New construction for generator backup

[Dr. Hillbilly]

There are many threads addressing the retrofit of generator support for existing construction. Doing this legally and functionally is not a trivial task. However I believe that new construction should be simple. Attached is my schematic and I invite corrections.

Note that the ground and neutral are bonded at the first point past the meter as codes specify.
Bonding precedes the transfer switch so that they are not bonded when the F-150 is used as a generator.
As bonding has already been performed the only panel is a sub-panel, with the green bonding screw removed and a grounding bar added.

What have I missed?

Sponsored

 

[Maquis]

You only need a 3 pole transfer switch. The EGC (Equipment Grounding Conductor) should not be switched.

You need a service disconnect ahead of the transfer switch unless it‘s listed as “Suitable for use as service equipment.” Not all of them are.

What year code cycle are you on?


Edit - Ohio has adopted the 2023 NEC so an “Emergency Disconnect” is also required. See 230.85.

 

[GDN]

That is no different for existing construction. In a couple of hours you can retrofit anything into the path of the wiring. It's the price of the 3 and 4 pole breakers/transfer switches I think that make it very low on the totem pole of options.

 

[Dr. Hillbilly]

You only need a 3 pole transfer switch. The EGC (Equipment Grounding Conductor) should not be switched.

You need a service disconnect ahead of the transfer switch unless it‘s listed as “Suitable for use as service equipment.” Not all of them are.

What year code cycle are you on?


Edit - Ohio has adopted the 2023 NEC so an “Emergency Disconnect” is also required. See 230.85.

You are correct, and thanks for catching that. I had missed it.

 

[Dr. Hillbilly]

You are correct, and thanks for catching that. I had missed it.

I am also building a workshop which is not for human habitation. It appears that the emergency disconnect is not required for that?
And if the transfer switch has an intermediate Off position does that constitute an emergency disconnect?

 

[Danface]

This worked well for me.

https://www.f150lightningforum.com/...or-lockout-kit-to-feed-the-whole-panel.20465/


This is for a temporary backup situation.

 

[chl]

There are many threads addressing the retrofit of generator support for existing construction. Doing this legally and functionally is not a trivial task. However I believe that new construction should be simple. Attached is my schematic and I invite corrections.

Note that the ground and neutral are bonded at the first point past the meter as codes specify.
Bonding precedes the transfer switch so that they are not bonded when the F-150 is used as a generator.
As bonding has already been performed the only panel is a sub-panel, with the green bonding screw removed and a grounding bar added.

What have I missed?

Just a point of clarification...

You are not expecting the Lightning 30A 240V to power the whole house are you?
Or will the whole house not exceed the 7.2Kw capability of the Lightning?
Maybe you will switch off some load breakers in the panel when using the Lightning to not overload it?
That would be my only concern with what you are suggesting.

But I really don't think retrofitting is all that much more complicated.
A $400 manual transfer switch, a generator inlet and connecting wire, and a generator cord to the Lightning is all you need. You simply re-route the hots and neutrals of the circuits you will be transferring from the main panel to the transfer switch using the wiring that comes with it. You add a 60A breaker to the main panel to power the transfer switch.
But that's just me.

By the way there was a YouTube video of that type of install, here's a screen shot:

The video is at:

 

[chl]

There may be some things the Lightning 30A, 240V, 7.2kW out will not be able to handle.

Without start up current limiting with a "soft start" add on circuit, a central air conditioning system alone could pop the 30A Lightning breaker. Someone posted that was an issue until the put a soft start on. They are a bit pricey, but they lengthen the life span of your AC as well as allow using a smaller generator.

It seems a typical whole home generator might supply 8,000 running watts, so maybe 7.2kW would actually be enough with some soft start circuitry.

There are plenty of on-line calculators to determine what size generator might be needed.

Here's one with running and starting watt table for many typical items:

https://www.toolnut.com/generator-size-calculator

 

[Dr. Hillbilly]

Just a point of clarification...

You are not expecting the Lightning 30A 240V to power the whole house are you?
Or will the whole house not exceed the 7.2Kw capability of the Lightning?
Maybe you will switch off some load breakers in the panel when using the Lightning to not overload it?
That would be my only concern with what you are suggesting.

