Fastener question

[bluedog225]

Good morning,

I’ve got a large DC disconnect that I want to place at my solar array. It’s got mounting holes down the centerline.

It’s going on a 4” schedule 40 rigid conduit. A threaded screw seems iffy. And if rather not through bolt it. I can u bolt it if needed but would still like to pin it in place.

I think I need something like an expanding drywall anchor but obviously heavier. Preferably galvanized. Searching expansion bolt isn’t helping. Getting concrete stuff.

What would you call this?

Thanks

 

[Firebrick43]

Toggle bolt

 

[BillK]

So its actually going to be mounted on the 4" pipe ? I would use Rivnuts.

 

[LeonardY]

This is typically what is done to mount a box to a pole.

Or

 

[bluedog225]

Yes, mounted to the pole.

There is some security concern. Country place. Attached inside box helps a little.

Got it. Thanks all.

 

[BrandonV]

Yes, mounted to the pole.

There is some security concern. Country place. Attached inside box helps a little.

Got it. Thanks all.

I would swap out the hardware with security hardware but the pole mounts are your best bet.

 

[bluedog225]

I would swap out the hardware with security hardware but the pole mounts are your best bet.

Could you give me some more info? A more secure disco? Or something to attach it?

 

[BrandonV]

Could you give me some more info? A more secure disco? Or something to attach it?

Whenever I attach an enclosure to a pole, I replace any standard hardware (bolts, nuts, etc.) that can be removed with regular hand tools with security-style fasteners.

Will that stop someone who's determined to cause serious damage? Absolutely not. But it does prevent tampering by kids, opportunists, or people under the influence. It's the same principle as using a locking gas cap. Won't stop a determined bad actor, but it keeps the neighborhood kid from pouring sugar in your tank.

 

[bluedog225]

Got it. thanks.

That’s one of the reasons I wanted to put something through those middle fastener holes. They’ll have to work a bit to remove it.

 

[BrandonV]

Got it. thanks.

That’s one of the reasons I wanted to put something through those middle fastener holes. They’ll have to work a bit to remove it.

A toggle bolt like @Firebrick43 pointed out would excel at that.

Even if it loosens it's not like they're going to be able to back it out.

 

[LeonardY]

Got it. thanks.

That’s one of the reasons I wanted to put something through those middle fastener holes. They’ll have to work a bit to remove it.

Is a disconnect box that attractive of an item to steal? And do you have a lot of theft or vandalism in your area?

You might be overthinking this. Using tamper resistant fasteners is usually enough. You can also use permanent locktite.

 

[bluedog225]

Unfortunately, Mr. Methhead will spend all day under a house cutting out copper. And cut the wiring out of your house.

 

[CraigStu]

I think the u-bolts in the first pic in LeonardY's post could be adjusted a bit to fit into the holes in the box. Or new holes drilled would work too. Once the pole fasteners are inside all you need to do is a combination lock to hold the door closed.

 

[cannuck]

This is actually a no brainer. Have to be a lot more creative in use of Unistrut. Cut 2 pieces of strut full width of box. come into backside of strut with U bolts so nuts are inside and only can be tighteed with a socket with box off. Where the back of the box has 2 x 2 holes (not the 1 + 1 on centerline) pug side strut nuts in place to received bolt through 4 holes - that will need a spacer/washer(s) to keep the depressed center of the 1 + 1 centerline bolts holes from bottoming on strut. At least they will have to open box to gain access. no room to swing wrench from open ends to get u-bolt nuts off.

Now let my electrical ignorance be clearly displayed: OP called the disconnect DC, but every one I have ever seen is rated ** amps for each AC voltage and a much lower amperage for DC. If this is supposed to be a DC device, why does it have 3 terminals? Is this the result of marketing hype from the solar industry?

 

[manwithtools]

If this is supposed to be a DC device, why does it have 3 terminals?

If you look closely, the disconnects has contacts 1 and 2 wired in series.

So incoming DC+ goes to top of contact 1, outgoing DC+ goes to bottom of contact 2.

DC- incoming to top of contact 3, outgoing DC- to bottom of contact 3.

This allows use at the rated DC amperage and provides a longer arc extinguishing opening across multiple contacts. This aids in disconnecting under load as DC current has no zero crossing voltage that AC has.

Sometimes all three contacts are wired in series and only the DC+ is connected / disconnected. This allows a higher DC current rating due to the longer arc extinguishing property.

In reality this is a 3 phase AC disconnect properly wired for use in a DC application.

 

[cannuck]

If you look closely, the disconnects has contacts 1 and 2 wired in series.

So incoming DC+ goes to top of contact 1, outgoing DC+ goes to bottom of contact 2.

DC- incoming to top of contact 3, outgoing DC- to bottom of contact 3.

This allows use at the rated DC amperage and provides a longer arc extinguishing opening across multiple contacts. This aids in disconnecting under load as DC current has no zero crossing voltage that AC has.

Sometimes all three contacts are wired in series and only the DC+ is connected / disconnected. This allows a higher DC current rating due to the longer arc extinguishing property.

In reality this is a 3 phase AC disconnect properly wired for use in a DC application.

Thanks for explaining that! I enjoy this site so much because I learn something new and worthwhile every day.