100+ Amps Neutral Switching Transfer Switch

[sansnom]

Bit late to the party here - so late that the Reliance Panel/Link X Series is already discontinued.

My critical loads are scattered across 16 circuits, all using GFCI/AFCI breakers, so Generac HomeLink probably isn’t going to work. Also, my main panel is full, so a simple generator hookup isn’t an option. I’ll need a subpanel either way.

After digging around online for a bit, I came across two ideas, but doesn’t seem like folks here talked about either:

1. Nature’s Generator Automatic Transfer Switch - an ATS with a builtin breaker panel. The 125A model has 24 breaker slots and is very attractively priced, almost the same as the Generac 9854. There are also 50A and 30A versions. That said, I’m a bit hesitant since it doesn’t seem to be UL listed (yet). Fine print says certification is in progress. Also, it can’t be flush mounted (semi-flush at the best), not aesthetically pleasing. Anyone here tried / thought about this one?

2. Industrial transfer switches like the ABB OT100F3C. It's a bit pricy but not ridiculously. Paired with a flush mounted 100A subpanel, this could make for a very clean installation. It is UL listed and seems common in industrial installs, but I’m wondering why they’re rarely seen in residential setups. Is there something I’m missing?

Thank you in advance.

[1] https://naturesgenerator.com/collec...witch/products/125a-automatic-transfer-switch
[2] https://new.abb.com/products/1SCA105008R1001/ot100f3c

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[chl]

Well if you are thinking about using ProPower OnBoard for your bonded source, it is limited to 30A at 240V so that's your limit.

That's why so many Lightning owners, myself included have opted for the HomeLink.

However, if you want to be able to choose which circuits you have on by using your main service panel, being careful not to exceed 30A, you could do like this with a large transfer switch (really a disconnect box):



I took a screen shot and labeled things FYI:

 

[Runaway Tractor]

You could free up two slots in your main panel with two double mini breakers. Make yourself a 240v slot adjacent to the main and install a UL listed interlock kit. This maximizes your flexibility since you can now choose what to power up, rather than being limited to only what you have on a subpanel. As long you handle the ground issue appropriately and safely, it is pretty kick ass. When power goes out, it takes me less than 5 minutes to repower the entire house, and don't even need to leave the garage or go outside.

Since plugging in the Pro Power is a completely manual task, IMO an ATS is a waste of money and resources. If you can get one cheap and install for the cool factor, that's great. But there's no functional purpose.

 

[chl]

The Lightning inverter generator is a bonded generator and you will be using it to power a dwelling so there are NEC safety codes that apply and should be followed.

A neutral switching transfer switch is the code compliant, and safest way to use this backup power.

We spend $50k or more on the truck, so why complain about spending $400 or so on Generac transfer switch, or a bit more for the disconnect in the video, plus install costs, which would be code compliant and safe?

It's way cheaper than the SunRun HIS system, and more reliable.

 

[v2h8484]

2. Industrial transfer switches like the ABB OT100F3C. It's a bit pricy but not ridiculously. Paired with a flush mounted 100A subpanel, this could make for a very clean installation. It is UL listed and seems common in industrial installs, but I’m wondering why they’re rarely seen in residential setups. Is there something I’m missing?

It may be UL listed but it's still not allowed as service entrance equipment which seems to be your plan based on the 100A requirement.

 

[chl]

I believe in the video the electrician used a double throw service rated disconnect, so it operates as the first service disconnect in the house system and as a transfer switch after the service is disconnected.

I believe the code merely requires the transfer switch to be after the first service disconnect, which is the way that video setup operates, in order to prevent back-feeding from the generator to the utility.

The service is disconnect before the generator is connected in that setup.

The electrician separated the neutrals and grounds, unbonded the neutral in the house panel, as she described in the video making it essentially a sub-panel.

The only thing I would be concerned about in a set up like this would be overloading the Lightning by having too many load circuits drawing too much current from the Lightning. One would have to turn off some breakers to reduce the load and reset the Lightning breaker in that event.