But I really don't think retrofitting is all that much more complicated.
A $400 manual transfer switch, a generator inlet and connecting wire, and a generator cord to the Lightning is all you need. You simply re-route the hots and neutrals of the circuits you will be transferring from the main panel to the transfer switch using the wiring that comes with it. You add a 60A breaker to the main panel to power the transfer switch.
But that's just me.

By the way there was a YouTube video of that type of install, here's a screen shot:

The video is at:

Thanks for the link to the youtube. That video was actually part of the inspiration for the circuit I posted. The 30 amp version of the switch shown only costs $450, but the 200 amp version actually shown costs $3,600. Of course the 30 amp version would be OK if an existing panel is left in place and just a few emergency circuits are moved to the new sub panel. However I want the flexibility to run any circuit in the home on the generator as long as I switch off others (in this corner of Ohio power outages are the norm). For example if I want to run one of my milling machines in the shop I will need to kill the AC, microwave, and hot water for a while. I am doing that now to power construction while still off-grid and the AC, microwave, and hot water do not yet exist (milling machines are obviously the priority!), I have not found 200 Amp UL listed switches for attractive pricing. I have found imported switches built to the CE specifications rather than UL, and they were previously identified by others in this forum. I have 40 years of international machine tool experience and have found the CE specs to be very robust and arguably superior to UL (the same could be stated for J.IS.), but I doubt that I could convince an inspector in ultra-rural America of that (they simply have not been exposed to CE and J.I.S equipment so how would they know). So are there reasonably priced UL switches for 200 amps?

 

[Dr. Hillbilly]

There may be some things the Lightning 30A, 240V, 7.2kW out will not be able to handle.

Without start up current limiting with a "soft start" add on circuit, a central air conditioning system alone could pop the 30A Lightning breaker. Someone posted that was an issue until the put a soft start on. They are a bit pricey, but they lengthen the life span of your AC as well as allow using a smaller generator.

It seems a typical whole home generator might supply 8,000 running watts, so maybe 7.2kW would actually be enough with some soft start circuitry.

There are plenty of on-line calculators to determine what size generator might be needed.

Here's one with running and starting watt table for many typical items:

https://www.toolnut.com/generator-size-calculator

I am running a few lathes and milling machines on 7.2kW now (but only one at a time), but using VFD inverters for 3-phase which offer soft start. They cost under $200. Can they be inserted in front of the heat pump (obviously a single-phase version)???
Note that my shop and home combined are only 1800 sq. ft. and my heat pump will be geothermal, so my 200 amp service is gratuitous, and only based on the fantasy of acquiring some bigger machine tools in the future. If I am not working in the shop the 7.2kW will be OK

 

[Maquis]

I am also building a workshop which is not for human habitation. It appears that the emergency disconnect is not required for that?
And if the transfer switch has an intermediate Off position does that constitute an emergency disconnect?

The way I read it, the emergency disconnect is only required for the dwelling.

It could qualify if it meets all of the stipulations set forth in 230.85. For example it must be installed “…on or within sight of the dwelling unit.”

 

[Dr. Hillbilly]

I found this 200 Amp transfer switch on Amazon. The price is about 10% of other 200A alternatives, which is both exhilarating and disconcerting.
https://www.amazon.com/dp/B0DCFZ1H7J?ref=ppx_yo2ov_dt_b_fed_asin_title
I ordered it, and will report on the results...

 

[Maquis]

I found this 200 Amp transfer switch on Amazon. The price is about 10% of other 200A alternatives, which is both exhilarating and disconcerting.
https://www.amazon.com/dp/B0DCFZ1H7J?ref=ppx_yo2ov_dt_b_fed_asin_title
I ordered it, and will report on the results...

It doesn’t appear to be listed as suitable for use as service equipment, so you’ll need a service disconnect between it and the meter.

 

[Dr. Hillbilly]

Thanks, I did not catch that, but I think it is OK as the meter will include a disconnect.

 

[Maquis]

Thanks, I did not catch that, but I think it is OK as the meter will include a disconnect.

In that case, just be sure that the connection to the grounding electrode is in the meter/main and you run 4 wires from the meter/main to the transfer switch.

Sponsored