inlet box

Then just use a NEMA L14-30 cord. w/ a male plug on one end and a female receptacle on the other end, to plug the generator into the house.

In addition to moving the power feed for the furnace and the water heater from the main panel to the sub panel, also move some lighting circuits, the refrigerator circuit, a TV circuit and the Internet circuit. That way food doesn't go bad, you don't bump into stuff and talking to the wife isn't required.

The portable generator gets ground and neutral from the 4-wire NEMA L14-30 cord.

This solution provides a safe implementation w/ the 30A generator and provides an upgrade path if a larger generator is purchased in the future, just swapping the external 30A circuit and moving more circuits from the main panel to the sub panel.

Here is mine, as-shown in this topic.


 

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Discussion Starter #6
Thanks - the generator is the 56380i. While I appreciate the time you took to write that all out, it's just overkill for what I want. I just want a simple switch so I can power my furnace with an extension cord. The power doesn't go out here that often, and the hookup is merely insurance. I'm thinking something like this -> https://www.amazon.com/EZ-GENERATOR-SWITCH-Generator-UNIVERSAL/dp/B00FADDE0A/

I really just need to know if you need to share the neutral or switch it, where the neutral/ground bond should be, whether the frame of the generator needs to be grounded, and if so, can I ground it to my house ground.

Thanks,
LP
 

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Properly wire that EZ Generator Switch to the furnace.

When the power dies, safely run a standard NEMA 1-15 or 1-20 three prong extension cord from the generator to that switch.

Fire up the generator, flip the switch and stay warm.

The ground and the neutral are both properly handled by the properly wired switch.

Done.
 

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Discussion Starter #8
:tango_face_smile_bi I'd love to believe it's that simple....but you've hit on why I started this thread in the first place. My whole question revolves around what you called the 'properly wired switch'.

The switch can be wired with a switched neutral, or a shared neutral. I don't know which is correct based on the apparent contradiction between what the generator manual says, and what the video I originally posted says.

Oh well... I guess there's just no simple answer. Maybe the electrician can explain it when he gets here.

Thanks,
LP
 

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Just watched the videos.

According to pg 37 on your generator manual, the generator is a floating neutral generator, w/ no connection from neutral to ground in the generator.

Do the rework in the video to make it work w/ a floating neutral generator.
 

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@LeafPeeper , if all you want is to use extension cords to power a couple of gas appliances, do the following:

1. Turn off the circuit breakers serving the furnace and water heater.

2. Find a location in the feeder circuits with a little room for play and cut the romex cleanly. Strip the wiring and install a 3-prong male plug on the appliance side and a female plug on the side going to the breaker box (see photo). Plug them back together and turn on the circuit breakers.

3. When the power fails, start your generator, and then unplug the junctions. Plug extension cords from the appliance-side plugs to the generator output receptacles. If you're fortunate, the two circuit junctions may be able to have a proximity that allows a single duplex cord to service both.

I did this with my oil furnace and a small generator for years before installing a full-house GenerLink transfer switch and generator.
 

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The term "neutral" is confusing and a bit of a misnomer; it is a current carrying conductor and, with regard to your generator, is not physically connected with ground - thus the term "floating".

If you connect using male/female plugs, such as tabora suggests, you will have a safe appliance connection that is physically separated from home wiring. Very Important!

If you connect using any other means make sure the generator hot wire (normally color black) and the generator neutral (normally color white) are kept completely separate from house wiring.
The green "ground" wire is connected to generator frame ground via the factory hard wired plug on the generator.

If you keep in mind that both black and white wires will have potential with respect to ground then you can better visualize connections.

By the way, I worked for Verizon (Cantwell's Tier Two Power group) in large and small, ac and dc power plants on the east coast. I worked with engineers and manager staff - perhaps we met? You'd know because Cantwell was a bit of a character, not easily forgotten.
 

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There is not such thing as a floating neutral. The neutral is either 100% stand alone bonded or not, period. If you doubt this, take your or a RMS meter an read the resistance between any neutral an ground, on the Generator or distribution panel. This applies to you home panel as well. If you had a true neutral like a quality UPS system has there would be 4 wires coming into your home instead of only 3 for a single phase service. The utility calls it a neutral, OK I'll by that, but explain why it's bonded to a ground rod? Now thinking about that, many transformers are fed with a primary voltage with no Neutral attached, yet the secondary side has a neutral---OR--- is it just a potential hook up? The amount of misunderstanding about neutrals even in the industry is huge. Old habitats die hard.
 