Of course that could happen with any transfer switch if the transferred loads are not thoughtfully chosen to avoid the possibility of an overload.

EDIT:
Disclaimer

I am an electrical engineer but not a licensed electrician.

The information provided in this post is provided for information purposes only and does not constitute any endorsement or recommendation. No warranty, expressed or implied, is made regarding the accuracy, adequacy, completeness, legality, reliability, or usefulness of any information found in this post. It is your responsibility to verify and investigate this information.

 

[Maquis]

It may be UL listed but it's still not allowed as service entrance equipment which seems to be your plan based on the 100A requirement.

He’s powering a subpanel so it will not be used as service equipment.

 

[v2h8484]

He’s powering a subpanel so it will not be used as service equipment.

That's seems unclear from the OP. If it's for a critical loads subpanel then why a 100A switch? PPOB can only supply 30A.

 

[v2h8484]

If the goal is to setup a critical loads subpanel for PPOB then a 3-pole 30A double throw switch like this would be more appropriate:

https://shop.dominionelectric.com/buy/product/square-d/254912

 

[chl]

If the goal is to setup a critical loads subpanel for PPOB then a 3-pole 30A double throw switch like this would be more appropriate:

https://shop.dominionelectric.com/buy/product/square-d/254912

So for a service rated disconnect (3 pole double-throw 200A) used as a transfer switch, see what I think may be the Siemens DTNF324R in this video.



It is like having a house with service from an external bonded disconnect. Having that, btw is now mandated in the 2020 NEC code for new and upgraded homes apparently.

In the 2020 NEC® there will be [a requirement for an emergency disconnect to be located outside of the one or two family home]. This new code language ensures that first responders will have a suitable exterior disconnecting means in the event of natural disaster, fire, flooding and the like. Pulling the electrical meter because the main service disconnect is located on the inside of the home is not acceptable.

Existing residential service installations will likely be allowed to remain as they are, but new installations and service upgrades performed after the adoption of the 2020 NEC® will be required to incorporate a readily accessible exterior emergency disconnect. A service disconnect switch or main circuit breaker located outside of the home can serve this purpose....

In many of the colder states, a main breaker type service panel is located inside the home and supplied by a short run of service conductors from the utility meter, just on the opposite side of the exterior wall. It’s no fun to venture outside in the cold to reset a circuit breaker should one trip. These types of service configurations will only comply with the new code language if an emergency disconnect is installed outside.

https://www.electricallicenserenewa...ation-Courses/NEC-Content.php?sectionID=847.0

Since the external disconnect can be a double-throw, it can also serve as a transfer switch, which at least the electrician in the video believes is compliant with the NEC code.

The indoor panel that USED to be the service panel with the main breaker being the first disconnect, is now essentially an sub-panel which is unbonded, as long as the rewiring has been done correctly (separated grounds and neutrals, unbonded neutrals) which will operate with any bonded source/generator like the Lightning. The bonding of the neutral to ground for the utility service is done in the external disconnect.
-----
Disclaimer

I am an electrical engineer but not a licensed electrician.

The information provided in this post is provided for information purposes only and does not constitute any endorsement or recommendation. No warranty, expressed or implied, is made regarding the accuracy, adequacy, completeness, legality, reliability, or usefulness of any information found in this post. It is your responsibility to verify and investigate this information.

 

[chl]

So for a service rated disconnect (3 pole double-throw 200A) used as a transfer switch, see what I think may be the Siemens DTNF324R in this video.



It is like having a house with service from an external bonded disconnect. Having that, btw is now mandated in the 2020 NEC code for new and upgraded homes apparently.

In the 2020 NEC® there will be [a requirement for an emergency disconnect to be located outside of the one or two family home]. This new code language ensures that first responders will have a suitable exterior disconnecting means in the event of natural disaster, fire, flooding and the like. Pulling the electrical meter because the main service disconnect is located on the inside of the home is not acceptable.

Existing residential service installations will likely be allowed to remain as they are, but new installations and service upgrades performed after the adoption of the 2020 NEC® will be required to incorporate a readily accessible exterior emergency disconnect. A service disconnect switch or main circuit breaker located outside of the home can serve this purpose....

