NEC 408.36(D) compliant single-pole breakers

[sgtcrumb]

Hi All,

It's been a while since I posted here. I'm building an off-gird system using Sunny Island battery inverters/chargers. The Sunny Island AC1 terminal connects to a stand-alone breaker panel via a 70A single-pole breaker. This breaker is obviously back-fed by the Sunny Island. NEC 2017, rule 408.36(D), states

Plug-in-type overcurrent protection devices or plug-in type main lug assemblies that are backfed and used to terminate field-installed ungrounded supply conductors shall be secured in place by an additional fastener that requires other than a pull to release the device from the mounting means on the panel.

I have been searching for breaker panels that have a hold down kit for a single-pole breaker, and options appear limited. I was told Square D QO panels do not have such a kit. Siemens PN panels don't appear to either. What are you folks using? I wouldn't want to fail an inspection on such a trivial issue.

Thanks!

 

[OzSolar]

My shaky memory is that since your inverter is UL listed as grid interactive you don't need to. Here is where is found the below.

 

[ncsolarelectric]

Eaton panels, and Eaton breakers have the hold-down kit. That's what I use, that's what Enphase uses. I don't use 1-pole breakers however. Idk about that. You can use a 2P breaker and just not use 1 pole.

 

[sgtcrumb]

Hi @ncsolarelectric,

Your suggestion sounds like an option. Thanks for the advice. Are you familiar with Eaton CH125RBCS (link: https://www.eaton.com/us/en-us/skuPage.CH125RBCS.html)? Product descriptions on the internet claim this works for 1, 2, and 3-pole breakers.

Hi @OzSolar, thanks for the response. However, I think 705.12(B)5 exception will apply to the Sunny Boy PV inverter, which is listed as a UL 1741 device. If you unplug the Sunny Boy's breaker, it will interpret that as a grid-down situation and stop sending A/C to the grid. The Sunny Islands form the stand-alone grid which is required for the Sunny Boys to energize the breaker panel.

 

[goldserve]

Square d QO panels do have hold down kits. Zoro: G3078826

 

[zanydroid]

I think whatever is gridforming needs a tiedown. The interactive ones don't.

That looks similar to what I use for my Siemens breakers. The hold down type for your panel ought to be listed either in the catalog page and/or the wiring diagram sticker on your panel. On Siemens it works for every 2 pole breaker I've used it for. Never had a need to use it on 1 pole. I've used plenty of 2 pole breakers for 1 pole and MWBC applications.

If you don't have a breaker yet 70A double pole breaker may be easier to buy than single pole and repurpose in the future. 70A single pole is pretty niche.

If I were you I would just buy one and figure out how it fits together. That's faster than trying to find the PDF/diagrams online. Should be pretty self-explanatory how it works and what it's compatible with if you have the hold down, breaker, and panel all in one place.

 

[OzSolar]

Can you help better me understand better what you're doing? My memory is that AC1 on the Sunny Island is for the Grid/Generator. AC2 is the out for the loads which is where it will form the grid.

 

[sgtcrumb]

Thanks everyone. I appreciate the feedback. The system will be a split phase system with two Sunny Islands. I have some Siemens 2-pole breakers, and as far as I can tell, they're just two 1-pole breakers mechanically connected to trip together. If this is the case, one 2-pole Q270 breaker can be used instead of two 1-pole Q170 breakers. The Sunny Islands shouldn't know the difference, and Siemens does have a retaining clip for the 2-pole breakers (model #ECMBR2). Anyone aware of potential NEC violations with this solution?

@OzSolar, check the Sunny Island manual. AC1 is for loads and grid tie inverters (i.e sunny boys) and AC2 is for grid and/or generator. I'm building a stand-alone off-grid system with Sunny Islands in a split phase config and sunny boy PV inverters. They will all connect to the same breaker panel.

 

[zanydroid]

Anyone aware of potential NEC violations with this solution?

Only one I can think of is if there are instructions in the inverter manual that deviate from code.

Reread your OP. PN and SN panels from Siemens should support it. Minor caveats:

• I am pretty sure it will not work with 1-pole frames. The clamp goes into a slot in the middle of a breaker, if you have 2 1-pole breakers this slot will be empty space basically.
• they only make hold down clamp for breakers in the left side, but you can put it anywhere on the left row.
• the hold down will block 2 spaces in the opposite side. don't make mistake I made and get too small of a panel. this may also prevent you from using the 120% to the max since you have 2 spaces on the bottom row now instead of 4. I think for an off-grid system you will not have two power sources anyway so you don't need 120% rule.
• the terminal cover clip only fits larger breakers (60A and bigger?). I've passed inspection with smaller breakers.

 

[OzSolar]

@OzSolar, check the Sunny Island manual. AC1 is for loads and grid tie inverters (i.e sunny boys) and AC2 is for grid and/or generator. I'm building a stand-alone off-grid system with Sunny Islands in a split phase config and sunny boy PV inverters. They will all connect to the same breaker panel.

Ah... I see that now! I'd blame it on the drink but I wasn't. I was out of the normal worn out at the end of a long week and very sleepy. Side note: Where are you building that off grid gets inspected?

Home Depot has a BR hold down kit that might work for you.

Could you use a main breaker style load center and feed the Sunny Islands to the Main breaker?