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Discussion Starter #13
Just watched the videos.

According to pg 37 on your generator manual, the generator is a floating neutral generator, w/ no connection from neutral to ground in the generator.

Do the rework in the video to make it work w/ a floating neutral generator.
The problem with this is that the rework sets the switch to share the neutral, which according to my manual, is NOT what I'm supposed to do with my generator.

LP
 

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Discussion Starter #14
@LeafPeeper , if all you want is to use extension cords to power a couple of gas appliances, do the following:

1. Turn off the circuit breakers serving the furnace and water heater.

2. Find a location in the feeder circuits with a little room for play and cut the romex cleanly. Strip the wiring and install a 3-prong male plug on the appliance side and a female plug on the side going to the breaker box (see photo). Plug them back together and turn on the circuit breakers.

3. When the power fails, start your generator, and then unplug the junctions. Plug extension cords from the appliance-side plugs to the generator output receptacles. If you're fortunate, the two circuit junctions may be able to have a proximity that allows a single duplex cord to service both.

I did this with my oil furnace and a small generator for years before installing a full-house GenerLink transfer switch and generator.
Thanks Tabora - that's actually a pretty good idea. I will take a look to see how difficult it will be to get to the feed.

That said, won't this now leave the neutral and ground unbonded? Do I need to bond them at the generator? (Acceptable, but not really my preference because it will use up an outlet) Do I need to ground the generator frame, or will that be automatic since the ground of the furnace is connected to my house ground? If I have to ground the generator frame, can I connect it to my house ground?

Thanks,
LP
 

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Thanks for the info. It looks like the generator is either this Wen 56380i 3800W Generator or this Wen DF475T 3800W Generator.
Thanks - the generator is the 56380i.
According to pg 37 on your generator manual, the generator is a floating neutral generator, w/ no connection from neutral to ground in the generator.

Do the rework in the video to make it work w/ a floating neutral generator.
The problem with this is that the rework sets the switch to share the neutral, which according to my manual, is NOT what I'm supposed to do with my generator.
What page / section details that requirement?
 

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Discussion Starter #16
The term "neutral" is confusing and a bit of a misnomer; it is a current carrying conductor and, with regard to your generator, is not physically connected with ground - thus the term "floating".

If you connect using male/female plugs, such as tabora suggests, you will have a safe appliance connection that is physically separated from home wiring. Very Important!

If you connect using any other means make sure the generator hot wire (normally color black) and the generator neutral (normally color white) are kept completely separate from house wiring.
The green "ground" wire is connected to generator frame ground via the factory hard wired plug on the generator.

If you keep in mind that both black and white wires will have potential with respect to ground then you can better visualize connections.

By the way, I worked for Verizon (Cantwell's Tier Two Power group) in large and small, ac and dc power plants on the east coast. I worked with engineers and manager staff - perhaps we met? You'd know because Cantwell was a bit of a character, not easily forgotten.
Thanks Melson - this falls more in line with what I was thinking, but I still question where the neutral/ground bond is/should be created since I believe it is required for modern, high efficiency furnaces. I'm also a bit unclear on whether I need to do anything with the generator frame ground lug to be safe.

With regard to meeting, if you were referring to me, I doubt it - I've been working for IBM on microprocessor development in Vermont for the last 30 years.

Thanks again to all for your help here...
LP
 

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Note that if the house wiring is modified as tabora instructs to add an in-line NEMA 1-15 plug / receptacle, then when that junction is detached the furnace becomes ungrounded.

If that is then connected to the generator it will remain ungrounded, unless a ground wire is additionally connected to the generator ground screw.

If operating this way, also ensure that the generator ground wire is properly attached.
 

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Discussion Starter #20
Vermont is one of my all time favorite states
:tango_face_smile: It IS nice here. I'm a NJ transplant - and I much prefer Vermont. However, now that I'm approaching retirement, I'm just not sure I want use up my retirement savings here. It ain't cheap - and the winters are long! :rolleyes:

LP
 
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