In many of the colder states, a main breaker type service panel is located inside the home and supplied by a short run of service conductors from the utility meter, just on the opposite side of the exterior wall. It’s no fun to venture outside in the cold to reset a circuit breaker should one trip. These types of service configurations will only comply with the new code language if an emergency disconnect is installed outside.

https://www.electricallicenserenewa...ation-Courses/NEC-Content.php?sectionID=847.0

Since the external disconnect can be a double-throw, it can also serve as a transfer switch, which at least the electrician in the video believes is compliant with the NEC code.

The indoor panel that USED to be the service panel with the main breaker being the first disconnect, is now essentially an sub-panel which is unbonded, as long as the rewiring has been done correctly (separated grounds and neutrals, unbonded neutrals) which will operate with any bonded source/generator like the Lightning. The bonding of the neutral to ground for the utility service is done in the external disconnect.
-----
Disclaimer

I am an electrical engineer but not a licensed electrician.

The information provided in this post is provided for information purposes only and does not constitute any endorsement or recommendation. No warranty, expressed or implied, is made regarding the accuracy, adequacy, completeness, legality, reliability, or usefulness of any information found in this post. It is your responsibility to verify and investigate this information.

Which makes me wonder about automatic transfer switches with back up power and the requirement for an external emergency shut off for emergency personnel...

It seems to me that the exterior MANUAL disconnect will only shut off the utility UNLESS it is also used as a manual transfer switch which can shut off backup power from a generator, battery, solar system, wind system or Lightning, eh?

Somehow the emergency responders need to shut off the utility AND the backup power for safety.

So I read the NEC requires a disconnect for the permanently installed backup/standby generator system.

Seems logical to combine that with the Utility disconnect doesn't it?

 

[sansnom]

Thank you for all the information, and I apologize for the confusion.

Basically, here is what I'm thinking about:

I have 16 circuits that I want to back up:

• 2× 30A - Well pump (240V)
• 1× 20A - Water heater (gas-powered)
• 1× 20A - Refrigerators
• 1× 20A - Range hood + microwave combo
• 1× 20A - Garage door opener
• 1× 20A - Network equipment (including security cameras)
• 1× 15A - HRV and furnace (gas-powered)
• 1× 15A - Water filter (and power outlets on the same circuit)
• 7× 15A - Lights (and power outlets on the same circuit)

The first problem with the Generac HomeLink is that it just doesn’t have enough slots. All 14 of the 120V circuits use PON GFCI/AFCI breakers, so they don’t fit with the 8-slot HomeLink.

But the bigger issue is the 50A limit. The house wiring is poorly designed - critical loads (e.g. lights) are mixed in with non-critical ones (e.g. outlets). We can carefully keep the load low during an outage (no hair dryers, microwaves, dishwashers, etc.), but that’s not really doable during normal times.

That’s why I want a 100A subpanel, even though PPOB or generator inlet only supports 30A or 50A.

 

[Runaway Tractor]

So much work when a simple and safe generator inlet with interlock breaker solves every goal for about $200 in parts including lunch.

 

[P-38]

That makes sense and the ABB would work for that. Slap a 100 amp breaker in the main, run the right size wire and then you have what you want.

Why not use a service level switch as Chi has said? This would save relocating all your circuits. You would have more neutrals to make sure they don't touch ground to avoid the GFCI on the truck, but then you don't have to relocate the circuits... So it's really which way is less work. No circuit relocation but more neutrals to track down vs. relocating but only having to correct those few circuits.

Personally I use an interlock kit, feed entire 200amp panel and my generator does not have GFCI, only 30amps and just manage the load. My truck lacks the 30amp outlet because none were available in the color I wanted at the time of purchase

 

[P-38]

Interlock would trip GFCI on truck unless you lift the ground wire....which is a whole debate thing I don't feel like touching with a 10 foot pole.

If OP wants to lift the ground then interlock is way to go.

If OP does not want to lift the ground wire to make truck work as backup power then a neutral switching transfer switch of some type is the way to go.

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