Contradictions and Confusion re: Transfer Switch and Ground/Neutral Bond - Power Equipment Forum : Power Equipment Forums
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post #1 of 33 (permalink) Old 01-21-2020, 04:42 PM Thread Starter
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Question Contradictions and Confusion re: Transfer Switch and Ground/Neutral Bond

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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post #2 of 33 (permalink) Old 01-21-2020, 07:36 PM
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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


it has a provision to safely install an approved generator mechanical transfer switch interlock, consuming the top four breaker positions, as-shown in http://forum.toolsinaction.com/topic/15475-wingless%E2%80%99-zinsco-to-siemens-home-circuit-breaker-panel-exchange/?tab=comments#comment-206428.

It is reasonable to me that the lines would be disconnected / transferred, but not the neutral.
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post #3 of 33 (permalink) Old 01-21-2020, 07:55 PM Thread Starter
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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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post #4 of 33 (permalink) Old 01-21-2020, 07:56 PM Thread Starter
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Red face

Thanks for the welcome, BTW.
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post #5 of 33 (permalink) Old 01-21-2020, 09:35 PM
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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.



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.





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



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



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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post #6 of 33 (permalink) Old 01-21-2020, 09:45 PM Thread Starter
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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 ->



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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post #7 of 33 (permalink) Old 01-21-2020, 10:54 PM
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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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post #8 of 33 (permalink) Old 01-21-2020, 11:01 PM Thread Starter
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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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post #9 of 33 (permalink) Old 01-21-2020, 11:12 PM
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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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post #10 of 33 (permalink) Old 01-21-2020, 11:32 PM
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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.

Last edited by tabora; 01-21-2020 at 11:35 PM.
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