Generator panel

[James L]

I'm wiring a new construction home right now, and the homeowner asked me to price pre-wiring for a backup generator.

I've wired a few, but it's something I only do about once every 5 years or so.

One question relates to 445.13(a)

Must size the conductors at 115% unless the design and operation of the generator prevents overloading

I'm thinking about suggesting a 15kw generator, but maybe 25kw

Thinking about installing a 100-amp emergency panel with built-in ATS from Honeywell

I think it's already full of breakers, none of which are arc fault. Does the listing of this panel specifically include all of those breakers or can they be changed?

If using either 15kw or 25kw, does a 60- or 100-amp disconnect outside constitute overload protection so as to circumvent the 115% requirement?

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[LarryFine]

If it was me, I'd use a stand-alone, service-rated transfer switch and a standard panel for the genny loads.

 

[hillbilly1]

Unfortunately different generator manufacturers may not be compatible with the transferswitch you installed. Different control systems. Some use “smart” switches, others use “dumb” switches.

 

[James L]

If it was me, I'd use a stand-alone, service-rated transfer switch and a standard panel for the genny loads.

I thought about the same thing, that way I wouldn't be limited to the number of spaces in that one panel.

Could use SER/g to feed the subpanel, and circle all the way around it to leave enough cable for adding a transfer switch later without getting into the either of the two panels.

 

[James L]

Unfortunately different generator manufacturers may not be compatible with the transferswitch you installed. Different control systems. Some use “smart” switches, others use “dumb” switches.

Didn't consider that one. Very good food for thought. Thanks

 

[augie47]

The 115% you are referencing is from the generator output to the 1st distribution device which is often within the generator itself.
What I normally see is what Larry suggests. A standard, stand-alone panel and a ATS. As stated, the customer needs to decide on manufacturer so the correct ATS can be installed for the future generator.

 

[James L]

The 115% you are referencing is from the generator output to the 1st distribution device which is often within the generator itself.
What I normally see is what Larry suggests. A standard, stand-alone panel and a ATS. As stated, the customer needs to decide on manufacturer so the correct ATS can be installed for the future generator.

My first thought was to simply put in the sub panel and call it good until he decides on a genetator. Then I saw that sub panel with the ATS built in and thought it looked interesting enough.

I think that's the way I'll go

 

[brantmacga]

I’ve stopped doing dedicated backup panels in residential, unless there is a very specific need identified by the customer.

Every residential standby generator offers some sort of load shedding device now.

The way i build services now is to install a trough at the meter, and set a disconnect on top of it. When they decided on a generator in the future, you can take the disconnect off and drop a service rated transfer switch in place.

See example pic below…. This homeowner decided halfway through he wanted a 38kw, and luckily I had not installed the disconnects yet, but you can see how I do the trough. This was last week btw, still waiting on my disco labels.

Here’s another where the customer didn’t buy the generator yet. But I’ve got one on order now and this disconnect will be replaced with two SE rated ATS; he’s adding a shop building right now that will also be powered by the generator. It was a planned addition which is why the trough was sized to accommodate an additional switch.

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[brantmacga]

Another option if you’re set on having a dedicated backup panel is to set an outdoor enclosure and loop the backup panel feeder, so they can set an ATS in the future. That’s how I used to do it.

Dedicated backup panel to the right. I nippled between them so I’m a worst case scenario if something needed to be moved it could be done easily.

Enclosure…. I ended up installing a generator here a couple of years ago, this made it much easier.

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[hillbilly1]

Transferswitches are getting hard to find, I have two 200 amp Asco’s on order for two poultry houses. They have an existing service rated manual transferswitch, and a permanent generator, but the grower’s contract calls for automatic. Getting rid of the HPS lighting, and changing to LED too. Been waiting 6 weeks now.